On Thu, Jun 28, 2012 at 11:44:36PM -0300, Christiano F. Haesbaert wrote:
> Although the idea for using -k with -u is a good one, I don't think
> it's necessary, I for one think we should change semantics as the
> first mail suggested.
>
> The only real for using connected UDP sockets is to get the ICMP async
> errors at the socket level, ICMP port unreachable mainly.
>
> I see no reason why not to change the semantics to *not* use connected
> UDP sockets, since the server will *never* write anything back to the
> client.
But then we would have to drop print "connection received from...",
which is being introduced in another diff. Now I'm more inclined in
going for the -k, that way we know when to supress the message.
>
>
> On Mon, Jun 25, 2012 at 01:41:48PM +0300, Lazaros Koromilas wrote:
> > On Sun, Jun 24, 2012 at 11:23:05PM +0200, Ariane van der Steldt wrote:
> > > On Mon, Jun 25, 2012 at 12:09:33AM +0300, dsp wrote:
> > > > We observe the following behaviour when running nc -ul.
> > > > The server begins on a recvfrom() and when data arrives it
> > > > connects() the socket.
> > > > When the client dies , the server remains in a connected state
> > > > therefore ignoring subsequent data arriving on the port.
> > > > Is this really the intended logic for a connectionless protocol like
> > > > UDP? We proceeded to comment out the connect statement and we were
> > > > able to receive data from multiple *sessions* as expected.
> > > > Can you shed some light on the matter???
> > >
> > > Reading the man page, I think you want to add the -k option to nc.
> >
> > The -k option does nothing when used with -u because the readwrite()
> > session cannot end. Would the following be a reasonable change?
> > It has the side effect of letting UDP packets to interleave.
> >
> >
> > Index: nc.1
> > ===================================================================
> > RCS file: /cvs/src/usr.bin/nc/nc.1,v
> > retrieving revision 1.60
> > diff -u -p -r1.60 nc.1
> > --- nc.1 7 Feb 2012 12:11:43 -0000 1.60
> > +++ nc.1 25 Jun 2012 10:40:15 -0000
> > @@ -119,6 +119,10 @@ is completed.
> > It is an error to use this option without the
> > .Fl l
> > option.
> > +When used together with the
> > +.Fl u
> > +option all UDP datagrams arriving on the port are received;
> > +not just those sent by the first client to connect.
> > .It Fl l
> > Used to specify that
> > .Nm
> > Index: netcat.c
> > ===================================================================
> > RCS file: /cvs/src/usr.bin/nc/netcat.c,v
> > retrieving revision 1.105
> > diff -u -p -r1.105 netcat.c
> > --- netcat.c 9 Feb 2012 06:25:35 -0000 1.105
> > +++ netcat.c 25 Jun 2012 10:40:15 -0000
> > @@ -364,9 +364,12 @@ main(int argc, char *argv[])
> > if (rv < 0)
> > err(1, "recvfrom");
> >
> > - rv = connect(s, (struct sockaddr *)&z, len);
> > - if (rv < 0)
> > - err(1, "connect");
> > + if (!kflag) {
> > + rv = connect(s, (struct sockaddr *)&z,
> > + len);
> > + if (rv < 0)
> > + err(1, "connect");
> > + }
> >
> > readwrite(s);
> > } else {
