[PATCH 7/9] port_fwd: Split TCP and UDP cases for get_bound_ports()

[David Gibson <david@gibson.dropbear.id.au>]

Currently get_bound_ports() takes a parameter to determine if it scans for
UDP or TCP bound ports, but in fact there's almost nothing in common
between those two paths.  The parameter appears primarily to have been
a convenience for when we needed to invoke this function via NS_CALL().

Now that we don't need that, split it into separate TCP and UDP versions.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 port_fwd.c | 76 ++++++++++++++++++++++++++++++------------------------
 port_fwd.h |  3 ++-
 tcp.c      |  4 +--
 3 files changed, 47 insertions(+), 36 deletions(-)

diff --git a/port_fwd.c b/port_fwd.c
index b91eafe..e6b3b14 100644
--- a/port_fwd.c
+++ b/port_fwd.c
@@ -68,45 +68,55 @@ static void procfs_scan_listen(int fd, unsigned int lstate,
 }
 
 /**
- * get_bound_ports() - Get maps of ports with bound sockets
+ * get_bound_ports_tcp() - Get maps of TCP ports with bound sockets
  * @c:		Execution context
  * @ns:		If set, set bitmaps for ports to tap/ns -- to init otherwise
- * @proto:	Protocol number (IPPROTO_TCP or IPPROTO_UDP)
  */
-void get_bound_ports(struct ctx *c, int ns, uint8_t proto)
+void get_bound_ports_tcp(struct ctx *c, int ns)
 {
-	uint8_t *udp_map, *udp_excl, *tcp_map, *tcp_excl;
+	uint8_t *map, *excl;
 
 	if (ns) {
-		udp_map = c->udp.fwd_in.f.map;
-		udp_excl = c->udp.fwd_out.f.map;
-		tcp_map = c->tcp.fwd_in.map;
-		tcp_excl = c->tcp.fwd_out.map;
+		map = c->tcp.fwd_in.map;
+		excl = c->tcp.fwd_out.map;
 	} else {
-		udp_map = c->udp.fwd_out.f.map;
-		udp_excl = c->udp.fwd_in.f.map;
-		tcp_map = c->tcp.fwd_out.map;
-		tcp_excl = c->tcp.fwd_in.map;
+		map = c->tcp.fwd_out.map;
+		excl = c->tcp.fwd_in.map;
 	}
 
-	if (proto == IPPROTO_UDP) {
-		memset(udp_map, 0, PORT_BITMAP_SIZE);
-		procfs_scan_listen(c->proc_net_udp[V4][ns],
-				   UDP_LISTEN, udp_map, udp_excl);
-		procfs_scan_listen(c->proc_net_udp[V6][ns],
-				   UDP_LISTEN, udp_map, udp_excl);
-
-		procfs_scan_listen(c->proc_net_tcp[V4][ns],
-				   TCP_LISTEN, udp_map, udp_excl);
-		procfs_scan_listen(c->proc_net_tcp[V6][ns],
-				   TCP_LISTEN, udp_map, udp_excl);
-	} else if (proto == IPPROTO_TCP) {
-		memset(tcp_map, 0, PORT_BITMAP_SIZE);
-		procfs_scan_listen(c->proc_net_tcp[V4][ns],
-				   TCP_LISTEN, tcp_map, tcp_excl);
-		procfs_scan_listen(c->proc_net_tcp[V6][ns],
-				   TCP_LISTEN, tcp_map, tcp_excl);
+	memset(map, 0, PORT_BITMAP_SIZE);
+	procfs_scan_listen(c->proc_net_tcp[V4][ns], TCP_LISTEN, map, excl);
+	procfs_scan_listen(c->proc_net_tcp[V6][ns], TCP_LISTEN, map, excl);
+}
+
+/**
+ * get_bound_ports_udp() - Get maps of UDP ports with bound sockets
+ * @c:		Execution context
+ * @ns:		If set, set bitmaps for ports to tap/ns -- to init otherwise
+ */
+void get_bound_ports_udp(struct ctx *c, int ns)
+{
+	uint8_t *map, *excl;
+
+	if (ns) {
+		map = c->udp.fwd_in.f.map;
+		excl = c->udp.fwd_out.f.map;
+	} else {
+		map = c->udp.fwd_out.f.map;
+		excl = c->udp.fwd_in.f.map;
 	}
+
+	memset(map, 0, PORT_BITMAP_SIZE);
+	procfs_scan_listen(c->proc_net_udp[V4][ns], UDP_LISTEN, map, excl);
+	procfs_scan_listen(c->proc_net_udp[V6][ns], UDP_LISTEN, map, excl);
+
+	/* Also forward UDP ports with the same numbers as bound TCP ports.
+	 * This is useful for a handful of protocols (e.g. iperf3) where a TCP
+	 * control port is used to set up transfers on a corresponding UDP
+	 * port.
+	 */
+	procfs_scan_listen(c->proc_net_tcp[V4][ns], TCP_LISTEN, map, excl);
+	procfs_scan_listen(c->proc_net_tcp[V6][ns], TCP_LISTEN, map, excl);
 }
 
