ip_fragment: fix subtracting PPPOE_SES_HLEN from mtu twice

6c79bf0f subtracts PPPOE_SES_HLEN from mtu at
the front of ip_fragment(). So the later subtraction should be removed. The
MTU of 802.1q is also 1500, so MTU should not be changed.
Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Signed-off-by: Bart De Schuymer <bdschuym@pandora.bo>
----
 net/ipv4/ip_output.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)
Signed-off-by: Bart De Schuymer <bdschuym@pandora.bo>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_output.c

@@ -446,7 +446,7 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 	int ptr;
 	struct net_device *dev;
 	struct sk_buff *skb2;
-	unsigned int mtu, hlen, left, len, ll_rs, pad;
+	unsigned int mtu, hlen, left, len, ll_rs;
 	int offset;
 	__be16 not_last_frag;
 	struct rtable *rt = skb_rtable(skb);
@@ -585,9 +585,7 @@ int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
 	/* for bridged IP traffic encapsulated inside f.e. a vlan header,
 	 * we need to make room for the encapsulating header
 	 */
-	pad = nf_bridge_pad(skb);
-	ll_rs = LL_RESERVED_SPACE_EXTRA(rt->dst.dev, pad);
-	mtu -= pad;
+	ll_rs = LL_RESERVED_SPACE_EXTRA(rt->dst.dev, nf_bridge_pad(skb));
 
 	/*
 	 *	Fragment the datagram.