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Diffstat (limited to 'Documentation/networking/ip-sysctl.rst')
| -rw-r--r-- | Documentation/networking/ip-sysctl.rst | 708 |
1 files changed, 653 insertions, 55 deletions
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index 837d51f9e1fa..bd50df6a5a42 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -25,7 +25,8 @@ ip_default_ttl - INTEGER 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 + destination will be set to the smallest of the old MTU to + this destination and 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. @@ -49,7 +50,8 @@ ip_no_pmtu_disc - INTEGER Default: FALSE min_pmtu - INTEGER - default 552 - minimum discovered Path MTU + default 552 - minimum Path MTU. Unless this is changed manually, + each cached pmtu will never be lower than this setting. ip_forward_use_pmtu - BOOLEAN By default we don't trust protocol path MTUs while forwarding @@ -99,6 +101,35 @@ fib_multipath_hash_policy - INTEGER - 0 - Layer 3 - 1 - Layer 4 - 2 - Layer 3 or inner Layer 3 if present + - 3 - Custom multipath hash. Fields used for multipath hash calculation + are determined by fib_multipath_hash_fields sysctl + +fib_multipath_hash_fields - UNSIGNED INTEGER + When fib_multipath_hash_policy is set to 3 (custom multipath hash), the + fields used for multipath hash calculation are determined by this + sysctl. + + This value is a bitmask which enables various fields for multipath hash + calculation. + + Possible fields are: + + ====== ============================ + 0x0001 Source IP address + 0x0002 Destination IP address + 0x0004 IP protocol + 0x0008 Unused (Flow Label) + 0x0010 Source port + 0x0020 Destination port + 0x0040 Inner source IP address + 0x0080 Inner destination IP address + 0x0100 Inner IP protocol + 0x0200 Inner Flow Label + 0x0400 Inner source port + 0x0800 Inner destination port + ====== ============================ + + Default: 0x0007 (source IP, destination IP and IP protocol) fib_sync_mem - UNSIGNED INTEGER Amount of dirty memory from fib entries that can be backlogged before @@ -125,6 +156,9 @@ route/max_size - INTEGER From linux kernel 3.6 onwards, this is deprecated for ipv4 as route cache is no longer used. + From linux kernel 6.3 onwards, this is deprecated for ipv6 + as garbage collection manages cached route entries. + neigh/default/gc_thresh1 - INTEGER Minimum number of entries to keep. Garbage collector will not purge entries if there are fewer than this number. @@ -171,6 +205,12 @@ neigh/default/unres_qlen - INTEGER Default: 101 +neigh/default/interval_probe_time_ms - INTEGER + The probe interval for neighbor entries with NTF_MANAGED flag, + the min value is 1. + + Default: 5000 + mtu_expires - INTEGER Time, in seconds, that cached PMTU information is kept. @@ -178,6 +218,27 @@ 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 @@ -215,6 +276,13 @@ ipfrag_max_dist - INTEGER from different IP datagrams, which could result in data corruption. Default: 64 +bc_forwarding - INTEGER + bc_forwarding enables the feature described in rfc1812#section-5.3.5.2 + and rfc2644. It allows the router to forward directed broadcast. + To enable this feature, the 'all' entry and the input interface entry + should be set to 1. + Default: 0 + INET peer storage ================= @@ -253,6 +321,7 @@ tcp_abort_on_overflow - BOOLEAN option can harm clients of your server. tcp_adv_win_scale - INTEGER + Obsolete since linux-6.6 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. @@ -272,6 +341,8 @@ 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. + Possible values are [0, 31], inclusive. + Default: 31 tcp_autocorking - BOOLEAN @@ -571,6 +642,16 @@ tcp_recovery - INTEGER Default: 0x1 +tcp_reflect_tos - BOOLEAN + For listening sockets, reuse the DSCP value of the initial SYN message + for outgoing packets. This allows to have both directions of a TCP + stream to use the same DSCP value, assuming DSCP remains unchanged for + the lifetime of the connection. + + This options affects both IPv4 and IPv6. + + Default: 0 (disabled) + tcp_reordering - INTEGER Initial reordering level of packets in a TCP stream. TCP stack can then dynamically adjust flow reordering level @@ -630,16 +711,15 @@ tcp_rmem - vector of 3 INTEGERs: min, default, max