Subject: [PATCH 24/48] net: change skb->mac_header when Generic XDP calls adjust_head

From: Edward Cree <[email-masked]>
Date: Tue, 19 Sep 2017 18:45:56 +0100

[ 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 <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/core/dev.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 86b4b0a79e7a..6fa30a4c60ef 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:
-- 
2.13.6