[PATCH 0/2] docs: net: sysctl documentation improvements

[PATCH 0/2] docs: net: sysctl documentation improvements

[Abdelrahman Fekry]

This series cleans up and clarifies networking sysctl documentation,
specially the boolean parameters:

Patch 1: Fixes typos, adds missing defaults, and standardizes 
	boolean representation.
         
Patch 2: Adds value constraint clarifications for parameters with u8
	implementation details , fixes typos.


Abdelrahman Fekry (2):
  docs: net: sysctl documentation cleanup
  docs: net: clarify sysctl value constraints

 Documentation/networking/ip-sysctl.rst | 87 ++++++++++++++++++++++----
 1 file changed, 76 insertions(+), 11 deletions(-)

-- 
2.25.1

[PATCH 1/2] docs: net: sysctl documentation cleanup

[Abdelrahman Fekry]

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. 

- Fixed typo in cipso_rbm_struct_valid
- Added missing default value declarations
- Standardized boolean representation (0/1 with enabled/disabled)

Signed-off-by: Abdelrahman Fekry <abdelrahmanfekry375@gmail.com>
---
 Documentation/networking/ip-sysctl.rst | 37 +++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 6 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index 0f1251cce314..f7ff8c53f412 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -75,7 +75,7 @@ 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.
 
-	Default: 0
+	Default: 0 (disabled)
 
 fib_multipath_use_neigh - BOOLEAN
 	Use status of existing neighbor entry when determining nexthop for
@@ -368,7 +368,7 @@ tcp_autocorking - BOOLEAN
 	queue. Applications can still use TCP_CORK for optimal behavior
 	when they know how/when to uncork their sockets.
 
-	Default : 1
+	Default : 1 (enabled)
 
 tcp_available_congestion_control - STRING
 	Shows the available congestion control choices that are registered.
@@ -407,6 +407,12 @@ 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
@@ -623,6 +629,8 @@ 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)
 
 tcp_no_ssthresh_metrics_save - BOOLEAN
 	Controls whether TCP saves ssthresh metrics in the route cache.
@@ -684,6 +692,8 @@ 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)
 
 tcp_retries1 - INTEGER
 	This value influences the time, after which TCP decides, that
@@ -739,6 +749,8 @@ tcp_rmem - vector of 3 INTEGERs: min, default, max
 
 tcp_sack - BOOLEAN
 	Enable select acknowledgments (SACKS).
+
+	Default: 1 (enabled)
 
 tcp_comp_sack_delay_ns - LONG INTEGER
 	TCP tries to reduce number of SACK sent, using a timer
@@ -766,7 +778,7 @@ 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.
 
-	Default : true
+	Default : 1 (enabled)
 
 tcp_slow_start_after_idle - BOOLEAN
 	If set, provide RFC2861 behavior and time out the congestion
@@ -781,7 +793,7 @@ tcp_stdurg - BOOLEAN
 	Most hosts use the older BSD interpretation, so if you turn this on
 	Linux might not communicate correctly with them.
 
-	Default: FALSE
+	Default: 0 (disabled)
 
 tcp_synack_retries - INTEGER
 	Number of times SYNACKs for a passive TCP connection attempt will
@@ -1018,6 +1030,10 @@ tcp_tw_reuse_delay - UNSIGNED INTEGER
 
 tcp_window_scaling - BOOLEAN
 	Enable window scaling as defined in RFC1323.
+	- 0 - Disabled.
+	- 1 - Enabled.
+
+	Default: 1 (enabled)
 
 tcp_shrink_window - BOOLEAN
 	This changes how the TCP receive window is calculated.
@@ -1160,7 +1176,7 @@ tcp_plb_enabled - BOOLEAN
 	congestion measure (e.g. ce_ratio). PLB needs a congestion measure to
 	make repathing decisions.
 
