diff options
author | Daniel Borkmann <daniel@iogearbox.net> | 2015-08-31 13:58:47 (GMT) |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2015-08-31 19:34:00 (GMT) |
commit | c3a8d9474684d391b0afc3970d9b249add15ec07 (patch) | |
tree | f12130b61955f4471ebd61474244ecf9ebdc0858 /net/ipv4/tcp_cong.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_cong.c')
-rw-r--r-- | net/ipv4/tcp_cong.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c index a2ed23c..93c4dc3 100644 --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -114,16 +114,19 @@ void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca) } EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control); -u32 tcp_ca_get_key_by_name(const char *name) +u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca) { const struct tcp_congestion_ops *ca; - u32 key; + u32 key = TCP_CA_UNSPEC; might_sleep(); rcu_read_lock(); ca = __tcp_ca_find_autoload(name); - key = ca ? ca->key : TCP_CA_UNSPEC; + if (ca) { + key = ca->key; + *ecn_ca = ca->flags & TCP_CONG_NEEDS_ECN; + } rcu_read_unlock(); return key; |