Merge branch 'per-route-dctcp-receive-side'

Daniel Borkmann says:

====================
tcp: receive-side per route dctcp handling

Original cover letter:

  Currently, the following case doesn't use DCTCP, even if it should:

    - responder has f.e. cubic as system wide default
    - 'ip route congctl dctcp $src' was set

  Then, DCTCP is NOT used if a DCTCP sender attempts to connect from a
  host in the $src range: ECT(0) is set, but listen_sk is not dctcp, so
  we fail the INET_ECN_is_not_ect sanity check.

  We also have to examine the dst used for the SYN/ACK reply to make
  this case work.

  In order to minimize additional cost, store the 'ecn is must have'
  information is the dst_features field.

  The set targets -next instead of -net since this doesn't seem to be a
  serious bug and to give the change more soak time until it hits linus
  tree.

v1 -> v2:
 - Addressed Dave's feedback, not exposing any bits to user space
 - Added patch 3 to reject incorrect configurations
 - Rest as is, rebased and retested
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 14 insertions, 5 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)
 {
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 4a7b03947a38..0cab28cd43a9 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -888,7 +888,7 @@ void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
 extern struct tcp_congestion_ops tcp_reno;
 
 struct tcp_congestion_ops *tcp_ca_find_key(u32 key);
-u32 tcp_ca_get_key_by_name(const char *name);
+u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca);
 #ifdef CONFIG_INET
 char *tcp_ca_get_name_by_key(u32 key, char *buffer);
 #else
diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index 0d3d3cc43356..702024769c74 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -418,10 +418,13 @@ enum {
 
 #define RTAX_MAX (__RTAX_MAX - 1)
 
-#define RTAX_FEATURE_ECN	0x00000001
-#define RTAX_FEATURE_SACK	0x00000002
-#define RTAX_FEATURE_TIMESTAMP	0x00000004
-#define RTAX_FEATURE_ALLFRAG	0x00000008
+#define RTAX_FEATURE_ECN	(1 << 0)
+#define RTAX_FEATURE_SACK	(1 << 1)
+#define RTAX_FEATURE_TIMESTAMP	(1 << 2)
+#define RTAX_FEATURE_ALLFRAG	(1 << 3)
+
+#define RTAX_FEATURE_MASK	(RTAX_FEATURE_ECN | RTAX_FEATURE_SACK | \
+				 RTAX_FEATURE_TIMESTAMP | RTAX_FEATURE_ALLFRAG)
 
 struct rta_session {
 	__u8	proto;