[PATCH ipsec] esp: choose the correct inner protocol for GSO on inter address family tunnels

[PATCH ipsec] esp: choose the correct inner protocol for GSO on inter address family tunnels

[Sabrina Dubroca]

Commit 23c7f8d7989e ("net: Fix esp GSO on inter address family
tunnels.") is incomplete. It passes to skb_eth_gso_segment the
protocol for the outer IP version, instead of the inner IP version, so
we end up calling inet_gso_segment on an inner IPv6 packet and
ipv6_gso_segment on an inner IPv4 packet and the packets are dropped.

This patch completes the fix by selecting the correct protocol based
on the inner mode's family.

Fixes: c35fe4106b92 ("xfrm: Add mode handlers for IPsec on layer 2")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
---
 net/ipv4/esp4_offload.c | 5 ++++-
 net/ipv6/esp6_offload.c | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/esp4_offload.c b/net/ipv4/esp4_offload.c
index 935026f4c807..170152772d33 100644
--- a/net/ipv4/esp4_offload.c
+++ b/net/ipv4/esp4_offload.c
@@ -110,7 +110,10 @@ static struct sk_buff *xfrm4_tunnel_gso_segment(struct xfrm_state *x,
 						struct sk_buff *skb,
 						netdev_features_t features)
 {
-	return skb_eth_gso_segment(skb, features, htons(ETH_P_IP));
+	__be16 type = x->inner_mode.family == AF_INET6 ? htons(ETH_P_IPV6)
+						       : htons(ETH_P_IP);
+
+	return skb_eth_gso_segment(skb, features, type);
 }
 
 static struct sk_buff *xfrm4_transport_gso_segment(struct xfrm_state *x,
diff --git a/net/ipv6/esp6_offload.c b/net/ipv6/esp6_offload.c
index 3a293838a91d..79d43548279c 100644
--- a/net/ipv6/esp6_offload.c
+++ b/net/ipv6/esp6_offload.c
@@ -145,7 +145,10 @@ static struct sk_buff *xfrm6_tunnel_gso_segment(struct xfrm_state *x,
 						struct sk_buff *skb,
 						netdev_features_t features)
 {
-	return skb_eth_gso_segment(skb, features, htons(ETH_P_IPV6));
+	__be16 type = x->inner_mode.family == AF_INET ? htons(ETH_P_IP)
+						      : htons(ETH_P_IPV6);
+
+	return skb_eth_gso_segment(skb, features, type);
 }
 
 static struct sk_buff *xfrm6_transport_gso_segment(struct xfrm_state *x,
-- 
2.37.2

Re: [PATCH ipsec] esp: choose the correct inner protocol for GSO on inter address family tunnels

[Steffen Klassert]

On Thu, Aug 25, 2022 at 05:16:51PM +0200, Sabrina Dubroca wrote:
> Commit 23c7f8d7989e ("net: Fix esp GSO on inter address family
> tunnels.") is incomplete. It passes to skb_eth_gso_segment the
> protocol for the outer IP version, instead of the inner IP version, so
> we end up calling inet_gso_segment on an inner IPv6 packet and
> ipv6_gso_segment on an inner IPv4 packet and the packets are dropped.
> 
> This patch completes the fix by selecting the correct protocol based
> on the inner mode's family.
> 
> Fixes: c35fe4106b92 ("xfrm: Add mode handlers for IPsec on layer 2")
> Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>

Applied, thanks a lot Sabrina!