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[73.241.150.70]) by smtp.gmail.com with ESMTPSA id 192sm20582422pfb.110.2019.10.14.05.46.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Oct 2019 05:46:04 -0700 (PDT) Subject: Re: [PATCH net] net: sched: act_mirred: drop skb's dst_entry in ingress redirection To: Zhiyuan Hou , Jamal Hadi Salim , Cong Wang , Jiri Pirko , "David S . Miller" Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20191012071620.8595-1-zhiyuan2048@linux.alibaba.com> <2d816fb6-befb-aaeb-328b-539507022a22@gmail.com> <31b4e85e-bdf8-6462-dc79-06ff8d98b6cf@linux.alibaba.com> From: Eric Dumazet Message-ID: <4d23d69d-f716-afb4-8db6-c21b5ccd7c44@gmail.com> Date: Mon, 14 Oct 2019 05:46:02 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <31b4e85e-bdf8-6462-dc79-06ff8d98b6cf@linux.alibaba.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 >>> --- >>>   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 >>>   #include >>>   #include >>> +#include >>>   #include >>>   #include >>>   #include >>> @@ -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.