network: Allow af_packet to transmit +4 bytes for VLAN packets.
Ben Greear [Fri, 11 Feb 2011 09:35:18 +0000 (09:35 +0000)]
This allows user-space to send a '1500' MTU VLAN packet on a
1500 MTU ethernet frame.  The extra 4 bytes of a VLAN header is
not usually charged against the MTU when other parts of the
network stack is transmitting vlans...

Signed-off-by: Ben Greear <greearb@candelatech.com>
Reviewed-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/packet/af_packet.c

index c60649e..5efef5b 100644 (file)
@@ -465,7 +465,7 @@ retry:
         */
 
        err = -EMSGSIZE;
-       if (len > dev->mtu + dev->hard_header_len)
+       if (len > dev->mtu + dev->hard_header_len + VLAN_HLEN)
                goto out_unlock;
 
        if (!skb) {
@@ -496,6 +496,19 @@ retry:
                goto retry;
        }
 
+       if (len > (dev->mtu + dev->hard_header_len)) {
+               /* Earlier code assumed this would be a VLAN pkt,
+                * double-check this now that we have the actual
+                * packet in hand.
+                */
+               struct ethhdr *ehdr;
+               skb_reset_mac_header(skb);
+               ehdr = eth_hdr(skb);
+               if (ehdr->h_proto != htons(ETH_P_8021Q)) {
+                       err = -EMSGSIZE;
+                       goto out_unlock;
+               }
+       }
 
        skb->protocol = proto;
        skb->dev = dev;
@@ -1199,7 +1212,7 @@ static int packet_snd(struct socket *sock,
        }
 
        err = -EMSGSIZE;
-       if (!gso_type && (len > dev->mtu+reserve))
+       if (!gso_type && (len > dev->mtu + reserve + VLAN_HLEN))
                goto out_unlock;
 
        err = -ENOBUFS;
@@ -1224,6 +1237,20 @@ static int packet_snd(struct socket *sock,
        if (err < 0)
                goto out_free;
 
+       if (!gso_type && (len > dev->mtu + reserve)) {
+               /* Earlier code assumed this would be a VLAN pkt,
+                * double-check this now that we have the actual
+                * packet in hand.
+                */
+               struct ethhdr *ehdr;
+               skb_reset_mac_header(skb);
+               ehdr = eth_hdr(skb);
+               if (ehdr->h_proto != htons(ETH_P_8021Q)) {
+                       err = -EMSGSIZE;
+                       goto out_free;
+               }
+       }
+
        skb->protocol = proto;
        skb->dev = dev;
        skb->priority = sk->sk_priority;