Commit 64235eab authored by Antoine Tenart's avatar Antoine Tenart Committed by David S. Miller
Browse files

udp: prevent local UDP tunnel packets from being GROed 



GRO has a fundamental issue with UDP tunnel packets as it can't detect
those in a foolproof way and GRO could happen before they reach the
tunnel endpoint. Previous commits have fixed issues when UDP tunnel
packets come from a remote host, but if those packets are issued locally
they could run into checksum issues.

If the inner packet has a partial checksum the information will be lost
in the GRO logic, either in udp4/6_gro_complete or in
udp_gro_complete_segment and packets will have an invalid checksum when
leaving the host.

Prevent local UDP tunnel packets from ever being GROed at the outer UDP
level.

Due to skb->encapsulation being wrongly used in some drivers this is
actually only preventing UDP tunnel packets with a partial checksum to
be GROed (see iptunnel_handle_offloads) but those were also the packets
triggering issues so in practice this should be sufficient.

Fixes: 9fd1ff5d ("udp: Support UDP fraglist GRO/GSO.")
Fixes: 36707061 ("udp: allow forwarding of plain (non-fraglisted) UDP GRO packets")
Suggested-by: default avatarPaolo Abeni <pabeni@redhat.com>
Signed-off-by: default avatarAntoine Tenart <atenart@kernel.org>
Reviewed-by: default avatarWillem de Bruijn <willemb@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f0b8c303

net/ipv4/udp_offload.c

+6 −0
Original line number Diff line number Diff line
@@ -559,6 +559,12 @@ struct sk_buff *udp_gro_receive(struct list_head *head, struct sk_buff *skb, 
	 */

	NAPI_GRO_CB(skb)->is_flist = 0;

	if (!sk || !udp_sk(sk)->gro_receive) {

		/* If the packet was locally encapsulated in a UDP tunnel that

		 * wasn't detected above, do not GRO.

		 */

		if (skb->encapsulation)

			goto out;



		if (skb->dev->features & NETIF_F_GRO_FRAGLIST)

			NAPI_GRO_CB(skb)->is_flist = sk ? !udp_test_bit(GRO_ENABLED, sk) : 1;