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>

diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index af503f518278b21f274afe355acbe6815492d15b..a6fe3397728cc8ae23ca56eed367120f64da357c 100644 (file)
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -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;