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Diffstat (limited to 'Documentation/networking/ip-sysctl.rst')
| -rw-r--r-- | Documentation/networking/ip-sysctl.rst | 1605 |
1 files changed, 1366 insertions, 239 deletions
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index b72f89d5694c..bc9a01606daf 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -8,15 +8,19 @@ IP Sysctl ============================== 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) + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + 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. @@ -25,7 +29,8 @@ 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. @@ -36,8 +41,8 @@ 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 @@ -49,7 +54,8 @@ 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 @@ -60,20 +66,25 @@ ip_forward_use_pmtu - BOOLEAN kernel honoring this information. This is normally not the case. - Default: 0 (disabled) - Possible values: - - 0 - disabled - - 1 - enabled + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) 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 + If disabled, these packets have a fwmark of zero. If enabled, they have the fwmark of the packet they are replying to. - Default: 0 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) fib_multipath_use_neigh - BOOLEAN Use status of existing neighbor entry when determining nexthop for @@ -81,12 +92,12 @@ fib_multipath_use_neigh - BOOLEAN 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 + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) fib_multipath_hash_policy - INTEGER Controls which hash policy to use for multipath routes. Only valid @@ -99,6 +110,49 @@ 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_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 @@ -125,6 +179,9 @@ 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. @@ -152,7 +209,7 @@ neigh/default/unres_qlen_bytes - INTEGER Setting negative value is meaningless and will return error. - Default: SK_WMEM_MAX, (same as net.core.wmem_default). + Default: SK_WMEM_DEFAULT, (same as net.core.wmem_default). Exact value depends on architecture and kernel options, but should be enough to allow queuing 256 packets @@ -171,6 +228,12 @@ 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 +241,27 @@ 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 +299,13 @@ 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 +344,7 @@ 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 +364,8 @@ 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 @@ -283,7 +377,12 @@ tcp_autocorking - BOOLEAN queue. Applications can still use TCP_CORK for optimal behavior when they know how/when to uncork their sockets. - Default : 1 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) tcp_available_congestion_control - STRING Shows the available congestion control choices that are registered. @@ -323,9 +422,16 @@ tcp_congestion_control - STRING tcp_dsack - BOOLEAN Allows TCP to send "duplicate" SACKs. + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) + tcp_early_retrans - INTEGER Tail loss probe (TLP) converts RTOs occurring due to tail - losses into fast recovery (draft-ietf-tcpm-rack). Note that + losses into fast recovery (RFC8985). Note that TLP requires RACK to function properly (see tcp_recovery below) Possible values: @@ -337,23 +443,56 @@ tcp_early_retrans - INTEGER 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. + 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. A host that supports ECN both sends ECN at the IP layer and + feeds back ECN at the TCP layer. The highest variant of ECN feedback + that both peers support is chosen by the ECN negotiation (Accurate ECN, + ECN, or no ECN). + + The highest negotiated variant for incoming connection requests + and the highest variant requested by outgoing connection + attempts: + + ===== ==================== ==================== + Value Incoming connections Outgoing connections + ===== ==================== ==================== + 0 No ECN No ECN + 1 ECN ECN + 2 ECN No ECN + 3 AccECN AccECN + 4 AccECN ECN + 5 AccECN No ECN + ===== ==================== ==================== + + Default: 2 + +tcp_ecn_option - INTEGER + Control Accurate ECN (AccECN) option sending when AccECN has been + successfully negotiated during handshake. Send logic inhibits + sending AccECN options regarless of this setting when no AccECN + option has been seen for the reverse direction. 