[MINOR] log: add support for passing the forwarded hostname

Haproxy does not include the hostname rather the IP of the machine in
the syslog headers it sends. Unfortunately this means that for each log
line rsyslog does a reverse dns on the client IP and in the case of
non-routable IPs one gets the public hostname not the internal one.

While this is valid according to RFC3164 as one might imagine this is
troublsome if you have some machines with public IPs, internal IPs, no
reverse DNS entries, etc and you want a standardized hostname based log
directory structure. The rfc says the preferred value is the hostname.

This patch adds a global "log-send-hostname" statement which accepts an
optional string to force the host name. If unset, the local host name
is used.

doc/configuration.txt

@@ -435,6 +435,7 @@ The following keywords are supported in the "global" section :
    - gid
    - group
    - log
+   - log-send-hostname
    - nbproc
    - pidfile
    - uid
@@ -527,6 +528,13 @@ log <address> <facility> [max level [min level]]
 
 	  emerg  alert  crit   err    warning notice info  debug
 
+log-send-hostname [<string>]
+  Sets the hostname field in the syslog header. If optional "string" parameter
+  is set the header is set to the string contents, otherwise uses the hostname
+  of the system. Generally used if one is not relaying logs through an
+  intermediate syslog server or for simply customizing the hostname printed in
+  the logs.
+
 nbproc <number>
   Creates <number> processes when going daemon. This requires the "daemon"
   mode. By default, only one process is created, which is the recommended mode

include/types/global.h

@@ -80,6 +80,7 @@ struct global {
 	int loglev1, loglev2;
 	int minlvl1, minlvl2;
 	struct logsrv logsrv1, logsrv2;
+	char *log_send_hostname;   /* set hostname in syslog header */
 	struct {
 		int maxpollevents; /* max number of poll events at once */
 		int maxaccept;     /* max number of consecutive accept() */

src/cfgparse.c

@@ -966,6 +966,28 @@ int cfg_parse_global(const char *file, int linenum, char **args, int kwm)
 			err_code |= ERR_ALERT | ERR_FATAL;
 		}
 	}
+	else if (!strcmp(args[0], "log-send-hostname")) { /* set the hostname in syslog header */
+		char *name;
+		int len;
+
+		if (global.log_send_hostname != NULL) {
+			Alert("parsing [%s:%d] : '%s' already specified. Continuing.\n", file, linenum, args[0]);
+			err_code |= ERR_ALERT;
+			goto out;
+		}
+
+		if (*(args[1]))
+			name = args[1];
+		else
+			name = hostname;
+
+		len = strlen(name);
+
+		/* We'll add a space after the name to respect the log format */
+		free(global.log_send_hostname);
+		global.log_send_hostname = malloc(len + 2);
+		snprintf(global.log_send_hostname, len + 2, "%s ", name);
+	}
 	else if (!strcmp(args[0], "spread-checks")) {  /* random time between checks (0-50) */
 		if (global.spread_checks != 0) {
 			Alert("parsing [%s:%d]: spread-checks already specified. Continuing.\n", file, linenum);

src/haproxy.c

@@ -867,6 +867,7 @@ void deinit(void)
 
 	protocol_unbind_all();
 
+	free(global.log_send_hostname); global.log_send_hostname = NULL;
 	free(global.chroot);  global.chroot = NULL;
 	free(global.pidfile); global.pidfile = NULL;
 	free(global.node);    global.node = NULL;

src/log.c

@@ -189,9 +189,10 @@ void send_log(struct proxy *p, int level, const char *message, ...)
 		get_localtime(tvsec, &tm);
 
 		hdr_len = snprintf(logmsg, sizeof(logmsg),
-				   "<<<<>%s %2d %02d:%02d:%02d %s[%d]: ",
+				   "<<<<>%s %2d %02d:%02d:%02d %s%s[%d]: ",
 				   monthname[tm.tm_mon],
 				   tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec,
+				   global.log_send_hostname ? global.log_send_hostname : "",
 				   progname, pid);
 		/* WARNING: depending upon implementations, snprintf may return
 		 * either -1 or the number of bytes that would be needed to store