Re: [RFA] Remote UDP support

[Daniel Jacobowitz <drow@mvista.com>]

On Sat, May 11, 2002 at 03:13:02PM -0400, Andrew Cagney wrote:
> >No.  I think it need to be in the users face.  I don't think GDB should 
> >>silently let the user to use a broken mechanism.
> >
> >
> >I really don't agree, but your call.  Could I at least persuade you
> >down to a one-line warning and no confirmation query?
> 
> Oh! All right then :-)

How's this look?  I wasn't quite sure what to put in the text of the
warning.  Also added one to the manual.

-- 
Daniel Jacobowitz                           Carnegie Mellon University
MontaVista Software                         Debian GNU/Linux Developer

Index: ser-tcp.c
===================================================================
RCS file: /cvs/src/src/gdb/ser-tcp.c,v
retrieving revision 1.10
diff -u -p -r1.10 ser-tcp.c
--- ser-tcp.c	18 Dec 2001 18:54:18 -0000	1.10
+++ ser-tcp.c	11 May 2002 21:19:41 -0000
@@ -38,12 +38,15 @@
 #include <netdb.h>
 #include <sys/socket.h>
 #include <netinet/tcp.h>
+#include <netinet/udp.h>
 
 #include <signal.h>
 #include "gdb_string.h"
 
-static int tcp_open (struct serial *scb, const char *name);
-static void tcp_close (struct serial *scb);
+static int udp_warning = 0;
+
+static int net_open (struct serial *scb, const char *name);
+static void net_close (struct serial *scb);
 extern int (*ui_loop_hook) (int);
 void _initialize_ser_tcp (void);
 
@@ -55,17 +58,35 @@ void _initialize_ser_tcp (void);
 /* Open a tcp socket */
 
 static int
-tcp_open (struct serial *scb, const char *name)
+net_open (struct serial *scb, const char *name)
 {
   char *port_str, hostname[100];
   int n, port, tmp;
+  int use_udp;
   struct hostent *hostent;
   struct sockaddr_in sockaddr;
 
+  use_udp = 0;
+  if (strncmp (name, "udp:", 4) == 0)
+    {
+      use_udp = 1;
+      name = name + 4;
+
+      if (udp_warning == 0)
+	{
+	  udp_warning = 1;
+	  warning ("UDP debugging is unreliable.");
+	  warning ("Some events may be lost, rendering further debugging "
+		   "impossible.");
+	}
+    }
+  else if (strncmp (name, "tcp:", 4) == 0)
+    name = name + 4;
+
   port_str = strchr (name, ':');
 
   if (!port_str)
-    error ("tcp_open: No colon in host name!");	   /* Shouldn't ever happen */
+    error ("net_open: No colon in host name!");	   /* Shouldn't ever happen */
 
   tmp = min (port_str - name, (int) sizeof hostname - 1);
   strncpy (hostname, name, tmp);	/* Don't want colon */
@@ -84,7 +105,11 @@ tcp_open (struct serial *scb, const char
       return -1;
     }
 
-  scb->fd = socket (PF_INET, SOCK_STREAM, 0);
+  if (use_udp)
+    scb->fd = socket (PF_INET, SOCK_DGRAM, 0);
+  else
+    scb->fd = socket (PF_INET, SOCK_STREAM, 0);
+
   if (scb->fd < 0)
     return -1;
   
@@ -102,7 +127,7 @@ tcp_open (struct serial *scb, const char
 
   if (n < 0 && errno != EINPROGRESS)
     {
-      tcp_close (scb);
+      net_close (scb);
       return -1;
     }
 
