Support unix domain sockets in nc(1) with -Uu.

Previously, using -U with -u was an error that was not documented
in the man page.  Now it will use a unix socket in datagram mode.

Bidirectional unix datagram communication requires a socket at
both ends, so in client mode (without -l), a temporary socket is
created so that responses from the server can be received.
If -s is specified with -U and -u, it specifies the location of
the temporary socket to create.

This was mostly written way back in 2007.  Since then, various
improvements implemented based on suggestions from guenther@,
tedu@, and nicm@. Man page help from nicm@ and jmc@.

Unix datagram support requires a small change to atomicio.c
in order to function correctly, this will be committed separately
shortly.

OK nicm@

2 files changed, 83 insertions, 25 deletions

diff --git a/usr.bin/nc/nc.1 b/usr.bin/nc/nc.1
index c2599ce3f13..8745528040b 100644
--- a/usr.bin/nc/nc.1
+++ b/usr.bin/nc/nc.1
@@ -1,4 +1,4 @@
-.\"     $OpenBSD: nc.1,v 1.55 2010/07/25 07:51:39 guenther Exp $
+.\"     $OpenBSD: nc.1,v 1.56 2011/01/08 00:44:19 jeremy Exp $
 .\"
 .\" Copyright (c) 1996 David Sacerdote
 .\" All rights reserved.
@@ -25,7 +25,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: July 25 2010 $
+.Dd $Mdocdate: January 8 2011 $
 .Dt NC 1
 .Os
 .Sh NAME
@@ -155,6 +155,10 @@ assigns them.
 Enables the RFC 2385 TCP MD5 signature option.
 .It Fl s Ar source_ip_address
 Specifies the IP of the interface which is used to send the packets.
+For
+.Ux Ns -domain
+datagram sockets, specifies the local temporary socket file
+to create and use so that datagrams can be received.
 It is an error to use this option in conjunction with the
 .Fl l
 option.
@@ -179,6 +183,16 @@ Specifies to use
 sockets.
 .It Fl u
 Use UDP instead of the default option of TCP.
+For
+.Ux Ns -domain
+sockets, use a datagram socket instead of a stream socket.
+If a
+.Ux Ns -domain
+socket is used, a temporary receiving socket is created in
+.Pa /tmp
+unless the
+.Fl s
+flag is given.
 .It Fl V Ar rtable
 Set the routing table to be used.
 The default is 0.
diff --git a/usr.bin/nc/netcat.c b/usr.bin/nc/netcat.c
index e471182b2ad..7b9fe41ba46 100644
--- a/usr.bin/nc/netcat.c
+++ b/usr.bin/nc/netcat.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: netcat.c,v 1.98 2010/07/03 04:44:51 guenther Exp $ */
+/* $OpenBSD: netcat.c,v 1.99 2011/01/08 00:44:19 jeremy Exp $ */
 /*
  * Copyright (c) 2001 Eric Jackson <ericj@monkey.org>
  *
@@ -62,6 +62,7 @@
 
 #define PORT_MAX	65535
 #define PORT_MAX_LEN	6
+#define UNIX_DG_TMP_SOCKET_SIZE	19
 
 /* Command Line Options */
 int	dflag;					/* detached, no stdin */
@@ -89,6 +90,7 @@ u_int	rtableid;
 int timeout = -1;
 int family = AF_UNSPEC;
 char *portlist[PORT_MAX+1];
+char *unix_dg_tmp_socket;
 
 void	atelnet(int, unsigned char *, unsigned int);
 void	build_ports(char *);
@@ -99,6 +101,7 @@ int	remote_connect(const char *, const char *, struct addrinfo);
 int	socks_connect(const char *, const char *, struct addrinfo,
 	    const char *, const char *, struct addrinfo, int, const char *);
 int	udptest(int);
+int	unix_bind(char *);
 int	unix_connect(char *);
 int	unix_listen(char *);
 void	set_common_sockopts(int);
@@ -117,6 +120,7 @@ main(int argc, char *argv[])
 	char *proxy;
 	const char *errstr, *proxyhost = "", *proxyport = NULL;
 	struct addrinfo proxyhints;
+	char unix_dg_tmp_socket_buf[UNIX_DG_TMP_SOCKET_SIZE];
 
 	ret = 1;
 	s = 0;
@@ -241,8 +245,6 @@ main(int argc, char *argv[])
 
 	/* Cruft to make sure options are clean, and used properly. */
 	if (argv[0] && !argv[1] && family == AF_UNIX) {
-		if (uflag)
-			errx(1, "cannot use -u and -U");
 		host = argv[0];
 		uport = NULL;
 	} else if (argv[0] && !argv[1]) {
@@ -265,6 +267,19 @@ main(int argc, char *argv[])
 	if (!lflag && kflag)
 		errx(1, "must use -l with -k");
 
