Messages in this thread | | | Subject | Re: [PATCH net] net: sched: act_mirred: drop skb's dst_entry in ingress redirection | From | Zhiyuan Hou <> | Date | Fri, 18 Oct 2019 00:33:53 +0800 |
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On 2019/10/16 8:13 下午, Eyal Birger wrote: > Hi, > > On Wed, 16 Oct 2019 01:22:01 +0800 > Zhiyuan Hou <zhiyuan2048@linux.alibaba.com> wrote: > >> On 2019/10/15 1:57 上午, Cong Wang wrote: >>> On Sat, Oct 12, 2019 at 12:16 AM Zhiyuan Hou >>> <zhiyuan2048@linux.alibaba.com> wrote: >>>> 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); >>>> + } >>> Good catch! > Indeed! Thanks for fixing this! > >>> I don't want to be picky, but it seems this is only needed >>> when redirecting from egress to ingress, right? That is, >>> ingress to ingress, or ingress to egress is okay? If not, >>> please fix all the cases while you are on it? >> Sure. But I think this patch is also needed when redirecting from >> ingress to ingress. Because we cannot assure that a skb has null dst >> in ingress redirection path. For example, if redirecting a skb from >> loopback's ingress to other device's ingress, the skb will take a >> dst. >> >> As commit logs point out, skb with valid dst cannot be made routing >> decision in following process. original dst may cause skb loss or >> other unexpected behavior. > On the other hand, removing the dst on ingress-to-ingress redirection > may remove LWT information on incoming packets, which may be undesired. Sorry, I do not understand why lwt information is needed on ingress-to-ingress redirection. lwt is used on output path, isn't it? Can you please give more information? > Eyal.
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