[PATCH net] rxrpc: Fix ipv6 path MTU discovery

[David Howells <dhowells@redhat.com>]

rxrpc path MTU discovery currently only makes use of ICMPv4, but not
ICMPv6, which means that pmtud for IPv6 doesn't work correctly.  Fix it to
check for ICMPv6 messages also.

Fixes: eeaedc5449d9 ("rxrpc: Implement path-MTU probing using padded PING ACKs (RFC8899)")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Paolo Abeni <pabeni@redhat.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: netdev@vger.kernel.org
---
 net/rxrpc/peer_event.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/rxrpc/peer_event.c b/net/rxrpc/peer_event.c
index e874c31fa901..bc283da9ee40 100644
--- a/net/rxrpc/peer_event.c
+++ b/net/rxrpc/peer_event.c
@@ -169,6 +169,13 @@ void rxrpc_input_error(struct rxrpc_local *local, struct sk_buff *skb)
 		goto out;
 	}
 
+	if ((serr->ee.ee_origin == SO_EE_ORIGIN_ICMP6 &&
+	     serr->ee.ee_type == ICMPV6_PKT_TOOBIG &&
+	     serr->ee.ee_code == 0)) {
+		rxrpc_adjust_mtu(peer, serr->ee.ee_info);
+		goto out;
+	}
+
 	rxrpc_store_error(peer, skb);
 out:
 	rxrpc_put_peer(peer, rxrpc_peer_put_input_error);