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| author |   Daniel Borkmann <daniel@iogearbox.net> | 2015-08-31 15:58:47 +0200 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2015-08-31 12:34:00 -0700 |
| commit | c3a8d9474684d391b0afc3970d9b249add15ec07 (patch) | |
| tree | f12130b61955f4471ebd61474244ecf9ebdc0858 /include/net/dst.h | |
| parent | fib, fib6: reject invalid feature bits (diff) | |
| download | linux-dev-c3a8d9474684d391b0afc3970d9b249add15ec07.tar.xz linux-dev-c3a8d9474684d391b0afc3970d9b249add15ec07.zip | |
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 'include/net/dst.h')
| -rw-r--r-- | include/net/dst.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/include/net/dst.h b/include/net/dst.h index 4c4801645371..9261d928303d 100644 --- a/include/net/dst.h +++ b/include/net/dst.h @@ -207,6 +207,12 @@ static inline void dst_metric_set(struct dst_entry *dst, int metric, u32 val) p[metric-1] = val; } +/* Kernel-internal feature bits that are unallocated in user space. */ +#define DST_FEATURE_ECN_CA (1 << 31) + +#define DST_FEATURE_MASK (DST_FEATURE_ECN_CA) +#define DST_FEATURE_ECN_MASK (DST_FEATURE_ECN_CA | RTAX_FEATURE_ECN) + static inline u32 dst_feature(const struct dst_entry *dst, u32 feature) { |