Merge branch 'ipv6-avoid-atomic-fragment-on-gso-output'

Yan Zhai says:

====================
ipv6: avoid atomic fragment on GSO output

When the ipv6 stack output a GSO packet, if its gso_size is larger than
dst MTU, then all segments would be fragmented. However, it is possible
for a GSO packet to have a trailing segment with smaller actual size
than both gso_size as well as the MTU, which leads to an "atomic
fragment". Atomic fragments are considered harmful in RFC-8021. An
Existing report from APNIC also shows that atomic fragments are more
likely to be dropped even it is equivalent to a no-op [1].

The series contains following changes:
* drop feature RTAX_FEATURE_ALLFRAG, which has been broken. This helps
  simplifying other changes in this set.
* refactor __ip6_finish_output code to separate GSO and non-GSO packet
  processing, mirroring IPv4 side logic.
* avoid generating atomic fragment on GSO packets.

Link: https://www.potaroo.net/presentations/2022-03-01-ipv6-frag.pdf [1]

V4: https://lore.kernel.org/netdev/[email protected]/
V3: https://lore.kernel.org/netdev/[email protected]/
V2: https://lore.kernel.org/netdev/ZS1%[email protected]/
====================

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/net/ipv6/xfrm6_output.c b/net/ipv6/xfrm6_output.c
index ad07904642ca..5f7b1fdbffe6 100644
--- a/net/ipv6/xfrm6_output.c
+++ b/net/ipv6/xfrm6_output.c
@@ -95,7 +95,7 @@ static int __xfrm6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 		return -EMSGSIZE;
 	}
 
-	if (toobig || dst_allfrag(skb_dst(skb)))
+	if (toobig)
 		return ip6_fragment(net, sk, skb,
 				    __xfrm6_output_finish);