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@

1 files changed, 16 insertions, 2 deletions

diff --git a/src/usr.bin/nc/nc.1 b/src/usr.bin/nc/nc.1
index c2599ce3f1..8745528040 100644
--- a/src/usr.bin/nc/nc.1
+++ b/src/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.