-	Default: FALSE
+	Default: 0 (disabled)
 
 tcp_plb_idle_rehash_rounds - INTEGER
 	Number of consecutive congested rounds (RTT) seen after which
@@ -1352,7 +1368,7 @@ cipso_rbm_optfmt - BOOLEAN
 
 	Default: 0
 
-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
@@ -1933,10 +1949,15 @@ mcast_resolicit - INTEGER
 
 disable_policy - BOOLEAN
 	Disable IPSEC policy (SPD) for this interface
+
+	Default: 0
+
 
 disable_xfrm - BOOLEAN
 	Disable IPSEC encryption on this interface, whatever the policy
 
+	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 +1972,15 @@ igmpv3_unsolicited_report_interval - INTEGER
 
 ignore_routes_with_linkdown - BOOLEAN
         Ignore routes whose link is down when performing a FIB lookup.
+
+        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.
+
+	Default: 0 (disabled)
 
 drop_unicast_in_l2_multicast - BOOLEAN
 	Drop any unicast IP packets that are received in link-layer
-- 
2.25.1

Re: [PATCH 1/2] docs: net: sysctl documentation cleanup

[Jacob Keller]

On 6/12/2025 9:29 AM, Abdelrahman Fekry wrote:
> 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. 
> 
> - Fixed typo in cipso_rbm_struct_valid
> - Added missing default value declarations
> - Standardized boolean representation (0/1 with enabled/disabled)
> 
> Signed-off-by: Abdelrahman Fekry <abdelrahmanfekry375@gmail.com>
> ---

Thank you for the documentation improvements! I do think its a bit more
clear to include the "(enabled)" or "(disabled)".

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>

>  Documentation/networking/ip-sysctl.rst | 37 +++++++++++++++++++++-----
>  1 file changed, 31 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
> index 0f1251cce314..f7ff8c53f412 100644
> --- a/Documentation/networking/ip-sysctl.rst
> +++ b/Documentation/networking/ip-sysctl.rst
> @@ -407,6 +407,12 @@ tcp_congestion_control - STRING
>  
>  tcp_dsack - BOOLEAN
>  	Allows TCP to send "duplicate" SACKs.
> +	Possible values:
> +		- 0 disabled
> +		- 1 enabled
> +
> +	Default: 1 (enabled)
>  

Would it make sense to use "0 (disabled)" and "1 (enabled)" with
parenthesis for consistency with the default value?

Re: [PATCH 1/2] docs: net: sysctl documentation cleanup

[ALOK TIWARI]

On 12-06-2025 21:59, Abdelrahman Fekry wrote:
> 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.
> 
> - Fixed typo in cipso_rbm_struct_valid
> - Added missing default value declarations
> - Standardized boolean representation (0/1 with enabled/disabled)
> 
> Signed-off-by: Abdelrahman Fekry <abdelrahmanfekry375@gmail.com>
> ---
>   Documentation/networking/ip-sysctl.rst | 37 +++++++++++++++++++++-----
>   1 file changed, 31 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
> index 0f1251cce314..f7ff8c53f412 100644
> --- a/Documentation/networking/ip-sysctl.rst
> +++ b/Documentation/networking/ip-sysctl.rst
> @@ -75,7 +75,7 @@ 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.
>   
> -	Default: 0
> +	Default: 0 (disabled)
>   
>   fib_multipath_use_neigh - BOOLEAN
>   	Use status of existing neighbor entry when determining nexthop for
> @@ -368,7 +368,7 @@ tcp_autocorking - BOOLEAN
>   	queue. Applications can still use TCP_CORK for optimal behavior
>   	when they know how/when to uncork their sockets.
>   
> -	Default : 1
> +	Default : 1 (enabled)

for consistency
remove extra space before colon
Default: 1 (enabled)

