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Diffstat (limited to 'Documentation/networking/ip-sysctl.rst')
| -rw-r--r-- | Documentation/networking/ip-sysctl.rst | 82 |
1 files changed, 78 insertions, 4 deletions
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index bd50df6a5a42..0f1251cce314 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -37,8 +37,8 @@ ip_no_pmtu_disc - INTEGER 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 + protocols for which pmtu events will be honored are TCP and + SCTP 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 @@ -131,6 +131,20 @@ fib_multipath_hash_fields - UNSIGNED INTEGER Default: 0x0007 (source IP, destination IP and IP protocol) +fib_multipath_hash_seed - UNSIGNED INTEGER + The seed value used when calculating hash for multipath routes. Applies + to both IPv4 and IPv6 datapath. Only present for kernels built with + CONFIG_IP_ROUTE_MULTIPATH enabled. + + When set to 0, the seed value used for multipath routing defaults to an + internal random-generated one. + + The actual hashing algorithm is not specified -- there is no guarantee + that a next hop distribution effected by a given seed will keep stable + across kernel versions. + + Default: 0 (random) + fib_sync_mem - UNSIGNED INTEGER Amount of dirty memory from fib entries that can be backlogged before synchronize_rcu is forced. @@ -691,6 +705,8 @@ tcp_retries2 - INTEGER seconds and is a lower bound for the effective timeout. TCP will effectively time out at the first RTO which exceeds the hypothetical timeout. + If tcp_rto_max_ms is decreased, it is recommended to also + change tcp_retries2. RFC 1122 recommends at least 100 seconds for the timeout, which corresponds to a value of at least 8. @@ -719,7 +735,7 @@ tcp_rmem - vector of 3 INTEGERs: min, default, max 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. + Default: between 131072 and 32MB, depending on RAM size. tcp_sack - BOOLEAN Enable select acknowledgments (SACKS). @@ -986,6 +1002,20 @@ tcp_tw_reuse - INTEGER Default: 2 +tcp_tw_reuse_delay - UNSIGNED INTEGER + The delay in milliseconds before a TIME-WAIT socket can be reused by a + new connection, if TIME-WAIT socket reuse is enabled. The actual reuse + threshold is within [N, N+1] range, where N is the requested delay in + milliseconds, to ensure the delay interval is never shorter than the + configured value. + + This setting contains an assumption about the other TCP timestamp clock + tick interval. It should not be set to a value lower than the peer's + clock tick for PAWS (Protection Against Wrapped Sequence numbers) + mechanism work correctly for the reused connection. + + Default: 1000 (milliseconds) + tcp_window_scaling - BOOLEAN Enable window scaling as defined in RFC1323. @@ -1069,7 +1099,7 @@ tcp_limit_output_bytes - INTEGER limits the number of bytes on qdisc or device to reduce artificial RTT/cwnd and reduce bufferbloat. - Default: 1048576 (16 * 65536) + Default: 4194304 (4 MB) tcp_challenge_ack_limit - INTEGER Limits number of Challenge ACK sent per second, as recommended @@ -1196,6 +1226,30 @@ tcp_pingpong_thresh - INTEGER Default: 1 +tcp_rto_min_us - INTEGER + Minimal TCP retransmission timeout (in microseconds). Note that the + rto_min route option has the highest precedence for configuring this + setting, followed by the TCP_BPF_RTO_MIN and TCP_RTO_MIN_US socket + options, followed by this tcp_rto_min_us sysctl. + + The recommended practice is to use a value less or equal to 200000 + microseconds. + + Possible Values: 1 - INT_MAX + + Default: 200000 + +tcp_rto_max_ms - INTEGER + Maximal TCP retransmission timeout (in ms). + Note that TCP_RTO_MAX_MS socket option has higher precedence. + + When changing tcp_rto_max_ms, it is important to understand + that tcp_retries2 might need a change. + + Possible Values: 1000 - 120,000 + + Default: 120,000 + UDP variables ============= @@ -2143,6 +2197,12 @@ nexthop_compat_mode - BOOLEAN 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. + + Note that as a backward-compatible mode, dumping of modern features + might be incomplete or wrong. For example, resilient groups will not be + shown as such, but rather as just a list of next hops. Also weights that + do not fit into 8 bits will show incorrectly. + Default: true (backward compat mode) fib_notify_on_flag_change - INTEGER @@ -2335,6 +2395,20 @@ ra_honor_pio_life - BOOLEAN Default: 0 (disabled) +ra_honor_pio_pflag - BOOLEAN + The Prefix Information Option P-flag indicates the network can + allocate a unique IPv6 prefix per client using DHCPv6-PD. + This sysctl can be enabled when a userspace DHCPv6-PD client + is running to cause the P-flag to take effect: i.e. the + P-flag suppresses any effects of the A-flag within the same + PIO. For a given PIO, P=1 and A=1 is treated as A=0. + + - If disabled, the P-flag is ignored. + - If enabled, the P-flag will disable SLAAC autoconfiguration + for the given Prefix Information Option. + + Default: 0 (disabled) + accept_ra_rt_info_min_plen - INTEGER Minimum prefix length of Route Information in RA. |