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Sat, 14 Jun 2025 15:54:05 -0700 (PDT) From: Abdelrahman Fekry To: corbet@lwn.net, davem@davemloft.net, edumazet@google.com, horms@kernel.org, kuba@kernel.org, pabeni@redhat.com Cc: linux-doc@vger.kernel.org, linux-kernel-mentees@lists.linux.dev, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, skhan@linuxfoundation.com, jacob.e.keller@intel.com, alok.a.tiwari@oracle.com, Abdelrahman Fekry Subject: [PATCH v2 1/2] docs: net: sysctl documentation cleanup Date: Sun, 15 Jun 2025 01:53:23 +0300 Message-Id: <20250614225324.82810-2-abdelrahmanfekry375@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20250614225324.82810-1-abdelrahmanfekry375@gmail.com> References: <20250614225324.82810-1-abdelrahmanfekry375@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" I noticed that some boolean parameters have missing default values (enabled/disabled) in the documentation so i checked the initialization functions to get their default values, also there was some inconsistency in the representation. During the process , i stumbled upon a typo in cipso_rbm_struct_valid instead of cipso_rbm_struct_valid. Thanks for the review. On Thu, 12 Jun 2025, Jacob Keller wrote: > Would it make sense to use "0 (disabled)" and "1 (enabled)" with > parenthesis for consistency with the default value? Used as suggested. On Fri, 13 Jun 2025, ALOK TIWARI wrote: > for consistency > remove extra space before colon > Default: 1 (enabled) Fixed.=20 On Sat, 14 Jun 2025 10:46:29 -0700, Jakub Kicinski wrote: > You need to repost the entire series. Make sure you read: > https://www.kernel.org/doc/html/next/process/maintainer-netdev.html > before you do. Reposted the entire series, Thanks for you patiency. Signed-off-by: Abdelrahman Fekry --- v2: - Deleted space before colon for consistency - Standardized more boolean representation (0/1 with enabled/disabled) v1: https://lore.kernel.org/all/20250612162954.55843-2-abdelrahmanfekry375@= gmail.com/ - Fixed typo in cipso_rbm_struct_valid - Added missing default value declarations - Standardized boolean representation (0/1 with enabled/disabled) Documentation/networking/ip-sysctl.rst | 47 ++++++++++++++++++++------ 1 file changed, 37 insertions(+), 10 deletions(-) diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/network= ing/ip-sysctl.rst index 0f1251cce314..68778532faa5 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -8,14 +8,16 @@ IP Sysctl =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D =20 ip_forward - BOOLEAN - - 0 - disabled (default) - - not 0 - enabled + - 0 (disabled) + - not 0 (enabled) =20 Forward Packets between interfaces. =20 This variable is special, its change resets all configuration parameters to their default state (RFC1122 for hosts, RFC1812 for routers) + + Default: 0 (disabled) =20 ip_default_ttl - INTEGER Default value of TTL field (Time To Live) for outgoing (but not @@ -75,7 +77,7 @@ fwmark_reflect - BOOLEAN If unset, these packets have a fwmark of zero. If set, they have the fwmark of the packet they are replying to. =20 - Default: 0 + Default: 0 (disabled) =20 fib_multipath_use_neigh - BOOLEAN Use status of existing neighbor entry when determining nexthop for @@ -368,7 +370,7 @@ tcp_autocorking - BOOLEAN queue. Applications can still use TCP_CORK for optimal behavior when they know how/when to uncork their sockets. =20 - Default : 1 + Default: 1 (enabled) =20 tcp_available_congestion_control - STRING Shows the available congestion control choices that are registered. @@ -407,6 +409,12 @@ tcp_congestion_control - STRING =20 tcp_dsack - BOOLEAN Allows TCP to send "duplicate" SACKs. + + Possible values: + - 0 (disabled) + - 1 (enabled) + + Default: 1 (enabled) =20 tcp_early_retrans - INTEGER Tail loss probe (TLP) converts RTOs occurring due to tail @@ -623,6 +631,8 @@ tcp_no_metrics_save - BOOLEAN increases overall performance, but may sometimes cause performance degradation. If set, TCP will not cache metrics on closing connections. + + Default: 0 (disabled) =20 tcp_no_ssthresh_metrics_save - BOOLEAN Controls whether TCP saves ssthresh metrics in the route cache. @@ -684,6 +694,8 @@ tcp_retrans_collapse - BOOLEAN Bug-to-bug compatibility with some broken printers. On retransmit try to send bigger packets to work around bugs in certain TCP stacks. + + Default: 1 (enabled) =20 tcp_retries1 - INTEGER This value influences the time, after which TCP decides, that @@ -739,6 +751,8 @@ tcp_rmem - vector of 3 INTEGERs: min, default, max =20 tcp_sack - BOOLEAN Enable select acknowledgments (SACKS). + + Default: 1 (enabled) =20 tcp_comp_sack_delay_ns - LONG INTEGER TCP tries to reduce number of SACK sent, using a timer @@ -766,7 +780,7 @@ tcp_backlog_ack_defer - BOOLEAN one ACK for the whole queue. This helps to avoid potential long latencies at end of a TCP socket syscall. =20 - Default : true + Default: 1 (enabled) =20 tcp_slow_start_after_idle - BOOLEAN If set, provide RFC2861 behavior and time out the congestion @@ -781,7 +795,7 @@ tcp_stdurg - BOOLEAN Most hosts use the older BSD interpretation, so if you turn this on Linux might not communicate correctly with them. =20 - Default: FALSE + Default: 0 (disabled) =20 tcp_synack_retries - INTEGER Number of times SYNACKs for a passive TCP connection attempt will @@ -1018,6 +1032,10 @@ tcp_tw_reuse_delay - UNSIGNED INTEGER =20 tcp_window_scaling - BOOLEAN Enable window scaling as defined in RFC1323. + - 0 (disabled). + - 1 (enabled). + + Default: 1 (enabled) =20 tcp_shrink_window - BOOLEAN This changes how the TCP receive window is calculated. @@ -1160,7 +1178,7 @@ tcp_plb_enabled - BOOLEAN congestion measure (e.g. ce_ratio). PLB needs a congestion measure to make repathing decisions. =20 - Default: FALSE + Default: 0 (disabled) =20 tcp_plb_idle_rehash_rounds - INTEGER Number of consecutive congested rounds (RTT) seen after which @@ -1352,7 +1370,7 @@ cipso_rbm_optfmt - BOOLEAN =20 Default: 0 =20 -cipso_rbm_structvalid - BOOLEAN +cipso_rbm_strictvalid - BOOLEAN If set, do a very strict check of the CIPSO option when ip_options_compile() is called. If unset, relax the checks done during ip_options_compile(). Either way is "safe" as errors are caught else @@ -1543,7 +1561,7 @@ icmp_ignore_bogus_error_responses - BOOLEAN If this is set to TRUE, the kernel will not give such warnings, which will avoid log file clutter. =20 - Default: 1 + Default: 1 (enabled) =20 icmp_errors_use_inbound_ifaddr - BOOLEAN =20 @@ -1560,7 +1578,7 @@ 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. =20 - Default: 0 + Default: 0 (disabled) =20 igmp_max_memberships - INTEGER Change the maximum number of multicast groups we can subscribe to. @@ -1933,10 +1951,15 @@ mcast_resolicit - INTEGER =20 disable_policy - BOOLEAN Disable IPSEC policy (SPD) for this interface + + Default: 0 + =20 disable_xfrm - BOOLEAN Disable IPSEC encryption on this interface, whatever the policy =20 + Default: 0 + igmpv2_unsolicited_report_interval - INTEGER The interval in milliseconds in which the next unsolicited IGMPv1 or IGMPv2 report retransmit will take place. @@ -1951,11 +1974,15 @@ igmpv3_unsolicited_report_interval - INTEGER =20 ignore_routes_with_linkdown - BOOLEAN Ignore routes whose link is down when performing a FIB lookup. + + Default: 0 (disabled) =20 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. + + Default: 0 (disabled) =20 drop_unicast_in_l2_multicast - BOOLEAN Drop any unicast IP packets that are received in link-layer --=20 2.25.1 From nobody Fri Oct 10 09:39:03 2025 Received: from mail-wr1-f49.google.com (mail-wr1-f49.google.com [209.85.221.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7A2FE20E313; 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Sat, 14 Jun 2025 15:54:11 -0700 (PDT) Received: from localhost.localdomain ([154.182.223.70]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4532e2449f1sm94897025e9.23.2025.06.14.15.54.