From 381601e5bbae78d7c18d946fe874a63957edea13 Mon Sep 17 00:00:00 2001
From: Anders Franzen <Anders.Franzen@ericsson.com>
Date: Wed, 24 Nov 2010 05:47:18 +0000
Subject: [PATCH] Make the ip6_tunnel reflect the true mtu.
The ip6_tunnel always assumes it consumes 40 bytes (ip6 hdr) of the mtu of the
underlaying device. So for a normal ethernet bearer, the mtu of the ip6_tunnel is
1460.
However, when creating a tunnel the encap limit option is enabled by default, and it
consumes 8 bytes more, so the true mtu shall be 1452.
I dont really know if this breaks some statement in some RFC, so this is a request for
comments.
Signed-off-by: Anders Franzen <anders.franzen@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/ipv6/ip6_tunnel.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 2a59610c2a58..70e891a20fb9 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -1175,6 +1175,8 @@ static void ip6_tnl_link_config(struct ip6_tnl *t)
sizeof (struct ipv6hdr);
dev->mtu = rt->rt6i_dev->mtu - sizeof (struct ipv6hdr);
+ if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
+ dev->mtu-=8;
if (dev->mtu < IPV6_MIN_MTU)
dev->mtu = IPV6_MIN_MTU;
@@ -1363,12 +1365,17 @@ static const struct net_device_ops ip6_tnl_netdev_ops = {
static void ip6_tnl_dev_setup(struct net_device *dev)
{
+ struct ip6_tnl *t;
+
dev->netdev_ops = &ip6_tnl_netdev_ops;
dev->destructor = ip6_dev_free;
dev->type = ARPHRD_TUNNEL6;
dev->hard_header_len = LL_MAX_HEADER + sizeof (struct ipv6hdr);
dev->mtu = ETH_DATA_LEN - sizeof (struct ipv6hdr);
+ t = netdev_priv(dev);
+ if (!(t->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
+ dev->mtu-=8;
dev->flags |= IFF_NOARP;
dev->addr_len = sizeof(struct in6_addr);
dev->features |= NETIF_F_NETNS_LOCAL;
--
2.20.1