Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673 2674 2675 2676 2677 2678 2679 2680 2681 2682 2683 2684 2685 2686 2687 2688 2689 2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720 2721 2722 2723 2724 2725 2726 2727 2728 2729 2730 2731 2732 2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763 2764 2765 2766 2767 2768 | .. SPDX-License-Identifier: GPL-2.0
=========
IP Sysctl
=========
/proc/sys/net/ipv4/* Variables
==============================
ip_forward - BOOLEAN
- 0 - disabled (default)
- not 0 - enabled
Forward Packets between interfaces.
This variable is special, its change resets all configuration
parameters to their default state (RFC1122 for hosts, RFC1812
for routers)
ip_default_ttl - INTEGER
Default value of TTL field (Time To Live) for outgoing (but not
forwarded) IP packets. Should be between 1 and 255 inclusive.
Default: 64 (as recommended by RFC1700)
ip_no_pmtu_disc - INTEGER
Disable Path MTU Discovery. If enabled in mode 1 and a
fragmentation-required ICMP is received, the PMTU to this
destination will be set to min_pmtu (see below). You will need
to raise min_pmtu to the smallest interface MTU on your system
manually if you want to avoid locally generated fragments.
In mode 2 incoming Path MTU Discovery messages will be
discarded. Outgoing frames are handled the same as in mode 1,
implicitly setting IP_PMTUDISC_DONT on every created socket.
Mode 3 is a hardened pmtu discover mode. The kernel will only
accept fragmentation-needed errors if the underlying protocol
can verify them besides a plain socket lookup. Current
protocols for which pmtu events will be honored are TCP, SCTP
and DCCP as they verify e.g. the sequence number or the
association. This mode should not be enabled globally but is
only intended to secure e.g. name servers in namespaces where
TCP path mtu must still work but path MTU information of other
protocols should be discarded. If enabled globally this mode
could break other protocols.
Possible values: 0-3
Default: FALSE
min_pmtu - INTEGER
default 552 - minimum discovered Path MTU
ip_forward_use_pmtu - BOOLEAN
By default we don't trust protocol path MTUs while forwarding
because they could be easily forged and can lead to unwanted
fragmentation by the router.
You only need to enable this if you have user-space software
which tries to discover path mtus by itself and depends on the
kernel honoring this information. This is normally not the
case.
Default: 0 (disabled)
Possible values:
- 0 - disabled
- 1 - enabled
fwmark_reflect - BOOLEAN
Controls the fwmark of kernel-generated IPv4 reply packets that are not
associated with a socket for example, TCP RSTs or ICMP echo replies).
If unset, these packets have a fwmark of zero. If set, they have the
fwmark of the packet they are replying to.
Default: 0
fib_multipath_use_neigh - BOOLEAN
Use status of existing neighbor entry when determining nexthop for
multipath routes. If disabled, neighbor information is not used and
packets could be directed to a failed nexthop. Only valid for kernels
built with CONFIG_IP_ROUTE_MULTIPATH enabled.
Default: 0 (disabled)
Possible values:
- 0 - disabled
- 1 - enabled
fib_multipath_hash_policy - INTEGER
Controls which hash policy to use for multipath routes. Only valid
for kernels built with CONFIG_IP_ROUTE_MULTIPATH enabled.
Default: 0 (Layer 3)
Possible values:
- 0 - Layer 3
- 1 - Layer 4
- 2 - Layer 3 or inner Layer 3 if present
fib_sync_mem - UNSIGNED INTEGER
Amount of dirty memory from fib entries that can be backlogged before
synchronize_rcu is forced.
Default: 512kB Minimum: 64kB Maximum: 64MB
ip_forward_update_priority - INTEGER
Whether to update SKB priority from "TOS" field in IPv4 header after it
is forwarded. The new SKB priority is mapped from TOS field value
according to an rt_tos2priority table (see e.g. man tc-prio).
Default: 1 (Update priority.)
Possible values:
- 0 - Do not update priority.
- 1 - Update priority.
route/max_size - INTEGER
Maximum number of routes allowed in the kernel. Increase
this when using large numbers of interfaces and/or routes.
From linux kernel 3.6 onwards, this is deprecated for ipv4
as route cache is no longer used.
neigh/default/gc_thresh1 - INTEGER
Minimum number of entries to keep. Garbage collector will not
purge entries if there are fewer than this number.
Default: 128
neigh/default/gc_thresh2 - INTEGER
Threshold when garbage collector becomes more aggressive about
purging entries. Entries older than 5 seconds will be cleared
when over this number.
Default: 512
neigh/default/gc_thresh3 - INTEGER
Maximum number of non-PERMANENT neighbor entries allowed. Increase
this when using large numbers of interfaces and when communicating
with large numbers of directly-connected peers.
Default: 1024
neigh/default/unres_qlen_bytes - INTEGER
The maximum number of bytes which may be used by packets
queued for each unresolved address by other network layers.
(added in linux 3.3)
Setting negative value is meaningless and will return error.
Default: SK_WMEM_MAX, (same as net.core.wmem_default).
Exact value depends on architecture and kernel options,
but should be enough to allow queuing 256 packets
of medium size.
neigh/default/unres_qlen - INTEGER
The maximum number of packets which may be queued for each
unresolved address by other network layers.
(deprecated in linux 3.3) : use unres_qlen_bytes instead.
Prior to linux 3.3, the default value is 3 which may cause
unexpected packet loss. The current default value is calculated
according to default value of unres_qlen_bytes and true size of
packet.
Default: 101
mtu_expires - INTEGER
Time, in seconds, that cached PMTU information is kept.
min_adv_mss - INTEGER
The advertised MSS depends on the first hop route MTU, but will
never be lower than this setting.
fib_notify_on_flag_change - INTEGER
Whether to emit RTM_NEWROUTE notifications whenever RTM_F_OFFLOAD/
RTM_F_TRAP/RTM_F_OFFLOAD_FAILED flags are changed.
After installing a route to the kernel, user space receives an
acknowledgment, which means the route was installed in the kernel,
but not necessarily in hardware.
It is also possible for a route already installed in hardware to change
its action and therefore its flags. For example, a host route that is
trapping packets can be "promoted" to perform decapsulation following
the installation of an IPinIP/VXLAN tunnel.
The notifications will indicate to user-space the state of the route.
Default: 0 (Do not emit notifications.)
Possible values:
- 0 - Do not emit notifications.
- 1 - Emit notifications.
- 2 - Emit notifications only for RTM_F_OFFLOAD_FAILED flag change.
IP Fragmentation:
ipfrag_high_thresh - LONG INTEGER
Maximum memory used to reassemble IP fragments.
ipfrag_low_thresh - LONG INTEGER
(Obsolete since linux-4.17)
Maximum memory used to reassemble IP fragments before the kernel
begins to remove incomplete fragment queues to free up resources.
The kernel still accepts new fragments for defragmentation.
ipfrag_time - INTEGER
Time in seconds to keep an IP fragment in memory.
ipfrag_max_dist - INTEGER
ipfrag_max_dist is a non-negative integer value which defines the
maximum "disorder" which is allowed among fragments which share a
common IP source address. Note that reordering of packets is
not unusual, but if a large number of fragments arrive from a source
IP address while a particular fragment queue remains incomplete, it
probably indicates that one or more fragments belonging to that queue
have been lost. When ipfrag_max_dist is positive, an additional check
is done on fragments before they are added to a reassembly queue - if
ipfrag_max_dist (or more) fragments have arrived from a particular IP
address between additions to any IP fragment queue using that source
address, it's presumed that one or more fragments in the queue are
lost. The existing fragment queue will be dropped, and a new one
started. An ipfrag_max_dist value of zero disables this check.
Using a very small value, e.g. 1 or 2, for ipfrag_max_dist can
result in unnecessarily dropping fragment queues when normal
reordering of packets occurs, which could lead to poor application
performance. Using a very large value, e.g. 50000, increases the
likelihood of incorrectly reassembling IP fragments that originate
from different IP datagrams, which could result in data corruption.
Default: 64
INET peer storage
=================
inet_peer_threshold - INTEGER
The approximate size of the storage. Starting from this threshold
entries will be thrown aggressively. This threshold also determines
entries' time-to-live and time intervals between garbage collection
passes. More entries, less time-to-live, less GC interval.
inet_peer_minttl - INTEGER
Minimum time-to-live of entries. Should be enough to cover fragment
time-to-live on the reassembling side. This minimum time-to-live is
guaranteed if the pool size is less than inet_peer_threshold.
Measured in seconds.
inet_peer_maxttl - INTEGER
Maximum time-to-live of entries. Unused entries will expire after
this period of time if there is no memory pressure on the pool (i.e.
when the number of entries in the pool is very small).
Measured in seconds.
TCP variables
=============
somaxconn - INTEGER
Limit of socket listen() backlog, known in userspace as SOMAXCONN.
Defaults to 4096. (Was 128 before linux-5.4)
See also tcp_max_syn_backlog for additional tuning for TCP sockets.
tcp_abort_on_overflow - BOOLEAN
If listening service is too slow to accept new connections,
reset them. Default state is FALSE. It means that if overflow
occurred due to a burst, connection will recover. Enable this
option _only_ if you are really sure that listening daemon
cannot be tuned to accept connections faster. Enabling this
option can harm clients of your server.
tcp_adv_win_scale - INTEGER
Count buffering overhead as bytes/2^tcp_adv_win_scale
(if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale),
if it is <= 0.
Possible values are [-31, 31], inclusive.
Default: 1
tcp_allowed_congestion_control - STRING
Show/set the congestion control choices available to non-privileged
processes. The list is a subset of those listed in
tcp_available_congestion_control.
Default is "reno" and the default setting (tcp_congestion_control).
tcp_app_win - INTEGER
Reserve max(window/2^tcp_app_win, mss) of window for application
buffer. Value 0 is special, it means that nothing is reserved.
Default: 31
tcp_autocorking - BOOLEAN
Enable TCP auto corking :
When applications do consecutive small write()/sendmsg() system calls,
we try to coalesce these small writes as much as possible, to lower
total amount of sent packets. This is done if at least one prior
packet for the flow is waiting in Qdisc queues or device transmit
queue. Applications can still use TCP_CORK for optimal behavior
when they know how/when to uncork their sockets.
Default : 1
tcp_available_congestion_control - STRING
Shows the available congestion control choices that are registered.
More congestion control algorithms may be available as modules,
but not loaded.
tcp_base_mss - INTEGER
The initial value of search_low to be used by the packetization layer
Path MTU discovery (MTU probing). If MTU probing is enabled,
this is the initial MSS used by the connection.
tcp_mtu_probe_floor - INTEGER
If MTU probing is enabled this caps the minimum MSS used for search_low
for the connection.
Default : 48
tcp_min_snd_mss - INTEGER
TCP SYN and SYNACK messages usually advertise an ADVMSS option,
as described in RFC 1122 and RFC 6691.
If this ADVMSS option is smaller than tcp_min_snd_mss,
it is silently capped to tcp_min_snd_mss.
