Probably something like this is needed (untested).
This issue was discovered when looking at the skb_checksum path for the
netem corruption operation, but it is a general problem.
Network emulation operations like corruption and drop want to operate
on a per-packet (not per-segment) basis. This patch does GSO in software
if necessary to break up packets. Code is similar to logic in xfrm_output.
Although it appears that the operation is not work conserving, it is okay
because the higher level qdisc operations account for packets by incrementing
by gso_size.
Signed-off-by: Stephen Hemminger <shemminger@xxxxxxxxxx>
--- a/net/sched/sch_netem.c 2012-01-12 14:57:59.218796226 -0800
+++ b/net/sched/sch_netem.c 2012-01-12 15:21:07.614162912 -0800
@@ -128,6 +128,8 @@ struct netem_skb_cb {
psched_time_t time_to_send;
};
+static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch);
+
static inline struct netem_skb_cb *netem_skb_cb(struct sk_buff *skb)
{
BUILD_BUG_ON(sizeof(skb->cb) <
@@ -355,6 +357,41 @@ static int tfifo_enqueue(struct sk_buff
return qdisc_reshape_fail(nskb, sch);
}
+static int netem_enqueue_gso(struct sk_buff *skb, struct Qdisc *sch)
+{
+ struct sk_buff *segs;
+ int rc;
+
+ segs = skb_gso_segment(skb, 0);
+ kfree_skb(skb);
+
+ if (IS_ERR(segs)) {
+ sch->qstats.drops++;
+ return NET_XMIT_DROP;
+ }
+
+ do {
+ struct sk_buff *nskb = segs->next;
+ int ret;
+
+ segs->next = NULL;
+ ret = netem_enqueue(segs, sch);
+ if (ret == NET_XMIT_DROP) {
+ while ((segs = nskb)) {
+ nskb = segs->next;
+ segs->next = NULL;
+ kfree_skb(segs);
+ }
+ return ret;
+ }
+
+ segs = nskb;
+ } while (segs);
+
+ return NET_XMIT_SUCCESS;
+}
+
+
/*
* Insert one skb into qdisc.
* Note: parent depends on return value to account for queue length.
@@ -370,6 +407,10 @@ static int netem_enqueue(struct sk_buff
int ret;
int count = 1;
+ /* Want to operate on per-packet basis */
+ if (skb_is_gso(skb))
+ return netem_enqueue_gso(skb, sch);
+
/* Random duplication */
if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor))
++count;
--
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