[uml-devel] [PATCH] mconsole fixes

[uml-devel] [PATCH] mconsole fixes

[Dan Shearer]

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This makes uml_mconsole a bit more useful in scripts:

	1. it exits with '1' for an error, '0' for no error. So you can
	now tell if you have got a pty for a tty or not without scraping
	text

	2. has a more sensible error message where the pipe doesn't
	exist

	3. adds a local command called 'mconsole-version' (which will be
	more useful as UML matures and the design of having all the
	clever bits inside UML really shows its value.)

SGML docs not modified, because I don't know the convention for changing
them (eg, do you add new ENTITY entries for new authors, or does the
last author overwrite the previous...?)

-- 
Dan Shearer
dan@shearer.org

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--- uml_mconsole.c.orig	2004-01-26 11:30:54.000000000 +1030
+++ uml_mconsole.c	2004-01-26 13:00:21.000000000 +1030
@@ -1,5 +1,30 @@
-/* Copyright 2001 Jeff Dike and others
- * Licensed under the GPL
+/* (c) Copyright 2001-2004 Jeff Dike and others
+ * Licensed under the GPL, see file COPYING
+ *
+ * This is uml_console version 2, a tool for querying a User Mode Linux 
+ * instance over a local pipe connection. This tool does not
+ * (since uml_mconsole version 1) need to be in sync with the version
+ * of the UML kernel since the commands and their implementation 
+ * are within UML. uml_mconsole just displays what UML tells it to.
+ * There are a very few local commands that this program knows
+ * about, but by default everything gets processed by UML.
+ *
+ * The uml_mconsole documentation distributed with covers all mconsole
+ * commands, so the docs have to be kept in sync with the kernel.
+ * In future it should be possible for the docs to come from (or be
+ * in common with) something over in the kernel source.
+ *
+ * If you are looking for the command implementation, go to the
+ * files mconsole_kern.c in the Linux kernel source under arch/um.
+ * 
+ * The program exits with error values of:
+ *
+ *      0    No error
+ *      1    Error     (need better breakdown of error type in future)
+ *
+ * Future TODO: return commandline results as a shell variable assignment 
+ * eg: 'uml_mconsole config con0' might return "UML-CON=fd:0,fd:1"
+ *
  */
 
 #include <stdio.h>
@@ -27,7 +52,7 @@
   if(stat(file, &buf) == -1){
     fprintf(stderr, "Warning: couldn't stat file: %s - ", file);
     perror("");
-    return(-1);
+    return(1);
   }
   sun.sun_family = AF_UNIX;
   strncpy(sun.sun_path, file, sizeof(sun.sun_path));
@@ -183,7 +208,7 @@
   return(1);
 }
 
-static void default_cmd(int fd, char *command)
+static int default_cmd(int fd, char *command)
 {
   struct mconsole_request request;
   struct mconsole_reply reply;
@@ -192,7 +217,7 @@
 
   if((sscanf(command, "%128[^: \f\n\r\t\v]:", name) == 1) &&
      (*(name + 1) == ':')){
-    if(switch_common(name)) return;
+    if(switch_common(name)) return(1);
     command = strchr(command, ':');
     *command++ = '\0';
     while(isspace(*command)) command++;
@@ -210,18 +235,21 @@
 
   if(sendto(fd, &request, sizeof(request), 0, (struct sockaddr *) &sun, 
 	    sizeof(sun)) < 0){
-    fprintf(stderr, "Sending command to '%s' : ", sun.sun_path);
-    perror("");
-    return;
+    if (strlen(sun.sun_path)==0) {
+      fprintf(stderr, "No connection exists, cannot send command.\n");
+    } else {
+      fprintf(stderr, "While sending command to '%s' : ", sun.sun_path);
+      perror("");
+    }
+    return(1);
   }
 
   first = 1;
   do {
-    int len = sizeof(sun);
     n = recvfrom(fd, &reply, sizeof(reply), 0, NULL, 0);
     if(n < 0){
       perror("recvmsg");
-      return;
+      return(1);
     }
 
     if(first){
@@ -235,31 +263,35 @@
   } while(reply.more);
 
   printf("\n");
+  if (reply.err) return(1); else return(0);
 }
 
 char *local_help = 
 "Additional local mconsole commands:\n\
     quit - Quit mconsole\n\
     switch <socket-name> - Switch control to the given machine\n\
-    log -f <filename> - use contents of <filename> as UML log messages\n";
+    log -f <filename> - use contents of <filename> as UML log messages\n\
+    mconsole-version - version of this mconsole program\n";
 