Default : 48 (at least 8 bytes of payload per segment)
tcp_congestion_control - STRING
Set the congestion control algorithm to be used for new
connections. The algorithm "reno" is always available, but
additional choices may be available based on kernel configuration.
Default is set as part of kernel configuration.
For passive connections, the listener congestion control choice
is inherited.
[see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ]
tcp_dsack - BOOLEAN
Allows TCP to send "duplicate" SACKs.
tcp_early_retrans - INTEGER
Tail loss probe (TLP) converts RTOs occurring due to tail
losses into fast recovery (draft-ietf-tcpm-rack). Note that
TLP requires RACK to function properly (see tcp_recovery below)
Possible values:
- 0 disables TLP
- 3 or 4 enables TLP
Default: 3
tcp_ecn - INTEGER
Control use of Explicit Congestion Notification (ECN) by TCP.
ECN is used only when both ends of the TCP connection indicate
support for it. This feature is useful in avoiding losses due
to congestion by allowing supporting routers to signal
congestion before having to drop packets.
Possible values are:
= =====================================================
0 Disable ECN. Neither initiate nor accept ECN.
1 Enable ECN when requested by incoming connections and
also request ECN on outgoing connection attempts.
2 Enable ECN when requested by incoming connections
but do not request ECN on outgoing connections.
= =====================================================
Default: 2
tcp_ecn_fallback - BOOLEAN
If the kernel detects that ECN connection misbehaves, enable fall
back to non-ECN. Currently, this knob implements the fallback
from RFC3168, section 6.1.1.1., but we reserve that in future,
additional detection mechanisms could be implemented under this
knob. The value is not used, if tcp_ecn or per route (or congestion
control) ECN settings are disabled.
Default: 1 (fallback enabled)
tcp_fack - BOOLEAN
This is a legacy option, it has no effect anymore.
tcp_fin_timeout - INTEGER
The length of time an orphaned (no longer referenced by any
application) connection will remain in the FIN_WAIT_2 state
before it is aborted at the local end. While a perfectly
valid "receive only" state for an un-orphaned connection, an
orphaned connection in FIN_WAIT_2 state could otherwise wait
forever for the remote to close its end of the connection.
Cf. tcp_max_orphans
Default: 60 seconds
tcp_frto - INTEGER
Enables Forward RTO-Recovery (F-RTO) defined in RFC5682.
F-RTO is an enhanced recovery algorithm for TCP retransmission
timeouts. It is particularly beneficial in networks where the
RTT fluctuates (e.g., wireless). F-RTO is sender-side only
modification. It does not require any support from the peer.
By default it's enabled with a non-zero value. 0 disables F-RTO.
tcp_fwmark_accept - BOOLEAN
If set, incoming connections to listening sockets that do not have a
socket mark will set the mark of the accepting socket to the fwmark of
the incoming SYN packet. This will cause all packets on that connection
(starting from the first SYNACK) to be sent with that fwmark. The
listening socket's mark is unchanged. Listening sockets that already
have a fwmark set via setsockopt(SOL_SOCKET, SO_MARK, ...) are
unaffected.
Default: 0
tcp_invalid_ratelimit - INTEGER
Limit the maximal rate for sending duplicate acknowledgments
in response to incoming TCP packets that are for an existing
connection but that are invalid due to any of these reasons:
(a) out-of-window sequence number,
(b) out-of-window acknowledgment number, or
(c) PAWS (Protection Against Wrapped Sequence numbers) check failure
This can help mitigate simple "ack loop" DoS attacks, wherein
a buggy or malicious middlebox or man-in-the-middle can
rewrite TCP header fields in manner that causes each endpoint
to think that the other is sending invalid TCP segments, thus
causing each side to send an unterminating stream of duplicate
acknowledgments for invalid segments.
Using 0 disables rate-limiting of dupacks in response to
invalid segments; otherwise this value specifies the minimal
space between sending such dupacks, in milliseconds.
Default: 500 (milliseconds).
tcp_keepalive_time - INTEGER
How often TCP sends out keepalive messages when keepalive is enabled.
Default: 2hours.
tcp_keepalive_probes - INTEGER
How many keepalive probes TCP sends out, until it decides that the
connection is broken. Default value: 9.
tcp_keepalive_intvl - INTEGER
How frequently the probes are send out. Multiplied by
tcp_keepalive_probes it is time to kill not responding connection,
after probes started. Default value: 75sec i.e. connection
will be aborted after ~11 minutes of retries.
tcp_l3mdev_accept - BOOLEAN
Enables child sockets to inherit the L3 master device index.
Enabling this option allows a "global" listen socket to work
across L3 master domains (e.g., VRFs) with connected sockets
derived from the listen socket to be bound to the L3 domain in
which the packets originated. Only valid when the kernel was
compiled with CONFIG_NET_L3_MASTER_DEV.
Default: 0 (disabled)
tcp_low_latency - BOOLEAN
This is a legacy option, it has no effect anymore.
tcp_max_orphans - INTEGER
Maximal number of TCP sockets not attached to any user file handle,
held by system. If this number is exceeded orphaned connections are
reset immediately and warning is printed. This limit exists
only to prevent simple DoS attacks, you _must_ not rely on this
or lower the limit artificially, but rather increase it
(probably, after increasing installed memory),
if network conditions require more than default value,
and tune network services to linger and kill such states
more aggressively. Let me to remind again: each orphan eats
up to ~64K of unswappable memory.
tcp_max_syn_backlog - INTEGER
Maximal number of remembered connection requests (SYN_RECV),
which have not received an acknowledgment from connecting client.
This is a per-listener limit.
The minimal value is 128 for low memory machines, and it will
increase in proportion to the memory of machine.
If server suffers from overload, try increasing this number.
Remember to also check /proc/sys/net/core/somaxconn
A SYN_RECV request socket consumes about 304 bytes of memory.
tcp_max_tw_buckets - INTEGER
Maximal number of timewait sockets held by system simultaneously.
If this number is exceeded time-wait socket is immediately destroyed
and warning is printed. This limit exists only to prevent
simple DoS attacks, you _must_ not lower the limit artificially,
but rather increase it (probably, after increasing installed memory),
if network conditions require more than default value.
tcp_mem - vector of 3 INTEGERs: min, pressure, max
min: below this number of pages TCP is not bothered about its
memory appetite.
pressure: when amount of memory allocated by TCP exceeds this number
of pages, TCP moderates its memory consumption and enters memory
pressure mode, which is exited when memory consumption falls
under "min".
max: number of pages allowed for queueing by all TCP sockets.
Defaults are calculated at boot time from amount of available
memory.
tcp_min_rtt_wlen - INTEGER
The window length of the windowed min filter to track the minimum RTT.
A shorter window lets a flow more quickly pick up new (higher)
minimum RTT when it is moved to a longer path (e.g., due to traffic
engineering). A longer window makes the filter more resistant to RTT
inflations such as transient congestion. The unit is seconds.
Possible values: 0 - 86400 (1 day)
Default: 300
tcp_moderate_rcvbuf - BOOLEAN
If set, TCP performs receive buffer auto-tuning, attempting to
automatically size the buffer (no greater than tcp_rmem[2]) to
match the size required by the path for full throughput. Enabled by
default.
tcp_mtu_probing - INTEGER
Controls TCP Packetization-Layer Path MTU Discovery. Takes three
values:
- 0 - Disabled
- 1 - Disabled by default, enabled when an ICMP black hole detected
- 2 - Always enabled, use initial MSS of tcp_base_mss.
tcp_probe_interval - UNSIGNED INTEGER
Controls how often to start TCP Packetization-Layer Path MTU
Discovery reprobe. The default is reprobing every 10 minutes as
per RFC4821.
tcp_probe_threshold - INTEGER
Controls when TCP Packetization-Layer Path MTU Discovery probing
will stop in respect to the width of search range in bytes. Default
is 8 bytes.
tcp_no_metrics_save - BOOLEAN
By default, TCP saves various connection metrics in the route cache
when the connection closes, so that connections established in the
near future can use these to set initial conditions. Usually, this
increases overall performance, but may sometimes cause performance
degradation. If set, TCP will not cache metrics on closing
connections.
tcp_no_ssthresh_metrics_save - BOOLEAN
Controls whether TCP saves ssthresh metrics in the route cache.
Default is 1, which disables ssthresh metrics.
tcp_orphan_retries - INTEGER
This value influences the timeout of a locally closed TCP connection,
when RTO retransmissions remain unacknowledged.
See tcp_retries2 for more details.
The default value is 8.
If your machine is a loaded WEB server,
you should think about lowering this value, such sockets
may consume significant resources. Cf. tcp_max_orphans.
tcp_recovery - INTEGER
This value is a bitmap to enable various experimental loss recovery
features.
========= =============================================================
RACK: 0x1 enables the RACK loss detection for fast detection of lost
retransmissions and tail drops. It also subsumes and disables
RFC6675 recovery for SACK connections.
RACK: 0x2 makes RACK's reordering window static (min_rtt/4).
RACK: 0x4 disables RACK's DUPACK threshold heuristic
========= =============================================================
Default: 0x1
tcp_reordering - INTEGER
Initial reordering level of packets in a TCP stream.
TCP stack can then dynamically adjust flow reordering level
between this initial value and tcp_max_reordering
Default: 3
tcp_max_reordering - INTEGER
Maximal reordering level of packets in a TCP stream.
300 is a fairly conservative value, but you might increase it
if paths are using per packet load balancing (like bonding rr mode)
Default: 300
tcp_retrans_collapse - BOOLEAN
Bug-to-bug compatibility with some broken printers.
On retransmit try to send bigger packets to work around bugs in
certain TCP stacks.
tcp_retries1 - INTEGER
This value influences the time, after which TCP decides, that
something is wrong due to unacknowledged RTO retransmissions,
and reports this suspicion to the network layer.
See tcp_retries2 for more details.
RFC 1122 recommends at least 3 retransmissions, which is the
default.
tcp_retries2 - INTEGER
This value influences the timeout of an alive TCP connection,
when RTO retransmissions remain unacknowledged.
Given a value of N, a hypothetical TCP connection following
exponential backoff with an initial RTO of TCP_RTO_MIN would
retransmit N times before killing the connection at the (N+1)th RTO.
The default value of 15 yields a hypothetical timeout of 924.6
seconds and is a lower bound for the effective timeout.
TCP will effectively time out at the first RTO which exceeds the
hypothetical timeout.
RFC 1122 recommends at least 100 seconds for the timeout,
which corresponds to a value of at least 8.
tcp_rfc1337 - BOOLEAN
If set, the TCP stack behaves conforming to RFC1337. If unset,
we are not conforming to RFC, but prevent TCP TIME_WAIT
assassination.
Default: 0
tcp_rmem - vector of 3 INTEGERs: min, default, max
min: Minimal size of receive buffer used by TCP sockets.
It is guaranteed to each TCP socket, even under moderate memory
pressure.
