3.16.75-rc1 review patch. If anyone has any objections, please let me know.
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From: Jakub Kicinski jakub.kicinski@netronome.com
commit 177b8007463c4f36c9a2c7ce7aa9875a4cad9bd5 upstream.
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 Acked-by: Cong Wang xiyou.wangcong@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Ben Hutchings ben@decadent.org.uk --- net/sched/sch_netem.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)
--- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -440,8 +440,7 @@ static int netem_enqueue(struct sk_buff 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; @@ -495,6 +494,7 @@ static int netem_enqueue(struct sk_buff segs = netem_segment(skb, sch); if (!segs) return rc_drop; + qdisc_skb_cb(segs)->pkt_len = segs->len; } else { segs = skb; } @@ -575,6 +575,11 @@ static int netem_enqueue(struct sk_buff
finish_segs: if (segs) { + unsigned int len, last_len; + int nb = 0; + + len = skb->len; + while (segs) { skb2 = segs->next; segs->next = NULL; @@ -590,9 +595,7 @@ finish_segs: } 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; }