conf: Unify several paths in conf_ports()

In conf_ports() we have three different paths which actually do the setup
of an individual forwarded port: one for the "all" case, one for the
exclusions only case and one for the range of ports with possible
exclusions case.

We can unify those cases using a new helper which handles a single range
of ports, with a bitmap of exclusions.  Although this is slightly longer
(largely due to the new helpers function comment), it reduces duplicated
logic.  It will also make future improvements to the tracking of port
forwards easier.

The new conf_ports_range_except() function has a pretty prodigious
parameter list, but I still think it's an overall improvement in conceptual
complexity.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 90 insertions, 83 deletions

diff --git a/conf.c b/conf.c
index c760f79..0e2e8dc 100644
--- a/conf.c
+++ b/conf.c
@@ -124,6 +124,75 @@ static int parse_port_range(const char *s, char **endptr,
 }
 
 /**
+ * conf_ports_range_except() - Set up forwarding for a range of ports minus a
+ *                             bitmap of exclusions
+ * @c:		Execution context
+ * @optname:	Short option name, t, T, u, or U
+ * @optarg:	Option argument (port specification)
+ * @fwd:	Pointer to @fwd_ports to be updated
+ * @addr:	Listening address
+ * @ifname:	Listening interface
+ * @first:	First port to forward
+ * @last:	Last port to forward
+ * @exclude:	Bitmap of ports to exclude
+ * @to:		Port to translate @first to when forwarding
+ * @weak:	Ignore errors, as long as at least one port is mapped
+ */
+static void conf_ports_range_except(const struct ctx *c, char optname,
+				    const char *optarg, struct fwd_ports *fwd,
+				    const union inany_addr *addr,
+				    const char *ifname,
+				    uint16_t first, uint16_t last,
+				    const uint8_t *exclude, uint16_t to,
+				    bool weak)
+{
+	bool bound_one = false;
+	unsigned i;
+	int ret;
+
+	if (first == 0) {
+		die("Can't forward port 0 for option '-%c %s'",
+		    optname, optarg);
+	}
+
+	for (i = first; i <= last; i++) {
+		if (bitmap_isset(exclude, i))
+			continue;
+
+		if (bitmap_isset(fwd->map, i)) {
+			warn(
+"Altering mapping of already mapped port number: %s", optarg);
+		}
+
+		bitmap_set(fwd->map, i);
+		fwd->delta[i] = to - first;
+
+		if (optname == 't')
+			ret = tcp_sock_init(c, addr, ifname, i);
+		else if (optname == 'u')
+			ret = udp_sock_init(c, 0, addr, ifname, i);
+		else
+			/* No way to check in advance for -T and -U */
+			ret = 0;
+
+		if (ret == -ENFILE || ret == -EMFILE) {
+			die("Can't open enough sockets for port specifier: %s",
+			    optarg);
+		}
+
+		if (!ret) {
+			bound_one = true;
+		} else if (!weak) {
+			die("Failed to bind port %u (%s) for option '-%c %s'",
+			    i, strerror_(-ret), optname, optarg);
+		}
+	}
+
+	if (!bound_one)
+		die("Failed to bind any port for '-%c %s'", optname, optarg);
+}
+
+/**
  * conf_ports() - Parse port configuration options, initialise UDP/TCP sockets
  * @c:		Execution context
  * @optname:	Short option name, t, T, u, or U
@@ -135,10 +204,9 @@ static void conf_ports(const struct ctx *c, char optname, const char *optarg,
 {
 	union inany_addr addr_buf = inany_any6, *addr = &addr_buf;
 	char buf[BUFSIZ], *spec, *ifname = NULL, *p;
-	bool exclude_only = true, bound_one = false;
 	uint8_t exclude[PORT_BITMAP_SIZE] = { 0 };
+	bool exclude_only = true;
 	unsigned i;
-	int ret;
 
 	if (!strcmp(optarg, "none")) {
 		if (fwd->mode)
@@ -173,32 +241,15 @@ static void conf_ports(const struct ctx *c, char optname, const char *optarg,
 
 		fwd->mode = FWD_ALL;
 