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 14 Jun 2025 15:54:11 -0700 (PDT) From: Abdelrahman Fekry To: corbet@lwn.net, davem@davemloft.net, edumazet@google.com, horms@kernel.org, kuba@kernel.org, pabeni@redhat.com Cc: linux-doc@vger.kernel.org, linux-kernel-mentees@lists.linux.dev, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, skhan@linuxfoundation.com, jacob.e.keller@intel.com, alok.a.tiwari@oracle.com, Abdelrahman Fekry Subject: [PATCH v2 2/2] docs: net: clarify sysctl value constraints Date: Sun, 15 Jun 2025 01:53:24 +0300 Message-Id: <20250614225324.82810-3-abdelrahmanfekry375@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20250614225324.82810-1-abdelrahmanfekry375@gmail.com> References: <20250614225324.82810-1-abdelrahmanfekry375@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" So, i also noticed that some of the parameters represented as boolean have no value constrain checks and accept integer values due to u8 implementation, so i wrote a note for every boolean parameter that have no constrain checks in code. and fixed a typo in fmwark instead of fwmark. Added notes for 19 confirmed parameters, Verified by code inspection and runtime testing. - No changes for v2 in this patch , still waiting to be reviewed. Signed-off-by: Abdelrahman Fekry --- v2: - No change. v1: - Added notes for booleans that accept 0-255 not only 0/1. Documentation/networking/ip-sysctl.rst | 70 ++++++++++++++++++++------ 1 file changed, 55 insertions(+), 15 deletions(-) diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/network= ing/ip-sysctl.rst index 68778532faa5..38f2981290d6 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -70,6 +70,8 @@ ip_forward_use_pmtu - BOOLEAN =20 - 0 - disabled - 1 - enabled + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. =20 fwmark_reflect - BOOLEAN Controls the fwmark of kernel-generated IPv4 reply packets that are not @@ -91,6 +93,8 @@ fib_multipath_use_neigh - BOOLEAN =20 - 0 - disabled - 1 - enabled + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. =20 fib_multipath_hash_policy - INTEGER Controls which hash policy to use for multipath routes. Only valid @@ -490,7 +494,9 @@ tcp_fwmark_accept - BOOLEAN have a fwmark set via setsockopt(SOL_SOCKET, SO_MARK, ...) are unaffected. =20 - Default: 0 + Default: 0 (disabled) + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. =20 tcp_invalid_ratelimit - INTEGER Limit the maximal rate for sending duplicate acknowledgments @@ -605,6 +611,8 @@ tcp_moderate_rcvbuf - BOOLEAN automatically size the buffer (no greater than tcp_rmem[2]) to match the size required by the path for full throughput. Enabled by default. + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. =20 tcp_mtu_probing - INTEGER Controls TCP Packetization-Layer Path MTU Discovery. Takes three @@ -638,6 +646,8 @@ tcp_no_ssthresh_metrics_save - BOOLEAN Controls whether TCP saves ssthresh metrics in the route cache. =20 Default is 1, which disables ssthresh metrics. + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. =20 tcp_orphan_retries - INTEGER This value influences the timeout of a locally closed TCP connection, @@ -705,7 +715,9 @@ tcp_retries1 - INTEGER =20 RFC 1122 recommends at least 3 retransmissions, which is the default. - + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. + tcp_retries2 - INTEGER This value influences the timeout of an alive TCP connection, when RTO retransmissions remain unacknowledged. @@ -728,7 +740,7 @@ tcp_rfc1337 - BOOLEAN we are not conforming to RFC, but prevent TCP TIME_WAIT assassination. =20 - Default: 0 + Default: 0 (disabled) =20 tcp_rmem - vector of 3 INTEGERs: min, default, max min: Minimal size of receive buffer used by TCP sockets. @@ -753,6 +765,8 @@ tcp_sack - BOOLEAN Enable select acknowledgments (SACKS). =09 Default: 1 (enabled) + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. =20 tcp_comp_sack_delay_ns - LONG INTEGER TCP tries to reduce number of SACK sent, using a timer @@ -788,7 +802,9 @@ tcp_slow_start_after_idle - BOOLEAN the current RTO. If unset, the congestion window will not be timed out after an idle period. =20 - Default: 1 + Default: 1 (enabled) + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. =20 tcp_stdurg - BOOLEAN Use the Host requirements interpretation of the TCP urgent pointer field. @@ -796,6 +812,8 @@ tcp_stdurg - BOOLEAN Linux might not communicate correctly with them. =20 Default: 0 (disabled) + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. =20 tcp_synack_retries - INTEGER Number of times SYNACKs for a passive TCP connection