From: Daniel Borkmann Date: Mon, 31 Aug 2015 13:58:47 +0000 (+0200) Subject: tcp: use dctcp if enabled on the route to the initiator X-Git-Tag: omap-for-v4.3/fixes-rc1~110^2~25^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c3a8d9474684d391b0afc3970d9b249add15ec07;p=pandora-kernel.git 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 --- Reading git-diff-tree failed