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ip6_gre: Fix MTU setting for ip6gretap 

When creat an ip6gretap interface with an unreachable route,
the MTU is about 14 bytes larger than what was needed.

If the remote address is reachable:
ping6 2001:0:130::1 -c 2
PING 2001:0:130::1(2001:0:130::1) 56 data bytes
64 bytes from 2001:0:130::1: icmp_seq=1 ttl=64 time=1.46 ms
64 bytes from 2001:0:130::1: icmp_seq=2 ttl=64 time=81.1 ms

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Haishuang Yan 2016-05-21 18:17:34 +08:00 committed by David S. Miller
parent 54b9430f04
commit 1b227e5366
1 changed files with 2 additions and 0 deletions
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2
net/ipv6/ip6_gre.c
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@ -1027,6 +1027,8 @@ static int ip6gre_tunnel_init_common(struct net_device *dev)
dev->hard_header_len = LL_MAX_HEADER + t_hlen;
dev->mtu = ETH_DATA_LEN - t_hlen;
if (dev->type == ARPHRD_ETHER)
dev->mtu -= ETH_HLEN;
if (!(tunnel->parms.flags & IP6_TNL_F_IGN_ENCAP_LIMIT))
dev->mtu -= 8;