attempt will @@ -852,7 +870,7 @@ tcp_migrate_req - BOOLEAN migration by returning SK_DROP in the type of eBPF program, or disable this option. =20 - Default: 0 + Default: 0 (disabled) =20 tcp_fastopen - INTEGER Enable TCP Fast Open (RFC7413) to send and accept data in the opening @@ -1036,6 +1054,8 @@ tcp_window_scaling - BOOLEAN - 1 - Enabled. =09 Default: 1 (enabled) + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. =20 tcp_shrink_window - BOOLEAN This changes how the TCP receive window is calculated. @@ -1050,7 +1070,9 @@ tcp_shrink_window - BOOLEAN This only occurs if a non-zero receive window scaling factor is also in effect. =20 - Default: 0 + Default: 0 (disabled) + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. =20 tcp_wmem - vector of 3 INTEGERs: min, default, max min: Amount of memory reserved for send buffers for TCP sockets. @@ -1092,7 +1114,7 @@ tcp_workaround_signed_windows - BOOLEAN If unset, assume the remote TCP is not broken even if we do not receive a window scaling option from them. =20 - Default: 0 + Default: 0 (disabled) =20 tcp_thin_linear_timeouts - BOOLEAN Enable dynamic triggering of linear timeouts for thin streams. @@ -1105,8 +1127,10 @@ tcp_thin_linear_timeouts - BOOLEAN For more information on thin streams, see Documentation/networking/tcp-thin.rst =20 - Default: 0 - + Default: 0 (disabled) + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. + tcp_limit_output_bytes - INTEGER Controls TCP Small Queue limit per tcp socket. TCP bulk sender tends to increase packets in flight until it @@ -1350,7 +1374,7 @@ cipso_cache_enable - BOOLEAN invalidated when required when means you can safely toggle this on and off and the cache will always be "safe". =20 - Default: 1 + Default: 1 (enabled) =20 cipso_cache_bucket_size - INTEGER The CIPSO label cache consists of a fixed size hash table with each @@ -1368,7 +1392,10 @@ 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. =20 - Default: 0 + Default: 0 (disabled) + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. + =20 cipso_rbm_strictvalid - BOOLEAN If set, do a very strict check of the CIPSO option when @@ -1378,7 +1405,10 @@ cipso_rbm_strictvalid - BOOLEAN result in less work (i.e. it should be faster) but could cause problems with other implementations that require strict checking. =20 - Default: 0 + Default: 0 (disabled) + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. + =20 IP Variables =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D @@ -1439,6 +1469,9 @@ ip_nonlocal_bind - BOOLEAN which can be quite useful - but may break some applications. =20 Default: 0 + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. + =20 ip_autobind_reuse - BOOLEAN By default, bind() does not select the ports automatically even if @@ -1449,6 +1482,8 @@ ip_autobind_reuse - BOOLEAN option should only be set by experts. Default: 0 =20 + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. + 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 @@ -1478,13 +1513,16 @@ tcp_early_demux - BOOLEAN Enable early demux for established TCP sockets. =20 Default: 1 + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. + =20 udp_early_demux - BOOLEAN Enable early demux for connected UDP sockets. Disable this if your system could experience more unconnected load. =20 Default: 1 - + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. + icmp_echo_ignore_all - BOOLEAN If set non-zero, then the kernel will ignore all ICMP ECHO requests sent to it. @@ -1817,7 +1855,7 @@ src_valid_mark - BOOLEAN lookup. This permits rp_filter to function when the fwmark is used for routing traffic in both directions. =20 - This setting also affects the utilization of fmwark when + This setting also affects the utilization of fwmark when performing source address selection for ICMP replies, or determining addresses stored for the IPOPT_TS_TSANDADDR and IPOPT_RR IP options. @@ -2326,7 +2364,9 @@ fwmark_reflect - BOOLEAN fwmark of the packet they are replying to. =20 Default: 0 - + + note: Accepts integer values (0-255) but only 0/1 have defined behaviour. + ``conf/interface/*``: Change special settings per interface. =20 --=20 2.25.1