@@ -124,7 +149,7 @@ tcp_open (struct serial *scb, const char
 	      if (ui_loop_hook (0))
 		{
 		  errno = EINTR;
-		  tcp_close (scb);
+		  net_close (scb);
 		  return -1;
 		}
 	    }
@@ -142,7 +167,7 @@ tcp_open (struct serial *scb, const char
 	{
 	  if (polls > TIMEOUT * POLL_INTERVAL)
 	    errno = ETIMEDOUT;
-	  tcp_close (scb);
+	  net_close (scb);
 	  return -1;
 	}
     }
@@ -156,20 +181,23 @@ tcp_open (struct serial *scb, const char
       {
 	if (err)
 	  errno = err;
-	tcp_close (scb);
+	net_close (scb);
 	return -1;
       }
   } 
-  
+
   /* turn off nonblocking */
   tmp = 0;
   ioctl (scb->fd, FIONBIO, &tmp);
 
-  /* Disable Nagle algorithm. Needed in some cases. */
-  tmp = 1;
-  setsockopt (scb->fd, IPPROTO_TCP, TCP_NODELAY,
-	      (char *)&tmp, sizeof (tmp));
-  
+  if (use_udp == 0)
+    {
+      /* Disable Nagle algorithm. Needed in some cases. */
+      tmp = 1;
+      setsockopt (scb->fd, IPPROTO_TCP, TCP_NODELAY,
+		  (char *)&tmp, sizeof (tmp));
+    }
+
   /* If we don't do this, then GDB simply exits
      when the remote side dies.  */
   signal (SIGPIPE, SIG_IGN);
@@ -178,7 +206,7 @@ tcp_open (struct serial *scb, const char
 }
 
 static void
-tcp_close (struct serial *scb)
+net_close (struct serial *scb)
 {
   if (scb->fd < 0)
     return;
@@ -194,8 +222,8 @@ _initialize_ser_tcp (void)
   memset (ops, sizeof (struct serial_ops), 0);
   ops->name = "tcp";
   ops->next = 0;
-  ops->open = tcp_open;
-  ops->close = tcp_close;
+  ops->open = net_open;
+  ops->close = net_close;
   ops->readchar = ser_unix_readchar;
   ops->write = ser_unix_write;
   ops->flush_output = ser_unix_nop_flush_output;
Index: doc/gdb.texinfo
===================================================================
RCS file: /cvs/src/src/gdb/doc/gdb.texinfo,v
retrieving revision 1.98
diff -u -p -r1.98 gdb.texinfo
--- doc/gdb.texinfo	4 May 2002 16:00:30 -0000	1.98
+++ doc/gdb.texinfo	11 May 2002 21:21:23 -0000
@@ -10475,7 +10475,7 @@ of its pure text.
 Establish communication using the @code{target remote} command.
 Its argument specifies how to communicate with the target
 machine---either via a devicename attached to a direct serial line, or a
-TCP port (usually to a terminal server which in turn has a serial line
+TCP or UDP port (usually to a terminal server which in turn has a serial line
 to the target).  For example, to use a serial line connected to the
 device named @file{/dev/ttyb}:
 
@@ -10485,7 +10485,8 @@ target remote /dev/ttyb
 
 @cindex TCP port, @code{target remote}
 To use a TCP connection, use an argument of the form
-@code{@var{host}:port}.  For example, to connect to port 2828 on a
+@code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
+For example, to connect to port 2828 on a
 terminal server named @code{manyfarms}:
 
 @smallexample
@@ -10503,6 +10504,21 @@ target remote :1234
 @noindent
 
 Note that the colon is still required here.
+
+@cindex UDP port, @code{target remote}
+To use a UDP connection, use an argument of the form
+@code{udp:@var{host}:@var{port}}.  For example, to connect to UDP port 2828
+on a terminal server named @code{manyfarms}:
+
+@smallexample
+target remote udp:manyfarms:2828
+@end smallexample
+
+When using a UDP connection for remote debugging, you should keep in mind
+that the `U' stands for ``Unreliable''.  UDP can silently drop packets on
+busy or unreliable networks, which will cause havoc with your debugging
+session.
+
 @end enumerate
 
 Now you can use all the usual commands to examine and change data and to