Patch "ip6_gre: update mtu properly in ip6gre_err" has been added to the 4.12-stable tree

[<gregkh@linuxfoundation.org>]

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

    ip6_gre: update mtu properly in ip6gre_err

to the 4.12-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_gre-update-mtu-properly-in-ip6gre_err.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Thu Sep 14 23:20:23 PDT 2017
From: Xin Long <lucien.xin@gmail.com>
Date: Tue, 5 Sep 2017 17:26:33 +0800
Subject: ip6_gre: update mtu properly in ip6gre_err

From: Xin Long <lucien.xin@gmail.com>


[ Upstream commit 5c25f30c93fdc5bf25e62101aeaae7a4f9b421b3 ]

Now when probessing ICMPV6_PKT_TOOBIG, ip6gre_err only subtracts the
offset of gre header from mtu info. The expected mtu of gre device
should also subtract gre header. Otherwise, the next packets still
can't be sent out.

Jianlin found this issue when using the topo:
  client(ip6gre)<---->(nic1)route(nic2)<----->(ip6gre)server

and reducing nic2's mtu, then both tcp and sctp's performance with
big size data became 0.

This patch is to fix it by also subtracting grehdr (tun->tun_hlen)
from mtu info when updating gre device's mtu in ip6gre_err(). It
also needs to subtract ETH_HLEN if gre dev'type is ARPHRD_ETHER.

Reported-by: Jianlin Shi <jishi@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv6/ip6_gre.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -432,7 +432,9 @@ static void ip6gre_err(struct sk_buff *s
 		}
 		break;
 	case ICMPV6_PKT_TOOBIG:
-		mtu = be32_to_cpu(info) - offset;
+		mtu = be32_to_cpu(info) - offset - t->tun_hlen;
+		if (t->dev->type == ARPHRD_ETHER)
+			mtu -= ETH_HLEN;
 		if (mtu < IPV6_MIN_MTU)
 			mtu = IPV6_MIN_MTU;
 		t->dev->mtu = mtu;


Patches currently in stable-queue which might be from lucien.xin@gmail.com are

queue-4.12/ip6_gre-update-mtu-properly-in-ip6gre_err.patch
queue-4.12/ipv6-set-dst.obsolete-when-a-cached-route-has-expired.patch
queue-4.12/ipv6-do-not-set-sk_destruct-in-ipv6_addrform-sockopt.patch
queue-4.12/sctp-avoid-out-of-bounds-reads-from-address-storage.patch