default: initial size of receive buffer used by TCP sockets. This value overrides net.core.rmem_default used by other protocols. - Default: 87380 bytes. This value results in window of 65535 with - default setting of tcp_adv_win_scale and tcp_app_win:0 and a bit - less for default tcp_app_win. See below about these variables. + 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 87380B and 6MB, depending on RAM size. + Default: between 131072 and 6MB, depending on RAM size. tcp_sack - BOOLEAN Enable select acknowledgments (SACKS). @@ -665,6 +745,13 @@ tcp_comp_sack_nr - INTEGER Default : 44 +tcp_backlog_ack_defer - BOOLEAN + If set, user thread processing socket backlog tries sending + one ACK for the whole queue. This helps to avoid potential + long latencies at end of a TCP socket syscall. + + Default : true + 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 @@ -712,6 +799,31 @@ tcp_syncookies - INTEGER network connections you can set this knob to 2 to enable unconditionally generation of syncookies. +tcp_migrate_req - BOOLEAN + The incoming connection is tied to a specific listening socket when + the initial SYN packet is received during the three-way handshake. + When a listener is closed, in-flight request sockets during the + handshake and established sockets in the accept queue are aborted. + + If the listener has SO_REUSEPORT enabled, other listeners on the + same port should have been able to accept such connections. This + option makes it possible to migrate such child sockets to another + listener after close() or shutdown(). + + The BPF_SK_REUSEPORT_SELECT_OR_MIGRATE type of eBPF program should + usually be used to define the policy to pick an alive listener. + Otherwise, the kernel will randomly pick an alive listener only if + this option is enabled. + + Note that migration between listeners with different settings may + crash applications. Let's say migration happens from listener A to + B, and only B has TCP_SAVE_SYN enabled. B cannot read SYN data from + the requests migrated from A. To avoid such a situation, cancel + migration by returning SK_DROP in the type of eBPF program, or + disable this option. + + Default: 0 + tcp_fastopen - INTEGER Enable TCP Fast Open (RFC7413) to send and accept data in the opening SYN packet. @@ -752,7 +864,7 @@ tcp_fastopen_blackhole_timeout_sec - INTEGER initial value when the blackhole issue goes away. 0 to disable the blackhole detection. - By default, it is set to 1hr. + By default, it is set to 0 (feature is disabled). tcp_fastopen_key - list of comma separated 32-digit hexadecimal INTEGERs The list consists of a primary key and an optional backup key. The @@ -777,9 +889,10 @@ tcp_fastopen_key - list of comma separated 32-digit hexadecimal INTEGERs 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. + is 6, which corresponds to 67seconds (with tcp_syn_linear_timeouts = 4) + 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 131seconds. tcp_timestamps - INTEGER Enable timestamps as defined in RFC1323. @@ -802,6 +915,29 @@ tcp_min_tso_segs - INTEGER Default: 2 +tcp_tso_rtt_log - INTEGER + Adjustment of TSO packet sizes based on min_rtt + + Starting from linux-5.18, TCP autosizing can be tweaked + for flows having small RTT. + + Old autosizing was splitting the pacing budget to send 1024 TSO + per second. + + tso_packet_size = sk->sk_pacing_rate / 1024; + + With the new mechanism, we increase this TSO sizing using: + + distance = min_rtt_usec / (2^tcp_tso_rtt_log) + tso_packet_size += gso_max_size >> distance; + + This means that flows between very close hosts can use bigger + TSO packets, reducing their cpu costs. + + If you want to use the old autosizing, set this sysctl to 0. + + Default: 9 (2^9 = 512 usec) + 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) @@ -819,6 +955,16 @@ tcp_pacing_ca_ratio - INTEGER Default: 120 +tcp_syn_linear_timeouts - INTEGER + The number of times for an active TCP connection to retransmit SYNs with + a linear backoff timeout before defaulting to an exponential backoff + timeout. This has no effect on SYNACK at the passive TCP side. + + With an initial RTO of 1 and tcp_syn_linear_timeouts = 4 we would + expect SYN RTOs to be: 1, 1, 1, 1, 1, 2, 4, ... (4 linear timeouts, + and the first