| Message ID | 20190617181111.5025-2-jakub.kicinski@netronome.com |
|---|---|
| State | Accepted |
| Delegated to: | David Miller |
| Headers | show |
| Series | net: netem: fix issues with corrupting GSO frames | expand |
On Mon, Jun 17, 2019 at 11:11 AM Jakub Kicinski <jakub.kicinski@netronome.com> wrote: > > When GSO frame has to be corrupted netem uses skb_gso_segment() > to produce the list of frames, and re-enqueues the segments one > by one. The backlog length has to be adjusted to account for > new frames. > > The current calculation is incorrect, leading to wrong backlog > lengths in the parent qdisc (both bytes and packets), and > incorrect packet backlog count in netem itself. > > Parent backlog goes negative, netem's packet backlog counts > all non-first segments twice (thus remaining non-zero even > after qdisc is emptied). > > Move the variables used to count the adjustment into local > scope to make 100% sure they aren't used at any stage in > backports. > > Fixes: 6071bd1aa13e ("netem: Segment GSO packets on enqueue") > Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com> > Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com> Looks good! Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index 956ff3da81f4..3b3e2d772c3b 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -439,8 +439,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct netem_skb_cb *cb; struct sk_buff *skb2; struct sk_buff *segs = NULL; - unsigned int len = 0, last_len, prev_len = qdisc_pkt_len(skb); - int nb = 0; + unsigned int prev_len = qdisc_pkt_len(skb); int count = 1; int rc = NET_XMIT_SUCCESS; int rc_drop = NET_XMIT_DROP; @@ -497,6 +496,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, segs = netem_segment(skb, sch, to_free); if (!segs) return rc_drop; + qdisc_skb_cb(segs)->pkt_len = segs->len; } else { segs = skb; } @@ -593,6 +593,11 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, finish_segs: if (segs) { + unsigned int len, last_len; + int nb = 0; + + len = skb->len; + while (segs) { skb2 = segs->next; skb_mark_not_on_list(segs); @@ -608,9 +613,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, } segs = skb2; } - sch->q.qlen += nb; - if (nb > 1) - qdisc_tree_reduce_backlog(sch, 1 - nb, prev_len - len); + qdisc_tree_reduce_backlog(sch, -nb, prev_len - len); } return NET_XMIT_SUCCESS; }
When GSO frame has to be corrupted netem uses skb_gso_segment() to produce the list of frames, and re-enqueues the segments one by one. The backlog length has to be adjusted to account for new frames. The current calculation is incorrect, leading to wrong backlog lengths in the parent qdisc (both bytes and packets), and incorrect packet backlog count in netem itself. Parent backlog goes negative, netem's packet backlog counts all non-first segments twice (thus remaining non-zero even after qdisc is emptied). Move the variables used to count the adjustment into local scope to make 100% sure they aren't used at any stage in backports. Fixes: 6071bd1aa13e ("netem: Segment GSO packets on enqueue") Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com> Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com> --- net/sched/sch_netem.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)