Update usage text and manual for -b listen option

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

man/syslogd.8

@@ -206,42 +206,39 @@ can contain special characters of a shell-style pattern such as
 .Ql * .
 .El
 .It Fl b Ar addr[:port][%iface]
-Bind to a specific address and/or port.  By default,
+Bind to, or listen to, a specific address and/or port.  By default,
 .Nm
-listens on all interfaces on UDP port 514, unless started with the
-.Fl s
-option.  Multiple
+listens to UDP port 514 on all interfaces, unless started in secure
+.Fl ( s )
+mode.  Multiple
 .Fl b
 options may be specified to bind to several addresses and/or ports.
 .Pp
-The
-.Ar name
-argument may be any of the following:
-.Bl -tag -width 'address[:port]' -offset indent
-.It address[:port][%iface]
-Hostname or an IP address, with the port as a service name, see
-.Xr services 5 ,
-or port number.  IPv6 addresses should be enclosed with
+.Bl -tag -width 'group[:port][%iface]' -offset indent
+.It address[:port]
+Hostname or IP address, IPv6 addresses should be enclosed in
 .Ql \&[
 and
-.Ql \&] .
-The
-.Op %iface
-is for multicast and joins the group on the given interface.
+.Ql \&]
+.It group[:port][%iface]
+Join the given multicast group on the optional inbound interface.
+If
+.Ql %iface
+is omitted, the kernel will rely on the routing table to determine which
+interface to listen to, which is usually not what you want
 .It :port
-Service name or UDP port number.  The default service is
+Service name or UDP port number, see
+.Xr services 5 .
+The default service is
 .Ql syslog
-(UDP), port 512
+(UDP/514)
 .El
 .Pp
 Both unicast IP and multicast group addresses are supported.  Multicast
 groups are "joined" using an OS-level
 .Fn setsockopt
 call, most operating systems translate this to IGMP/MLD membership
-reports on the network.  If
-.Op %iface
-is omitted, the routing table is used, which is usually not what you
-want in a multihoming setup.
+reports on the network.
 .It Fl C Ar file
 File to use for caching last read kernel sequence number from
 .Pa /dev/kmsg ,

src/syslogd.c

@@ -404,7 +404,7 @@ static void sys_seqno_save(void)
 int usage(int code)
 {
 	printf("Usage:\n"
-	       "  syslogd [-468AdFHKknsTtv?] [-a PEER] [-b NAME] [-f FILE] [-m MINS] [-M SIZE]\n"
+	       "  syslogd [-468AdFHKknsTtv?] [-a PEER] [-b ADDR] [-f FILE] [-m MINS] [-M SIZE]\n"
 	       "                             [-P PID_FILE] [-p SOCK_PATH] [-r SIZE[:NUM]]\n"
 	       "Options:\n"
 	       "  -4        Force IPv4 only\n"
@@ -422,13 +422,17 @@ int usage(int code)
 	       "                                    address.  'domainname' may contain special\n"
 	       "                                    shell-style pattern characters like '*'\n"
 	       "\n"
-	       "  -b NAME   Bind to a specific address and/or port. Multiple -b options may be\n"
-	       "            specified. Default is to listen on all interfaces on UDP port 514,\n"
-	       "            unless also started with -s:\n"
+	       "  -b ADDR   Bind, or listen, to a specific address and/or port. Multiple '-b'\n"
+	       "            invocations are supported:\n"
 	       "              address[:port]        Hostname or IP address, IPv6 addresses\n"
 	       "                                    must be enclosed in '[' and ']'\n"
+	       "              group[:port][%%iface]  Join the given multicast group, optional\n"
+	       "                                    custom port, and inbound interface\n"
 	       "              :port                 UDP port number, or service name\n"
 	       "                                    default: 'syslog', port 514\n"
+	       "            By default, UDP port 514 is open on all interfaces, unless started\n"
+	       "            in secure mode (see -s, below).  For multicast, the routing table\n"
+	       "            will be used if %%iface is omitted"
 	       "\n"
 	       "  -C FILE   File to cache last read kernel seqno, default: %s\n"
 	       "            Note: syslogd relies on this file being removed at system reboot.\n"