Default: 4K
default: initial size of receive buffer used by TCP sockets.
This value overrides net.core.rmem_default used by other protocols.
Default: 131072 bytes.
This value results in initial window of 65535.
max: maximal size of receive buffer allowed for automatically
selected receiver buffers for TCP socket. This value does not override
net.core.rmem_max. Calling setsockopt() with SO_RCVBUF disables
automatic tuning of that socket's receive buffer size, in which
case this value is ignored.
Default: between 131072 and 6MB, depending on RAM size.
tcp_sack - BOOLEAN
Enable select acknowledgments (SACKS).
tcp_comp_sack_delay_ns - LONG INTEGER
TCP tries to reduce number of SACK sent, using a timer
based on 5% of SRTT, capped by this sysctl, in nano seconds.
The default is 1ms, based on TSO autosizing period.
Default : 1,000,000 ns (1 ms)
tcp_comp_sack_slack_ns - LONG INTEGER
This sysctl control the slack used when arming the
timer used by SACK compression. This gives extra time
for small RTT flows, and reduces system overhead by allowing
opportunistic reduction of timer interrupts.
Default : 100,000 ns (100 us)
tcp_comp_sack_nr - INTEGER
Max number of SACK that can be compressed.
Using 0 disables SACK compression.
Default : 44
tcp_slow_start_after_idle - BOOLEAN
If set, provide RFC2861 behavior and time out the congestion
window after an idle period. An idle period is defined at
the current RTO. If unset, the congestion window will not
be timed out after an idle period.
Default: 1
tcp_stdurg - BOOLEAN
Use the Host requirements interpretation of the TCP urgent pointer field.
Most hosts use the older BSD interpretation, so if you turn this on
Linux might not communicate correctly with them.
Default: FALSE
tcp_synack_retries - INTEGER
Number of times SYNACKs for a passive TCP connection attempt will
be retransmitted. Should not be higher than 255. Default value
is 5, which corresponds to 31seconds till the last retransmission
with the current initial RTO of 1second. With this the final timeout
for a passive TCP connection will happen after 63seconds.
tcp_syncookies - INTEGER
Only valid when the kernel was compiled with CONFIG_SYN_COOKIES
Send out syncookies when the syn backlog queue of a socket
overflows. This is to prevent against the common 'SYN flood attack'
Default: 1
Note, that syncookies is fallback facility.
It MUST NOT be used to help highly loaded servers to stand
against legal connection rate. If you see SYN flood warnings
in your logs, but investigation shows that they occur
because of overload with legal connections, you should tune
another parameters until this warning disappear.
See: tcp_max_syn_backlog, tcp_synack_retries, tcp_abort_on_overflow.
syncookies seriously violate TCP protocol, do not allow
to use TCP extensions, can result in serious degradation
of some services (f.e. SMTP relaying), visible not by you,
but your clients and relays, contacting you. While you see
SYN flood warnings in logs not being really flooded, your server
is seriously misconfigured.
If you want to test which effects syncookies have to your
network connections you can set this knob to 2 to enable
unconditionally generation of syncookies.
tcp_fastopen - INTEGER
Enable TCP Fast Open (RFC7413) to send and accept data in the opening
SYN packet.
The client support is enabled by flag 0x1 (on by default). The client
then must use sendmsg() or sendto() with the MSG_FASTOPEN flag,
rather than connect() to send data in SYN.
The server support is enabled by flag 0x2 (off by default). Then
either enable for all listeners with another flag (0x400) or
enable individual listeners via TCP_FASTOPEN socket option with
the option value being the length of the syn-data backlog.
The values (bitmap) are
===== ======== ======================================================
0x1 (client) enables sending data in the opening SYN on the client.
0x2 (server) enables the server support, i.e., allowing data in
a SYN packet to be accepted and passed to the
application before 3-way handshake finishes.
0x4 (client) send data in the opening SYN regardless of cookie
availability and without a cookie option.
0x200 (server) accept data-in-SYN w/o any cookie option present.
0x400 (server) enable all listeners to support Fast Open by
default without explicit TCP_FASTOPEN socket option.
===== ======== ======================================================
Default: 0x1
Note that additional client or server features are only
effective if the basic support (0x1 and 0x2) are enabled respectively.
tcp_fastopen_blackhole_timeout_sec - INTEGER
Initial time period in second to disable Fastopen on active TCP sockets
when a TFO firewall blackhole issue happens.
This time period will grow exponentially when more blackhole issues
get detected right after Fastopen is re-enabled and will reset to
initial value when the blackhole issue goes away.
0 to disable the blackhole detection.
By default, it is set to 1hr.
tcp_fastopen_key - list of comma separated 32-digit hexadecimal INTEGERs
The list consists of a primary key and an optional backup key. The
primary key is used for both creating and validating cookies, while the
optional backup key is only used for validating cookies. The purpose of
the backup key is to maximize TFO validation when keys are rotated.
A randomly chosen primary key may be configured by the kernel if
the tcp_fastopen sysctl is set to 0x400 (see above), or if the
TCP_FASTOPEN setsockopt() optname is set and a key has not been
previously configured via sysctl. If keys are configured via
setsockopt() by using the TCP_FASTOPEN_KEY optname, then those
per-socket keys will be used instead of any keys that are specified via
sysctl.
A key is specified as 4 8-digit hexadecimal integers which are separated
by a '-' as: xxxxxxxx-xxxxxxxx-xxxxxxxx-xxxxxxxx. Leading zeros may be
omitted. A primary and a backup key may be specified by separating them
by a comma. If only one key is specified, it becomes the primary key and
any previously configured backup keys are removed.
tcp_syn_retries - INTEGER
Number of times initial SYNs for an active TCP connection attempt
will be retransmitted. Should not be higher than 127. Default value
is 6, which corresponds to 63seconds till the last retransmission
with the current initial RTO of 1second. With this the final timeout
for an active TCP connection attempt will happen after 127seconds.
tcp_timestamps - INTEGER
Enable timestamps as defined in RFC1323.
- 0: Disabled.
- 1: Enable timestamps as defined in RFC1323 and use random offset for
each connection rather than only using the current time.
- 2: Like 1, but without random offsets.
Default: 1
tcp_min_tso_segs - INTEGER
Minimal number of segments per TSO frame.
Since linux-3.12, TCP does an automatic sizing of TSO frames,
depending on flow rate, instead of filling 64Kbytes packets.
For specific usages, it's possible to force TCP to build big
TSO frames. Note that TCP stack might split too big TSO packets
if available window is too small.
Default: 2
tcp_pacing_ss_ratio - INTEGER
sk->sk_pacing_rate is set by TCP stack using a ratio applied
to current rate. (current_rate = cwnd * mss / srtt)
If TCP is in slow start, tcp_pacing_ss_ratio is applied
to let TCP probe for bigger speeds, assuming cwnd can be
doubled every other RTT.
Default: 200
tcp_pacing_ca_ratio - INTEGER
sk->sk_pacing_rate is set by TCP stack using a ratio applied
to current rate. (current_rate = cwnd * mss / srtt)
If TCP is in congestion avoidance phase, tcp_pacing_ca_ratio
is applied to conservatively probe for bigger throughput.
Default: 120
tcp_tso_win_divisor - INTEGER
This allows control over what percentage of the congestion window
can be consumed by a single TSO frame.
The setting of this parameter is a choice between burstiness and
building larger TSO frames.
Default: 3
tcp_tw_reuse - INTEGER
Enable reuse of TIME-WAIT sockets for new connections when it is
safe from protocol viewpoint.
- 0 - disable
- 1 - global enable
- 2 - enable for loopback traffic only
It should not be changed without advice/request of technical
experts.
Default: 2
tcp_window_scaling - BOOLEAN
Enable window scaling as defined in RFC1323.
tcp_wmem - vector of 3 INTEGERs: min, default, max
min: Amount of memory reserved for send buffers for TCP sockets.
Each TCP socket has rights to use it due to fact of its birth.
Default: 4K
default: initial size of send buffer used by TCP sockets. This
value overrides net.core.wmem_default used by other protocols.
It is usually lower than net.core.wmem_default.
Default: 16K
max: Maximal amount of memory allowed for automatically tuned
send buffers for TCP sockets. This value does not override
net.core.wmem_max. Calling setsockopt() with SO_SNDBUF disables
automatic tuning of that socket's send buffer size, in which case
this value is ignored.
Default: between 64K and 4MB, depending on RAM size.
tcp_notsent_lowat - UNSIGNED INTEGER
A TCP socket can control the amount of unsent bytes in its write queue,
thanks to TCP_NOTSENT_LOWAT socket option. poll()/select()/epoll()
reports POLLOUT events if the amount of unsent bytes is below a per
socket value, and if the write queue is not full. sendmsg() will
also not add new buffers if the limit is hit.
This global variable controls the amount of unsent data for
sockets not using TCP_NOTSENT_LOWAT. For these sockets, a change
to the global variable has immediate effect.
Default: UINT_MAX (0xFFFFFFFF)
tcp_workaround_signed_windows - BOOLEAN
If set, assume no receipt of a window scaling option means the
remote TCP is broken and treats the window as a signed quantity.
If unset, assume the remote TCP is not broken even if we do
not receive a window scaling option from them.
Default: 0
tcp_thin_linear_timeouts - BOOLEAN
Enable dynamic triggering of linear timeouts for thin streams.
If set, a check is performed upon retransmission by timeout to
determine if the stream is thin (less than 4 packets in flight).
As long as the stream is found to be thin, up to 6 linear
timeouts may be performed before exponential backoff mode is
initiated. This improves retransmission latency for
non-aggressive thin streams, often found to be time-dependent.
For more information on thin streams, see
Documentation/networking/tcp-thin.rst
Default: 0
tcp_limit_output_bytes - INTEGER
Controls TCP Small Queue limit per tcp socket.
TCP bulk sender tends to increase packets in flight until it
gets losses notifications. With SNDBUF autotuning, this can
result in a large amount of packets queued on the local machine
(e.g.: qdiscs, CPU backlog, or device) hurting latency of other
flows, for typical pfifo_fast qdiscs. tcp_limit_output_bytes
limits the number of bytes on qdisc or device to reduce artificial
RTT/cwnd and reduce bufferbloat.
Default: 1048576 (16 * 65536)
tcp_challenge_ack_limit - INTEGER
Limits number of Challenge ACK sent per second, as recommended
in RFC 5961 (Improving TCP's Robustness to Blind In-Window Attacks)
Default: 1000
tcp_rx_skb_cache - BOOLEAN
Controls a per TCP socket cache of one skb, that might help
performance of some workloads. This might be dangerous
on systems with a lot of TCP sockets, since it increases
memory usage.
Default: 0 (disabled)
UDP variables
=============
udp_l3mdev_accept - BOOLEAN
Enabling this option allows a "global" bound socket to work
across L3 master domains (e.g., VRFs) with packets capable of
being received regardless of the L3 domain in which they
originated. Only valid when the kernel was compiled with
CONFIG_NET_L3_MASTER_DEV.
