From b83557bc6f560433fe5d727e241069f8db5ba709 Mon Sep 17 00:00:00 2001 From: Paolo Abeni Date: Mon, 2 Feb 2026 12:43:14 +0100 Subject: [PATCH] net: gro: fix outer network offset [ Upstream commit 5c2c3c38be396257a6a2e55bd601a12bb9781507 ] The udp GRO complete stage assumes that all the packets inserted the RX have the `encapsulation` flag zeroed. Such assumption is not true, as a few H/W NICs can set such flag when H/W offloading the checksum for an UDP encapsulated traffic, the tun driver can inject GSO packets with UDP encapsulation and the problematic layout can also be created via a veth based setup. Due to the above, in the problematic scenarios, udp4_gro_complete() uses the wrong network offset (inner instead of outer) to compute the outer UDP header pseudo checksum, leading to csum validation errors later on in packet processing. Address the issue always clearing the encapsulation flag at GRO completion time. Such flag will be set again as needed for encapsulated packets by udp_gro_complete(). Fixes: 5ef31ea5d053 ("net: gro: fix udp bad offset in socket lookup by adding {inner_}network_offset to napi_gro_cb") Reviewed-by: Willem de Bruijn Signed-off-by: Paolo Abeni Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/562638dbebb3b15424220e26a180274b387e2a88.1770032084.git.pabeni@redhat.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/core/gro.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/core/gro.c b/net/core/gro.c index 0ad549b07e03..40aaac4e04f3 100644 --- a/net/core/gro.c +++ b/net/core/gro.c @@ -265,6 +265,8 @@ static void napi_gro_complete(struct napi_struct *napi, struct sk_buff *skb) goto out; } + /* NICs can feed encapsulated packets into GRO */ + skb->encapsulation = 0; rcu_read_lock(); list_for_each_entry_rcu(ptype, head, list) { if (ptype->type != type || !ptype->callbacks.gro_complete)