exponential backoff using 2^0 * initial_RTO). + Default: 4 + tcp_tso_win_divisor - INTEGER This allows control over what percentage of the congestion window can be consumed by a single TSO frame. @@ -843,6 +989,21 @@ tcp_tw_reuse - INTEGER tcp_window_scaling - BOOLEAN Enable window scaling as defined in RFC1323. +tcp_shrink_window - BOOLEAN + This changes how the TCP receive window is calculated. + + RFC 7323, section 2.4, says there are instances when a retracted + window can be offered, and that TCP implementations MUST ensure + that they handle a shrinking window, as specified in RFC 1122. + + - 0 - Disabled. The window is never shrunk. + - 1 - Enabled. The window is shrunk when necessary to remain within + the memory limit set by autotuning (sk_rcvbuf). + This only occurs if a non-zero receive window + scaling factor is also in effect. + + Default: 0 + 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. @@ -913,15 +1074,127 @@ tcp_limit_output_bytes - INTEGER 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 + Note that this per netns rate limit can allow some side channel + attacks and probably should not be enabled. + TCP stack implements per TCP socket limits anyway. + Default: INT_MAX (unlimited) -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. +tcp_ehash_entries - INTEGER + Show the number of hash buckets for TCP sockets in the current + networking namespace. - Default: 0 (disabled) + A negative value means the networking namespace does not own its + hash buckets and shares the initial networking namespace's one. + +tcp_child_ehash_entries - INTEGER + Control the number of hash buckets for TCP sockets in the child + networking namespace, which must be set before clone() or unshare(). + + If the value is not 0, the kernel uses a value rounded up to 2^n + as the actual hash bucket size. 0 is a special value, meaning + the child networking namespace will share the initial networking + namespace's hash buckets. + + Note that the child will use the global one in case the kernel + fails to allocate enough memory. In addition, the global hash + buckets are spread over available NUMA nodes, but the allocation + of the child hash table depends on the current process's NUMA + policy, which could result in performance differences. + + Note also that the default value of tcp_max_tw_buckets and + tcp_max_syn_backlog depend on the hash bucket size. + + Possible values: 0, 2^n (n: 0 - 24 (16Mi)) + + Default: 0 + +tcp_plb_enabled - BOOLEAN + If set and the underlying congestion control (e.g. DCTCP) supports + and enables PLB feature, TCP PLB (Protective Load Balancing) is + enabled. PLB is described in the following paper: + https://doi.org/10.1145/3544216.3544226. Based on PLB parameters, + upon sensing sustained congestion, TCP triggers a change in + flow label field for outgoing IPv6 packets. A change in flow label + field potentially changes the path of outgoing packets for switches + that use ECMP/WCMP for routing. + + PLB changes socket txhash which results in a change in IPv6 Flow Label + field, and currently no-op for IPv4 headers. It is possible + to apply PLB for IPv4 with other network header fields (e.g. TCP + or IPv4 options) or using encapsulation where outer header is used + by switches to determine next hop. In either case, further host + and switch side changes will be needed. + + When set, PLB assumes that congestion signal (e.g. ECN) is made + available and used by congestion control module to estimate a + congestion measure (e.g. ce_ratio). PLB needs a congestion measure to + make repathing decisions. + + Default: FALSE + +tcp_plb_idle_rehash_rounds - INTEGER + Number of consecutive congested rounds (RTT) seen after which + a rehash can be performed, given there are no packets in flight. + This is referred to as M in PLB paper: + https://doi.org/10.1145/3544216.3544226. + + Possible Values: 0 - 31 + + Default: 3 + +tcp_plb_rehash_rounds - INTEGER + Number of consecutive congested rounds (RTT) seen after which + a forced rehash can be performed. Be careful when setting this + parameter, as a small value increases the risk of retransmissions. + This is referred to as N in PLB paper: + https://doi.org/10.1145/3544216.3544226. + + Possible Values: 0 - 31 + + Default: 12 + +tcp_plb_suspend_rto_sec - INTEGER + Time, in seconds, to suspend PLB in event of an RTO. In order to avoid + having PLB repath onto a connectivity "black hole", after an RTO a TCP + connection suspends PLB repathing for a random duration between 1x and + 2x of this parameter. Randomness is added to avoid concurrent rehashing + of multiple TCP connections. This should be set corresponding to the + amount of time it takes to repair a failed link. + + Possible Values: 0 - 255 + + Default: 60 + +tcp_plb_cong_thresh - INTEGER + Fraction of packets marked with congestion over a round (RTT) to + tag that round as congested. This is referred to as K in the PLB paper: + https://doi.org/10.1145/3544216.3544226. + + The 0-1 fraction range is mapped to 0-256 range to avoid floating + point operations. For example, 128 means that if at least 50% of + the packets in a round were marked as congested then the round + will be tagged as congested. + + Setting threshold to 0 means that PLB repaths every RTT regardless + of congestion. This is not intended behavior for PLB and should be + used only for experimentation purpose. + + Possible Values: 0 - 256 + + Default: 128 + +tcp_pingpong_thresh - INTEGER + The number of estimated data replies sent for estimated incoming data + requests that must happen before TCP considers that a connection is a + "ping-pong" (request-response) connection for which delayed + acknowledgments can provide benefits. + + This threshold is 1 by default, but some applications may need a higher + threshold for optimal performance. + + Possible Values: 1 - 255 + + Default: 1 UDP variables ============= @@ -938,13 +1211,11 @@ udp_l3mdev_accept - BOOLEAN 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. + min: Number of pages allowed for queueing by all UDP sockets. pressure: This value was introduced to follow format of tcp_mem. - max: Number of pages allowed for queueing by all UDP sockets. + max: This value was introduced to follow format of tcp_mem. Default is calculated at boot time from amount of available memory. @@ -956,11 +1227,34 @@ udp_rmem_min - INTEGER 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. + UDP does not have tx memory accounting and this tunable has no effect. + +udp_hash_entries - INTEGER + Show the number of hash buckets for UDP sockets in the current + networking namespace. + + A negative value means the networking namespace does not own its + hash buckets and shares the initial networking namespace's one. + +udp_child_ehash_entries - INTEGER + Control the number of hash buckets for UDP sockets in the child + networking namespace, which must be set before clone() or unshare(). + + If the value is not 0, the kernel uses a value rounded up to 2^n + as the actual hash bucket size. 0 is a special value, meaning + the child networking namespace will share the initial networking + namespace's hash buckets. + + Note that the child will use the global one in case the kernel + fails to allocate enough memory. In addition, the global hash + buckets are spread over available NUMA nodes, but the allocation + of the child hash table depends on the current process's NUMA + policy, which could result in performance differences. + + Possible values: 0, 2^n (n: 7 (128) - 16 (64K)) + + Default: 0 - Default: 4K RAW variables ============= @@ -989,7 +1283,7 @@ cipso_cache_enable - BOOLEAN 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 + the number of entries in each hash bucket; the larger the value is, 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. @@ -1053,7 +1347,9 @@ ip_local_reserved_ports - list of comma separated ranges 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. + 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 @@ -1081,7 +1377,7 @@ ip_autobind_reuse - BOOLEAN option should only be set by experts. Default: 0 -ip_dynaddr - BOOLEAN +ip_dynaddr - INTEGER 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 @@ -1103,8 +1399,8 @@ 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. + to the single group. "0 4294967294" would enable it for the world, "100 + 4294967294" would enable it for the users, but not daemons. tcp_early_demux - BOOLEAN Enable early demux for established TCP sockets. @@ -1123,6 +1419,12 @@ icmp_echo_ignore_all - BOOLEAN 