From: Simon Horman <horms@kernel.org>
To: Julius Bairaktaris <julius@bairaktaris.de>
Cc: netdev@vger.kernel.org, dsahern@kernel.org, idosch@nvidia.com,
davem@davemloft.net, edumazet@kernel.org, kuba@kernel.org,
pabeni@redhat.com, steffen.klassert@secunet.com,
willemb@google.com, jiayuan.chen@linux.dev,
mfleming@cloudflare.com, almasrymina@google.com,
bigeasy@linutronix.de, richardbgobert@gmail.com,
ecree.xilinx@gmail.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net v4 4/4] ipmr: do not drop GSO packets that fit the MTU after segmentation
Date: Tue, 3 Nov 2026 12:44:38 +0000 [thread overview]
Message-ID: <20261103124438.GM865646@horms.kernel.org> (raw)
In-Reply-To: <3733295a358d34df6220ea924d2b710ca537cf6d.1792838740.git.julius@bairaktaris.de>
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@bairaktaris.de>
Reviewed-by: Simon Horman <horms@kernel.org>
next prev parent reply other threads:[~2026-11-03 12:44 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-01 16:42 [PATCH net v4 0/4] ipmr: forward GSO multicast packets Julius Bairaktaris
2026-11-01 16:42 ` [PATCH net v4 1/4] net: make room for the tunnel header in skb_segment_list() Julius Bairaktaris
2026-11-03 12:43 ` Simon Horman
2026-11-03 13:05 ` Eric Dumazet
2026-11-04 3:42 ` Henry Martin
2026-11-01 16:42 ` [PATCH net v4 2/4] net: gso: count the inner UDP header of encapsulated UDP GSO packets Julius Bairaktaris
2026-11-03 12:44 ` Simon Horman
2026-11-03 13:08 ` Eric Dumazet
2026-11-01 16:42 ` [PATCH net v4 3/4] ipmr: set up GSO state for tunnel vifs Julius Bairaktaris
2026-11-03 12:44 ` Simon Horman
2026-11-03 13:13 ` Eric Dumazet
2026-11-01 16:42 ` [PATCH net v4 4/4] ipmr: do not drop GSO packets that fit the MTU after segmentation Julius Bairaktaris
2026-11-03 12:44 ` Simon Horman [this message]
2026-11-03 13:15 ` Eric Dumazet
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