rds: Fix heartbeat

RDS' heartbeat mechanism sends probes back and forth from source port
zero to destination port zero. uek-4.1-qu7 commit 041dc3e
("Backport multipath RDS from upstream to UEK4") tosses all receives
where said ports are zero.

The consequence is that no heartbeat pongs are ever sent back, and the
active heart-beater will time-out and tear down the connection.

Orabug: 30418039

Fixes: 041dc3e ("Backport multipath RDS from upstream to UEK4")
Signed-off-by: Håkon Bugge <[email protected]>
Tested-by: Michael Nowak <[email protected]>
Reviewed-by: Ka-Cheong Poon <[email protected]>

---

v1->v2:
	* Tightened the check for probes, which must have zero-length
          and one and only one of the heartbeat probe bits is set in
          the header.

v2->v3:
	* Re-factored inline function rds_valid_hb_flags() in rds.h
          into rds_recv_local() to avoid code duplication, as
          suggested by Ka-Cheong.
	* Added Ka-Cheong's r-b

Signed-off-by: Somasundaram Krishnasamy <[email protected]>

Author: Hakon-Bugge

net/rds/rds.h

@@ -402,6 +402,7 @@ void rds_conn_net_set(struct rds_connection *conn, struct net *net)
 #define RDS_FLAG_RETRANSMITTED		0x04
 #define RDS_FLAG_HB_PING		0x08
 #define RDS_FLAG_HB_PONG		0x10
+#define RDS_FLAG_ANY_HB			(RDS_FLAG_HB_PING | RDS_FLAG_HB_PONG)
 #define RDS_FLAG_EXTHDR_EXTENSION	0x20
 #define RDS_MAX_ADV_CREDIT		127
 

net/rds/recv.c

@@ -685,14 +685,23 @@ rds_recv_local(struct rds_conn_path *cp, struct in6_addr *saddr,
 	cp->cp_next_rx_seq = inc_hdr_h_sequence + 1;
 
 	if (rds_sysctl_ping_enable && inc->i_hdr.h_dport == 0) {
-		if (inc->i_hdr.h_sport == 0) {
+		bool is_hb_ping = (inc->i_hdr.h_flags & RDS_FLAG_ANY_HB) == RDS_FLAG_HB_PING;
+		bool is_hb_pong = (inc->i_hdr.h_flags & RDS_FLAG_ANY_HB) == RDS_FLAG_HB_PONG;
+
+		if (inc->i_hdr.h_len) {
+			rdsdebug("ignore ping with non-zero length from %pI6c\n", &saddr);
+			goto out;
+		}
+
+		/* One and only one of the heart-beat flags must be set */
+		if (inc->i_hdr.h_sport == 0 && !(is_hb_ping ^ is_hb_pong)) {
 			rdsdebug("ignore ping with 0 sport from %pI6c\n",
 				 &saddr);
 			goto out;
 		}
-		if (inc->i_hdr.h_flags & RDS_FLAG_HB_PING) {
+		if (is_hb_ping) {
 			rds_send_hb(conn, 1);
-		} else if (inc->i_hdr.h_flags & RDS_FLAG_HB_PONG) {
+		} else if (is_hb_pong) {
 			cp->cp_hb_start = 0;
 		} else {
 			rds_stats_inc(s_recv_ping);