From c3a8d9474684d391b0afc3970d9b249add15ec07 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Mon, 31 Aug 2015 15:58:47 +0200 Subject: tcp: use dctcp if enabled on the route to the initiator Currently, the following case doesn't use DCTCP, even if it should: A responder has f.e. Cubic as system wide default, but for a specific route to the initiating host, DCTCP is being set in RTAX_CC_ALGO. The initiating host then uses DCTCP as congestion control, but since the initiator sets ECT(0), tcp_ecn_create_request() doesn't set ecn_ok, and we have to fall back to Reno after 3WHS completes. We were thinking on how to solve this in a minimal, non-intrusive way without bloating tcp_ecn_create_request() needlessly: lets cache the CA ecn option flag in RTAX_FEATURES. In other words, when ECT(0) is set on the SYN packet, set ecn_ok=1 iff route RTAX_FEATURES contains the unexposed (internal-only) DST_FEATURE_ECN_CA. This allows to only do a single metric feature lookup inside tcp_ecn_create_request(). Joint work with Florian Westphal. Signed-off-by: Daniel Borkmann Signed-off-by: Florian Westphal Signed-off-by: David S. Miller --- net/ipv4/fib_semantics.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'net/ipv4/fib_semantics.c') diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c index 115a08e70d43..992a9597daf8 100644 --- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -879,6 +879,7 @@ static bool fib_valid_prefsrc(struct fib_config *cfg, __be32 fib_prefsrc) static int fib_convert_metrics(struct fib_info *fi, const struct fib_config *cfg) { + bool ecn_ca = false; struct nlattr *nla; int remaining; @@ -898,7 +899,7 @@ fib_convert_metrics(struct fib_info *fi, const struct fib_config *cfg) char tmp[TCP_CA_NAME_MAX]; nla_strlcpy(tmp, nla, sizeof(tmp)); - val = tcp_ca_get_key_by_name(tmp); + val = tcp_ca_get_key_by_name(tmp, &ecn_ca); if (val == TCP_CA_UNSPEC) return -EINVAL; } else { @@ -913,6 +914,9 @@ fib_convert_metrics(struct fib_info *fi, const struct fib_config *cfg) fi->fib_metrics[type - 1] = val; } + if (ecn_ca) + fi->fib_metrics[RTAX_FEATURES - 1] |= DST_FEATURE_ECN_CA; + return 0; } -- cgit v1.2.3