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. - = ===================================================== + = ============================================================ + 0 Never send AccECN option. This also disables sending AccECN + option in SYN/ACK during handshake. + 1 Send AccECN option sparingly according to the minimum option + rules outlined in draft-ietf-tcpm-accurate-ecn. + 2 Send AccECN option on every packet whenever it fits into TCP + option space. + = ============================================================ Default: 2 +tcp_ecn_option_beacon - INTEGER + Control Accurate ECN (AccECN) option sending frequency per RTT and it + takes effect only when tcp_ecn_option is set to 2. + + Default: 3 (AccECN will be send at least 3 times per RTT) + tcp_ecn_fallback - BOOLEAN If the kernel detects that ECN connection misbehaves, enable fall back to non-ECN. Currently, this knob implements the fallback @@ -362,7 +501,12 @@ tcp_ecn_fallback - BOOLEAN knob. The value is not used, if tcp_ecn or per route (or congestion control) ECN settings are disabled. - Default: 1 (fallback enabled) + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) tcp_fack - BOOLEAN This is a legacy option, it has no effect anymore. @@ -389,7 +533,7 @@ tcp_frto - INTEGER 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 + If enabled, 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 @@ -397,7 +541,12 @@ tcp_fwmark_accept - BOOLEAN have a fwmark set via setsockopt(SOL_SOCKET, SO_MARK, ...) are unaffected. - Default: 0 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) tcp_invalid_ratelimit - INTEGER Limit the maximal rate for sending duplicate acknowledgments @@ -443,6 +592,11 @@ tcp_l3mdev_accept - BOOLEAN which the packets originated. Only valid when the kernel was compiled with CONFIG_NET_L3_MASTER_DEV. + Possible values: + + - 0 (disabled) + - 1 (enabled) + Default: 0 (disabled) tcp_low_latency - BOOLEAN @@ -508,10 +662,26 @@ tcp_min_rtt_wlen - INTEGER Default: 300 tcp_moderate_rcvbuf - BOOLEAN - If set, TCP performs receive buffer auto-tuning, attempting to + If enabled, 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. + match the size required by the path for full throughput. + + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) + +tcp_rcvbuf_low_rtt - INTEGER + rcvbuf autotuning can over estimate final socket rcvbuf, which + can lead to cache trashing for high throughput flows. + + For small RTT flows (below tcp_rcvbuf_low_rtt usecs), we can relax + rcvbuf growth: Few additional ms to reach the final (and smaller) + rcvbuf is a good tradeoff. + + Default : 1000 (1 ms) tcp_mtu_probing - INTEGER Controls TCP Packetization-Layer Path MTU Discovery. Takes three @@ -536,13 +706,26 @@ tcp_no_metrics_save - BOOLEAN 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 + degradation. If enabled, TCP will not cache metrics on closing connections. + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + tcp_no_ssthresh_metrics_save - BOOLEAN Controls whether TCP saves ssthresh metrics in the route cache. + If enabled, ssthresh metrics are disabled. - Default is 1, which disables ssthresh metrics. + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) tcp_orphan_retries - INTEGER This value influences the timeout of a locally closed TCP connection, @@ -560,9 +743,11 @@ tcp_recovery - INTEGER 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: 0x1 enables RACK loss detection, for fast detection of lost + retransmissions and tail drops, and resilience to + reordering. currently, setting this bit to 0 has no + effect, since RACK is the only supported loss detection + algorithm. RACK: 0x2 makes RACK's reordering window static (min_rtt/4). @@ -571,6 +756,21 @@ 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. + + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + tcp_reordering - INTEGER Initial reordering level of packets in a TCP stream. TCP stack can then dynamically adjust flow reordering level @@ -590,6 +790,13 @@ tcp_retrans_collapse - BOOLEAN On retransmit try to send bigger packets to work around bugs in certain TCP stacks. + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) + tcp_retries1 - INTEGER This value influences the time, after which TCP decides, that something is wrong due to unacknowledged RTO retransmissions, @@ -610,16 +817,23 @@ 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. tcp_rfc1337 - BOOLEAN - If set, the TCP stack behaves conforming to RFC1337. If unset, + If enabled, the TCP stack behaves conforming to RFC1337. If unset, we are not conforming to RFC, but prevent TCP TIME_WAIT assassination. - Default: 0 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) tcp_rmem - vector of 3 INTEGERs: min, default, max min: Minimal size of receive buffer used by TCP sockets. @@ -630,23 +844,38 @@ 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 + selected receiver buffers for TCP socket. + 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 32MB, depending on RAM size. tcp_sack - BOOLEAN Enable select acknowledgments (SACKS). + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) + +tcp_comp_sack_rtt_percent - INTEGER + Percentage of SRTT used for the compressed SACK feature. + See tcp_comp_sack_nr, tcp_comp_sack_delay_ns, tcp_comp_sack_slack_ns. + + Possible values : 1 - 1000 + + Default : 33 % + 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. + TCP tries to reduce number of SACK sent, using a