From: Cong Wang xiyou.wangcong@gmail.com
[ Upstream commit 3f05e6886a595c9a29a309c52f45326be917823c ]
For qdisc's that support TC filters and set TCQ_F_CAN_BYPASS, notably fq_codel, it makes no sense to let packets bypass the TC filters we setup in any scenario, otherwise our packets steering policy could not be enforced.
This can be reproduced easily with the following script:
ip li add dev dummy0 type dummy ifconfig dummy0 up tc qd add dev dummy0 root fq_codel tc filter add dev dummy0 parent 8001: protocol arp basic action mirred egress redirect dev lo tc filter add dev dummy0 parent 8001: protocol ip basic action mirred egress redirect dev lo ping -I dummy0 192.168.112.1
Without this patch, packets are sent directly to dummy0 without hitting any of the filters. With this patch, packets are redirected to loopback as expected.
This fix is not perfect, it only unsets the flag but does not set it back because we have to save the information somewhere in the qdisc if we really want that. Note, both fq_codel and sfq clear this flag in their ->bind_tcf() but this is clearly not sufficient when we don't use any class ID.
Fixes: 23624935e0c4 ("net_sched: TCQ_F_CAN_BYPASS generalization") Cc: Eric Dumazet edumazet@google.com Signed-off-by: Cong Wang xiyou.wangcong@gmail.com Reviewed-by: Eric Dumazet edumazet@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sched/cls_api.c | 1 + net/sched/sch_fq_codel.c | 2 -- net/sched/sch_sfq.c | 2 -- 3 files changed, 1 insertion(+), 4 deletions(-)
--- a/net/sched/cls_api.c +++ b/net/sched/cls_api.c @@ -1325,6 +1325,7 @@ replay: tcf_chain_tp_insert(chain, &chain_info, tp); tfilter_notify(net, skb, n, tp, block, q, parent, fh, RTM_NEWTFILTER, false); + q->flags &= ~TCQ_F_CAN_BYPASS; } else { if (tp_created) tcf_proto_destroy(tp, NULL); --- a/net/sched/sch_fq_codel.c +++ b/net/sched/sch_fq_codel.c @@ -600,8 +600,6 @@ static unsigned long fq_codel_find(struc static unsigned long fq_codel_bind(struct Qdisc *sch, unsigned long parent, u32 classid) { - /* we cannot bypass queue discipline anymore */ - sch->flags &= ~TCQ_F_CAN_BYPASS; return 0; }
--- a/net/sched/sch_sfq.c +++ b/net/sched/sch_sfq.c @@ -828,8 +828,6 @@ static unsigned long sfq_find(struct Qdi static unsigned long sfq_bind(struct Qdisc *sch, unsigned long parent, u32 classid) { - /* we cannot bypass queue discipline anymore */ - sch->flags &= ~TCQ_F_CAN_BYPASS; return 0; }