Commit 18bed891 authored Mar 18, 2019 by Yoshiki Komachi Committed by David S. Miller Mar 18, 2019

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: 75c65772 ("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>

parent a4dc6a49

net/packet/af_packet.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -1852,7 +1852,8 @@ oom:

		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);
		}

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