timer based + on tcp_comp_sack_rtt_percent 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) @@ -656,8 +885,9 @@ tcp_comp_sack_slack_ns - LONG INTEGER timer used by SACK compression. This gives extra time for small RTT flows, and reduces system overhead by allowing opportunistic reduction of timer interrupts. + Too big values might reduce goodput. - Default : 100,000 ns (100 us) + Default : 10,000 ns (10 us) tcp_comp_sack_nr - INTEGER Max number of SACK that can be compressed. @@ -665,20 +895,42 @@ tcp_comp_sack_nr - INTEGER Default : 44 +tcp_backlog_ack_defer - BOOLEAN + If enabled, 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. + + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) + tcp_slow_start_after_idle - BOOLEAN - If set, provide RFC2861 behavior and time out the congestion + If enabled, 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 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) 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 + Most hosts use the older BSD interpretation, so if enabled, Linux might not communicate correctly with them. - Default: FALSE + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) tcp_synack_retries - INTEGER Number of times SYNACKs for a passive TCP connection attempt will @@ -712,6 +964,36 @@ 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. + + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + tcp_fastopen - INTEGER Enable TCP Fast Open (RFC7413) to send and accept data in the opening SYN packet. @@ -741,7 +1023,7 @@ tcp_fastopen - INTEGER Default: 0x1 - Note that that additional client or server features are only + 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 @@ -752,7 +1034,7 @@ 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 +1059,10 @@ 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 +1085,29 @@ 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 +1125,16 @@ 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. @@ -840,9 +1156,47 @@ 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. + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) + +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. + + Possible values: + + - 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 (disabled) + 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. @@ -878,16 +1232,21 @@ tcp_notsent_lowat - UNSIGNED INTEGER Default: UINT_MAX (0xFFFFFFFF) tcp_workaround_signed_windows - BOOLEAN - If set, assume no receipt of a window scaling option means the + If enabled, 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 + If disabled, assume the remote TCP is not broken even if we do not receive a window scaling option from them. - Default: 0 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) 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 + If enabled, 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 @@ -896,7 +1255,12 @@ tcp_thin_linear_timeouts - BOOLEAN For more information on thin streams, see Documentation/networking/tcp-thin.rst - Default: 0 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) tcp_limit_output_bytes - INTEGER Controls TCP Small Queue limit per tcp socket. @@ -908,21 +1272,162 @@ 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 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_ehash_entries - INTEGER + Show the number of hash buckets for TCP 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. + +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. -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. + Possible values: 0, 2^n (n: 0 - 24 (16Mi)) + + Default: 0 + +tcp_plb_enabled - BOOLEAN + If enabled 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. + + If enabled, 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. + + Possible values: + + - 0 (disabled) + - 1 (enabled) Default: 0 (disabled) +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 + +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 ============= @@ -933,18 +1438,21 @@ udp_l3mdev_accept - BOOLEAN originated. Only valid when the kernel was compiled with CONFIG_NET_L3_MASTER_DEV. + Possible values: + + - 0 (disabled) + - 1 (enabled) + 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. + 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 +1464,34 @@ 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_hash_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 ============= @@ -972,24 +1503,34 @@ raw_l3mdev_accept - BOOLEAN originated. Only valid when the kernel was compiled with CONFIG_NET_L3_MASTER_DEV. + Possible values: + + - 0 (disabled) + - 1 (enabled) + 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 + If enabled, enable additions to and lookups from the CIPSO label mapping + cache. If disabled, 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 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) 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. @@ -1002,17 +1543,27 @@ cipso_rbm_optfmt - BOOLEAN 