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authorDaniel Borkmann <daniel@iogearbox.net>2015-08-31 15:58:47 +0200
committerDavid S. Miller <davem@davemloft.net>2015-08-31 12:34:00 -0700
commitc3a8d9474684d391b0afc3970d9b249add15ec07 (patch)
treef12130b61955f4471ebd61474244ecf9ebdc0858 /net/core
parentb8d3e4163a3562d7cba486687904383e78e7dd6a (diff)
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 <daniel@iogearbox.net> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/rtnetlink.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 788ceed39463..a466821d1441 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -678,6 +678,12 @@ int rtnetlink_put_metrics(struct sk_buff *skb, u32 *metrics)
continue;
if (nla_put_string(skb, i + 1, name))
goto nla_put_failure;
+ } else if (i == RTAX_FEATURES - 1) {
+ u32 user_features = metrics[i] & RTAX_FEATURE_MASK;
+
+ BUILD_BUG_ON(RTAX_FEATURE_MASK & DST_FEATURE_MASK);
+ if (nla_put_u32(skb, i + 1, user_features))
+ goto nla_put_failure;
} else {
if (nla_put_u32(skb, i + 1, metrics[i]))
goto nla_put_failure;

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