From: Eric Dumazet <eric.dumazet@gmail.com>
To: Zhiyuan Hou <zhiyuan2048@linux.alibaba.com>,
Jamal Hadi Salim <jhs@mojatatu.com>,
Cong Wang <xiyou.wangcong@gmail.com>,
Jiri Pirko <jiri@resnulli.us>,
"David S . Miller" <davem@davemloft.net>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net] net: sched: act_mirred: drop skb's dst_entry in ingress redirection
Date: Mon, 14 Oct 2019 05:46:02 -0700 [thread overview]
Message-ID: <4d23d69d-f716-afb4-8db6-c21b5ccd7c44@gmail.com> (raw)
In-Reply-To: <31b4e85e-bdf8-6462-dc79-06ff8d98b6cf@linux.alibaba.com>
On 10/14/19 12:07 AM, Zhiyuan Hou wrote:
>
> On 2019/10/12 6:59 下午, Eric Dumazet wrote:
>>
>> On 10/12/19 12:16 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
>>> (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
>>> skb.
>>>
>>> Signed-off-by: Zhiyuan Hou <zhiyuan2048@linux.alibaba.com>
>>> ---
>>> 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
>>> @@ -18,6 +18,7 @@
>>> #include <linux/gfp.h>
>>> #include <linux/if_arp.h>
>>> #include <net/net_namespace.h>
>>> +#include <net/dst.h>
>>> #include <net/netlink.h>
>>> #include <net/pkt_sched.h>
>>> #include <net/pkt_cls.h>
>>> @@ -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 (err) {
>>> out:
>>>
>> Why is dst_discard used ?
> When send a skb from local to external, the dst->dst_input will be
> assigned dst_discard after routing decision. So if we redirect these
> skbs to ingress stack, it will be dropped.
>
> For ipvlan l2 mode or macvlan, clsact egress filters on master deivce
> may also meet these skbs even if they came from slave device. Ingress
> redirection on these skbs may drop them on l3 stack.
Can you please add a test, so that we can see what you are trying to do exactly ?
>> This could actually drop packets, for loopback.
>>
>> A Fixes: tag would tremendously help, I wonder if you are not working around
>> the other issue Wei was tracking yesterday ( https://www.spinics.net/lists/netdev/msg604397.html )
> No, this is a different issue ^_^.
Please add a Fixes: tag then.
Thanks.
next prev parent reply other threads:[~2019-10-14 12:46 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-12 7:16 [PATCH net] net: sched: act_mirred: drop skb's dst_entry in ingress redirection Zhiyuan Hou
2019-10-12 10:59 ` Eric Dumazet
2019-10-14 7:07 ` Zhiyuan Hou
2019-10-14 12:46 ` Eric Dumazet [this message]
2019-10-17 16:08 ` Zhiyuan Hou
2019-10-12 19:34 ` Sergei Shtylyov
2019-10-14 7:08 ` Zhiyuan Hou
2019-10-14 17:57 ` Cong Wang
2019-10-15 17:22 ` Zhiyuan Hou
2019-10-16 12:13 ` Eyal Birger
2019-10-17 16:33 ` Zhiyuan Hou
2019-10-18 21:25 ` Eyal Birger
2019-10-21 13:06 ` Zhiyuan Hou
2019-10-21 20:50 ` Cong Wang
2019-10-22 10:37 ` Eyal Birger
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