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 + Possible values: -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 + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + +cipso_rbm_strictvalid - BOOLEAN + If enabled, do a very strict check of the CIPSO option when + ip_options_compile() is called. If disabled, 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 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) IP Variables ============ @@ -1053,7 +1604,9 @@ 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 @@ -1067,10 +1620,15 @@ ip_unprivileged_port_start - INTEGER Default: 1024 ip_nonlocal_bind - BOOLEAN - If set, allows processes to bind() to non-local IP addresses, + If enabled, allows processes to bind() to non-local IP addresses, which can be quite useful - but may break some applications. - Default: 0 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) ip_autobind_reuse - BOOLEAN By default, bind() does not select the ports automatically even if @@ -1079,9 +1637,15 @@ ip_autobind_reuse - BOOLEAN 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 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + +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 @@ -1097,37 +1661,73 @@ ip_early_demux - BOOLEAN It may add an additional cost for pure routing workloads that reduces overall throughput, in such case you should disable it. - Default: 1 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) 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. - Default: 1 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) udp_early_demux - BOOLEAN Enable early demux for connected UDP sockets. Disable this if your system could experience more unconnected load. - Default: 1 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) icmp_echo_ignore_all - BOOLEAN - If set non-zero, then the kernel will ignore all ICMP ECHO + If enabled, then the kernel will ignore all ICMP ECHO requests sent to it. - Default: 0 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + +icmp_echo_enable_probe - BOOLEAN + If enabled, then the kernel will respond to RFC 8335 PROBE + requests sent to it. + + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) icmp_echo_ignore_broadcasts - BOOLEAN - If set non-zero, then the kernel will ignore all ICMP ECHO and + If enabled, then the kernel will ignore all ICMP ECHO and TIMESTAMP requests sent to it via broadcast/multicast. - Default: 1 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) icmp_ratelimit - INTEGER Limit the maximal rates for sending ICMP packets whose type matches @@ -1142,13 +1742,15 @@ 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 @@ -1182,19 +1784,24 @@ icmp_ratemask - INTEGER 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 + If enabled, the kernel will not give such warnings, which will avoid log file clutter. - Default: 1 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) icmp_errors_use_inbound_ifaddr - BOOLEAN - If zero, icmp error messages are sent with the primary address of + If disabled, 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 + If enabled, 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. @@ -1202,7 +1809,29 @@ icmp_errors_use_inbound_ifaddr - BOOLEAN then the primary address of the first non-loopback interface that has one will be used regardless of this setting. - Default: 0 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + +icmp_errors_extension_mask - UNSIGNED INTEGER + Bitmask of ICMP extensions to append to ICMPv4 error messages + ("Destination Unreachable", "Time Exceeded" and "Parameter Problem"). + The original datagram is trimmed / padded to 128 bytes in order to be + compatible with applications that do not comply with RFC 4884. + + Possible extensions are: + + ==== ============================================================== + 0x01 Incoming IP interface information according to RFC 5837. + Extension will include the index, IPv4 address (if present), + name and MTU of the IP interface that received the datagram + which elicited the ICMP error. + ==== ============================================================== + + Default: 0x00 (no extensions) igmp_max_memberships - INTEGER Change the maximum number of multicast groups we can subscribe to. @@ -1332,10 +1961,18 @@ proxy_arp_pvlan - BOOLEAN 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). + - 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). + +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. @@ -1423,6 +2060,25 @@ 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 +2158,15 @@ 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 +2175,19 @@ 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). + + Possible values: + + - 0 (disabled) - Do not clear ARP cache on NOCARRIER events + - 1 (enabled) - Clear the ARP cache on NOCARRIER events + + Default: 1 (enabled) + mcast_solicit - INTEGER The maximum number of multicast probes in INCOMPLETE state, when the