netdev - [PATCH] net: sched: tbf: handle GSO_BY

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Message-Id: <20180205033433.23647-1-dja@axtens.net>
Date:   Mon,  5 Feb 2018 14:34:33 +1100
From:   Daniel Axtens <dja@...ens.net>
To:     netdev@...r.kernel.org
Cc:     Daniel Axtens <dja@...ens.net>
Subject: [PATCH] net: sched: tbf: handle GSO_BY_FRAGS case in enqueue

tbf_enqueue() checks the size of a packet before enqueuing it.
However, the GSO size check does not consider the GSO_BY_FRAGS
case, and so will drop GSO SCTP packets, causing a massive drop
in throughput.

Use skb_gso_validate_mac_len() instead, as it does consider that
case.

---

skb_gso_validate_mac_len() is an out-of-line call, but so is
skb_gso_mac_seglen(), so this is slower but not much slower. I
will send a patch to make the skb_gso_validate_* functions
inline-able shortly.

Also, GSO_BY_FRAGS considered harmful - I'm pretty sure this is
not the only place it causes issues.

Signed-off-by: Daniel Axtens <dja@...ens.net>
---
 net/sched/sch_tbf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c
index 229172d509cc..03225a8df973 100644
--- a/net/sched/sch_tbf.c
+++ b/net/sched/sch_tbf.c
@@ -188,7 +188,8 @@ static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 	int ret;

 	if (qdisc_pkt_len(skb) > q->max_size) {
-		if (skb_is_gso(skb) && skb_gso_mac_seglen(skb) <= q->max_size)
+		if (skb_is_gso(skb) &&
+		    skb_gso_validate_mac_len(skb, q->max_size))
 			return tbf_segment(skb, sch, to_free);
 		return qdisc_drop(skb, sch, to_free);
 	}
-- 
2.14.1