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| author | Daniel Borkmann <daniel@iogearbox.net> | 2015-08-31 16:58:47 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-08-31 22:34:00 +0300 |
| commit | c3a8d9474684d391b0afc3970d9b249add15ec07 (patch) | |
| tree | f12130b61955f4471ebd61474244ecf9ebdc0858 /net/core | |
| parent | b8d3e4163a3562d7cba486687904383e78e7dd6a (diff) | |
| download | linux-c3a8d9474684d391b0afc3970d9b249add15ec07.tar.xz | |
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.c | 6 |
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; |