ceph: discard incoming messages with bad seq #

We can get old message seq #'s after a tcp reconnect for stateful sessions
(i.e., the MDS).  If we get a higher seq #, that is an error, and we
shouldn't see any bad seq #'s for stateless (mon, osd) connections.
Signed-off-by: Sage Weil <sage@newdream.net>

fs/ceph/messenger.c

@@ -1334,6 +1334,7 @@ static int read_partial_message(struct ceph_connection *con)
 	unsigned front_len, middle_len, data_len, data_off;
 	int datacrc = con->msgr->nocrc;
 	int skip;
+	u64 seq;
 
 	dout("read_partial_message con %p msg %p\n", con, m);
 
@@ -1368,6 +1369,25 @@ static int read_partial_message(struct ceph_connection *con)
 		return -EIO;
 	data_off = le16_to_cpu(con->in_hdr.data_off);
 
+	/* verify seq# */
+	seq = le64_to_cpu(con->in_hdr.seq);
+	if ((s64)seq - (s64)con->in_seq < 1) {
+		pr_info("skipping %s%lld %s seq %lld, expected %lld\n",
+			ENTITY_NAME(con->peer_name),
+			pr_addr(&con->peer_addr.in_addr),
+			seq, con->in_seq + 1);
+		con->in_base_pos = -front_len - middle_len - data_len -
+			sizeof(m->footer);
+		con->in_tag = CEPH_MSGR_TAG_READY;
+		con->in_seq++;
+		return 0;
+	} else if ((s64)seq - (s64)con->in_seq > 1) {
+		pr_err("read_partial_message bad seq %lld expected %lld\n",
+		       seq, con->in_seq + 1);
+		con->error_msg = "bad message sequence # for incoming message";
+		return -EBADMSG;
+	}
+
 	/* allocate message? */
 	if (!con->in_msg) {
 		dout("got hdr type %d front %d data %d\n", con->in_hdr.type,