-		/* Skip port 0.  It has special meaning for many socket APIs, so
-		 * trying to bind it is not really safe.
-		 */
-		for (i = 1; i < NUM_PORTS; i++) {
+		/* Exclude ephemeral ports */
+		for (i = 0; i < NUM_PORTS; i++)
 			if (fwd_port_is_ephemeral(i))
-				continue;
-
-			bitmap_set(fwd->map, i);
-			if (optname == 't') {
-				ret = tcp_sock_init(c, NULL, NULL, i);
-				if (ret == -ENFILE || ret == -EMFILE)
-					goto enfile;
-				if (!ret)
-					bound_one = true;
-			} else if (optname == 'u') {
-				ret = udp_sock_init(c, 0, NULL, NULL, i);
-				if (ret == -ENFILE || ret == -EMFILE)
-					goto enfile;
-				if (!ret)
-					bound_one = true;
-			}
-		}
-
-		if (!bound_one)
-			goto bind_all_fail;
+				bitmap_set(exclude, i);
 
+		conf_ports_range_except(c, optname, optarg, fwd,
+					NULL, NULL,
+					1, NUM_PORTS - 1, exclude,
+					1, true);
 		return;
 	}
 
@@ -275,37 +326,15 @@ static void conf_ports(const struct ctx *c, char optname, const char *optarg,
 	} while ((p = next_chunk(p, ',')));
 
 	if (exclude_only) {
-		/* Skip port 0.  It has special meaning for many socket APIs, so
-		 * trying to bind it is not really safe.
-		 */
-		for (i = 1; i < NUM_PORTS; i++) {
-			if (fwd_port_is_ephemeral(i) ||
-			    bitmap_isset(exclude, i))
-				continue;
-
-			bitmap_set(fwd->map, i);
-
-			if (optname == 't') {
-				ret = tcp_sock_init(c, addr, ifname, i);
-				if (ret == -ENFILE || ret == -EMFILE)
-					goto enfile;
-				if (!ret)
-					bound_one = true;
-			} else if (optname == 'u') {
-				ret = udp_sock_init(c, 0, addr, ifname, i);
-				if (ret == -ENFILE || ret == -EMFILE)
-					goto enfile;
-				if (!ret)
-					bound_one = true;
-			} else {
-				/* No way to check in advance for -T and -U */
-				bound_one = true;
-			}
-		}
-
-		if (!bound_one)
-			goto bind_all_fail;
+		/* Exclude ephemeral ports */
+		for (i = 0; i < NUM_PORTS; i++)
+			if (fwd_port_is_ephemeral(i))
+				bitmap_set(exclude, i);
 
+		conf_ports_range_except(c, optname, optarg, fwd,
+					addr, ifname,
+					1, NUM_PORTS - 1, exclude,
+					1, true);
 		return;
 	}
 
@@ -334,40 +363,18 @@ static void conf_ports(const struct ctx *c, char optname, const char *optarg,
 		if ((*p != '\0')  && (*p != ',')) /* Garbage after the ranges */
 			goto bad;
 
-		for (i = orig_range.first; i <= orig_range.last; i++) {
-			if (bitmap_isset(fwd->map, i))
-				warn(
-"Altering mapping of already mapped port number: %s", optarg);
-
-			if (bitmap_isset(exclude, i))
-				continue;
-
-			bitmap_set(fwd->map, i);
-
-			fwd->delta[i] = mapped_range.first - orig_range.first;
-
-			ret = 0;
-			if (optname == 't')
-				ret = tcp_sock_init(c, addr, ifname, i);
-			else if (optname == 'u')
-				ret = udp_sock_init(c, 0, addr, ifname, i);
-			if (ret)
-				goto bind_fail;
-		}
+		conf_ports_range_except(c, optname, optarg, fwd,
+					addr, ifname,
+					orig_range.first, orig_range.last,
+					exclude,
+					mapped_range.first, false);
 	} while ((p = next_chunk(p, ',')));
 
 	return;
-enfile:
-	die("Can't open enough sockets for port specifier: %s", optarg);
 bad:
 	die("Invalid port specifier %s", optarg);
 mode_conflict:
 	die("Port forwarding mode '%s' conflicts with previous mode", optarg);
-bind_fail:
-	die("Failed to bind port %u (%s) for option '-%c %s', exiting",
-	    i, strerror_(-ret), optname, optarg);
-bind_all_fail:
-	die("Failed to bind any port for '-%c %s', exiting", optname, optarg);
 }
 
 /**