-static void help_cmd(int fd, char *command)
+static int help_cmd(int fd, char *command)
 {
   default_cmd(fd, command);
   printf("%s", local_help);
+  return(0);
 }
 
-static void switch_cmd(int fd, char *command)
+static int switch_cmd(int fd, char *command)
 {
   char *ptr;
 
   ptr = &command[strlen("switch")];
   while(isspace(*ptr)) ptr++;
-  if(switch_common(ptr)) return;
+  if(switch_common(ptr)) return(1);
   printf("Switched to '%s'\n", ptr);
+  return(0);
 }
 
-static void log_cmd(int fd, char *command)
+static int log_cmd(int fd, char *command)
 {
   int len, max, chunk, input_fd;
   char *ptr, buf[sizeof(((struct mconsole_request *) NULL)->data)];
@@ -299,16 +331,23 @@
       ptr += chunk;
     }
   }
+  return(0);
 }
 
-static void quit_cmd(int fd, char *command)
+static int quit_cmd(int fd, char *command)
 {
   exit(0);
 }
 
+static int mversion_cmd(int fd, char *command)
+{
+  printf("uml_mconsole client version %d\n",MCONSOLE_VERSION);
+  return(0);
+}
+
 struct cmd {
   char *command;
-  void (*proc)(int, char *);
+  int (*proc)(int, char *);
 };
 
 static struct cmd cmds[] = {
@@ -316,14 +355,16 @@
   { "help", help_cmd },
   { "switch", switch_cmd },
   { "log", log_cmd },
+  { "mconsole-version", mversion_cmd },
   { NULL, default_cmd }
+  /* default_cmd means "send it to the UML" */
 };
 
 /* sends a command */
 int issue_command(int fd, char *command)
 {
   char *ptr;
-  int i;
+  int i=0,ret=0;
 
   /* Trim trailing spaces left by readline's filename completion */
   ptr = &command[strlen(command) - 1];
@@ -332,20 +373,20 @@
   for(i = 0; i < sizeof(cmds)/sizeof(cmds[0]); i++){
     if((cmds[i].command == NULL) || 
        !strncmp(cmds[i].command, command, strlen(cmds[i].command))){
-      (*cmds[i].proc)(fd, command);
+      ret=(int)(*cmds[i].proc)(fd, command);
       break;
     }
   }
     
-  /* in future, return command status */
-  return 0;
+  return(ret);
+
 }
 
 /* sends a command in argv style array */
 int issue_commandv(int fd, char **argv)
 {
   char *command;
-  int len, i, status;
+  int len=-1, i=0, status=-2;
 
   len = 1;  /* space for trailing null */
   for(i = 0; argv[i] != NULL; i++)
@@ -354,7 +395,7 @@
   command = malloc(len);
   if(command == NULL){
     perror("issue_command");
-    return(-1);
+    return(1);
   }
   command[0] = '\0';
 
@@ -401,7 +442,7 @@
   }
 
   if(argc>2)
-    return issue_commandv(fd, argv+2);
+    exit(issue_commandv(fd,argv+2));
 
   while(1){
     char *command, prompt[1 + sizeof(uml_name) + 2 + 1];
@@ -416,5 +457,5 @@
     free(command);
   }
   printf("\n");
-  return(0);
+  exit(0);
 }

[uml-devel] Re: [PATCH] mconsole fixes

[Jeff Dike]

dan@shearer.org said:
> + * instance over a local pipe connection. This tool does not 
> + * (since uml_mconsole version 1) need to be in sync with the version
> + * of the UML kernel since the commands and their implementation 
> + * are within UML.

