MFC r275864: Make sequence numbers checks more strict.

While we don't support MCS, hole in received sequence numbers may mean
only PDU loss.  While we don't support lost PDU recovery, terminate the
connection to avoid stuck commands.

While there, improve handling of sequence numbers wrap after 2^32 PDUs.

2 files changed, 31 insertions, 21 deletions

diff --git a/sys/dev/iscsi/iscsi.c b/sys/dev/iscsi/iscsi.c
index c823c0a..ed49835 100644
--- a/sys/dev/iscsi/iscsi.c
+++ b/sys/dev/iscsi/iscsi.c
@@ -197,7 +197,7 @@ iscsi_pdu_prepare(struct icl_pdu *request)
 	 * Data-Out PDU does not contain CmdSN.
 	 */
 	if (bhssc->bhssc_opcode != ISCSI_BHS_OPCODE_SCSI_DATA_OUT) {
-		if (is->is_cmdsn > is->is_maxcmdsn &&
+		if (ISCSI_SNGT(is->is_cmdsn, is->is_maxcmdsn) &&
 		    (bhssc->bhssc_opcode & ISCSI_BHS_OPCODE_IMMEDIATE) == 0) {
 			/*
 			 * Current MaxCmdSN prevents us from sending any more
@@ -206,8 +206,10 @@ iscsi_pdu_prepare(struct icl_pdu *request)
 			 * or by maintenance thread.
 			 */
 #if 0
-			ISCSI_SESSION_DEBUG(is, "postponing send, CmdSN %d, ExpCmdSN %d, MaxCmdSN %d, opcode 0x%x",
-			    is->is_cmdsn, is->is_expcmdsn, is->is_maxcmdsn, bhssc->bhssc_opcode);
+			ISCSI_SESSION_DEBUG(is, "postponing send, CmdSN %u, "
+			    "ExpCmdSN %u, MaxCmdSN %u, opcode 0x%x",
+			    is->is_cmdsn, is->is_expcmdsn, is->is_maxcmdsn,
+			    bhssc->bhssc_opcode);
 #endif
 			return (true);
 		}
@@ -616,7 +618,7 @@ iscsi_pdu_update_statsn(const struct icl_pdu *response)
 {
 	const struct iscsi_bhs_data_in *bhsdi;
 	struct iscsi_session *is;
-	uint32_t expcmdsn, maxcmdsn;
+	uint32_t expcmdsn, maxcmdsn, statsn;
 
 	is = PDU_SESSION(response);
 
@@ -635,26 +637,27 @@ iscsi_pdu_update_statsn(const struct icl_pdu *response)
 	 */
 	if (bhsdi->bhsdi_opcode != ISCSI_BHS_OPCODE_SCSI_DATA_IN ||
 	    (bhsdi->bhsdi_flags & BHSDI_FLAGS_S) != 0) {
-		if (ntohl(bhsdi->bhsdi_statsn) < is->is_statsn) {
-			ISCSI_SESSION_WARN(is,
-			    "PDU StatSN %d >= session StatSN %d, opcode 0x%x",
-			    is->is_statsn, ntohl(bhsdi->bhsdi_statsn),
-			    bhsdi->bhsdi_opcode);
+		statsn = ntohl(bhsdi->bhsdi_statsn);
+		if (statsn != is->is_statsn && statsn != (is->is_statsn + 1)) {
+			/* XXX: This is normal situation for MCS */
+			ISCSI_SESSION_WARN(is, "PDU 0x%x StatSN %u != "
+			    "session ExpStatSN %u (or + 1); reconnecting",
+			    bhsdi->bhsdi_opcode, statsn, is->is_statsn);
+			iscsi_session_reconnect(is);
 		}
-		is->is_statsn = ntohl(bhsdi->bhsdi_statsn);
+		if (ISCSI_SNGT(statsn, is->is_statsn))
+			is->is_statsn = statsn;
 	}
 
 	expcmdsn = ntohl(bhsdi->bhsdi_expcmdsn);
 	maxcmdsn = ntohl(bhsdi->bhsdi_maxcmdsn);
 
-	/*
-	 * XXX: Compare using Serial Arithmetic Sense.
-	 */
-	if (maxcmdsn + 1 < expcmdsn) {
-		ISCSI_SESSION_DEBUG(is, "PDU MaxCmdSN %d + 1 < PDU ExpCmdSN %d; ignoring",
+	if (ISCSI_SNLT(maxcmdsn + 1, expcmdsn)) {
+		ISCSI_SESSION_DEBUG(is,
+		    "PDU MaxCmdSN %u + 1 < PDU ExpCmdSN %u; ignoring",
 		    maxcmdsn, expcmdsn);
 	} else {
-		if (maxcmdsn > is->is_maxcmdsn) {
+		if (ISCSI_SNGT(maxcmdsn, is->is_maxcmdsn)) {
 			is->is_maxcmdsn = maxcmdsn;
 
 			/*
@@ -663,15 +666,19 @@ iscsi_pdu_update_statsn(const struct icl_pdu *response)
 			 */
 			if (!STAILQ_EMPTY(&is->is_postponed))
 				cv_signal(&is->is_maintenance_cv);
-		} else if (maxcmdsn < is->is_maxcmdsn) {
-			ISCSI_SESSION_DEBUG(is, "PDU MaxCmdSN %d < session MaxCmdSN %d; ignoring",
+		} else if (ISCSI_SNLT(maxcmdsn, is->is_maxcmdsn)) {
+			/* XXX: This is normal situation for MCS */
+			ISCSI_SESSION_DEBUG(is,
+			    "PDU MaxCmdSN %u < session MaxCmdSN %u; ignoring",
 			    maxcmdsn, is->is_maxcmdsn);
 		}
 
-		if (expcmdsn > is->is_expcmdsn) {
+		if (ISCSI_SNGT(expcmdsn, is->is_expcmdsn)) {
 			is->is_expcmdsn = expcmdsn;
-		} else if (expcmdsn < is->is_expcmdsn) {
-			ISCSI_SESSION_DEBUG(is, "PDU ExpCmdSN %d < session ExpCmdSN %d; ignoring",
+		} else if (ISCSI_SNLT(expcmdsn, is->is_expcmdsn)) {
+			/* XXX: This is normal situation for MCS */
+			ISCSI_SESSION_DEBUG(is,
+			    "PDU ExpCmdSN %u < session ExpCmdSN %u; ignoring",
 			    expcmdsn, is->is_expcmdsn);
 		}
 	}
diff --git a/sys/dev/iscsi/iscsi_proto.h b/sys/dev/iscsi/iscsi_proto.h
index 97d73a7..46572ce 100644
--- a/sys/dev/iscsi/iscsi_proto.h
+++ b/sys/dev/iscsi/iscsi_proto.h
@@ -38,6 +38,9 @@
 #define __CTASSERT(x, y)	typedef char __assert_ ## y [(x) ? 1 : -1]
 #endif
 
+#define	ISCSI_SNGT(x, y)	((int32_t)(x) - (int32_t)(y) > 0)
+#define	ISCSI_SNLT(x, y)	((int32_t)(x) - (int32_t)(y) < 0)
+
 #define	ISCSI_BHS_SIZE			48
 #define	ISCSI_HEADER_DIGEST_SIZE	4
 #define	ISCSI_DATA_DIGEST_SIZE		4