Re: [PATCH net] net: sched: act_mirred: drop skb's dst_entry in ingress redirection

From: Zhiyuan Hou
Date: Mon Oct 14 2019 - 03:08:59 EST

On 2019/10/13 3:34 äå, Sergei Shtylyov wrote:

On 10/12/2019 10:16 AM, Zhiyuan Hou wrote:

In act_mirred's ingress redirection, if the skb's dst_entry is valid
when call function netif_receive_skb, the fllowing l3 stack process
Following or flowing?
Sorry, it should be following. I will change it in next version.
(ip_rcv_finish_core) will check dst_entry and skip the routing
decision. Using the old dst_entry is unexpected and may discard the
skb in some case. For example dst->dst_input points to dst_discard.

This patch drops the skb's dst_entry before calling netif_receive_skb
so that the skb can be made routing decision like a normal ingress

Signed-off-by: Zhiyuan Hou<zhiyuan2048@xxxxxxxxxxxxxxxxx>
net/sched/act_mirred.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
index 9ce073a05414..6108a64c0cd5 100644
--- a/net/sched/act_mirred.c
+++ b/net/sched/act_mirred.c
@@ -298,8 +299,10 @@ static int tcf_mirred_act(struct sk_buff *skb, const struct tc_action *a,
if (!want_ingress)
err = dev_queue_xmit(skb2);
- else
+ else {
+ skb_dst_drop(skb2);
err = netif_receive_skb(skb2);
+ }
If you introduce {} in one *if* branch, {} should be added to the other branches as well,
says CodingStyle.
I will change it in next version . Thanks.

MBR, Sergei