Default: 0 (disabled)
udp_mem - vector of 3 INTEGERs: min, pressure, max
Number of pages allowed for queueing by all UDP sockets.
min: Below this number of pages UDP is not bothered about its
memory appetite. When amount of memory allocated by UDP exceeds
this number, UDP starts to moderate memory usage.
pressure: This value was introduced to follow format of tcp_mem.
max: Number of pages allowed for queueing by all UDP sockets.
Default is calculated at boot time from amount of available memory.
udp_rmem_min - INTEGER
Minimal size of receive buffer used by UDP sockets in moderation.
Each UDP socket is able to use the size for receiving data, even if
total pages of UDP sockets exceed udp_mem pressure. The unit is byte.
Default: 4K
udp_wmem_min - INTEGER
Minimal size of send buffer used by UDP sockets in moderation.
Each UDP socket is able to use the size for sending data, even if
total pages of UDP sockets exceed udp_mem pressure. The unit is byte.
Default: 4K
RAW variables
=============
raw_l3mdev_accept - BOOLEAN
Enabling this option allows a "global" bound socket to work
across L3 master domains (e.g., VRFs) with packets capable of
being received regardless of the L3 domain in which they
originated. Only valid when the kernel was compiled with
CONFIG_NET_L3_MASTER_DEV.
Default: 1 (enabled)
CIPSOv4 Variables
=================
cipso_cache_enable - BOOLEAN
If set, enable additions to and lookups from the CIPSO label mapping
cache. If unset, additions are ignored and lookups always result in a
miss. However, regardless of the setting the cache is still
invalidated when required when means you can safely toggle this on and
off and the cache will always be "safe".
Default: 1
cipso_cache_bucket_size - INTEGER
The CIPSO label cache consists of a fixed size hash table with each
hash bucket containing a number of cache entries. This variable limits
the number of entries in each hash bucket; the larger the value the
more CIPSO label mappings that can be cached. When the number of
entries in a given hash bucket reaches this limit adding new entries
causes the oldest entry in the bucket to be removed to make room.
Default: 10
cipso_rbm_optfmt - BOOLEAN
Enable the "Optimized Tag 1 Format" as defined in section 3.4.2.6 of
the CIPSO draft specification (see Documentation/netlabel for details).
This means that when set the CIPSO tag will be padded with empty
categories in order to make the packet data 32-bit aligned.
Default: 0
cipso_rbm_structvalid - BOOLEAN
If set, do a very strict check of the CIPSO option when
ip_options_compile() is called. If unset, relax the checks done during
ip_options_compile(). Either way is "safe" as errors are caught else
where in the CIPSO processing code but setting this to 0 (False) should
result in less work (i.e. it should be faster) but could cause problems
with other implementations that require strict checking.
Default: 0
IP Variables
============
ip_local_port_range - 2 INTEGERS
Defines the local port range that is used by TCP and UDP to
choose the local port. The first number is the first, the
second the last local port number.
If possible, it is better these numbers have different parity
(one even and one odd value).
Must be greater than or equal to ip_unprivileged_port_start.
The default values are 32768 and 60999 respectively.
ip_local_reserved_ports - list of comma separated ranges
Specify the ports which are reserved for known third-party
applications. These ports will not be used by automatic port
assignments (e.g. when calling connect() or bind() with port
number 0). Explicit port allocation behavior is unchanged.
The format used for both input and output is a comma separated
list of ranges (e.g. "1,2-4,10-10" for ports 1, 2, 3, 4 and
10). Writing to the file will clear all previously reserved
ports and update the current list with the one given in the
input.
Note that ip_local_port_range and ip_local_reserved_ports
settings are independent and both are considered by the kernel
when determining which ports are available for automatic port
assignments.
You can reserve ports which are not in the current
ip_local_port_range, e.g.::
$ cat /proc/sys/net/ipv4/ip_local_port_range
32000 60999
$ cat /proc/sys/net/ipv4/ip_local_reserved_ports
8080,9148
although this is redundant. However such a setting is useful
if later the port range is changed to a value that will
include the reserved ports. Also keep in mind, that overlapping
of these ranges may affect probability of selecting ephemeral
ports which are right after block of reserved ports.
Default: Empty
ip_unprivileged_port_start - INTEGER
This is a per-namespace sysctl. It defines the first
unprivileged port in the network namespace. Privileged ports
require root or CAP_NET_BIND_SERVICE in order to bind to them.
To disable all privileged ports, set this to 0. They must not
overlap with the ip_local_port_range.
Default: 1024
ip_nonlocal_bind - BOOLEAN
If set, allows processes to bind() to non-local IP addresses,
which can be quite useful - but may break some applications.
Default: 0
ip_autobind_reuse - BOOLEAN
By default, bind() does not select the ports automatically even if
the new socket and all sockets bound to the port have SO_REUSEADDR.
ip_autobind_reuse allows bind() to reuse the port and this is useful
when you use bind()+connect(), but may break some applications.
The preferred solution is to use IP_BIND_ADDRESS_NO_PORT and this
option should only be set by experts.
Default: 0
ip_dynaddr - BOOLEAN
If set non-zero, enables support for dynamic addresses.
If set to a non-zero value larger than 1, a kernel log
message will be printed when dynamic address rewriting
occurs.
Default: 0
ip_early_demux - BOOLEAN
Optimize input packet processing down to one demux for
certain kinds of local sockets. Currently we only do this
for established TCP and connected UDP sockets.
It may add an additional cost for pure routing workloads that
reduces overall throughput, in such case you should disable it.
Default: 1
ping_group_range - 2 INTEGERS
Restrict ICMP_PROTO datagram sockets to users in the group range.
The default is "1 0", meaning, that nobody (not even root) may
create ping sockets. Setting it to "100 100" would grant permissions
to the single group. "0 4294967295" would enable it for the world, "100
4294967295" would enable it for the users, but not daemons.
tcp_early_demux - BOOLEAN
Enable early demux for established TCP sockets.
Default: 1
udp_early_demux - BOOLEAN
Enable early demux for connected UDP sockets. Disable this if
your system could experience more unconnected load.
Default: 1
icmp_echo_ignore_all - BOOLEAN
If set non-zero, then the kernel will ignore all ICMP ECHO
requests sent to it.
Default: 0
icmp_echo_enable_probe - BOOLEAN
If set to one, then the kernel will respond to RFC 8335 PROBE
requests sent to it.
Default: 0
icmp_echo_ignore_broadcasts - BOOLEAN
If set non-zero, then the kernel will ignore all ICMP ECHO and
TIMESTAMP requests sent to it via broadcast/multicast.
Default: 1
icmp_ratelimit - INTEGER
Limit the maximal rates for sending ICMP packets whose type matches
icmp_ratemask (see below) to specific targets.
0 to disable any limiting,
otherwise the minimal space between responses in milliseconds.
Note that another sysctl, icmp_msgs_per_sec limits the number
of ICMP packets sent on all targets.
Default: 1000
icmp_msgs_per_sec - INTEGER
Limit maximal number of ICMP packets sent per second from this host.
Only messages whose type matches icmp_ratemask (see below) are
controlled by this limit. For security reasons, the precise count
of messages per second is randomized.
Default: 1000
icmp_msgs_burst - INTEGER
icmp_msgs_per_sec controls number of ICMP packets sent per second,
while icmp_msgs_burst controls the burst size of these packets.
For security reasons, the precise burst size is randomized.
Default: 50
icmp_ratemask - INTEGER
Mask made of ICMP types for which rates are being limited.
Significant bits: IHGFEDCBA9876543210
Default mask: 0000001100000011000 (6168)
Bit definitions (see include/linux/icmp.h):
= =========================
0 Echo Reply
3 Destination Unreachable [1]_
4 Source Quench [1]_
5 Redirect
8 Echo Request
B Time Exceeded [1]_
C Parameter Problem [1]_
D Timestamp Request
E Timestamp Reply
F Info Request
G Info Reply
H Address Mask Request
I Address Mask Reply
= =========================
.. [1] These are rate limited by default (see default mask above)
icmp_ignore_bogus_error_responses - BOOLEAN
Some routers violate RFC1122 by sending bogus responses to broadcast
frames. Such violations are normally logged via a kernel warning.
If this is set to TRUE, the kernel will not give such warnings, which
will avoid log file clutter.
Default: 1
icmp_errors_use_inbound_ifaddr - BOOLEAN
If zero, icmp error messages are sent with the primary address of
the exiting interface.
If non-zero, the message will be sent with the primary address of
the interface that received the packet that caused the icmp error.
This is the behaviour many network administrators will expect from
a router. And it can make debugging complicated network layouts
much easier.
Note that if no primary address exists for the interface selected,
then the primary address of the first non-loopback interface that
has one will be used regardless of this setting.
Default: 0
igmp_max_memberships - INTEGER
Change the maximum number of multicast groups we can subscribe to.
Default: 20
Theoretical maximum value is bounded by having to send a membership
report in a single datagram (i.e. the report can't span multiple
datagrams, or risk confusing the switch and leaving groups you don't
intend to).
The number of supported groups 'M' is bounded by the number of group
report entries you can fit into a single datagram of 65535 bytes.
M = 65536-sizeof (ip header)/(sizeof(Group record))
Group records are variable length, with a minimum of 12 bytes.
So net.ipv4.igmp_max_memberships should not be set higher than:
(65536-24) / 12 = 5459
The value 5459 assumes no IP header options, so in practice
this number may be lower.
igmp_max_msf - INTEGER
Maximum number of addresses allowed in the source filter list for a
multicast group.
Default: 10
igmp_qrv - INTEGER
Controls the IGMP query robustness variable (see RFC2236 8.1).
Default: 2 (as specified by RFC2236 8.1)
Minimum: 1 (as specified by RFC6636 4.5)
force_igmp_version - INTEGER
- 0 - (default) No enforcement of a IGMP version, IGMPv1/v2 fallback
allowed. Will back to IGMPv3 mode again if all IGMPv1/v2 Querier
Present timer expires.
- 1 - Enforce to use IGMP version 1. Will also reply IGMPv1 report if
receive IGMPv2/v3 query.
- 2 - Enforce to use IGMP version 2. Will fallback to IGMPv1 if receive
IGMPv1 query message. Will reply report if receive IGMPv3 query.
- 3 - Enforce to use IGMP version 3. The same react with default 0.
.. note::
this is not the same with force_mld_version because IGMPv3 RFC3376
Security Considerations does not have clear description that we could
ignore other version messages completely as MLDv2 RFC3810. So make
this value as default 0 is recommended.
