radvd: Install and configure radvd

The *radvd* role and `radvd.yml` playbook can be used to configure the
`radvd` IPv6 SLAAC router advertisement daemon on Linux.

roles/radvd/templates/confd.radvd.j2

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+# Copyright 1999-2005 Gentoo Foundation
+# Distributed under the terms of the GNU General Public License v2
+# $Header: /var/cvsroot/gentoo-x86/net-misc/radvd/files/radvd.conf,v 1.1 2006/07/19 13:02:36 uberlord Exp $
+
+# Extra options to pass to radvd
+OPTIONS=""
+
+# Set this to "no" to tell the init script NOT to set up IPv6 forwarding
+# using /proc/sys/net/ipv6/conf/all/forwarding
+# Only change this if you know what you're doing!
+FORWARD="yes"
+
+rc_need="!net {% for i in radvd_interfaces %}net.{{ i.interface }}{% if not loop.last %} {% endif %}{% endfor %}"

roles/radvd/templates/radvd.conf.j2

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+{% for iface in radvd_interfaces %}
+interface {{ iface.interface }}
+{
+	AdvSendAdvert on;
+{% if iface.other_config|d(False) %}
+	AdvOtherConfigFlag on;
+{% endif %}
+
+	prefix {{ iface.prefix }} {
+		AdvOnLink {% if iface.on_link|d(True) %}on{% else %}off{% endif %};
+		AdvAutonomous {% if iface.autonomous|d(True) %}on{% else %}off{% endif %};
+	};
+{% if iface.rdnss is defined %}
+{% for address in iface.rdnss %}
+
+	RDNSS {{ address }} {
+	};
+{% endfor %}
+{% endif %}
+{% if iface.dnssl is defined %}
+{% for domain in iface.dnssl %}
+
+	DNSSL {{ domain }} {
+	};
+{% endfor %}
+{% endif %}
+};
+{% endfor %}