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net: correctly handle tunneled traffic on IPV6_CSUM GSO fallback 

NETIF_F_IPV6_CSUM only advertises support for checksum offload of
packets without IPv6 extension headers. Packets with extension
headers must fall back onto software checksumming. Since TSO
depends on checksum offload, those must revert to GSO.

The below commit introduces that fallback. It always checks
network header length. For tunneled packets, the inner header length
must be checked instead. Extend the check accordingly.

A special case is tunneled packets without inner IP protocol. Such as
RFC 6951 SCTP in UDP. Those are not standard IPv6 followed by
transport header either, so also must revert to the software GSO path.

Cc: stable@vger.kernel.org
Fixes: 864e339697 ("net: gso: Forbid IPv6 TSO with extensions on devices with only IPV6_CSUM")
Reported-by: Tangxin Xie <xietangxin@yeah.net>
Closes: https://lore.kernel.org/netdev/0414e7e2-9a1c-4d7c-a99d-b9039cf68f40@yeah.net/
Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260320190148.2409107-1-willemdebruijn.kernel@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Willem de Bruijn 2026-03-20 15:01:46 -04:00 committed by Paolo Abeni
parent d9c2a509c9
commit c4336a07eb
1 changed files with 17 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
net/core/dev.c
View File

@ -3769,6 +3769,22 @@ static netdev_features_t dflt_features_check(struct sk_buff *skb,
return vlan_features_check(skb, features);
}
static bool skb_gso_has_extension_hdr(const struct sk_buff *skb)
{
if (!skb->encapsulation)
return ((skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6 ||
(skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4 &&
vlan_get_protocol(skb) == htons(ETH_P_IPV6))) &&
skb_transport_header_was_set(skb) &&
skb_network_header_len(skb) != sizeof(struct ipv6hdr));
else
return (!skb_inner_network_header_was_set(skb) ||
((skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6 ||
(skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4 &&
inner_ip_hdr(skb)->version == 6)) &&
skb_inner_network_header_len(skb) != sizeof(struct ipv6hdr)));
}
static netdev_features_t gso_features_check(const struct sk_buff *skb,
struct net_device *dev,
netdev_features_t features)
@ -3816,11 +3832,7 @@ static netdev_features_t gso_features_check(const struct sk_buff *skb,
* so neither does TSO that depends on it.
*/
if (features & NETIF_F_IPV6_CSUM &&
(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6 ||
(skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4 &&
vlan_get_protocol(skb) == htons(ETH_P_IPV6))) &&
skb_transport_header_was_set(skb) &&
skb_network_header_len(skb) != sizeof(struct ipv6hdr))
skb_gso_has_extension_hdr(skb))
features &= ~(NETIF_F_IPV6_CSUM | NETIF_F_TSO6 | NETIF_F_GSO_UDP_L4);
return features;