Add GRACEFUL_SHUTDOWN example to bgpd.conf

OK phessler@

src/etc/examples/bgpd.conf

@@ -1,4 +1,4 @@
-# $OpenBSD: bgpd.conf,v 1.4 2016/06/03 17:36:37 benno Exp $
+# $OpenBSD: bgpd.conf,v 1.5 2017/07/04 09:33:36 job Exp $
 # sample bgpd configuration file
 # see bgpd.conf(5)
 
@@ -87,6 +87,10 @@ allow from any inet6 prefixlen 16 - 48
 #allow from any prefix 0.0.0.0/0
 #allow from any prefix ::/0
 
+# Honor requests to gracefully shutdown BGP sessions
+# https://tools.ietf.org/html/draft-ietf-grow-bgp-gshut
+match from any community GRACEFUL_SHUTDOWN set { localpref 0 }
+
 # https://www.arin.net/announcements/2014/20140130.html
 # This block will be subject to a minimum size allocation of /28 and a
 # maximum size allocation of /24. ARIN should use sparse allocation when