[PATCH net-next] netem: add ECN capability

[Eric Dumazet <eric.dumazet@gmail.com>]

From: Eric Dumazet <edumazet@google.com>

Add ECN (Explicit Congestion Notification) marking capability to netem

tc qdisc add dev eth0 root netem drop 0.5 ecn

Instead of dropping packets, try to ECN mark them.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Hagen Paul Pfeifer <hagen@jauu.net>
Cc: Stephen Hemminger <shemminger@vyatta.com>
---
 include/linux/pkt_sched.h |    1 +
 net/sched/sch_netem.c     |   18 +++++++++++++++---
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
index 410b33d..ffe975c 100644
--- a/include/linux/pkt_sched.h
+++ b/include/linux/pkt_sched.h
@@ -509,6 +509,7 @@ enum {
 	TCA_NETEM_CORRUPT,
 	TCA_NETEM_LOSS,
 	TCA_NETEM_RATE,
+	TCA_NETEM_ECN,
 	__TCA_NETEM_MAX,
 };
 
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 1109731..231cd11 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -26,6 +26,7 @@
 
 #include <net/netlink.h>
 #include <net/pkt_sched.h>
+#include <net/inet_ecn.h>
 
 #define VERSION "1.3"
 
@@ -78,6 +79,7 @@ struct netem_sched_data {
 	psched_tdiff_t jitter;
 
 	u32 loss;
+	u32 ecn;
 	u32 limit;
 	u32 counter;
 	u32 gap;
@@ -374,9 +376,12 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 		++count;
 
 	/* Drop packet? */
-	if (loss_event(q))
-		--count;
-
+	if (loss_event(q)) {
+		if (q->ecn && INET_ECN_set_ce(skb))
+			sch->qstats.drops++; /* mark packet */
+		else
+			--count;
+	}
 	if (count == 0) {
 		sch->qstats.drops++;
 		kfree_skb(skb);
@@ -706,6 +711,7 @@ static const struct nla_policy netem_policy[TCA_NETEM_MAX + 1] = {
 	[TCA_NETEM_CORRUPT]	= { .len = sizeof(struct tc_netem_corrupt) },
 	[TCA_NETEM_RATE]	= { .len = sizeof(struct tc_netem_rate) },
 	[TCA_NETEM_LOSS]	= { .type = NLA_NESTED },
+	[TCA_NETEM_ECN]		= { .type = NLA_U32 },
 };
 
 static int parse_attr(struct nlattr *tb[], int maxtype, struct nlattr *nla,
@@ -776,6 +782,9 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt)
 	if (tb[TCA_NETEM_RATE])
 		get_rate(sch, tb[TCA_NETEM_RATE]);
 
+	if (tb[TCA_NETEM_ECN])
+		q->ecn = nla_get_u32(tb[TCA_NETEM_ECN]);
+
 	q->loss_model = CLG_RANDOM;
 	if (tb[TCA_NETEM_LOSS])
 		ret = get_loss_clg(sch, tb[TCA_NETEM_LOSS]);
@@ -902,6 +911,9 @@ static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
 	if (nla_put(skb, TCA_NETEM_RATE, sizeof(rate), &rate))
 		goto nla_put_failure;
 
+	if (q->ecn && nla_put_u32(skb, TCA_NETEM_ECN, q->ecn))
+		goto nla_put_failure;
+
 	if (dump_loss_model(q, skb) != 0)
 		goto nla_put_failure;