>   
>   tcp_available_congestion_control - STRING
>   	Shows the available congestion control choices that are registered.
> @@ -407,6 +407,12 @@ 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
> @@ -623,6 +629,8 @@ 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)
>   
>   tcp_no_ssthresh_metrics_save - BOOLEAN
>   	Controls whether TCP saves ssthresh metrics in the route cache.
> @@ -684,6 +692,8 @@ 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)
>   
>   tcp_retries1 - INTEGER
>   	This value influences the time, after which TCP decides, that
> @@ -739,6 +749,8 @@ tcp_rmem - vector of 3 INTEGERs: min, default, max
>   
>   tcp_sack - BOOLEAN
>   	Enable select acknowledgments (SACKS).
> +
> +	Default: 1 (enabled)
>   
>   tcp_comp_sack_delay_ns - LONG INTEGER
>   	TCP tries to reduce number of SACK sent, using a timer
> @@ -766,7 +778,7 @@ 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.
>   
> -	Default : true
> +	Default : 1 (enabled)

Default: 1 (enabled)

>   
>   tcp_slow_start_after_idle - BOOLEAN
>   	If set, provide RFC2861 behavior and time out the congestion
> @@ -781,7 +793,7 @@ tcp_stdurg - BOOLEAN
>   	Most hosts use the older BSD interpretation, so if you turn this on
>   	Linux might not communicate correctly with them.


Thanks,
Alok

[PATCH v2 1/2] docs: net: sysctl documentation cleanup

[Abdelrahman Fekry]

Changes in v2:
- Deleted space before colon for consistency
- Standardized more boolean representation (0/1 with enabled/disabled)

Signed-off-by: Abdelrahman Fekry <abdelrahmanfekry375@gmail.com>
---
 Documentation/networking/ip-sysctl.rst | 47 ++++++++++++++++++++------
 1 file changed, 37 insertions(+), 10 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/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
 ==============================
 
 ip_forward - BOOLEAN
-	- 0 - disabled (default)
-	- not 0 - enabled
+	- 0 (disabled)
+	- 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)
+
+	Default: 0 (disabled)
 
 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.
 
-	Default: 0
+	Default: 0 (disabled)
 
 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.
 
-	Default : 1
+	Default: 1 (enabled)
 
 tcp_available_congestion_control - STRING
 	Shows the available congestion control choices that are registered.
@@ -407,6 +409,12 @@ 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
@@ -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)
 
 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)
 
 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
 
 tcp_sack - BOOLEAN
 	Enable select acknowledgments (SACKS).
+
+	Default: 1 (enabled)
 
 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.
 
-	Default : true
+	Default: 1 (enabled)
 
 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.
 
-	Default: FALSE
+	Default: 0 (disabled)
 
 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
 
 tcp_window_scaling - BOOLEAN
 	Enable window scaling as defined in RFC1323.
+	- 0 (disabled)
+	- 1 (enabled)
+
+	Default: 1 (enabled)
 
 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.
 
-	Default: FALSE
+	Default: 0 (disabled)
 
 tcp_plb_idle_rehash_rounds - INTEGER
 	Number of consecutive congested rounds (RTT) seen after which
@@ -1352,7 +1370,7 @@ cipso_rbm_optfmt - BOOLEAN
 
 	Default: 0
 
-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.
 
-	Default: 1
+	Default: 1 (enabled)
 
 icmp_errors_use_inbound_ifaddr - BOOLEAN
 
@@ -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.
 
-	Default: 0
+	Default: 0 (disabled)
 
 igmp_max_memberships - INTEGER
 	Change the maximum number of multicast groups we can subscribe to.
@@ -1933,10 +1951,15 @@ mcast_resolicit - INTEGER
 
 disable_policy - BOOLEAN
 	Disable IPSEC policy (SPD) for this interface
+
+	Default: 0
+
 
 disable_xfrm - BOOLEAN
 	Disable IPSEC encryption on this interface, whatever the policy
 
+	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
 
 ignore_routes_with_linkdown - BOOLEAN
         Ignore routes whose link is down when performing a FIB lookup.
+
+        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.
+
+	Default: 0 (disabled)
 
 drop_unicast_in_l2_multicast - BOOLEAN
 	Drop any unicast IP packets that are received in link-layer
-- 
2.25.1

Re: [PATCH v2 1/2] docs: net: sysctl documentation cleanup

[Jakub Kicinski]

On Sat, 14 Jun 2025 12:25:42 +0300 Abdelrahman Fekry wrote:
> Changes in v2:
> - Deleted space before colon for consistency
> - Standardized more boolean representation (0/1 with enabled/disabled)

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.

