diff options
| 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/ipv4/tcp_input.c | |
| 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/ipv4/tcp_input.c')
| -rw-r--r-- | net/ipv4/tcp_input.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index dc08e2352665..a8f515bb19c4 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -6003,14 +6003,17 @@ static void tcp_ecn_create_request(struct request_sock *req, const struct net *net = sock_net(listen_sk); bool th_ecn = th->ece && th->cwr; bool ect, ecn_ok; + u32 ecn_ok_dst; if (!th_ecn) return; ect = !INET_ECN_is_not_ect(TCP_SKB_CB(skb)->ip_dsfield); - ecn_ok = net->ipv4.sysctl_tcp_ecn || dst_feature(dst, RTAX_FEATURE_ECN); + ecn_ok_dst = dst_feature(dst, DST_FEATURE_ECN_MASK); + ecn_ok = net->ipv4.sysctl_tcp_ecn || ecn_ok_dst; - if ((!ect && ecn_ok) || tcp_ca_needs_ecn(listen_sk)) + if ((!ect && ecn_ok) || tcp_ca_needs_ecn(listen_sk) || + (ecn_ok_dst & DST_FEATURE_ECN_CA)) inet_rsk(req)->ecn_ok = 1; } |