Hi Guillaume,

On Thu, Oct 02, 2025 at 04:43:44PM +0200, Guillaume Nault wrote:

On Fri, Sep 19, 2025 at 12:54:01PM +0200, Guillaume Nault wrote:

quoted

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?

Nope, I was attending a conference last week and didn't have time to
look at this patch.

I'll try to have a look later today.  Thanks for the ping!


Have a lovely day!
Alex

quoted

Signed-off-by: Guillaume Nault <redacted>
---
 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

-- 
<https://www.alejandro-colomar.es>
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