MINOR: startup: set HAPROXY_LOCALPEER only once

Before this patch HAPROXY_LOCALPEER variable could be set in init_early(),
in init_args() and in cfg_parse_global(). In master-worker mode, if localpeer
keyword set in the global section, HAPROXY_LOCALPEER in the worker
environment is set to this keyword's value, but in the master environment it
still keeps the default, a localhost name. This is confusing.

To fix it, let's set HAPROXY_LOCALPEER only once, when a worker or process in a
standalone mode has finished to parse its configuration. And let's set this
variable only for the worker process or for the process in a standalone mode,
because the master doesn't need it.

HAPROXY_LOCALPEER takes the value saved in localpeer global variable, which is
always set by default in init_early() to the local hostname. Then, localpeer
could be reset in init_args (-L option) and in cfg_parse_global() (while
parsing "localpeer" keyword).

src/cfgparse-global.c

@@ -845,7 +845,6 @@ int cfg_parse_global(const char *file, int linenum, char **args, int kwm)
 			err_code |= ERR_ALERT | ERR_FATAL;
 			goto out;
 		}
-		setenv("HAPROXY_LOCALPEER", localpeer, 1);
 	}
 	else if (strcmp(args[0], "numa-cpu-mapping") == 0) {
 		global.numa_cpu_mapping = (kwm == KWM_NO) ? 0 : 1;

src/haproxy.c

@@ -1573,7 +1573,7 @@ static void init_early(int argc, char **argv)
 
 	/* preset some environment variables */
 	localpeer = strdup(hostname);
-	if (!localpeer || setenv("HAPROXY_LOCALPEER", localpeer, 1) < 0) {
+	if (!localpeer) {
 		ha_alert("Cannot allocate memory for local peer.\n");
 		exit(EXIT_FAILURE);
 	}
@@ -1874,7 +1874,6 @@ static void init_args(int argc, char **argv)
 						ha_alert("Cannot allocate memory for local peer.\n");
 						exit(EXIT_FAILURE);
 					}
-					setenv("HAPROXY_LOCALPEER", localpeer, 1);
 					global.localpeer_cmdline = 1;
 					break;
 				case 'f' :
@@ -3840,6 +3839,13 @@ int main(int argc, char **argv)
 		/* all sections have been parsed, we can free the content */
 		list_for_each_entry_safe(cfg, cfg_tmp, &cfg_cfgfiles, list)
 			ha_free(&cfg->content);
+
+		/* localpeer could be redefined via 'localpeer' keyword from the
+		 * global section, in master-worker mode it's parsed only by
+		 * worker, so let set HAPROXY_LOCALPEER explicitly here
+		 */
+		if (localpeer != NULL)
+			setenv("HAPROXY_LOCALPEER", localpeer, 1);
 		usermsgs_clr(NULL);
 	}