Re: [PATCH net v4 4/4] ipmr: do not drop GSO packets that fit the MTU after segmentation

[Eric Dumazet]

Le mar. 3 nov. 2026 à 13:44, Simon Horman <horms@xxxxxxxxxx> a écrit :
>
> On Sun, Nov 01, 2026 at 05:42:32PM +0100, Julius Bairaktaris wrote:
> > ipmr_prepare_xmit() drops a packet with DF set when skb->len exceeds the
> > route MTU, without checking whether it is a GSO packet. A UDP multicast
> > stream received with fraglist GRO or UDP GRO forwarding enabled is
> > aggregated into GSO packets, and every aggregate is dropped with
> > FragFails, while ip_forward() lets the same packets pass by checking
> > skb_gso_validate_network_len(). Do the same for multicast routing,
> > leaving room for the outer header on tunnel vifs. ip6mr has no such
> > check and leaves GSO packets to ip6_output().
> >
> > On an IPQ8074 router with fraglist GRO on, a 10 Mbit/s stream of
> > 1316-byte DF datagrams routed by igmpproxy loses 14.5 to 15.5% (n=3)
> > and 0% with this change.
> >
> > Fixes: 9fd1ff5d2ac7 ("udp: Support UDP fraglist GRO/GSO.")
> > Signed-off-by: Julius Bairaktaris <julius@xxxxxxxxxxxxxx>
>
> Reviewed-by: Simon Horman <horms@xxxxxxxxxx>

Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>