[PATCH 2/2] docs: net: clarify sysctl value constraints

[Abdelrahman Fekry]

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.

Signed-off-by: Abdelrahman Fekry <abdelrahmanfekry375@gmail.com>
---
 Documentation/networking/ip-sysctl.rst | 50 +++++++++++++++++++++++---
 1 file changed, 45 insertions(+), 5 deletions(-)

diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index f7ff8c53f412..99e786915204 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -68,6 +68,8 @@ ip_forward_use_pmtu - BOOLEAN
 
 	- 0 - disabled
 	- 1 - enabled
+
+	note: Accepts integer values (0-255) but only 0/1 have defined behaviour.
 
 fwmark_reflect - BOOLEAN
 	Controls the fwmark of kernel-generated IPv4 reply packets that are not
@@ -89,6 +91,8 @@ fib_multipath_use_neigh - BOOLEAN
 
 	- 0 - disabled
 	- 1 - enabled
+
+	note: Accepts integer values (0-255) but only 0/1 have defined behaviour.
 
 fib_multipath_hash_policy - INTEGER
 	Controls which hash policy to use for multipath routes. Only valid
@@ -489,6 +493,8 @@ tcp_fwmark_accept - BOOLEAN
 	unaffected.
 
 	Default: 0
+
+	note: Accepts integer values (0-255) but only 0/1 have defined behaviour.
 
 tcp_invalid_ratelimit - INTEGER
 	Limit the maximal rate for sending duplicate acknowledgments
@@ -603,6 +609,8 @@ 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.
 
 tcp_mtu_probing - INTEGER
 	Controls TCP Packetization-Layer Path MTU Discovery.  Takes three
@@ -636,6 +644,8 @@ tcp_no_ssthresh_metrics_save - BOOLEAN
 	Controls whether TCP saves ssthresh metrics in the route cache.
 
 	Default is 1, which disables ssthresh metrics.
+
+	note: Accepts integer values (0-255) but only 0/1 have defined behaviour.
 
 tcp_orphan_retries - INTEGER
 	This value influences the timeout of a locally closed TCP connection,
@@ -703,7 +713,9 @@ tcp_retries1 - INTEGER
 
 	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.
@@ -751,6 +763,8 @@ tcp_sack - BOOLEAN
 	Enable select acknowledgments (SACKS).
 	
 	Default: 1 (enabled)
+
+	note: Accepts integer values (0-255) but only 0/1 have defined behaviour.
 
 tcp_comp_sack_delay_ns - LONG INTEGER
 	TCP tries to reduce number of SACK sent, using a timer
@@ -787,6 +801,8 @@ tcp_slow_start_after_idle - BOOLEAN
 	be timed out after an idle period.
 
 	Default: 1
+
+	note: Accepts integer values (0-255) but only 0/1 have defined behaviour.
 
 tcp_stdurg - BOOLEAN
 	Use the Host requirements interpretation of the TCP urgent pointer field.
@@ -794,6 +810,8 @@ tcp_stdurg - BOOLEAN
 	Linux might not communicate correctly with them.
 
 	Default: 0 (disabled)
+
+	note: Accepts integer values (0-255) but only 0/1 have defined behaviour.
 
 tcp_synack_retries - INTEGER
 	Number of times SYNACKs for a passive TCP connection attempt will
@@ -1034,6 +1052,8 @@ tcp_window_scaling - BOOLEAN
 	- 1 - Enabled.
 	
