Adjust the config to -current bgpd which makes it a lot more readable.

OK phessler@

src/etc/examples/bgpd.conf

@@ -1,4 +1,4 @@
-# $OpenBSD: bgpd.conf,v 1.13 2018/09/09 12:49:44 benno Exp $
+# $OpenBSD: bgpd.conf,v 1.14 2018/09/10 09:10:36 claudio Exp $
 # example bgpd configuration file, see bgpd.conf(5)
 
 # define our own ASN as a macro
@@ -14,6 +14,35 @@ prefix-set mynetworks {		\
 	2001:db8:abcd::/48	\
 }
 
+# define bogon prefixes which should not be part of the DFZ
+prefix-set bogons {
+	0.0.0.0/8		# 'this' network [RFC1122]
+	10.0.0.0/8		# private space [RFC1918]
+	100.64.0.0/10		# CGN Shared [RFC6598]
+	127.0.0.0/8		# localhost [RFC1122]
+	169.254.0.0/16		# link local [RFC3927]
+	172.16.0.0/12		# private space [RFC1918]
+	192.0.2.0/24		# TEST-NET-1 [RFC5737]
+	192.88.99.0/24		# 6to4 anycast relay [RFC7526]
+	192.168.0.0/16		# private space [RFC1918]
+	198.18.0.0/15		# benchmarking [RFC2544]
+	198.51.100.0/24		# TEST-NET-2 [RFC5737]
+	203.0.113.0/24		# TEST-NET-3 [RFC5737]
+	224.0.0.0/4		# multicast
+	240.0.0.0/4		# reserved for future use
+	::/8			# RFC 4291 IPv4-compatible, loopback, et al
+	0100::/64		# Discard-Only [RFC6666]
+	2001:2::/48		# BMWG [RFC5180]
+	2001:10::/28		# ORCHID [RFC4843]
+	2001:db8::/32		# docu range [RFC3849]
+	2002::/16		# 6to4 anycast relay [RFC7526]
+	3ffe::/16		# old 6bone
+	fc00::/7		# unique local unicast
+	fe80::/10		# link local unicast
+	fec0::/10		# old site local unicast
+	ff00::/8		# multicast
+}
+
 # Generate routes for the networks our ASN will originate.
 # The communities (read 'tags') are later used to match on what
 # is announced to EBGP neighbors
@@ -85,29 +114,16 @@ allow from any inet6 prefixlen 16 - 48
 # https://tools.ietf.org/html/rfc8326
 match from any community GRACEFUL_SHUTDOWN set { localpref 0 }
 
-# See http://bgpfilterguide.nlnog.net/guides/bogon_prefixes/ for
-# an elaboration why each prefix is a bogon
-prefix-set bogons {						\
-	0.0.0.0/8 or-longer 10.0.0.0/8 or-longer		\
-	100.64.0.0/10 or-longer 127.0.0.0/8 or-longer		\
-	169.254.0.0/16 or-longer 172.16.0.0/12 or-longer 	\
-	192.0.2.0/24 or-longer 192.88.99.0/24 or-longer		\
-	192.168.0.0/16 or-longer 198.18.0.0/15 or-longer	\
-	198.51.100.0/24 or-longer 203.0.113.0/24 or-longer	\
-	224.0.0.0/4 or-longer 240.0.0.0/4 or-longer		\
-	::/8 or-longer 0100::/64 or-longer			\
-	2001:2::/48 or-longer 2001:10::/28 or-longer		\
-	2001:db8::/32 or-longer 2002::/16 or-longer		\
-	3ffe::/16 or-longer fc00::/7 or-longer			\
-	fe80::/10 or-longer fec0::/10 or-longer			\
-	ff00::/8 or-longer					\
-}
-# use above prefix-set to reject the bogons
-deny quick from any prefix-set bogons
+# use prefix-set to reject the bogons
+deny quick from any prefix-set bogons or-longer
 
 # filter bogon AS numbers
-# see http://bgpfilterguide.nlnog.net/guides/bogon_asns/ for more
-# information why these ASNs are bogons.
+# AS_TRANS (23456) is not supposed to show up in any path and indicates a 
+# missconfiguration. Additionally Private or Reserved ASNs have no place in
+# the public DFZ. http://www.iana.org/assignments/as-numbers/as-numbers.xhtml
 deny quick from any AS 23456
 deny quick from any AS 64496 - 131071
 deny quick from any AS 4200000000 - 4294967295
+
+# filter out too long paths
+deny from any max-as-len 100