``conf/interface/*``
changes special settings per interface (where
interface" is the name of your network interface)
``conf/all/*``
is special, changes the settings for all interfaces
log_martians - BOOLEAN
Log packets with impossible addresses to kernel log.
log_martians for the interface will be enabled if at least one of
conf/{all,interface}/log_martians is set to TRUE,
it will be disabled otherwise
accept_redirects - BOOLEAN
Accept ICMP redirect messages.
accept_redirects for the interface will be enabled if:
- both conf/{all,interface}/accept_redirects are TRUE in the case
forwarding for the interface is enabled
or
- at least one of conf/{all,interface}/accept_redirects is TRUE in the
case forwarding for the interface is disabled
accept_redirects for the interface will be disabled otherwise
default:
- TRUE (host)
- FALSE (router)
forwarding - BOOLEAN
Enable IP forwarding on this interface. This controls whether packets
received _on_ this interface can be forwarded.
mc_forwarding - BOOLEAN
Do multicast routing. The kernel needs to be compiled with CONFIG_MROUTE
and a multicast routing daemon is required.
conf/all/mc_forwarding must also be set to TRUE to enable multicast
routing for the interface
medium_id - INTEGER
Integer value used to differentiate the devices by the medium they
are attached to. Two devices can have different id values when
the broadcast packets are received only on one of them.
The default value 0 means that the device is the only interface
to its medium, value of -1 means that medium is not known.
Currently, it is used to change the proxy_arp behavior:
the proxy_arp feature is enabled for packets forwarded between
two devices attached to different media.
proxy_arp - BOOLEAN
Do proxy arp.
proxy_arp for the interface will be enabled if at least one of
conf/{all,interface}/proxy_arp is set to TRUE,
it will be disabled otherwise
proxy_arp_pvlan - BOOLEAN
Private VLAN proxy arp.
Basically allow proxy arp replies back to the same interface
(from which the ARP request/solicitation was received).
This is done to support (ethernet) switch features, like RFC
3069, where the individual ports are NOT allowed to
communicate with each other, but they are allowed to talk to
the upstream router. As described in RFC 3069, it is possible
to allow these hosts to communicate through the upstream
router by proxy_arp'ing. Don't need to be used together with
proxy_arp.
This technology is known by different names:
In RFC 3069 it is called VLAN Aggregation.
Cisco and Allied Telesyn call it Private VLAN.
Hewlett-Packard call it Source-Port filtering or port-isolation.
Ericsson call it MAC-Forced Forwarding (RFC Draft).
shared_media - BOOLEAN
Send(router) or accept(host) RFC1620 shared media redirects.
Overrides secure_redirects.
shared_media for the interface will be enabled if at least one of
conf/{all,interface}/shared_media is set to TRUE,
it will be disabled otherwise
default TRUE
secure_redirects - BOOLEAN
Accept ICMP redirect messages only to gateways listed in the
interface's current gateway list. Even if disabled, RFC1122 redirect
rules still apply.
Overridden by shared_media.
secure_redirects for the interface will be enabled if at least one of
conf/{all,interface}/secure_redirects is set to TRUE,
it will be disabled otherwise
default TRUE
send_redirects - BOOLEAN
Send redirects, if router.
send_redirects for the interface will be enabled if at least one of
conf/{all,interface}/send_redirects is set to TRUE,
it will be disabled otherwise
Default: TRUE
bootp_relay - BOOLEAN
Accept packets with source address 0.b.c.d destined
not to this host as local ones. It is supposed, that
BOOTP relay daemon will catch and forward such packets.
conf/all/bootp_relay must also be set to TRUE to enable BOOTP relay
for the interface
default FALSE
Not Implemented Yet.
accept_source_route - BOOLEAN
Accept packets with SRR option.
conf/all/accept_source_route must also be set to TRUE to accept packets
with SRR option on the interface
default
- TRUE (router)
- FALSE (host)
accept_local - BOOLEAN
Accept packets with local source addresses. In combination with
suitable routing, this can be used to direct packets between two
local interfaces over the wire and have them accepted properly.
default FALSE
route_localnet - BOOLEAN
Do not consider loopback addresses as martian source or destination
while routing. This enables the use of 127/8 for local routing purposes.
default FALSE
rp_filter - INTEGER
- 0 - No source validation.
- 1 - Strict mode as defined in RFC3704 Strict Reverse Path
Each incoming packet is tested against the FIB and if the interface
is not the best reverse path the packet check will fail.
By default failed packets are discarded.
- 2 - Loose mode as defined in RFC3704 Loose Reverse Path
Each incoming packet's source address is also tested against the FIB
and if the source address is not reachable via any interface
the packet check will fail.
Current recommended practice in RFC3704 is to enable strict mode
to prevent IP spoofing from DDos attacks. If using asymmetric routing
or other complicated routing, then loose mode is recommended.
The max value from conf/{all,interface}/rp_filter is used
when doing source validation on the {interface}.
Default value is 0. Note that some distributions enable it
in startup scripts.
src_valid_mark - BOOLEAN
- 0 - The fwmark of the packet is not included in reverse path
route lookup. This allows for asymmetric routing configurations
utilizing the fwmark in only one direction, e.g., transparent
proxying.
- 1 - The fwmark of the packet is included in reverse path route
lookup. This permits rp_filter to function when the fwmark is
used for routing traffic in both directions.
This setting also affects the utilization of fmwark when
performing source address selection for ICMP replies, or
determining addresses stored for the IPOPT_TS_TSANDADDR and
IPOPT_RR IP options.
The max value from conf/{all,interface}/src_valid_mark is used.
Default value is 0.
arp_filter - BOOLEAN
- 1 - Allows you to have multiple network interfaces on the same
subnet, and have the ARPs for each interface be answered
based on whether or not the kernel would route a packet from
the ARP'd IP out that interface (therefore you must use source
based routing for this to work). In other words it allows control
of which cards (usually 1) will respond to an arp request.
- 0 - (default) The kernel can respond to arp requests with addresses
from other interfaces. This may seem wrong but it usually makes
sense, because it increases the chance of successful communication.
IP addresses are owned by the complete host on Linux, not by
particular interfaces. Only for more complex setups like load-
balancing, does this behaviour cause problems.
arp_filter for the interface will be enabled if at least one of
conf/{all,interface}/arp_filter is set to TRUE,
it will be disabled otherwise
arp_announce - INTEGER
Define different restriction levels for announcing the local
source IP address from IP packets in ARP requests sent on
interface:
- 0 - (default) Use any local address, configured on any interface
- 1 - Try to avoid local addresses that are not in the target's
subnet for this interface. This mode is useful when target
hosts reachable via this interface require the source IP
address in ARP requests to be part of their logical network
configured on the receiving interface. When we generate the
request we will check all our subnets that include the
target IP and will preserve the source address if it is from
such subnet. If there is no such subnet we select source
address according to the rules for level 2.
- 2 - Always use the best local address for this target.
In this mode we ignore the source address in the IP packet
and try to select local address that we prefer for talks with
the target host. Such local address is selected by looking
for primary IP addresses on all our subnets on the outgoing
interface that include the target IP address. If no suitable
local address is found we select the first local address
we have on the outgoing interface or on all other interfaces,
with the hope we will receive reply for our request and
even sometimes no matter the source IP address we announce.
The max value from conf/{all,interface}/arp_announce is used.
Increasing the restriction level gives more chance for
receiving answer from the resolved target while decreasing
the level announces more valid sender's information.
arp_ignore - INTEGER
Define different modes for sending replies in response to
received ARP requests that resolve local target IP addresses:
- 0 - (default): reply for any local target IP address, configured
on any interface
- 1 - reply only if the target IP address is local address
configured on the incoming interface
- 2 - reply only if the target IP address is local address
configured on the incoming interface and both with the
sender's IP address are part from same subnet on this interface
- 3 - do not reply for local addresses configured with scope host,
only resolutions for global and link addresses are replied
- 4-7 - reserved
- 8 - do not reply for all local addresses
The max value from conf/{all,interface}/arp_ignore is used
when ARP request is received on the {interface}
arp_notify - BOOLEAN
Define mode for notification of address and device changes.
== ==========================================================
0 (default): do nothing
1 Generate gratuitous arp requests when device is brought up
or hardware address changes.
== ==========================================================
arp_accept - BOOLEAN
Define behavior for gratuitous ARP frames who's IP is not
already present in the ARP table:
- 0 - don't create new entries in the ARP table
- 1 - create new entries in the ARP table
Both replies and requests type gratuitous arp will trigger the
ARP table to be updated, if this setting is on.
If the ARP table already contains the IP address of the
gratuitous arp frame, the arp table will be updated regardless
if this setting is on or off.
mcast_solicit - INTEGER
The maximum number of multicast probes in INCOMPLETE state,
when the associated hardware address is unknown. Defaults
to 3.
ucast_solicit - INTEGER
The maximum number of unicast probes in PROBE state, when
the hardware address is being reconfirmed. Defaults to 3.
app_solicit - INTEGER
The maximum number of probes to send to the user space ARP daemon
via netlink before dropping back to multicast probes (see
mcast_resolicit). Defaults to 0.
mcast_resolicit - INTEGER
The maximum number of multicast probes after unicast and
app probes in PROBE state. Defaults to 0.
disable_policy - BOOLEAN
Disable IPSEC policy (SPD) for this interface
disable_xfrm - BOOLEAN
Disable IPSEC encryption on this interface, whatever the policy
igmpv2_unsolicited_report_interval - INTEGER
The interval in milliseconds in which the next unsolicited
IGMPv1 or IGMPv2 report retransmit will take place.
Default: 10000 (10 seconds)
igmpv3_unsolicited_report_interval - INTEGER
The interval in milliseconds in which the next unsolicited
IGMPv3 report retransmit will take place.
Default: 1000 (1 seconds)
ignore_routes_with_linkdown - BOOLEAN
Ignore routes whose link is down when performing a FIB lookup.
promote_secondaries - BOOLEAN
When a primary IP address is removed from this interface
promote a corresponding secondary IP address instead of
removing all the corresponding secondary IP addresses.
drop_unicast_in_l2_multicast - BOOLEAN
Drop any unicast IP packets that are received in link-layer
multicast (or broadcast) frames.
This behavior (for multicast) is actually a SHOULD in RFC
1122, but is disabled by default for compatibility reasons.
Default: off (0)
drop_gratuitous_arp - BOOLEAN
Drop all gratuitous ARP frames, for example if there's a known
good ARP proxy on the network and such frames need not be used
(or in the case of 802.11, must not be used to prevent attacks.)
Default: off (0)
tag - INTEGER
Allows you to write a number, which can be used as required.
Default value is 0.
xfrm4_gc_thresh - INTEGER
(Obsolete since linux-4.14)
The threshold at which we will start garbage collecting for IPv4
destination cache entries. At twice this value the system will
refuse new allocations.
igmp_link_local_mcast_reports - BOOLEAN
Enable IGMP reports for link local multicast groups in the
224.0.0.X range.
Default TRUE
Alexey Kuznetsov.
kuznet@ms2.inr.ac.ru
Updated by:
- Andi Kleen
ak@muc.de
- Nicolas Delon
delon.nicolas@wanadoo.fr
/proc/sys/net/ipv6/* Variables
==============================
IPv6 has no global variables such as tcp_*. tcp_* settings under ipv4/ also
apply to IPv6 [XXX?].
bindv6only - BOOLEAN
Default value for IPV6_V6ONLY socket option,
which restricts use of the IPv6 socket to IPv6 communication
only.
