Patch "ip6_tunnel: allow ip6gre dev mtu to be set below 1280" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

ip6_tunnel: allow ip6gre dev mtu to be set below 1280

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:

     ip6_tunnel-allow-ip6gre-dev-mtu-to-be-set-below-1280.patch

and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Xin Long <[email protected]>
Date: Mon, 25 Dec 2017 14:45:12 +0800
Subject: ip6_tunnel: allow ip6gre dev mtu to be set below 1280

From: Xin Long <[email protected]>

[ Upstream commit 2fa771be953a17f8e0a9c39103464c2574444c62 ]

Commit 582442d6d5bc ("ipv6: Allow the MTU of ipip6 tunnel to be set below 1280") fixed a mtu setting issue. It works for ipip6 tunnel.

But ip6gre dev updates the mtu also with ip6_tnl_change_mtu. Since the inner packet over ip6gre can be ipv4 and it's mtu should also be allowed to set below 1280, the same issue also exists on ip6gre.

This patch is to fix it by simply changing to check if parms.proto is IPPROTO_IPV6 in ip6_tnl_change_mtu instead, to make ip6gre to go to 'else' branch.

---
 net/ipv6/ip6_tunnel.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

@@ -1684,11 +1684,11 @@ int ip6_tnl_change_mtu(struct net_device
 {
 	struct ip6_tnl *tnl = netdev_priv(dev);
 
-	if (tnl->parms.proto == IPPROTO_IPIP) {
-		if (new_mtu < ETH_MIN_MTU)
+	if (tnl->parms.proto == IPPROTO_IPV6) {
+		if (new_mtu < IPV6_MIN_MTU)
 			return -EINVAL;
 	} else {
-		if (new_mtu < IPV6_MIN_MTU)
+		if (new_mtu < ETH_MIN_MTU)
 			return -EINVAL;
 	}
 	if (new_mtu > 0xFFF8 - dev->hard_header_len)

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/ip_gre-remove-the-incorrect-mtu-limit-for-ipgre-tap.patch queue-4.14/ip6_gre-remove-the-incorrect-mtu-limit-for-ipgre-tap.patch queue-4.14/ip6_tunnel-allow-ip6gre-dev-mtu-to-be-set-below-1280.patch queue-4.14/vxlan-update-skb-dst-pmtu-on-tx-path.patch queue-4.14/ip6_tunnel-get-the-min-mtu-properly-in-ip6_tnl_xmit.patch queue-4.14/sctp-fix-the-issue-that-a-__u16-variable-may-overflow-in-sctp_ulpq_renege.patch