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[73.241.150.70]) by smtp.gmail.com with ESMTPSA id f17sm10481049pgd.8.2019.10.12.03.59.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 12 Oct 2019 03:59:17 -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> From: Eric Dumazet Message-ID: <2d816fb6-befb-aaeb-328b-539507022a22@gmail.com> Date: Sat, 12 Oct 2019 03:59:15 -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: <20191012071620.8595-1-zhiyuan2048@linux.alibaba.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 ? 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 )