ip6_tunnel: update mtu properly for ARPHRD_ETHER tunnel device in tx path

Now when updating mtu in tx path, it doesn't consider ARPHRD_ETHER tunnel
device, like ip6gre_tap tunnel, for which it should also subtract ether
header to get the correct mtu.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index f2f21c24915f..a1c24443cd9e 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -1043,6 +1043,7 @@ int ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev, __u8 dsfield,
         struct dst_entry *dst = NULL, *ndst = NULL;
         struct net_device *tdev;
         int mtu;
+        unsigned int eth_hlen = t->dev->type == ARPHRD_ETHER ? ETH_HLEN : 0;
         unsigned int psh_hlen = sizeof(struct ipv6hdr) + t->encap_hlen;
         unsigned int max_headroom = psh_hlen;
         bool use_cache = false;
@@ -1124,7 +1125,7 @@ route_lookup:
                                      t->parms.name);
                 goto tx_err_dst_release;
         }
-        mtu = dst_mtu(dst) - psh_hlen - t->tun_hlen;
+        mtu = dst_mtu(dst) - eth_hlen - psh_hlen - t->tun_hlen;
         if (encap_limit >= 0) {
                 max_headroom += 8;
                 mtu -= 8;
@@ -1133,7 +1134,7 @@ route_lookup:
                 mtu = IPV6_MIN_MTU;
         if (skb_dst(skb) && !t->parms.collect_md)
                 skb_dst(skb)->ops->update_pmtu(skb_dst(skb), NULL, skb, mtu);
-        if (skb->len - t->tun_hlen > mtu && !skb_is_gso(skb)) {
+        if (skb->len - t->tun_hlen - eth_hlen > mtu && !skb_is_gso(skb)) {
                 *pmtu = mtu;
                 err = -EMSGSIZE;
                 goto tx_err_dst_release;