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. @@ -1142,13 +1444,15 @@ icmp_ratelimit - INTEGER 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. + 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 @@ -1194,7 +1498,7 @@ icmp_errors_use_inbound_ifaddr - BOOLEAN 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 network many administrators will expect from + This is the behaviour many network administrators will expect from a router. And it can make debugging complicated network layouts much easier. @@ -1337,6 +1641,14 @@ proxy_arp_pvlan - BOOLEAN Hewlett-Packard call it Source-Port filtering or port-isolation. Ericsson call it MAC-Forced Forwarding (RFC Draft). +proxy_delay - INTEGER + Delay proxy response. + + Delay response to a neighbor solicitation when proxy_arp + or proxy_ndp is enabled. A random value between [0, proxy_delay) + will be chosen, setting to zero means reply with no delay. + Value in jiffies. Defaults to 80. + shared_media - BOOLEAN Send(router) or accept(host) RFC1620 shared media redirects. Overrides secure_redirects. @@ -1423,6 +1735,25 @@ rp_filter - INTEGER 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 @@ -1502,12 +1833,15 @@ arp_notify - BOOLEAN or hardware address changes. == ========================================================== -arp_accept - BOOLEAN - Define behavior for gratuitous ARP frames who's IP is not - already present in the ARP table: +arp_accept - INTEGER + Define behavior for accepting gratuitous ARP (garp) frames from devices + that are 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 + - 2 - create new entries only if the source IP address is in the same + subnet as an address configured on the interface that received the + garp message. Both replies and requests type gratuitous arp will trigger the ARP table to be updated, if this setting is on. @@ -1516,6 +1850,15 @@ arp_accept - BOOLEAN gratuitous arp frame, the arp table will be updated regardless if this setting is on or off. +arp_evict_nocarrier - BOOLEAN + Clears the ARP cache on NOCARRIER events. This option is important for + wireless devices where the ARP cache should not be cleared when roaming + between access points on the same network. In most cases this should + remain as the default (1). + + - 1 - (default): Clear the ARP cache on NOCARRIER events + - 0 - Do not clear ARP cache on NOCARRIER events + mcast_solicit - INTEGER The maximum number of multicast probes in INCOMPLETE state, when the associated hardware address is unknown. Defaults @@ -1552,6 +1895,9 @@ igmpv3_unsolicited_report_interval - INTEGER 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 @@ -1691,6 +2037,35 @@ fib_multipath_hash_policy - INTEGER - 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 + - 3 - Custom multipath hash. Fields used for multipath hash calculation + are determined by fib_multipath_hash_fields sysctl + +fib_multipath_hash_fields - UNSIGNED INTEGER + When fib_multipath_hash_policy is set to 3 (custom multipath hash), the + fields used for multipath hash calculation are determined by this + sysctl. + + This value is a bitmask which enables various fields for multipath hash + calculation. + + Possible fields are: + + ====== ============================ + 0x0001 Source IP address + 0x0002 Destination IP address + 0x0004 IP protocol + 0x0008 Flow Label + 0x0010 Source port + 0x0020 Destination port + 0x0040 Inner source IP address + 0x0080 Inner destination IP address + 0x0100 Inner IP protocol + 0x0200 Inner Flow Label + 0x0400 Inner source port + 0x0800 Inner destination port + ====== ============================ + + Default: 0x0007 (source IP, destination IP and IP protocol) anycast_src_echo_reply - BOOLEAN Controls the use of anycast addresses as source addresses for ICMPv6 @@ -1760,7 +2135,7 @@ skip_notify_on_dev_down - BOOLEAN 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 + prefixes. Backwards compatibility 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 @@ -1770,6 +2145,44 @@ nexthop_compat_mode - BOOLEAN 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. + +ioam6_id - INTEGER + Define the IOAM id of this node. Uses only 24 bits out of 32 in total. + + Min: 0 + Max: 0xFFFFFF + + Default: 0xFFFFFF + +ioam6_id_wide - LONG INTEGER + Define