associated hardware address is unknown. Defaults @@ -1537,9 +2209,23 @@ mcast_resolicit - INTEGER disable_policy - BOOLEAN Disable IPSEC policy (SPD) for this interface + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + disable_xfrm - BOOLEAN Disable IPSEC encryption on this interface, whatever the policy + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + igmpv2_unsolicited_report_interval - INTEGER The interval in milliseconds in which the next unsolicited IGMPv1 or IGMPv2 report retransmit will take place. @@ -1552,11 +2238,28 @@ 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. + + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + 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. + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + drop_unicast_in_l2_multicast - BOOLEAN Drop any unicast IP packets that are received in link-layer multicast (or broadcast) frames. @@ -1564,14 +2267,24 @@ drop_unicast_in_l2_multicast - BOOLEAN This behavior (for multicast) is actually a SHOULD in RFC 1122, but is disabled by default for compatibility reasons. - Default: off (0) + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) 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) + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) tag - INTEGER @@ -1615,20 +2328,24 @@ bindv6only - BOOLEAN which restricts use of the IPv6 socket to IPv6 communication only. - - TRUE: disable IPv4-mapped address feature - - FALSE: enable IPv4-mapped address feature + Possible values: - Default: FALSE (as specified in RFC3493) + - 0 (disabled) - enable IPv4-mapped address feature + - 1 (enabled) - disable IPv4-mapped address feature + + Default: 0 (disabled) 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 + Possible values: - Default: TRUE + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) auto_flowlabels - INTEGER Automatically generate flow labels based on a flow hash of the @@ -1654,10 +2371,13 @@ flowlabel_state_ranges - BOOLEAN reserved for the IPv6 flow manager facility, 0x80000-0xFFFFF is reserved for stateless flow labels as described in RFC6437. - - TRUE: enabled - - FALSE: disabled + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) - Default: true flowlabel_reflect - INTEGER Control flow label reflection. Needed for Path MTU @@ -1691,15 +2411,47 @@ 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 echo reply - - TRUE: enabled - - FALSE: disabled + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) - Default: FALSE idgen_delay - INTEGER Controls the delay in seconds after which time to retry @@ -1756,11 +2508,16 @@ skip_notify_on_dev_down - BOOLEAN 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) + Possible values: + + - 0 (disabled) - generate the message + - 1 (enabled) - skip generating the message + + Default: 0 (disabled) 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 @@ -1768,8 +2525,56 @@ 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 + 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. + + Possible value range: + + - 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. + + Possible value range: + + - Min: 0 + - Max: 0xFFFFFFFFFFFFFF + + Default: 0xFFFFFFFFFFFFFF + IPv6 Fragmentation: ip6frag_high_thresh - INTEGER @@ -1784,35 +2589,32 @@ 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. - IPv4 and IPv6 work differently here; e.g. netfilter must be used - to control which interfaces may forward packets and which not. + IPv4 and IPv6 work differently here; the ``force_forwarding`` flag must + be used to control which interfaces may forward packets. This also sets all interfaces' Host/Router setting 'forwarding' to the specified value. See below for details. @@ -1822,13 +2624,30 @@ conf/all/forwarding - BOOLEAN proxy_ndp - BOOLEAN Do proxy ndp. + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + +force_forwarding - BOOLEAN + Enable forwarding on this interface only -- regardless of the setting on + ``conf/all/forwarding``. When setting ``conf.all.forwarding`` to 0, + the ``force_forwarding`` flag will be reset on all interfaces. + 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 + If disabled, these packets have a fwmark of zero. If enabled, they have the fwmark of the packet they are replying to. - Default: 0 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) ``conf/interface/*``: Change special settings per interface. @@ -1866,6 +2685,16 @@ 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 +2717,14 @@ 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 +2733,35 @@ 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. + + Possible values: + + - 0 (disabled) - RFC4862 section 5.5.3e is used to determine + the valid lifetime of the address. + - 1 (enabled) - the PIO valid lifetime will always be honored. + + 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. + + Possible values: + + - 0 (disabled) - the P-flag is ignored. + - 1 (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. @@ -2013,10 +2879,15 @@ mtu - INTEGER Default: 1280 (IPv6 required minimum) ip_nonlocal_bind - BOOLEAN - If set, allows processes to bind() to non-local IPv6 addresses, + If enabled, allows processes to bind() to non-local IPv6 addresses, which can be quite useful - but may break some applications. - Default: 0 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) router_probe_interval - INTEGER Minimum interval (in seconds) between Router Probing described @@ -2046,7 +2917,12 @@ use_oif_addrs_only - BOOLEAN routed via this interface are restricted to the set of addresses configured on this interface (vis. RFC 6724, section 4). - Default: false + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) use_tempaddr - INTEGER Preference for Privacy Extensions (RFC3041). @@ -2063,12 +2939,18 @@ 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 +2972,16 @@ 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. @@ -2155,10 +3047,14 @@ force_tllao - BOOLEAN 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 + Possible values: + + - 0 (disabled) - do nothing + - 1 (enabled) - Generate unsolicited neighbour advertisements when device is brought up or hardware address changes. + Default: 0 (disabled) + ndisc_tclass - INTEGER The IPv6 Traffic Class to use by default when sending IPv6 Neighbor Discovery (Router Solicitation, Router Advertisement, Neighbor @@ -2169,6 +3065,19 @@ 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). + + Possible values: + + - 0 (disabled) - Do not clear neighbor discovery cache on NOCARRIER events. + - 1 (enabled) - Clear neighbor discover cache on NOCARRIER events. + + Default: 1 (enabled) + mldv1_unsolicited_report_interval - INTEGER The interval in milliseconds in which the next unsolicited MLDv1 report retransmit will take place. @@ -2196,25 +3105,34 @@ suppress_frag_ndisc - INTEGER 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. + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + + 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. + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + stable_secret - IPv6 address This IPv6 address will be used as a secret to generate IPv6 addresses for link-local addresses and autoconfigured @@ -2245,14 +3163,55 @@ 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. + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) 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. + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled). + +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 @@ -2262,7 +3221,12 @@ enhanced_dad - BOOLEAN The nonce option will be sent on an interface unless both of conf/{all,interface}/enhanced_dad are set to FALSE. - Default: TRUE + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) ``icmp/*``: =========== @@ -2291,22 +3255,66 @@ ratemask - list of comma separated ranges 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 + If enabled, then the kernel will ignore all ICMP ECHO requests sent to it over the IPv6 protocol. - Default: 0 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) echo_ignore_multicast - BOOLEAN - If set non-zero, then the kernel will ignore all ICMP ECHO + If enabled, then the kernel will ignore all ICMP ECHO requests sent to it over the IPv6 protocol via multicast. - Default: 0 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) echo_ignore_anycast - BOOLEAN - If set non-zero, then the kernel will ignore all ICMP ECHO + If enabled, then the kernel will ignore all ICMP ECHO requests sent to it over the IPv6 protocol destined to anycast address. - Default: 0 + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + +error_anycast_as_unicast - BOOLEAN + If enabled, 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. + + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 0 (disabled) + +errors_extension_mask - UNSIGNED INTEGER + Bitmask of ICMP extensions to append to ICMPv6 error messages + ("Destination Unreachable" and "Time Exceeded"). The original datagram + is trimmed / padded to 128 bytes in order to be compatible with + applications that do not comply with RFC 4884. + + Possible extensions are: + + ==== ============================================================== + 0x01 Incoming IP interface information according to RFC 5837. + Extension will include the index, IPv6 address (if present), + name and MTU of the IP interface that received the datagram + which elicited the ICMP error. + ==== ============================================================== + + Default: 0x00 (no extensions) xfrm6_gc_thresh - INTEGER (Obsolete since linux-4.14) @@ -2324,34 +3332,49 @@ YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org> ================================= bridge-nf-call-arptables - BOOLEAN - - 1 : pass bridged ARP traffic to arptables' FORWARD chain. - - 0 : disable this. - Default: 1 + Possible values: + + - 0 (disabled) - disable this. + - 1 (enabled) - pass bridged ARP traffic to