- TRUE: disable IPv4-mapped address feature
- FALSE: enable IPv4-mapped address feature
Default: FALSE (as specified in RFC3493)
flowlabel_consistency - BOOLEAN
Protect the consistency (and unicity) of flow label.
You have to disable it to use IPV6_FL_F_REFLECT flag on the
flow label manager.
- TRUE: enabled
- FALSE: disabled
Default: TRUE
auto_flowlabels - INTEGER
Automatically generate flow labels based on a flow hash of the
packet. This allows intermediate devices, such as routers, to
identify packet flows for mechanisms like Equal Cost Multipath
Routing (see RFC 6438).
= ===========================================================
0 automatic flow labels are completely disabled
1 automatic flow labels are enabled by default, they can be
disabled on a per socket basis using the IPV6_AUTOFLOWLABEL
socket option
2 automatic flow labels are allowed, they may be enabled on a
per socket basis using the IPV6_AUTOFLOWLABEL socket option
3 automatic flow labels are enabled and enforced, they cannot
be disabled by the socket option
= ===========================================================
Default: 1
flowlabel_state_ranges - BOOLEAN
Split the flow label number space into two ranges. 0-0x7FFFF is
reserved for the IPv6 flow manager facility, 0x80000-0xFFFFF
is reserved for stateless flow labels as described in RFC6437.
- TRUE: enabled
- FALSE: disabled
Default: true
flowlabel_reflect - INTEGER
Control flow label reflection. Needed for Path MTU
Discovery to work with Equal Cost Multipath Routing in anycast
environments. See RFC 7690 and:
https://tools.ietf.org/html/draft-wang-6man-flow-label-reflection-01
This is a bitmask.
- 1: enabled for established flows
Note that this prevents automatic flowlabel changes, as done
in "tcp: change IPv6 flow-label upon receiving spurious retransmission"
and "tcp: Change txhash on every SYN and RTO retransmit"
- 2: enabled for TCP RESET packets (no active listener)
If set, a RST packet sent in response to a SYN packet on a closed
port will reflect the incoming flow label.
- 4: enabled for ICMPv6 echo reply messages.
Default: 0
fib_multipath_hash_policy - INTEGER
Controls which hash policy to use for multipath routes.
Default: 0 (Layer 3)
Possible values:
- 0 - Layer 3 (source and destination addresses plus flow label)
- 1 - Layer 4 (standard 5-tuple)
- 2 - Layer 3 or inner Layer 3 if present
anycast_src_echo_reply - BOOLEAN
Controls the use of anycast addresses as source addresses for ICMPv6
echo reply
- TRUE: enabled
- FALSE: disabled
Default: FALSE
idgen_delay - INTEGER
Controls the delay in seconds after which time to retry
privacy stable address generation if a DAD conflict is
detected.
Default: 1 (as specified in RFC7217)
idgen_retries - INTEGER
Controls the number of retries to generate a stable privacy
address if a DAD conflict is detected.
Default: 3 (as specified in RFC7217)
mld_qrv - INTEGER
Controls the MLD query robustness variable (see RFC3810 9.1).
Default: 2 (as specified by RFC3810 9.1)
Minimum: 1 (as specified by RFC6636 4.5)
max_dst_opts_number - INTEGER
Maximum number of non-padding TLVs allowed in a Destination
options extension header. If this value is less than zero
then unknown options are disallowed and the number of known
TLVs allowed is the absolute value of this number.
Default: 8
max_hbh_opts_number - INTEGER
Maximum number of non-padding TLVs allowed in a Hop-by-Hop
options extension header. If this value is less than zero
then unknown options are disallowed and the number of known
TLVs allowed is the absolute value of this number.
Default: 8
max_dst_opts_length - INTEGER
Maximum length allowed for a Destination options extension
header.
Default: INT_MAX (unlimited)
max_hbh_length - INTEGER
Maximum length allowed for a Hop-by-Hop options extension
header.
Default: INT_MAX (unlimited)
skip_notify_on_dev_down - BOOLEAN
Controls whether an RTM_DELROUTE message is generated for routes
removed when a device is taken down or deleted. IPv4 does not
generate this message; IPv6 does by default. Setting this sysctl
to true skips the message, making IPv4 and IPv6 on par in relying
on userspace caches to track link events and evict routes.
Default: false (generate message)
nexthop_compat_mode - BOOLEAN
New nexthop API provides a means for managing nexthops independent of
prefixes. Backwards compatibilty with old route format is enabled by
default which means route dumps and notifications contain the new
nexthop attribute but also the full, expanded nexthop definition.
Further, updates or deletes of a nexthop configuration generate route
notifications for each fib entry using the nexthop. Once a system
understands the new API, this sysctl can be disabled to achieve full
performance benefits of the new API by disabling the nexthop expansion
and extraneous notifications.
Default: true (backward compat mode)
fib_notify_on_flag_change - INTEGER
Whether to emit RTM_NEWROUTE notifications whenever RTM_F_OFFLOAD/
RTM_F_TRAP/RTM_F_OFFLOAD_FAILED flags are changed.
After installing a route to the kernel, user space receives an
acknowledgment, which means the route was installed in the kernel,
but not necessarily in hardware.
It is also possible for a route already installed in hardware to change
its action and therefore its flags. For example, a host route that is
trapping packets can be "promoted" to perform decapsulation following
the installation of an IPinIP/VXLAN tunnel.
The notifications will indicate to user-space the state of the route.
Default: 0 (Do not emit notifications.)
Possible values:
- 0 - Do not emit notifications.
- 1 - Emit notifications.
- 2 - Emit notifications only for RTM_F_OFFLOAD_FAILED flag change.
IPv6 Fragmentation:
ip6frag_high_thresh - INTEGER
Maximum memory used to reassemble IPv6 fragments. When
ip6frag_high_thresh bytes of memory is allocated for this purpose,
the fragment handler will toss packets until ip6frag_low_thresh
is reached.
ip6frag_low_thresh - INTEGER
See ip6frag_high_thresh
ip6frag_time - INTEGER
Time in seconds to keep an IPv6 fragment in memory.
``conf/default/*``:
Change the interface-specific default settings.
These settings would be used during creating new interfaces.
``conf/all/*``:
Change all the interface-specific settings.
[XXX: Other special features than forwarding?]
conf/all/disable_ipv6 - BOOLEAN
Changing this value is same as changing ``conf/default/disable_ipv6``
setting and also all per-interface ``disable_ipv6`` settings to the same
value.
Reading this value does not have any particular meaning. It does not say
whether IPv6 support is enabled or disabled. Returned value can be 1
also in the case when some interface has ``disable_ipv6`` set to 0 and
has configured IPv6 addresses.
conf/all/forwarding - BOOLEAN
Enable global IPv6 forwarding between all interfaces.
IPv4 and IPv6 work differently here; e.g. netfilter must be used
to control which interfaces may forward packets and which not.
This also sets all interfaces' Host/Router setting
'forwarding' to the specified value. See below for details.
This referred to as global forwarding.
proxy_ndp - BOOLEAN
Do proxy ndp.
fwmark_reflect - BOOLEAN
Controls the fwmark of kernel-generated IPv6 reply packets that are not
associated with a socket for example, TCP RSTs or ICMPv6 echo replies).
If unset, these packets have a fwmark of zero. If set, they have the
fwmark of the packet they are replying to.
Default: 0
``conf/interface/*``:
Change special settings per interface.
The functional behaviour for certain settings is different
depending on whether local forwarding is enabled or not.
accept_ra - INTEGER
Accept Router Advertisements; autoconfigure using them.
It also determines whether or not to transmit Router
Solicitations. If and only if the functional setting is to
accept Router Advertisements, Router Solicitations will be
transmitted.
Possible values are:
== ===========================================================
0 Do not accept Router Advertisements.
1 Accept Router Advertisements if forwarding is disabled.
2 Overrule forwarding behaviour. Accept Router Advertisements
even if forwarding is enabled.
== ===========================================================
Functional default:
- enabled if local forwarding is disabled.
- disabled if local forwarding is enabled.
accept_ra_defrtr - BOOLEAN
Learn default router in Router Advertisement.
Functional default:
- enabled if accept_ra is enabled.
- disabled if accept_ra is disabled.
ra_defrtr_metric - UNSIGNED INTEGER
Route metric for default route learned in Router Advertisement. This value
will be assigned as metric for the default route learned via IPv6 Router
Advertisement. Takes affect only if accept_ra_defrtr is enabled.
Possible values:
1 to 0xFFFFFFFF
Default: IP6_RT_PRIO_USER i.e. 1024.
accept_ra_from_local - BOOLEAN
Accept RA with source-address that is found on local machine
if the RA is otherwise proper and able to be accepted.
Default is to NOT accept these as it may be an un-intended
network loop.
Functional default:
- enabled if accept_ra_from_local is enabled
on a specific interface.
- disabled if accept_ra_from_local is disabled
on a specific interface.
accept_ra_min_hop_limit - INTEGER
Minimum hop limit Information in Router Advertisement.
Hop limit Information in Router Advertisement less than this
variable shall be ignored.
Default: 1
accept_ra_pinfo - BOOLEAN
Learn Prefix Information in Router Advertisement.
Functional default:
- enabled if accept_ra is enabled.
- disabled if accept_ra is disabled.
accept_ra_rt_info_min_plen - INTEGER
Minimum prefix length of Route Information in RA.
Route Information w/ prefix smaller than this variable shall
be ignored.
Functional default:
* 0 if accept_ra_rtr_pref is enabled.
* -1 if accept_ra_rtr_pref is disabled.
accept_ra_rt_info_max_plen - INTEGER
Maximum prefix length of Route Information in RA.
Route Information w/ prefix larger than this variable shall
be ignored.
Functional default:
* 0 if accept_ra_rtr_pref is enabled.
* -1 if accept_ra_rtr_pref is disabled.
accept_ra_rtr_pref - BOOLEAN
Accept Router Preference in RA.
Functional default:
- enabled if accept_ra is enabled.
- disabled if accept_ra is disabled.
accept_ra_mtu - BOOLEAN
Apply the MTU value specified in RA option 5 (RFC4861). If
disabled, the MTU specified in the RA will be ignored.
Functional default:
- enabled if accept_ra is enabled.
- disabled if accept_ra is disabled.
accept_redirects - BOOLEAN
Accept Redirects.
Functional default:
- enabled if local forwarding is disabled.
- disabled if local forwarding is enabled.
accept_source_route - INTEGER
Accept source routing (routing extension header).
- >= 0: Accept only routing header type 2.
- < 0: Do not accept routing header.
Default: 0
autoconf - BOOLEAN
Autoconfigure addresses using Prefix Information in Router
Advertisements.
Functional default:
- enabled if accept_ra_pinfo is enabled.
- disabled if accept_ra_pinfo is disabled.
dad_transmits - INTEGER
The amount of Duplicate Address Detection probes to send.
