network: Allow af_packet to transmit +4 bytes for VLAN packets.
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>
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index c60649e..5efef5b 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -465,7 +465,7 @@
*/
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 @@
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 @@
}
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 @@
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;