Messages in this thread | | | Date | Wed, 16 Oct 2019 15:13:07 +0300 | From | Eyal Birger <> | Subject | Re: [PATCH net] net: sched: act_mirred: drop skb's dst_entry in ingress redirection |
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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.
Eyal.
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