Default: 1
forwarding - INTEGER
Configure interface-specific Host/Router behaviour.
.. note::
It is recommended to have the same setting on all
interfaces; mixed router/host scenarios are rather uncommon.
Possible values are:
- 0 Forwarding disabled
- 1 Forwarding enabled
**FALSE (0)**:
By default, Host behaviour is assumed. This means:
1. IsRouter flag is not set in Neighbour Advertisements.
2. If accept_ra is TRUE (default), transmit Router
Solicitations.
3. If accept_ra is TRUE (default), accept Router
Advertisements (and do autoconfiguration).
4. If accept_redirects is TRUE (default), accept Redirects.
**TRUE (1)**:
If local forwarding is enabled, Router behaviour is assumed.
This means exactly the reverse from the above:
1. IsRouter flag is set in Neighbour Advertisements.
2. Router Solicitations are not sent unless accept_ra is 2.
3. Router Advertisements are ignored unless accept_ra is 2.
4. Redirects are ignored.
Default: 0 (disabled) if global forwarding is disabled (default),
otherwise 1 (enabled).
hop_limit - INTEGER
Default Hop Limit to set.
Default: 64
mtu - INTEGER
Default Maximum Transfer Unit
Default: 1280 (IPv6 required minimum)
ip_nonlocal_bind - BOOLEAN
If set, allows processes to bind() to non-local IPv6 addresses,
which can be quite useful - but may break some applications.
Default: 0
router_probe_interval - INTEGER
Minimum interval (in seconds) between Router Probing described
in RFC4191.
Default: 60
router_solicitation_delay - INTEGER
Number of seconds to wait after interface is brought up
before sending Router Solicitations.
Default: 1
router_solicitation_interval - INTEGER
Number of seconds to wait between Router Solicitations.
Default: 4
router_solicitations - INTEGER
Number of Router Solicitations to send until assuming no
routers are present.
Default: 3
use_oif_addrs_only - BOOLEAN
When enabled, the candidate source addresses for destinations
routed via this interface are restricted to the set of addresses
configured on this interface (vis. RFC 6724, section 4).
Default: false
use_tempaddr - INTEGER
Preference for Privacy Extensions (RFC3041).
* <= 0 : disable Privacy Extensions
* == 1 : enable Privacy Extensions, but prefer public
addresses over temporary addresses.
* > 1 : enable Privacy Extensions and prefer temporary
addresses over public addresses.
Default:
* 0 (for most devices)
* -1 (for point-to-point devices and loopback devices)
temp_valid_lft - INTEGER
valid lifetime (in seconds) for temporary addresses.
Default: 172800 (2 days)
temp_prefered_lft - INTEGER
Preferred lifetime (in seconds) for temporary addresses.
Default: 86400 (1 day)
keep_addr_on_down - INTEGER
Keep all IPv6 addresses on an interface down event. If set static
global addresses with no expiration time are not flushed.
* >0 : enabled
* 0 : system default
* <0 : disabled
Default: 0 (addresses are removed)
max_desync_factor - INTEGER
Maximum value for DESYNC_FACTOR, which is a random value
that ensures that clients don't synchronize with each
other and generate new addresses at exactly the same time.
value is in seconds.
Default: 600
regen_max_retry - INTEGER
Number of attempts before give up attempting to generate
valid temporary addresses.
Default: 5
max_addresses - INTEGER
Maximum number of autoconfigured addresses per interface. Setting
to zero disables the limitation. It is not recommended to set this
value too large (or to zero) because it would be an easy way to
crash the kernel by allowing too many addresses to be created.
Default: 16
disable_ipv6 - BOOLEAN
Disable IPv6 operation. If accept_dad is set to 2, this value
will be dynamically set to TRUE if DAD fails for the link-local
address.
Default: FALSE (enable IPv6 operation)
When this value is changed from 1 to 0 (IPv6 is being enabled),
it will dynamically create a link-local address on the given
interface and start Duplicate Address Detection, if necessary.
When this value is changed from 0 to 1 (IPv6 is being disabled),
it will dynamically delete all addresses and routes on the given
interface. From now on it will not possible to add addresses/routes
to the selected interface.
accept_dad - INTEGER
Whether to accept DAD (Duplicate Address Detection).
== ==============================================================
0 Disable DAD
1 Enable DAD (default)
2 Enable DAD, and disable IPv6 operation if MAC-based duplicate
link-local address has been found.
== ==============================================================
DAD operation and mode on a given interface will be selected according
to the maximum value of conf/{all,interface}/accept_dad.
force_tllao - BOOLEAN
Enable sending the target link-layer address option even when
responding to a unicast neighbor solicitation.
Default: FALSE
Quoting from RFC 2461, section 4.4, Target link-layer address:
"The option MUST be included for multicast solicitations in order to
avoid infinite Neighbor Solicitation "recursion" when the peer node
does not have a cache entry to return a Neighbor Advertisements
message. When responding to unicast solicitations, the option can be
omitted since the sender of the solicitation has the correct link-
layer address; otherwise it would not have be able to send the unicast
solicitation in the first place. However, including the link-layer
address in this case adds little overhead and eliminates a potential
race condition where the sender deletes the cached link-layer address
prior to receiving a response to a previous solicitation."
ndisc_notify - BOOLEAN
Define mode for notification of address and device changes.
* 0 - (default): do nothing
* 1 - Generate unsolicited neighbour advertisements when device is brought
up or hardware address changes.
ndisc_tclass - INTEGER
The IPv6 Traffic Class to use by default when sending IPv6 Neighbor
Discovery (Router Solicitation, Router Advertisement, Neighbor
Solicitation, Neighbor Advertisement, Redirect) messages.
These 8 bits can be interpreted as 6 high order bits holding the DSCP
value and 2 low order bits representing ECN (which you probably want
to leave cleared).
* 0 - (default)
mldv1_unsolicited_report_interval - INTEGER
The interval in milliseconds in which the next unsolicited
MLDv1 report retransmit will take place.
Default: 10000 (10 seconds)
mldv2_unsolicited_report_interval - INTEGER
The interval in milliseconds in which the next unsolicited
MLDv2 report retransmit will take place.
Default: 1000 (1 second)
force_mld_version - INTEGER
* 0 - (default) No enforcement of a MLD version, MLDv1 fallback allowed
* 1 - Enforce to use MLD version 1
* 2 - Enforce to use MLD version 2
suppress_frag_ndisc - INTEGER
Control RFC 6980 (Security Implications of IPv6 Fragmentation
with IPv6 Neighbor Discovery) behavior:
* 1 - (default) discard fragmented neighbor discovery packets
* 0 - allow fragmented neighbor discovery packets
optimistic_dad - BOOLEAN
Whether to perform Optimistic Duplicate Address Detection (RFC 4429).
* 0: disabled (default)
* 1: enabled
Optimistic Duplicate Address Detection for the interface will be enabled
if at least one of conf/{all,interface}/optimistic_dad is set to 1,
it will be disabled otherwise.
use_optimistic - BOOLEAN
If enabled, do not classify optimistic addresses as deprecated during
source address selection. Preferred addresses will still be chosen
before optimistic addresses, subject to other ranking in the source
address selection algorithm.
* 0: disabled (default)
* 1: enabled
This will be enabled if at least one of
conf/{all,interface}/use_optimistic is set to 1, disabled otherwise.
stable_secret - IPv6 address
This IPv6 address will be used as a secret to generate IPv6
addresses for link-local addresses and autoconfigured
ones. All addresses generated after setting this secret will
be stable privacy ones by default. This can be changed via the
addrgenmode ip-link. conf/default/stable_secret is used as the
secret for the namespace, the interface specific ones can
overwrite that. Writes to conf/all/stable_secret are refused.
It is recommended to generate this secret during installation
of a system and keep it stable after that.
By default the stable secret is unset.
addr_gen_mode - INTEGER
Defines how link-local and autoconf addresses are generated.
= =================================================================
0 generate address based on EUI64 (default)
1 do no generate a link-local address, use EUI64 for addresses
generated from autoconf
2 generate stable privacy addresses, using the secret from
stable_secret (RFC7217)
3 generate stable privacy addresses, using a random secret if unset
= =================================================================
drop_unicast_in_l2_multicast - BOOLEAN
Drop any unicast IPv6 packets that are received in link-layer
multicast (or broadcast) frames.
By default this is turned off.
drop_unsolicited_na - BOOLEAN
Drop all unsolicited neighbor advertisements, for example if there's
a known good NA proxy on the network and such frames need not be used
(or in the case of 802.11, must not be used to prevent attacks.)
By default this is turned off.
enhanced_dad - BOOLEAN
Include a nonce option in the IPv6 neighbor solicitation messages used for
duplicate address detection per RFC7527. A received DAD NS will only signal
a duplicate address if the nonce is different. This avoids any false
detection of duplicates due to loopback of the NS messages that we send.
The nonce option will be sent on an interface unless both of
conf/{all,interface}/enhanced_dad are set to FALSE.
Default: TRUE
``icmp/*``:
===========
ratelimit - INTEGER
Limit the maximal rates for sending ICMPv6 messages.
0 to disable any limiting,
otherwise the minimal space between responses in milliseconds.
Default: 1000
ratemask - list of comma separated ranges
For ICMPv6 message types matching the ranges in the ratemask, limit
the sending of the message according to ratelimit parameter.
The format used for both input and output is a comma separated
list of ranges (e.g. "0-127,129" for ICMPv6 message type 0 to 127 and
129). Writing to the file will clear all previous ranges of ICMPv6
message types and update the current list with the input.
Refer to: https://www.iana.org/assignments/icmpv6-parameters/icmpv6-parameters.xhtml
for numerical values of ICMPv6 message types, e.g. echo request is 128
and echo reply is 129.
Default: 0-1,3-127 (rate limit ICMPv6 errors except Packet Too Big)
echo_ignore_all - BOOLEAN
If set non-zero, then the kernel will ignore all ICMP ECHO
requests sent to it over the IPv6 protocol.
Default: 0
echo_ignore_multicast - BOOLEAN
If set non-zero, then the kernel will ignore all ICMP ECHO
requests sent to it over the IPv6 protocol via multicast.
Default: 0
echo_ignore_anycast - BOOLEAN
If set non-zero, then the kernel will ignore all ICMP ECHO
requests sent to it over the IPv6 protocol destined to anycast address.
Default: 0
xfrm6_gc_thresh - INTEGER
(Obsolete since linux-4.14)
The threshold at which we will start garbage collecting for IPv6
destination cache entries. At twice this value the system will
refuse new allocations.
IPv6 Update by:
Pekka Savola <pekkas@netcore.fi>
YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org>
/proc/sys/net/bridge/* Variables:
=================================
bridge-nf-call-arptables - BOOLEAN
- 1 : pass bridged ARP traffic to arptables' FORWARD chain.
- 0 : disable this.
Default: 1
bridge-nf-call-iptables - BOOLEAN
- 1 : pass bridged IPv4 traffic to iptables' chains.
