Re: [PATCH net-next v4 4/4] net: gro: move L3 flush checks to tcp_gro_receive

Eric Dumazet wrote:

On Mon, Mar 25, 2024 at 7:27 PM Richard Gobert richardbgobert@gmail.com wrote:

...

{inet,ipv6}_gro_receive functions perform flush checks (ttl, flags, iph->id, ...) against all packets in a loop. These flush checks are used currently only in tcp flows in GRO.

I think this is a bug.

GRO should not aggregate packets if their ttl/tos fields do not match.

AFAIU, the only UDP flow where ttl/flush_id need to be checked is when udp_gro_receive_segment calls skb_gro_receive - could you confirm / point out if there are any other flows to which these flush checks may be relevant?

As I've discussed with Willem in v3 I prefer to fix this bug in a separate series.