From: Edward Cree <ecree@solarflare.com>
Date: Tue, 19 Sep 2017 17:45:56 +0000 (+0100)
Subject: net: change skb->mac_header when Generic XDP calls adjust_head
X-Git-Tag: v4.13.6~135
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=bf324b4822c9a2419d00b273ba8a5d36298203be;p=users%2Fdwmw2%2Flinux.git

net: change skb->mac_header when Generic XDP calls adjust_head


[ Upstream commit 92dd5452c1be873a1193561f4f691763103d22ac ]

Since XDP's view of the packet includes the MAC header, moving the start-
 of-packet with bpf_xdp_adjust_head needs to also update the offset of the
 MAC header (which is relative to skb->head, not to the skb->data that was
 changed).
Without this, tcpdump sees packets starting from the old MAC header rather
 than the new one, at least in my tests on the loopback device.

Fixes: b5cdae3291f7 ("net: Generic XDP")
Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/net/core/dev.c b/net/core/dev.c
index 86b4b0a79e7ab..6fa30a4c60eff 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4408,6 +4408,7 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
 		__skb_pull(skb, off);
 	else if (off < 0)
 		__skb_push(skb, -off);
+	skb->mac_header += off;
 
 	switch (act) {
 	case XDP_TX: