From: Stefano Brivio <sbrivio@redhat.com>
Date: Thu, 15 Mar 2018 16:17:13 +0000 (+0100)
Subject: vti6: Fix dev->max_mtu setting
X-Git-Tag: v5.15~9189^2~13^2~1
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=f8a554b4aa9686bb2c12f6bae516e58783289a03;p=platform%2Fkernel%2Flinux-starfive.git

vti6: Fix dev->max_mtu setting

We shouldn't allow a tunnel to have IP_MAX_MTU as MTU, because
another IPv6 header is going on top of our packets. Without this
patch, we might end up building packets bigger than IP_MAX_MTU.

Fixes: b96f9afee4eb ("ipv4/6: use core net MTU range checking")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Acked-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
---

diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
index 9711751..ce18cd2 100644
--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -879,7 +879,7 @@ static void vti6_dev_setup(struct net_device *dev)
 
 	dev->type = ARPHRD_TUNNEL6;
 	dev->min_mtu = IPV6_MIN_MTU;
-	dev->max_mtu = IP_MAX_MTU;
+	dev->max_mtu = IP_MAX_MTU - sizeof(struct ipv6hdr);
 	dev->flags |= IFF_NOARP;
 	dev->addr_len = sizeof(struct in6_addr);
 	netif_keep_dst(dev);