af_packet: when sending ethernet frames, parse header for skb->protocol

This may be necessary when the SKB is passed to other layers on the go,
which check the protocol field on their own. An example is a VLAN packet
sent out using AF_PACKET on a bridge interface. The bridging code checks
the SKB size, accounting for any VLAN header only if the protocol field
is set accordingly.

Note that eth_type_trans() sets skb->dev to the passed argument, so this
can be skipped in packet_snd() for ethernet frames, as well.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 2 deletions

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 4cb28a7f639b..71db35ecba39 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -88,6 +88,7 @@
 #include <linux/virtio_net.h>
 #include <linux/errqueue.h>
 #include <linux/net_tstamp.h>
+#include <linux/if_arp.h>
 
 #ifdef CONFIG_INET
 #include <net/inet_common.h>
@@ -2005,6 +2006,9 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
                 if (unlikely(err))
                         return err;
 
+                if (dev->type == ARPHRD_ETHER)
+                        skb->protocol = eth_type_trans(skb, dev);
+
                 data += dev->hard_header_len;
                 to_write -= dev->hard_header_len;
         }
@@ -2324,6 +2328,13 @@ static int packet_snd(struct socket *sock,
 
         sock_tx_timestamp(sk, &skb_shinfo(skb)->tx_flags);
 
+        if (dev->type == ARPHRD_ETHER) {
+                skb->protocol = eth_type_trans(skb, dev);
+        } else {
+                skb->protocol = proto;
+                skb->dev = dev;
+        }
+
         if (!gso_type && (len > dev->mtu + reserve + extra_len)) {
                 /* Earlier code assumed this would be a VLAN pkt,
                  * double-check this now that we have the actual
@@ -2338,8 +2349,6 @@ static int packet_snd(struct socket *sock,
                 }
         }
 
-        skb->protocol = proto;
-        skb->dev = dev;
         skb->priority = sk->sk_priority;
         skb->mark = sk->sk_mark;