summaryrefslogtreecommitdiffstats
path: root/net/ipv4/tcp_input.c
diff options
context:
space:
mode:
authorEric Dumazet <eric.dumazet@gmail.com>2011-09-22 20:02:19 +0000
committerDavid S. Miller <davem@davemloft.net>2011-09-27 00:58:44 -0400
commit7a269ffad72f3604b8982fa09c387670e0d2ee14 (patch)
tree3655a22066bcb1011e5e1b717a00a108143dfd85 /net/ipv4/tcp_input.c
parent0bdb0bd0139f3b6afa252de1487e3ce82a494db9 (diff)
downloadop-kernel-dev-7a269ffad72f3604b8982fa09c387670e0d2ee14.zip
op-kernel-dev-7a269ffad72f3604b8982fa09c387670e0d2ee14.tar.gz
tcp: ECN blackhole should not force quickack mode
While playing with a new ADSL box at home, I discovered that ECN blackhole can trigger suboptimal quickack mode on linux : We send one ACK for each incoming data frame, without any delay and eventual piggyback. This is because TCP_ECN_check_ce() considers that if no ECT is seen on a segment, this is because this segment was a retransmit. Refine this heuristic and apply it only if we seen ECT in a previous segment, to detect ECN blackhole at IP level. Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> CC: Jamal Hadi Salim <jhs@mojatatu.com> CC: Jerry Chu <hkchu@google.com> CC: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> CC: Jim Gettys <jg@freedesktop.org> CC: Dave Taht <dave.taht@gmail.com> Acked-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_input.c')
-rw-r--r--net/ipv4/tcp_input.c23
1 files changed, 16 insertions, 7 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a5d01b1..5a4408c 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -217,16 +217,25 @@ static inline void TCP_ECN_withdraw_cwr(struct tcp_sock *tp)
tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR;
}
-static inline void TCP_ECN_check_ce(struct tcp_sock *tp, struct sk_buff *skb)
+static inline void TCP_ECN_check_ce(struct tcp_sock *tp, const struct sk_buff *skb)
{
- if (tp->ecn_flags & TCP_ECN_OK) {
- if (INET_ECN_is_ce(TCP_SKB_CB(skb)->flags))
- tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
+ if (!(tp->ecn_flags & TCP_ECN_OK))
+ return;
+
+ switch (TCP_SKB_CB(skb)->flags & INET_ECN_MASK) {
+ case INET_ECN_NOT_ECT:
/* Funny extension: if ECT is not set on a segment,
- * it is surely retransmit. It is not in ECN RFC,
- * but Linux follows this rule. */
- else if (INET_ECN_is_not_ect((TCP_SKB_CB(skb)->flags)))
+ * and we already seen ECT on a previous segment,
+ * it is probably a retransmit.
+ */
+ if (tp->ecn_flags & TCP_ECN_SEEN)
tcp_enter_quickack_mode((struct sock *)tp);
+ break;
+ case INET_ECN_CE:
+ tp->ecn_flags |= TCP_ECN_DEMAND_CWR;
+ /* fallinto */
+ default:
+ tp->ecn_flags |= TCP_ECN_SEEN;
}
}
OpenPOWER on IntegriCloud