The version does need to match.  UML will only talk to one version of mconsole.

The smarts are all in the kernel, but they do need to agree on the format of
the request and the response.

> -    fprintf(stderr, "Sending command to '%s' : ", sun.sun_path);
> -    perror("");
> -    return;
> +    if (strlen(sun.sun_path)==0) {
> +      fprintf(stderr, "No connection exists, cannot send command.\n");
> +    } else {
> +      fprintf(stderr, "While sending command to '%s' : ", sun.sun_path);
> +      perror("");
> +    }
> +    return(1);

I don't see the point of the strlen(sun.sun_path)==0 check, so I'm leaving that
out until I see why it's necessary.

I applied most of the rest of that.  I got rid of the exits from main, since
I like returns better and I tidied up some other stuff.

				Jeff



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Re: [uml-devel] Re: [PATCH] mconsole fixes

[Dan Shearer]

On Tue, Jan 27, 2004 at 08:46:36PM -0500, Jeff Dike wrote:
 
> > -    fprintf(stderr, "Sending command to '%s' : ", sun.sun_path);
> > -    perror("");
> > -    return;
> > +    if (strlen(sun.sun_path)==0) {
> > +      fprintf(stderr, "No connection exists, cannot send command.\n");
> > +    } else {
> > +      fprintf(stderr, "While sending command to '%s' : ", sun.sun_path);
> > +      perror("");
> > +    }
> > +    return(1);
> 
> I don't see the point of the strlen(sun.sun_path)==0 check, so I'm
> leaving that out until I see why it's necessary.

My idea was that there's a difference between an error on a connection
and no connection at all. Having no connection at all can happen very
easily, especially if you happen to use uml_dir on the cmdline which
triggers a bug that puts the file in the wrong place.

> I applied most of the rest of that.  I got rid of the exits from main, since
> I like returns better and I tidied up some other stuff.

Minor portability potential. See
http://www.eskimo.com/~scs/C-faq/q11.16.html. (I looked it up once long
ago and supposedly _exit is more likely to work on more systems than
exit.)

-- 
Dan Shearer
dan@shearer.org


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Re: [uml-devel] Re: [PATCH] mconsole fixes

[Dan Shearer]

On Wed, Jan 28, 2004 at 12:46:52PM +1030, Dan Shearer wrote:
> On Tue, Jan 27, 2004 at 08:46:36PM -0500, Jeff Dike wrote:
 
> > I applied most of the rest of that.  I got rid of the exits from main, since
> > I like returns better and I tidied up some other stuff.
> 
> Minor portability potential. See
> http://www.eskimo.com/~scs/C-faq/q11.16.html. (I looked it up once long
> ago and supposedly _exit is more likely to work on more systems than
> exit.)

Actually on second thoughts that is not relevant (applies to functions
other than main.)

However there is only one way that the standard guarantees we can
indicate a status to the OS and that is exit(EXIT_FAILURE) or
EXIT_SUCCESS. return(whatever) works on the sane OSs that we're used to,
but the standard is there for a reason. So that should be used instead.

-- 
Dan Shearer
dan@shearer.org


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Re: [uml-devel] Re: [PATCH] mconsole fixes

[Jeff Dike]

dan@shearer.org said:
> My idea was that there's a difference between an error on a connection
> and no connection at all. Having no connection at all can happen very
> easily, especially if you happen to use uml_dir on the cmdline which
> triggers a bug that puts the file in the wrong place. 

OK, that being the case, it's better to complain before sending anything to
UML rather than after you've tried and failed.

> Minor portability potential. See http://www.eskimo.com/~scs/C-faq/
> q11.16.html. (I looked it up once long ago and supposedly _exit is
> more likely to work on more systems than exit.) 

You talked me into it.  I fixed that.

				Jeff



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