 	Default: 1 (enabled)
+
+	note: Accepts integer values (0-255) but only 0/1 have defined behaviour.
 
 tcp_shrink_window - BOOLEAN
 	This changes how the TCP receive window is calculated.
@@ -1049,6 +1069,8 @@ tcp_shrink_window - BOOLEAN
 			scaling factor is also in effect.
 
 	Default: 0
+
+	note: Accepts integer values (0-255) but only 0/1 have defined behaviour.
 
 tcp_wmem - vector of 3 INTEGERs: min, default, max
 	min: Amount of memory reserved for send buffers for TCP sockets.
@@ -1104,7 +1126,9 @@ tcp_thin_linear_timeouts - BOOLEAN
 	Documentation/networking/tcp-thin.rst
 
 	Default: 0
-
+
+	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
@@ -1367,6 +1391,9 @@ cipso_rbm_optfmt - BOOLEAN
 	categories in order to make the packet data 32-bit aligned.
 
 	Default: 0
+
+	note: Accepts integer values (0-255) but only 0/1 have defined behaviour.
+
 
 cipso_rbm_strictvalid - BOOLEAN
 	If set, do a very strict check of the CIPSO option when
@@ -1377,6 +1404,9 @@ cipso_rbm_strictvalid - BOOLEAN
 	with other implementations that require strict checking.
 
 	Default: 0
+
+	note: Accepts integer values (0-255) but only 0/1 have defined behaviour.
+
 
 IP Variables
 ============
@@ -1437,6 +1467,9 @@ ip_nonlocal_bind - BOOLEAN
 	which can be quite useful - but may break some applications.
 
 	Default: 0
+
+	note: Accepts integer values (0-255) but only 0/1 have defined behaviour.
+
 
 ip_autobind_reuse - BOOLEAN
 	By default, bind() does not select the ports automatically even if
@@ -1447,6 +1480,8 @@ ip_autobind_reuse - BOOLEAN
 	option should only be set by experts.
 	Default: 0
 
+	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
@@ -1476,13 +1511,16 @@ tcp_early_demux - BOOLEAN
 	Enable early demux for established TCP sockets.
 
 	Default: 1
+	note: Accepts integer values (0-255) but only 0/1 have defined behaviour.
+
 
 udp_early_demux - BOOLEAN
 	Enable early demux for connected UDP sockets. Disable this if
 	your system could experience more unconnected load.
 
 	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.
@@ -1815,7 +1853,7 @@ src_valid_mark - BOOLEAN
 	  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
+	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.
@@ -2324,7 +2362,9 @@ fwmark_reflect - BOOLEAN
 	fwmark of the packet they are replying to.
 
 	Default: 0
-
+
+	note: Accepts integer values (0-255) but only 0/1 have defined behaviour.
+
 ``conf/interface/*``:
 	Change special settings per interface.
 
-- 
2.25.1

Re: [PATCH 2/2] docs: net: clarify sysctl value constraints

[Jacob Keller]

On 6/12/2025 9:29 AM, Abdelrahman Fekry wrote:
> 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.
> 
> Signed-off-by: Abdelrahman Fekry <abdelrahmanfekry375@gmail.com>
> ---
>  Documentation/networking/ip-sysctl.rst | 50 +++++++++++++++++++++++---
>  1 file changed, 45 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
> index f7ff8c53f412..99e786915204 100644
> --- a/Documentation/networking/ip-sysctl.rst
> +++ b/Documentation/networking/ip-sysctl.rst
> @@ -68,6 +68,8 @@ ip_forward_use_pmtu - BOOLEAN
>  
>  	- 0 - disabled
>  	- 1 - enabled
> +
> +	note: Accepts integer values (0-255) but only 0/1 have defined behaviour.
>  

Hm. In many cases any non-zero value might be interpreted as "enabled" I
suppose that is simply "undefined behavior"?