Commit c56cae23 authored Sep 13, 2018 by Toke Høiland-Jørgensen Committed by David S. Miller Sep 13, 2018

gso_segment: Reset skb->mac_len after modifying network header



When splitting a GSO segment that consists of encapsulated packets, the
skb->mac_len of the segments can end up being set wrong, causing packet
drops in particular when using act_mirred and ifb interfaces in
combination with a qdisc that splits GSO packets.

This happens because at the time skb_segment() is called, network_header
will point to the inner header, throwing off the calculation in
skb_reset_mac_len(). The network_header is subsequently adjust by the
outer IP gso_segment handlers, but they don't set the mac_len.

Fix this by adding skb_reset_mac_len() calls to both the IPv4 and IPv6
gso_segment handlers, after they modify the network_header.

Many thanks to Eric Dumazet for his help in identifying the cause of
the bug.

Acked-by: Dave Taht <dave.taht@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent bffb9b51

net/ipv4/af_inet.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -1377,6 +1377,7 @@ struct sk_buff inet_gso_segment(struct sk_buff skb,
		if (encap)
		skb_reset_inner_headers(skb);
		skb->network_header = (u8 *)iph - skb->head;
		skb_reset_mac_len(skb);
		} while ((skb = skb->next));

		out:

net/ipv6/ip6_offload.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -115,6 +115,7 @@ static struct sk_buff ipv6_gso_segment(struct sk_buff skb,
		payload_len = skb->len - nhoff - sizeof(*ipv6h);
		ipv6h->payload_len = htons(payload_len);
		skb->network_header = (u8 *)ipv6h - skb->head;
		skb_reset_mac_len(skb);

		if (udpfrag) {
		int err = ip6_find_1stfragopt(skb, &prevhdr);