+	/* Get name of temporary socket for unix datagram client */
+	if ((family == AF_UNIX) && uflag && !lflag) {
+		if (sflag) {
+			unix_dg_tmp_socket = sflag;
+		} else {
+			strlcpy(unix_dg_tmp_socket_buf, "/tmp/nc.XXXXXXXXXX",
+				UNIX_DG_TMP_SOCKET_SIZE);
+			if (mktemp(unix_dg_tmp_socket_buf) == NULL)
+				err(1, "mktemp");
+			unix_dg_tmp_socket = unix_dg_tmp_socket_buf;
+		}
+	}
+
 	/* Initialize addrinfo structure. */
 	if (family != AF_UNIX) {
 		memset(&hints, 0, sizeof(struct addrinfo));
@@ -307,8 +322,12 @@ main(int argc, char *argv[])
 		int connfd;
 		ret = 0;
 
-		if (family == AF_UNIX)
-			s = unix_listen(host);
+		if (family == AF_UNIX) {
+			if (uflag)
+				s = unix_bind(host);
+			else
+				s = unix_listen(host);
+		}
 
 		/* Allow only one connection at a time, but stay alive. */
 		for (;;) {
@@ -337,17 +356,21 @@ main(int argc, char *argv[])
 				if (rv < 0)
 					err(1, "connect");
 
-				connfd = s;
+				readwrite(s);
 			} else {
 				len = sizeof(cliaddr);
 				connfd = accept(s, (struct sockaddr *)&cliaddr,
 				    &len);
+				readwrite(connfd);
+				close(connfd);
 			}
 
-			readwrite(connfd);
-			close(connfd);
 			if (family != AF_UNIX)
 				close(s);
+			else if (uflag) {
+				if (connect(s, NULL, 0) < 0)
+					err(1, "connect");
+			}
 
 			if (!kflag)
 				break;
@@ -361,6 +384,8 @@ main(int argc, char *argv[])
 		} else
 			ret = 1;
 
+		if (uflag)
+			unlink(unix_dg_tmp_socket);
 		exit(ret);
 
 	} else {
@@ -421,18 +446,19 @@ main(int argc, char *argv[])
 }
 
 /*
- * unix_connect()
- * Returns a socket connected to a local unix socket. Returns -1 on failure.
+ * unix_bind()
+ * Returns a unix socket bound to the given path
  */
 int
-unix_connect(char *path)
+unix_bind(char *path)
 {
 	struct sockaddr_un sun;
 	int s;
 
-	if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
+	/* Create unix domain socket. */
+	if ((s = socket(AF_UNIX, uflag ? SOCK_DGRAM : SOCK_STREAM,
+	     0)) < 0)
 		return (-1);
-	(void)fcntl(s, F_SETFD, 1);
 
 	memset(&sun, 0, sizeof(struct sockaddr_un));
 	sun.sun_family = AF_UNIX;
@@ -443,27 +469,32 @@ unix_connect(char *path)
 		errno = ENAMETOOLONG;
 		return (-1);
 	}
-	if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
+
+	if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
 		close(s);
 		return (-1);
 	}
 	return (s);
-
 }
 
 /*
- * unix_listen()
- * Create a unix domain socket, and listen on it.
+ * unix_connect()
+ * Returns a socket connected to a local unix socket. Returns -1 on failure.
  */
 int
-unix_listen(char *path)
+unix_connect(char *path)
 {
 	struct sockaddr_un sun;
 	int s;
 
-	/* Create unix domain socket. */
-	if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
-		return (-1);
+	if (uflag) {
+		if ((s = unix_bind(unix_dg_tmp_socket)) < 0)
+			return (-1);
+	} else {
+		if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
+			return (-1);
+	}
+	(void)fcntl(s, F_SETFD, 1);
 
 	memset(&sun, 0, sizeof(struct sockaddr_un));
 	sun.sun_family = AF_UNIX;
@@ -474,11 +505,24 @@ unix_listen(char *path)
 		errno = ENAMETOOLONG;
 		return (-1);
 	}
-
-	if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
+	if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
 		close(s);
 		return (-1);
 	}
+	return (s);
+
+}
+
+/*
+ * unix_listen()
+ * Create a unix domain socket, and listen on it.
+ */
+int
+unix_listen(char *path)
+{
+	int s;
+	if ((s = unix_bind(path)) < 0)
+		return (-1);
 
 	if (listen(s, 5) < 0) {
 		close(s);