Re: [PATCH] rtnetlink.7: Document metrics attributes (RTAX_*).

[Guillaume Nault <gnault@redhat.com>]

On Fri, Sep 19, 2025 at 12:54:01PM +0200, Guillaume Nault wrote:
> Add a brief explanation of the RTAX attributes that can be used in
> RTA_METRICS.

Hi,

I haven't got any feedback for this patch. Anything wrong with it?

> Signed-off-by: Guillaume Nault <gnault@redhat.com>
> ---
>  man/man7/rtnetlink.7 | 49 +++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 48 insertions(+), 1 deletion(-)
> 
> diff --git a/man/man7/rtnetlink.7 b/man/man7/rtnetlink.7
> index cb9f5155f..a04edce79 100644
> --- a/man/man7/rtnetlink.7
> +++ b/man/man7/rtnetlink.7
> @@ -342,7 +342,11 @@ RTA_OIF:int:Output interface index
>  RTA_GATEWAY:protocol address:The gateway of the route
>  RTA_PRIORITY:int:Priority of route
>  RTA_PREFSRC:protocol address:Preferred source address
> -RTA_METRICS:int:Route metric
> +RTA_METRICS::T{
> +Route metrics
> +.br
> +(see below).
> +T}
>  RTA_MULTIPATH::T{
>  Multipath nexthop data
>  .br
> @@ -384,6 +388,49 @@ routes (in seconds)
>  T}
>  .TE
>  .IP
> +.B RTA_METRICS
> +contains an array of
> +.I struct rtattr
> +with their corresponding attributes:
> +.IP
> +.in +4n
> +.TS
> +tab(:);
> +c s s
> +lb l l.
> +Attributes
> +rta_type:Value type:Description
> +_
> +RTAX_UNSPEC:-:unspecified
> +RTAX_LOCK:__u32:Bit field indicating which RTAX_* attributes are locked
> +RTAX_MTU:__u32:Maximum Transmission Unit for this route
> +RTAX_WINDOW:__u32:Maximum size of the receive window for this route
> +RTAX_RTT:__u32:Estimated round-trip time for this route
> +RTAX_RTTVAR:__u32:Estimated round-trip time variation for this route
> +RTAX_SSTHRESH:__u32:Slow start threshold to use for this route
> +RTAX_CWND:__u32:Maximum size of the congestion window for this route
> +RTAX_ADVMSS:__u32:Maximum Segment Size to advertise for this route
> +RTAX_REORDERING:__u32:Initial reordering level of packets for this route
> +RTAX_HOPLIMIT:__u32:Hop limit (TTL) to use for this route
> +RTAX_INITCWND:__u32:Initial congestion window to use for this route
> +RTAX_FEATURES:__u32:Features to enable for this route specifically
> +RTAX_RTO_MIN:__u32:Minimum Retransmission TimeOut to use for this route
> +RTAX_INITRWND:__u32:Initial size of the receive window for this route
> +RTAX_QUICKACK:__u32:Use quick ack for this route
> +RTAX_CC_ALGO:asciiz string:Congestion Control algorithm to use for this route
> +RTAX_FASTOPEN_NO_COOKIE:__u32:Allow TCP Fast Open without cookie
> +.TE
> +.IP
> +Metrics that are locked with
> +.B RTAX_LOCK
> +take precedence over the values normally used by the kernel
> +(computed or assigned by a sysctl or setsockopt(2)).
> +Therefore, some metrics, like
> +.BR RTAX_RTO_MIN ,
> +have no effect unless their bit is set in
> +.BR RTAX_LOCK .
> +.in
> +.IP
>  .B RTA_MULTIPATH
>  contains several packed instances of
>  .I struct rtnexthop
> -- 
> 2.47.3
>