Commit 8be33ecf authored Nov 09, 2020 by Alexander Lobakin Committed by Jakub Kicinski Nov 09, 2020

net: skb_vlan_untag(): don't reset transport offset if set by GRO layer

Similar to commit fda55eca
("net: introduce skb_transport_header_was_set()"), avoid resetting
transport offsets that were already set by GRO layer. This not only
mirrors the behavior of __netif_receive_skb_core(), but also makes
sense when it comes to UDP GSO fraglists forwarding: transport offset
of such skbs is set only once by GRO receive callback and remains
untouched and correct up to the xmitting driver in 1:1 case, but
becomes junk after untagging in ingress VLAN case and breaks UDP
GSO offload. This does not happen after this change, and all types
of forwarding of UDP GSO fraglists work as expected.

Since v1 [1]:
 - keep the code 1:1 with __netif_receive_skb_core() (Jakub).

[1] https://lore.kernel.org/netdev/zYurwsZRN7BkqSoikWQLVqHyxz18h4LhHU4NFa2Vw@cp4-web-038.plabs.ch



Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Link: https://lore.kernel.org/r/7JgIkgEztzt0W6ZtC9V9Cnk5qfkrUFYcpN871syCi8@cp4-web-040.plabs.ch


Signed-off-by: Jakub Kicinski <kuba@kernel.org>

parent 52643b78

net/core/skbuff.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -5441,6 +5441,7 @@ struct sk_buff skb_vlan_untag(struct sk_buff skb)
		goto err_free;

		skb_reset_network_header(skb);
		if (!skb_transport_header_was_set(skb))
		skb_reset_transport_header(skb);
		skb_reset_mac_len(skb);

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