Re: [RFA] Remote UDP support

Daniel Jacobowitz
2002-05-13T17:42:04Z

On Mon, May 13, 2002 at 12:44:15AM -0400, Andrew Cagney wrote:
> >How's this look? I wasn't quite sure what to put in the text of the
> >>>warning. Also added one to the manual.
> >
> >>
> >>Problem is, its in the wrong place, and I suspect getting it into the
> >>right place - remote.c - is tricky.
> >>
> >>I think adding a FIXME hack to remote.c (search for serial_open) that
> >>checks for ``udp:'' and then print a warning is the most pratical.
> >
> >
> >I don't understand. Why hoist it up into remote.c, before each call to
> >serial_open? That just descends through serial_open to call net_open
> >and the warning would arrive at the same position; the warning is
> >specific to ser-tcp, and seems to belong there.
>
> Sorry, yes the rationale was a big bit vague :-(
>
> serial_open() provides a generic serial connection. Data that goes in
> one end, hopefully, comes out the other end - it doesn't promise to be
> reliable though.
>
> remote.c, on the other hand, makes certain assumptions about the
> properties of the SERIAL object it is using (only data overrun is
> possible, single character transfers are reliable, ...). Hence, I think
> remote.c should be the one reporting a potential problem.
>
> Besides, if someone were to implement a remote-udp.c the warning would
> be wrong :-)

OK, that did it. Now I understand why you wanted it. Is this better?

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

2002-05-08 Daniel Jacobowitz <drow@mvista.com>

* ser-tcp.c: Include <netinet/udp.h>. Rename tcp_open
and tcp_close to net_open and net_close.
(net_open): Accept "udp:" and "tcp:" specifications. Connect
using UDP if requested. Don't try to disable Nagle on UDP
sockets.
* remote.c (remote_serial_open): New function. Warn about UDP.
(remote_open_1, remote_async_open_1, remote_cisco_open): Call it.

2002-05-08 Daniel Jacobowitz <drow@mvista.com>

* gdb.texinfo (Debug Session): Document new `udp:' and `tcp:'
options for `target remote'.

Index: remote.c
===================================================================
RCS file: /cvs/src/src/gdb/remote.c,v
retrieving revision 1.80
diff -u -p -r1.80 remote.c
--- remote.c 12 May 2002 01:02:58 -0000 1.80
+++ remote.c 13 May 2002 16:34:59 -0000
@@ -2222,6 +2222,26 @@ remote_check_symbols (struct objfile *ob
}
}

+static struct serial *
+remote_serial_open (char *name)
+{
+ static int udp_warning = 0;
+
+ /* FIXME: Parsing NAME here is a hack. But we want to warn here instead
+ of in ser-tcp.c, because it is the remote protocol assuming that the
+ serial connection is reliable and not the serial connection promising
+ to be. */
+ if (!udp_warning && strncmp (name, "udp:", 4) == 0)
+ {
+ warning ("The remote protocol may be unreliable over UDP.");
+ warning ("Some events may be lost, rendering further debugging "
+ "impossible.");
+ udp_warning = 1;
+ }
+
+ return serial_open (name);
+}
+
static void
remote_open_1 (char *name, int from_tty, struct target_ops *target,
int extended_p)
@@ -2239,7 +2259,7 @@ remote_open_1 (char *name, int from_tty,

unpush_target (target);

- remote_desc = serial_open (name);
+ remote_desc = remote_serial_open (name);
if (!remote_desc)
perror_with_name (name);

@@ -2337,7 +2357,7 @@ remote_async_open_1 (char *name, int fro

unpush_target (target);

- remote_desc = serial_open (name);
+ remote_desc = remote_serial_open (name);
if (!remote_desc)
perror_with_name (name);

@@ -5463,7 +5483,7 @@ remote_cisco_open (char *name, int from_

unpush_target (&remote_cisco_ops);

- remote_desc = serial_open (name);
+ remote_desc = remote_serial_open (name);
if (!remote_desc)
perror_with_name (name);

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 13 May 2002 16:34:59 -0000
@@ -38,12 +38,13 @@
#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 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 +56,27 @@ 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;
+ }
+ 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 +95,11 @@ 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 +117,7 @@ tcp_open (struct serial *scb, const char

if (n < 0 && errno != EINPROGRESS)
{
- tcp_close (scb);
+ net_close (scb);
return -1;
}

@@ -124,7 +139,7 @@ tcp_open (struct serial *scb, const char
if (ui_loop_hook (0))
{
errno = EINTR;
- tcp_close (scb);
+ net_close (scb);
return -1;
}
}
@@ -142,7 +157,7 @@ tcp_open (struct serial *scb, const char
{
if (polls > TIMEOUT * POLL_INTERVAL)
errno = ETIMEDOUT;
- tcp_close (scb);
+ net_close (scb);
return -1;
}
}
@@ -156,20 +171,23 @@ 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 +196,7 @@ 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 +212,8 @@ _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 13 May 2002 16:35:22 -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