af_packet: fix the tx skb protocol in raw sockets with ETH_P_ALL

I am using "protocol ip" filters in TC to manipulate TC flower
classifiers, which are only available with "protocol ip". However,
I faced an issue that packets sent via raw sockets with ETH_P_ALL
did not match the ip filters even if they did satisfy the condition
(e.g., DHCP offer from dhcpd).

I have determined that the behavior was caused by an unexpected
value stored in skb->protocol, namely, ETH_P_ALL instead of ETH_P_IP,
when packets were sent via raw sockets with ETH_P_ALL set.

IMHO, storing ETH_P_ALL in skb->protocol is not appropriate for
packets sent via raw sockets because ETH_P_ALL is not a real ether
type used on wire, but a virtual one.

This patch fixes the tx protocol selection in cases of transmission
via raw sockets created with ETH_P_ALL so that it asks the driver to
extract protocol from the Ethernet header.

Fixes: 75c65772c3 ("net/packet: Ask driver for protocol if not provided by user")
Signed-off-by: Yoshiki Komachi <komachi.yoshiki@lab.ntt.co.jp>
Acked-by: Willem de Bruijn <willemb@google.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 8754d7c93b84b2d6e873a2340f3203c8a92d3bdd..323655a256746604b2d25e226f33a95f0af57233 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1852,7 +1852,8 @@ static int packet_rcv_spkt(struct sk_buff *skb, struct net_device *dev,
 
 static void packet_parse_headers(struct sk_buff *skb, struct socket *sock)
 {
-       if (!skb->protocol && sock->type == SOCK_RAW) {
+       if ((!skb->protocol || skb->protocol == htons(ETH_P_ALL)) &&
+           sock->type == SOCK_RAW) {
                skb_reset_mac_header(skb);
                skb->protocol = dev_parse_header_protocol(skb);
        }