MINOR: config: allow no set-dumpable config option

in global config parsing, we currently expect to have a possible no
keyword (KWN_NO), but we never allow it in config parsing.
another patch could have been to simply remove the code handling a
possible KWN_NO.
take this opportunity to update documentation of set-dumpable.

Signed-off-by: William Dauchy <w.dauchy@criteo.com>

doc/configuration.txt

@@ -1141,22 +1141,23 @@ setenv <name> <value>
 
 set-dumpable
   This option is better left disabled by default and enabled only upon a
-  developer's request. It has no impact on performance nor stability but will
+  developer's request. If it has been enabled, it may still be forcibly
-  try hard to re-enable core dumps that were possibly disabled by file size
+  disabled by prefixing it with the "no" keyword. It has no impact on
-  limitations (ulimit -f), core size limitations (ulimit -c), or "dumpability"
+  performance nor stability but will try hard to re-enable core dumps that were
-  of a process after changing its UID/GID (such as /proc/sys/fs/suid_dumpable
+  possibly disabled by file size limitations (ulimit -f), core size limitations
-  on Linux). Core dumps might still be limited by the current directory's
+  (ulimit -c), or "dumpability" of a process after changing its UID/GID (such
-  permissions (check what directory the file is started from), the chroot
+  as /proc/sys/fs/suid_dumpable on Linux). Core dumps might still be limited by
-  directory's permission (it may be needed to temporarily disable the chroot
+  the current directory's permissions (check what directory the file is started
-  directive or to move it to a dedicated writable location), or any other
+  from), the chroot directory's permission (it may be needed to temporarily
-  system-specific constraint. For example, some Linux flavours are notorious
+  disable the chroot directive or to move it to a dedicated writable location),
-  for replacing the default core file with a path to an executable not even
+  or any other system-specific constraint. For example, some Linux flavours are
-  installed on the system (check /proc/sys/kernel/core_pattern). Often, simply
+  notorious for replacing the default core file with a path to an executable
-  writing "core", "core.%p" or "/var/log/core/core.%p" addresses the issue.
+  not even installed on the system (check /proc/sys/kernel/core_pattern). Often,
-  When trying to enable this option waiting for a rare issue to re-appear, it's
+  simply writing "core", "core.%p" or "/var/log/core/core.%p" addresses the
-  often a good idea to first try to obtain such a dump by issuing, for example,
+  issue. When trying to enable this option waiting for a rare issue to
-  "kill -11" to the haproxy process and verify that it leaves a core where
+  re-appear, it's often a good idea to first try to obtain such a dump by
-  expected when dying.
+  issuing, for example, "kill -11" to the haproxy process and verify that it
+  leaves a core where expected when dying.
 
 ssl-default-bind-ciphers <ciphers>
   This setting is only available when support for OpenSSL was built in. It sets

src/cfgparse.c

@@ -2147,9 +2147,12 @@ next_line:
 				args[arg] = args[arg+1];		// shift args after inversion
 		}
 
-		if (kwm != KWM_STD && strcmp(args[0], "option") != 0 && 	\
+		if (kwm != KWM_STD && strcmp(args[0], "option") != 0 &&
-		    strcmp(args[0], "log") != 0 && strcmp(args[0], "busy-polling")) {
+		    strcmp(args[0], "log") != 0 && strcmp(args[0], "busy-polling") != 0 &&
-			ha_alert("parsing [%s:%d]: negation/default currently supported only for options, log, and busy-polling.\n", file, linenum);
+		    strcmp(args[0], "set-dumpable") != 0) {
+			ha_alert("parsing [%s:%d]: negation/default currently "
+				 "supported only for options, log, busy-polling and "
+				 "set-dumpable.\n", file, linenum);
 			err_code |= ERR_ALERT | ERR_FATAL;
 		}