Customize 'permission denied' error.

From: Jan Safranek <jsafrane@redhat.com>

Add Fedora-specific message to error output when dumpcap cannot be started
because of permissions.

Signed-off-by: Jan Safranek <jsafrane@redhat.com>

diff -up wireshark-1.6.1/capture_sync.c.group-msg wireshark-1.6.1/capture_sync.c
--- wireshark-1.6.1/capture_sync.c.group-msg	2011-07-18 22:18:53.000000000 +0200
+++ wireshark-1.6.1/capture_sync.c	2011-07-21 10:52:28.962144991 +0200
@@ -351,6 +351,7 @@ sync_pipe_start(capture_options *capture
     gchar *signal_pipe_name;
 #else
     char errmsg[1024+1];
+    const char *securitymsg = "";
     int sync_pipe[2];                       /* pipe used to send messages from child to parent */
     enum PIPES { PIPE_READ, PIPE_WRITE };   /* Constants 0 and 1 for PIPE_READ and PIPE_WRITE */
 #endif
@@ -596,8 +597,10 @@ sync_pipe_start(capture_options *capture
       dup2(sync_pipe[PIPE_WRITE], 2);
       ws_close(sync_pipe[PIPE_READ]);
       execv(argv[0], (gpointer)argv);
-      g_snprintf(errmsg, sizeof errmsg, "Couldn't run %s in child process: %s",
-                argv[0], g_strerror(errno));
+      if (errno == EPERM || errno == EACCES)
+	      securitymsg = "\nAre you a member of the 'wireshark' group? Try running\n'usermod -a -G wireshark _your_username_' as root.";
+      g_snprintf(errmsg, sizeof errmsg, "Couldn't run %s in child process: %s%s",
+                argv[0], g_strerror(errno), securitymsg);
       sync_pipe_errmsg_to_parent(2, errmsg, "");
 
       /* Exit with "_exit()", so that we don't close the connection
@@ -687,6 +690,7 @@ sync_pipe_open_command(const char** argv
     int i;
 #else
     char errmsg[1024+1];
+    const char *securitymsg = "";
     int sync_pipe[2];                       /* pipe used to send messages from child to parent */
     int data_pipe[2];                       /* pipe used to send data from child to parent */
 #endif
@@ -811,8 +815,10 @@ sync_pipe_open_command(const char** argv
         ws_close(sync_pipe[PIPE_READ]);
         ws_close(sync_pipe[PIPE_WRITE]);
         execv(argv[0], (gpointer)argv);
-        g_snprintf(errmsg, sizeof errmsg, "Couldn't run %s in child process: %s",
-                   argv[0], g_strerror(errno));
+	if (errno == EPERM || errno == EACCES)
+		securitymsg = "\nAre you a member of the 'wireshark' group? Try running\n'usermod -a -G wireshark _your_username_' as root.";
+        g_snprintf(errmsg, sizeof errmsg, "Couldn't run %s in child process: %s%s",
+                   argv[0], g_strerror(errno), securitymsg);
         sync_pipe_errmsg_to_parent(2, errmsg, "");
 
         /* Exit with "_exit()", so that we don't close the connection