libceph: implement RECONNECT_SEQ feature

This is an old protocol extension that allows the client and server to
avoid resending old messages after a reconnect (following a socket error).
Instead, the exchange their sequence numbers during the handshake.  This
avoids sending a bunch of useless data over the socket.

It has been supported in the server code since v0.22 (Sep 2010).

Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Alex Elder <elder@inktank.com>

2 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/ceph/ceph_features.h b/include/linux/ceph/ceph_features.h
index 76554cecaab2..4c42080347af 100644
--- a/include/linux/ceph/ceph_features.h
+++ b/include/linux/ceph/ceph_features.h
@@ -41,6 +41,7 @@
  */
 #define CEPH_FEATURES_SUPPORTED_DEFAULT  \
         (CEPH_FEATURE_NOSRCADDR |               \
+         CEPH_FEATURE_RECONNECT_SEQ |           \
          CEPH_FEATURE_PGID64 |                  \
          CEPH_FEATURE_PGPOOL3 |                 \
          CEPH_FEATURE_OSDENC |                  \
@@ -51,6 +52,7 @@
 
 #define CEPH_FEATURES_REQUIRED_DEFAULT   \
         (CEPH_FEATURE_NOSRCADDR |        \
+         CEPH_FEATURE_RECONNECT_SEQ |    \
          CEPH_FEATURE_PGID64 |           \
          CEPH_FEATURE_PGPOOL3 |          \
          CEPH_FEATURE_OSDENC)
diff --git a/include/linux/ceph/msgr.h b/include/linux/ceph/msgr.h
index 680d3d648cac..3d94a73b5f30 100644
--- a/include/linux/ceph/msgr.h
+++ b/include/linux/ceph/msgr.h
@@ -87,6 +87,7 @@ struct ceph_entity_inst {
 #define CEPH_MSGR_TAG_BADPROTOVER  10  /* bad protocol version */
 #define CEPH_MSGR_TAG_BADAUTHORIZER 11 /* bad authorizer */
 #define CEPH_MSGR_TAG_FEATURES      12 /* insufficient features */
+#define CEPH_MSGR_TAG_SEQ           13 /* 64-bit int follows with seen seq number */
 
 
 /*