 /**
@@ -125,21 +135,21 @@ void port_fwd_init(struct ctx *c)
 	if (c->tcp.fwd_in.mode == FWD_AUTO) {
 		c->proc_net_tcp[V4][1] = open_in_ns(c, "/proc/net/tcp", flags);
 		c->proc_net_tcp[V6][1] = open_in_ns(c, "/proc/net/tcp6", flags);
-		get_bound_ports(c, 1, IPPROTO_TCP);
+		get_bound_ports_tcp(c, 1);
 	}
 	if (c->udp.fwd_in.f.mode == FWD_AUTO) {
 		c->proc_net_udp[V4][1] = open_in_ns(c, "/proc/net/udp", flags);
 		c->proc_net_udp[V6][1] = open_in_ns(c, "/proc/net/udp6", flags);
-		get_bound_ports(c, 1, IPPROTO_UDP);
+		get_bound_ports_udp(c, 1);
 	}
 	if (c->tcp.fwd_out.mode == FWD_AUTO) {
 		c->proc_net_tcp[V4][0] = open("/proc/net/tcp", flags);
 		c->proc_net_tcp[V6][0] = open("/proc/net/tcp6", flags);
-		get_bound_ports(c, 0, IPPROTO_TCP);
+		get_bound_ports_tcp(c, 0);
 	}
 	if (c->udp.fwd_out.f.mode == FWD_AUTO) {
 		c->proc_net_udp[V4][0] = open("/proc/net/udp", flags);
 		c->proc_net_udp[V6][0] = open("/proc/net/udp6", flags);
-		get_bound_ports(c, 0, IPPROTO_UDP);
+		get_bound_ports_udp(c, 0);
 	}
 }
diff --git a/port_fwd.h b/port_fwd.h
index ad8ed1f..2f8f526 100644
--- a/port_fwd.h
+++ b/port_fwd.h
@@ -31,7 +31,8 @@ struct port_fwd {
 	in_port_t delta[NUM_PORTS];
 };
 
-void get_bound_ports(struct ctx *c, int ns, uint8_t proto);
+void get_bound_ports_tcp(struct ctx *c, int ns);
+void get_bound_ports_udp(struct ctx *c, int ns);
 void port_fwd_init(struct ctx *c);
 
 #endif /* PORT_FWD_H */
diff --git a/tcp.c b/tcp.c
index 63a3c64..921bd2a 100644
--- a/tcp.c
+++ b/tcp.c
@@ -3240,13 +3240,13 @@ void tcp_timer(struct ctx *c, const struct timespec *ts)
 		struct tcp_port_rebind_arg rebind_arg = { c, 0 };
 
 		if (c->tcp.fwd_out.mode == FWD_AUTO) {
-			get_bound_ports(c, 0, IPPROTO_TCP);
+			get_bound_ports_tcp(c, 0);
 			rebind_arg.bind_in_ns = 1;
 			NS_CALL(tcp_port_rebind, &rebind_arg);
 		}
 
 		if (c->tcp.fwd_in.mode == FWD_AUTO) {
-			get_bound_ports(c, 1, IPPROTO_TCP);
+			get_bound_ports_tcp(c, 1);
 			rebind_arg.bind_in_ns = 0;
 			tcp_port_rebind(&rebind_arg);
 		}
-- 
@@ -3240,13 +3240,13 @@ void tcp_timer(struct ctx *c, const struct timespec *ts)
 		struct tcp_port_rebind_arg rebind_arg = { c, 0 };
 
 		if (c->tcp.fwd_out.mode == FWD_AUTO) {
-			get_bound_ports(c, 0, IPPROTO_TCP);
+			get_bound_ports_tcp(c, 0);
 			rebind_arg.bind_in_ns = 1;
 			NS_CALL(tcp_port_rebind, &rebind_arg);
 		}
 
 		if (c->tcp.fwd_in.mode == FWD_AUTO) {
-			get_bound_ports(c, 1, IPPROTO_TCP);
+			get_bound_ports_tcp(c, 1);
 			rebind_arg.bind_in_ns = 0;
 			tcp_port_rebind(&rebind_arg);
 		}
-- 
2.41.0