arptables' FORWARD chain. + + Default: 1 (enabled) bridge-nf-call-iptables - BOOLEAN - - 1 : pass bridged IPv4 traffic to iptables' chains. - - 0 : disable this. - Default: 1 + Possible values: + + - 0 (disabled) - disable this. + - 1 (enabled) - pass bridged IPv4 traffic to iptables' chains. + + Default: 1 (enabled) bridge-nf-call-ip6tables - BOOLEAN - - 1 : pass bridged IPv6 traffic to ip6tables' chains. - - 0 : disable this. - Default: 1 + Possible values: + + - 0 (disabled) - disable this. + - 1 (enabled) - pass bridged IPv6 traffic to ip6tables' chains. + + Default: 1 (enabled) 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 + Possible values: + + - 0 (disabled) - disable this. + - 1 (enabled) - pass bridged vlan-tagged ARP/IP/IPv6 traffic to {arp,ip,ip6}tables + + Default: 0 (disabled) bridge-nf-filter-pppoe-tagged - BOOLEAN - - 1 : pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables. - - 0 : disable this. - Default: 0 + Possible values: + + - 0 (disabled) - disable this. + - 1 (enabled) - pass bridged pppoe-tagged IP/IPv6 traffic to {ip,ip6}tables. + + Default: 0 (disabled) bridge-nf-pass-vlan-input-dev - BOOLEAN - 1: if bridge-nf-filter-vlan-tagged is enabled, try to find a vlan @@ -2374,11 +3397,12 @@ addip_enable - BOOLEAN the ability to dynamically add and remove new addresses for the SCTP associations. - 1: Enable extension. + Possible values: - 0: Disable extension. + - 0 (disabled) - disable extension. + - 1 (enabled) - enable extension - Default: 0 + Default: 0 (disabled) pf_enable - INTEGER Enable or disable pf (pf is short for potentially failed) state. A value @@ -2393,31 +3417,27 @@ pf_enable - INTEGER https://datatracker.ietf.org/doc/draft-ietf-tsvwg-sctp-failover for details. - 1: Enable pf. + Possible values: - 0: Disable pf. + - 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. + in the SCTP_PEER_ADDR_CHANGE event and access of SCTP_PF-state + transport info via SCTP_GET_PEER_ADDR_INFO sockopt. - 1: Disable pf state exposure. + Possible values: - 2: Enable pf state exposure. + - 0: Unset pf state exposure (compatible with old applications). No + event will be sent but the transport info can be queried. + - 1: Disable pf state exposure. No event will be sent and trying to + obtain transport info will return -EACCESS. + - 2: Enable pf state exposure. The event will be sent for a transport + becoming SCTP_PF state and transport info can be obtained. Default: 0 @@ -2447,19 +3467,23 @@ auth_enable - BOOLEAN required for secure operation of Dynamic Address Reconfiguration (ADD-IP) extension. - - 1: Enable this extension. - - 0: Disable this extension. + Possible values: - Default: 0 + - 0 (disabled) - disable extension. + - 1 (enabled) - enable extension + + Default: 0 (disabled) 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 + Possible values: - Default: 1 + - 0 (disabled) - disable extension. + - 1 (enabled) - enable extension + + Default: 1 (enabled) max_burst - INTEGER The limit of the number of new packets that can be initially sent. It @@ -2559,26 +3583,22 @@ 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 + Possible values: - Default: 1 + - 0 (disabled) - disable. + - 1 (enabled) - enable cookie lifetime extension. + + Default: 1 (enabled) 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 + * sha256 * 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. + Default: sha256 rcvbuf_policy - INTEGER Determines if the receive buffer is attributed to the socket or to @@ -2607,13 +3627,11 @@ sndbuf_policy - INTEGER 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. + * min: Below this number of pages SCTP is not bothered about its + memory usage. 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: Maximum number of allowed pages. Default is calculated at boot time from amount of available memory. @@ -2621,17 +3639,26 @@ 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. + * 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. + 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 + Control IPv4 address scoping (see + https://datatracker.ietf.org/doc/draft-stewart-tsvwg-sctp-ipv4/00/ + for details). - 0 - Disable IPv4 address scoping - 1 - Enable IPv4 address scoping @@ -2640,6 +3667,106 @@ 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". + + Possible values: + + - 0 (disabled) - Disable extension. + - 1 (enabled) - Enable extension. + + Default: 0 (disabled) + +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. + + Possible values: + + - 0 (disabled) - Disable extension. + - 1 (enabled) - Enable extension. + + Default: 0 (disabled) + +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. + + Possible values: + + - 0 (disabled) - Disable ecn. + - 1 (enabled) - Enable ecn. + + Default: 1 (enabled) + +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. + + Possible values: + + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) + ``/proc/sys/net/core/*`` ======================== |