- 0 : disable this.
Default: 1
bridge-nf-call-ip6tables - BOOLEAN
- 1 : pass bridged IPv6 traffic to ip6tables' chains.
- 0 : disable this.
Default: 1
bridge-nf-filter-vlan-tagged - BOOLEAN
- 1 : pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables.
- 0 : disable this.
Default: 0
bridge-nf-filter-pppoe-tagged - BOOLEAN
- 1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables.
- 0 : disable this.
Default: 0
bridge-nf-pass-vlan-input-dev - BOOLEAN
- 1: if bridge-nf-filter-vlan-tagged is enabled, try to find a vlan
interface on the bridge and set the netfilter input device to the
vlan. This allows use of e.g. "iptables -i br0.1" and makes the
REDIRECT target work with vlan-on-top-of-bridge interfaces. When no
matching vlan interface is found, or this switch is off, the input
device is set to the bridge interface.
- 0: disable bridge netfilter vlan interface lookup.
Default: 0
``proc/sys/net/sctp/*`` Variables:
==================================
addip_enable - BOOLEAN
Enable or disable extension of Dynamic Address Reconfiguration
(ADD-IP) functionality specified in RFC5061. This extension provides
the ability to dynamically add and remove new addresses for the SCTP
associations.
1: Enable extension.
0: Disable extension.
Default: 0
pf_enable - INTEGER
Enable or disable pf (pf is short for potentially failed) state. A value
of pf_retrans > path_max_retrans also disables pf state. That is, one of
both pf_enable and pf_retrans > path_max_retrans can disable pf state.
Since pf_retrans and path_max_retrans can be changed by userspace
application, sometimes user expects to disable pf state by the value of
pf_retrans > path_max_retrans, but occasionally the value of pf_retrans
or path_max_retrans is changed by the user application, this pf state is
enabled. As such, it is necessary to add this to dynamically enable
and disable pf state. See:
https://datatracker.ietf.org/doc/draft-ietf-tsvwg-sctp-failover for
details.
1: Enable pf.
0: Disable pf.
Default: 1
pf_expose - INTEGER
Unset or enable/disable pf (pf is short for potentially failed) state
exposure. Applications can control the exposure of the PF path state
in the SCTP_PEER_ADDR_CHANGE event and the SCTP_GET_PEER_ADDR_INFO
sockopt. When it's unset, no SCTP_PEER_ADDR_CHANGE event with
SCTP_ADDR_PF state will be sent and a SCTP_PF-state transport info
can be got via SCTP_GET_PEER_ADDR_INFO sockopt; When it's enabled,
a SCTP_PEER_ADDR_CHANGE event will be sent for a transport becoming
SCTP_PF state and a SCTP_PF-state transport info can be got via
SCTP_GET_PEER_ADDR_INFO sockopt; When it's diabled, no
SCTP_PEER_ADDR_CHANGE event will be sent and it returns -EACCES when
trying to get a SCTP_PF-state transport info via SCTP_GET_PEER_ADDR_INFO
sockopt.
0: Unset pf state exposure, Compatible with old applications.
1: Disable pf state exposure.
2: Enable pf state exposure.
Default: 0
addip_noauth_enable - BOOLEAN
Dynamic Address Reconfiguration (ADD-IP) requires the use of
authentication to protect the operations of adding or removing new
addresses. This requirement is mandated so that unauthorized hosts
would not be able to hijack associations. However, older
implementations may not have implemented this requirement while
allowing the ADD-IP extension. For reasons of interoperability,
we provide this variable to control the enforcement of the
authentication requirement.
== ===============================================================
1 Allow ADD-IP extension to be used without authentication. This
should only be set in a closed environment for interoperability
with older implementations.
0 Enforce the authentication requirement
== ===============================================================
Default: 0
auth_enable - BOOLEAN
Enable or disable Authenticated Chunks extension. This extension
provides the ability to send and receive authenticated chunks and is
required for secure operation of Dynamic Address Reconfiguration
(ADD-IP) extension.
- 1: Enable this extension.
- 0: Disable this extension.
Default: 0
prsctp_enable - BOOLEAN
Enable or disable the Partial Reliability extension (RFC3758) which
is used to notify peers that a given DATA should no longer be expected.
- 1: Enable extension
- 0: Disable
Default: 1
max_burst - INTEGER
The limit of the number of new packets that can be initially sent. It
controls how bursty the generated traffic can be.
Default: 4
association_max_retrans - INTEGER
Set the maximum number for retransmissions that an association can
attempt deciding that the remote end is unreachable. If this value
is exceeded, the association is terminated.
Default: 10
max_init_retransmits - INTEGER
The maximum number of retransmissions of INIT and COOKIE-ECHO chunks
that an association will attempt before declaring the destination
unreachable and terminating.
Default: 8
path_max_retrans - INTEGER
The maximum number of retransmissions that will be attempted on a given
path. Once this threshold is exceeded, the path is considered
unreachable, and new traffic will use a different path when the
association is multihomed.
Default: 5
pf_retrans - INTEGER
The number of retransmissions that will be attempted on a given path
before traffic is redirected to an alternate transport (should one
exist). Note this is distinct from path_max_retrans, as a path that
passes the pf_retrans threshold can still be used. Its only
deprioritized when a transmission path is selected by the stack. This
setting is primarily used to enable fast failover mechanisms without
having to reduce path_max_retrans to a very low value. See:
http://www.ietf.org/id/draft-nishida-tsvwg-sctp-failover-05.txt
for details. Note also that a value of pf_retrans > path_max_retrans
disables this feature. Since both pf_retrans and path_max_retrans can
be changed by userspace application, a variable pf_enable is used to
disable pf state.
Default: 0
ps_retrans - INTEGER
Primary.Switchover.Max.Retrans (PSMR), it's a tunable parameter coming
from section-5 "Primary Path Switchover" in rfc7829. The primary path
will be changed to another active path when the path error counter on
the old primary path exceeds PSMR, so that "the SCTP sender is allowed
to continue data transmission on a new working path even when the old
primary destination address becomes active again". Note this feature
is disabled by initializing 'ps_retrans' per netns as 0xffff by default,
and its value can't be less than 'pf_retrans' when changing by sysctl.
Default: 0xffff
rto_initial - INTEGER
The initial round trip timeout value in milliseconds that will be used
in calculating round trip times. This is the initial time interval
for retransmissions.
Default: 3000
rto_max - INTEGER
The maximum value (in milliseconds) of the round trip timeout. This
is the largest time interval that can elapse between retransmissions.
Default: 60000
rto_min - INTEGER
The minimum value (in milliseconds) of the round trip timeout. This
is the smallest time interval the can elapse between retransmissions.
Default: 1000
hb_interval - INTEGER
The interval (in milliseconds) between HEARTBEAT chunks. These chunks
are sent at the specified interval on idle paths to probe the state of
a given path between 2 associations.
Default: 30000
sack_timeout - INTEGER
The amount of time (in milliseconds) that the implementation will wait
to send a SACK.
Default: 200
valid_cookie_life - INTEGER
The default lifetime of the SCTP cookie (in milliseconds). The cookie
is used during association establishment.
Default: 60000
cookie_preserve_enable - BOOLEAN
Enable or disable the ability to extend the lifetime of the SCTP cookie
that is used during the establishment phase of SCTP association
- 1: Enable cookie lifetime extension.
- 0: Disable
Default: 1
cookie_hmac_alg - STRING
Select the hmac algorithm used when generating the cookie value sent by
a listening sctp socket to a connecting client in the INIT-ACK chunk.
Valid values are:
* md5
* sha1
* none
Ability to assign md5 or sha1 as the selected alg is predicated on the
configuration of those algorithms at build time (CONFIG_CRYPTO_MD5 and
CONFIG_CRYPTO_SHA1).
Default: Dependent on configuration. MD5 if available, else SHA1 if
available, else none.
rcvbuf_policy - INTEGER
Determines if the receive buffer is attributed to the socket or to
association. SCTP supports the capability to create multiple
associations on a single socket. When using this capability, it is
possible that a single stalled association that's buffering a lot
of data may block other associations from delivering their data by
consuming all of the receive buffer space. To work around this,
the rcvbuf_policy could be set to attribute the receiver buffer space
to each association instead of the socket. This prevents the described
blocking.
- 1: rcvbuf space is per association
- 0: rcvbuf space is per socket
Default: 0
sndbuf_policy - INTEGER
Similar to rcvbuf_policy above, this applies to send buffer space.
- 1: Send buffer is tracked per association
- 0: Send buffer is tracked per socket.
Default: 0
sctp_mem - vector of 3 INTEGERs: min, pressure, max
Number of pages allowed for queueing by all SCTP sockets.
min: Below this number of pages SCTP is not bothered about its
memory appetite. When amount of memory allocated by SCTP exceeds
this number, SCTP starts to moderate memory usage.
pressure: This value was introduced to follow format of tcp_mem.
max: Number of pages allowed for queueing by all SCTP sockets.
Default is calculated at boot time from amount of available memory.
sctp_rmem - vector of 3 INTEGERs: min, default, max
Only the first value ("min") is used, "default" and "max" are
ignored.
min: Minimal size of receive buffer used by SCTP socket.
It is guaranteed to each SCTP socket (but not association) even
under moderate memory pressure.
Default: 4K
sctp_wmem - vector of 3 INTEGERs: min, default, max
Currently this tunable has no effect.
addr_scope_policy - INTEGER
Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00
- 0 - Disable IPv4 address scoping
- 1 - Enable IPv4 address scoping
- 2 - Follow draft but allow IPv4 private addresses
- 3 - Follow draft but allow IPv4 link local addresses
Default: 1
udp_port - INTEGER
The listening port for the local UDP tunneling sock. Normally it's
using the IANA-assigned UDP port number 9899 (sctp-tunneling).
This UDP sock is used for processing the incoming UDP-encapsulated
SCTP packets (from RFC6951), and shared by all applications in the
same net namespace. This UDP sock will be closed when the value is
set to 0.
The value will also be used to set the src port of the UDP header
for the outgoing UDP-encapsulated SCTP packets. For the dest port,
please refer to 'encap_port' below.
Default: 0
encap_port - INTEGER
The default remote UDP encapsulation port.
This value is used to set the dest port of the UDP header for the
outgoing UDP-encapsulated SCTP packets by default. Users can also
change the value for each sock/asoc/transport by using setsockopt.
For further information, please refer to RFC6951.
Note that when connecting to a remote server, the client should set
this to the port that the UDP tunneling sock on the peer server is
listening to and the local UDP tunneling sock on the client also
must be started. On the server, it would get the encap_port from
the incoming packet's source port.
Default: 0
``/proc/sys/net/core/*``
========================
Please see: Documentation/admin-guide/sysctl/net.rst for descriptions of these entries.
``/proc/sys/net/unix/*``
========================
max_dgram_qlen - INTEGER
The maximum length of dgram socket receive queue
Default: 10
|