Re: [PATCH net v2] net: ipv4: fix stat increase when udp early demux drops the packet

[Sabrina Dubroca <sd@queasysnail.net>]

2025-07-01, 09:49:34 +0200, Antoine Tenart wrote:
> udp_v4_early_demux now returns drop reasons as it either returns 0 or
> ip_mc_validate_source, which returns itself a drop reason. However its
> use was not converted in ip_rcv_finish_core and the drop reason is
> ignored, leading to potentially skipping increasing LINUX_MIB_IPRPFILTER
> if the drop reason is SKB_DROP_REASON_IP_RPFILTER.
> 
> This is a fix and we're not converting udp_v4_early_demux to explicitly
> return a drop reason to ease backports; this can be done as a follow-up.
> 
> Fixes: d46f827016d8 ("net: ip: make ip_mc_validate_source() return drop reason")
> Cc: Menglong Dong <menglong8.dong@gmail.com>
> Reported-by: Sabrina Dubroca <sd@queasysnail.net>
> Signed-off-by: Antoine Tenart <atenart@kernel.org>
> ---
> Changes in v2:
>   - Reset the drop reason to NOT_SPECIFIED if not returning early. The
>     diff remains small and this aligns with the rest of the function.
> ---
>  net/ipv4/ip_input.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)

Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>

Thanks Antoine.

-- 
Sabrina