the wide IOAM id of this node. Uses only 56 bits out of 64 in + total. Can be different from ioam6_id. + + Min: 0 + Max: 0xFFFFFFFFFFFFFF + + Default: 0xFFFFFFFFFFFFFF + IPv6 Fragmentation: ip6frag_high_thresh - INTEGER @@ -1784,30 +2197,27 @@ ip6frag_low_thresh - INTEGER ip6frag_time - INTEGER Time in seconds to keep an IPv6 fragment in memory. -IPv6 Segment Routing: - -seg6_flowlabel - INTEGER - Controls the behaviour of computing the flowlabel of outer - IPv6 header in case of SR T.encaps - - == ======================================================= - -1 set flowlabel to zero. - 0 copy flowlabel from Inner packet in case of Inner IPv6 - (Set flowlabel to 0 in case IPv4/L2) - 1 Compute the flowlabel using seg6_make_flowlabel() - == ======================================================= - - Default is 0. - ``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. @@ -1866,6 +2276,16 @@ accept_ra_defrtr - BOOLEAN - 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. @@ -1888,6 +2308,14 @@ accept_ra_min_hop_limit - INTEGER Default: 1 +accept_ra_min_lft - INTEGER + Minimum acceptable lifetime value in Router Advertisement. + + RA sections with a lifetime less than this value shall be + ignored. Zero lifetimes stay unaffected. + + Default: 0 + accept_ra_pinfo - BOOLEAN Learn Prefix Information in Router Advertisement. @@ -1896,6 +2324,17 @@ accept_ra_pinfo - BOOLEAN - enabled if accept_ra is enabled. - disabled if accept_ra is disabled. +ra_honor_pio_life - BOOLEAN + Whether to use RFC4862 Section 5.5.3e to determine the valid + lifetime of an address matching a prefix sent in a Router + Advertisement Prefix Information Option. + + - If enabled, the PIO valid lifetime will always be honored. + - If disabled, RFC4862 section 5.5.3e is used to determine + the valid lifetime of the address. + + Default: 0 (disabled) + accept_ra_rt_info_min_plen - INTEGER Minimum prefix length of Route Information in RA. @@ -2063,12 +2502,18 @@ use_tempaddr - INTEGER * -1 (for point-to-point devices and loopback devices) temp_valid_lft - INTEGER - valid lifetime (in seconds) for temporary addresses. + valid lifetime (in seconds) for temporary addresses. If less than the + minimum required lifetime (typically 5-7 seconds), temporary addresses + will not be created. Default: 172800 (2 days) temp_prefered_lft - INTEGER - Preferred lifetime (in seconds) for temporary addresses. + Preferred lifetime (in seconds) for temporary addresses. If + temp_prefered_lft is less than the minimum required lifetime (typically + 5-7 seconds), the preferred lifetime is the minimum required. If + temp_prefered_lft is greater than temp_valid_lft, the preferred lifetime + is temp_valid_lft. Default: 86400 (1 day) @@ -2090,6 +2535,16 @@ max_desync_factor - INTEGER Default: 600 +regen_min_advance - INTEGER + How far in advance (in seconds), at minimum, to create a new temporary + address before the current one is deprecated. This value is added to + the amount of time that may be required for duplicate address detection + to determine when to create a new address. Linux permits setting this + value to less than the default of 2 seconds, but a value less than 2 + does not conform to RFC 8981. + + Default: 2 + regen_max_retry - INTEGER Number of attempts before give up attempting to generate valid temporary addresses. @@ -2169,6 +2624,15 @@ ndisc_tclass - INTEGER * 0 - (default) +ndisc_evict_nocarrier - BOOLEAN + Clears the neighbor discovery table on NOCARRIER events. This option is + important for wireless devices where the neighbor discovery cache should + not be cleared when roaming between access points on the same network. + In most cases this should remain as the default (1). + + - 1 - (default): Clear neighbor discover cache on NOCARRIER events. + - 0 - Do not clear neighbor discovery cache on NOCARRIER events. + mldv1_unsolicited_report_interval - INTEGER The interval in milliseconds in which the next unsolicited MLDv1 report retransmit will take place. @@ -2254,6 +2718,37 @@ drop_unsolicited_na - BOOLEAN By default this is turned off. +accept_untracked_na - INTEGER + Define behavior for accepting neighbor advertisements from devices that + are absent in the neighbor cache: + + - 0 - (default) Do not accept unsolicited and untracked