| Message ID | 394385d4-796a-9ada-8f01-53a52d73a418@solarflare.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | [net] net: change skb->mac_header when Generic XDP calls adjust_head | expand |
From: Edward Cree <ecree@solarflare.com> Date: Tue, 19 Sep 2017 18:45:56 +0100 > 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> Applied and queued up for -stable, thanks Edward.
diff --git a/net/core/dev.c b/net/core/dev.c index fb766d9..9a2254f 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3892,6 +3892,7 @@ 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_REDIRECT:
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> --- net/core/dev.c | 1 + 1 file changed, 1 insertion(+)