rresvport() in terms of bind() & bindresvport()

2 files changed, 15 insertions, 14 deletions

diff --git a/lib/libc/net/rcmd.3 b/lib/libc/net/rcmd.3
index 8452e395dba..add4faa3141 100644
--- a/lib/libc/net/rcmd.3
+++ b/lib/libc/net/rcmd.3
@@ -134,6 +134,9 @@ by
 and several other functions.  Privileged Internet ports are those
 in the range 0 to 1023.  Only the super-user
 is allowed to bind an address of this sort to a socket.
+.Fn rresvport
+needs to be seeded with a port number; if that port
+is not available it will find another.
 .Pp
 The
 .Fn iruserok
diff --git a/lib/libc/net/rcmd.c b/lib/libc/net/rcmd.c
index 22a956cfb05..28420d20ebe 100644
--- a/lib/libc/net/rcmd.c
+++ b/lib/libc/net/rcmd.c
@@ -228,21 +228,19 @@ rresvport(alport)
 	s = socket(AF_INET, SOCK_STREAM, 0);
 	if (s < 0)
 		return (-1);
-	for (;;) {
-		sin.sin_port = htons((u_short)*alport);
-		if (bind(s, (struct sockaddr *)&sin, sizeof(sin)) >= 0)
-			return (s);
-		if (errno != EADDRINUSE) {
-			(void)close(s);
-			return (-1);
-		}
-		(*alport)--;
-		if (*alport == IPPORT_RESERVED/2) {
-			(void)close(s);
-			errno = EAGAIN;		/* close */
-			return (-1);
-		}
+	sin.sin_port = htons((u_short)*alport);
+	if (bind(s, (struct sockaddr *)&sin, sizeof(sin)) >= 0)
+		return (s);
+	if (errno != EADDRINUSE) {
+		(void)close(s);
+		return (-1);
 	}
+	if (bindresvport(s, &sin) == -1) {
+		(void)close(s);
+		return (-1);
+	}
+	*alport = (int)ntohs(sin.sin_port);
+	return (s);
 }
 
 int	__check_rhosts_file = 1;