neighbor + advertisements. + + - 1 - Add a new neighbor cache entry in STALE state for routers on + receiving a neighbor advertisement (either solicited or unsolicited) + with target link-layer address option specified if no neighbor entry + is already present for the advertised IPv6 address. Without this knob, + NAs received for untracked addresses (absent in neighbor cache) are + silently ignored. + + This is as per router-side behavior documented in RFC9131. + + This has lower precedence than drop_unsolicited_na. + + This will optimize the return path for the initial off-link + communication that is initiated by a directly connected host, by + ensuring that the first-hop router which turns on this setting doesn't + have to buffer the initial return packets to do neighbor-solicitation. + The prerequisite is that the host is configured to send unsolicited + neighbor advertisements on interface bringup. This setting should be + used in conjunction with the ndisc_notify setting on the host to + satisfy this prerequisite. + + - 2 - Extend option (1) to add a new neighbor cache entry only if the + source IP address is in the same subnet as an address configured on + the interface that received the neighbor advertisement. + 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 @@ -2308,6 +2803,13 @@ echo_ignore_anycast - BOOLEAN Default: 0 +error_anycast_as_unicast - BOOLEAN + If set to 1, then the kernel will respond with ICMP Errors + resulting from requests sent to it over the IPv6 protocol destined + to anycast address essentially treating anycast as unicast. + + Default: 0 + xfrm6_gc_thresh - INTEGER (Obsolete since linux-4.14) The threshold at which we will start garbage collecting for IPv6 @@ -2408,7 +2910,7 @@ pf_expose - INTEGER 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_GET_PEER_ADDR_INFO sockopt; When it's disabled, 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. @@ -2628,7 +3130,14 @@ sctp_rmem - vector of 3 INTEGERs: min, default, max Default: 4K sctp_wmem - vector of 3 INTEGERs: min, default, max - Currently this tunable has no effect. + Only the first value ("min") is used, "default" and "max" are + ignored. + + min: Minimum size of send buffer that can be used by SCTP sockets. + It is guaranteed to each SCTP socket (but not association) even + under moderate memory pressure. + + Default: 4K addr_scope_policy - INTEGER Control IPv4 address scoping - draft-stewart-tsvwg-sctp-ipv4-00 @@ -2640,6 +3149,95 @@ addr_scope_policy - INTEGER 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 + +plpmtud_probe_interval - INTEGER + The time interval (in milliseconds) for the PLPMTUD probe timer, + which is configured to expire after this period to receive an + acknowledgment to a probe packet. This is also the time interval + between the probes for the current pmtu when the probe search + is done. + + PLPMTUD will be disabled when 0 is set, and other values for it + must be >= 5000. + + Default: 0 + +reconf_enable - BOOLEAN + Enable or disable extension of Stream Reconfiguration functionality + specified in RFC6525. This extension provides the ability to "reset" + a stream, and it includes the Parameters of "Outgoing/Incoming SSN + Reset", "SSN/TSN Reset" and "Add Outgoing/Incoming Streams". + + - 1: Enable extension. + - 0: Disable extension. + + Default: 0 + +intl_enable - BOOLEAN + Enable or disable extension of User Message Interleaving functionality + specified in RFC8260. This extension allows the interleaving of user + messages sent on different streams. With this feature enabled, I-DATA + chunk will replace DATA chunk to carry user messages if also supported + by the peer. Note that to use this feature, one needs to set this option + to 1 and also needs to set socket options SCTP_FRAGMENT_INTERLEAVE to 2 + and SCTP_INTERLEAVING_SUPPORTED to 1. + + - 1: Enable extension. + - 0: Disable extension. + + Default: 0 + +ecn_enable - BOOLEAN + Control use of Explicit Congestion Notification (ECN) by SCTP. + Like in TCP, ECN is used only when both ends of the SCTP 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. + + 1: Enable ecn. + 0: Disable ecn. + + Default: 1 + +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) + ``/proc/sys/net/core/*`` ======================== |