bfdd: add BFD package

Bidirectional Forwarding Detection (BFD) is a network protocol that is used to
detect faults between two forwarding engines connected by a link.

Signed-off-by: Lucian Cristian <lucian.cristian@gmail.com>

net/bfdd/files/bfdd.init

@@ -0,0 +1,17 @@
+#!/bin/sh /etc/rc.common
+
+START=99
+STOP=10
+USE_PROCD=1
+
+PROG="/usr/sbin/bfdd"
+CONF="/etc/bfdd/bfdd.json"
+
+start_service() {
+    procd_open_instance
+    procd_set_param command $PROG -c $CONF
+    procd_set_param stdout 1
+    procd_set_param stderr 1
+    procd_set_param respawn
+    procd_close_instance
+}

net/bfdd/files/bfdd.template.json

@@ -0,0 +1,57 @@
+{
+  "ipv4": [
+    {
+      "_create-only": "optional, defaults to false",
+      "_create-only-help": "If create-only is true then bfdd will return failure if a peer with the same target exists",
+      "create-only": true,
+
+      "_multihop": "optional defaults to false",
+      "multihop": false,
+
+      "_peer-address": "mandatory",
+      "peer-address": "127.0.0.1",
+
+      "_local-address": "mandatory on multihop",
+      "local-address": "127.0.0.1",
+
+      "_local-interface": "optional",
+      "local-interface": "enp0s3",
+
+      "_label": "optional",
+      "label": "peer1",
+
+      "_vxlan": "optional, defaults to 0",
+      "vxlan": 100,
+
+      "_vrf-name": "optional",
+      "vrf-name": "netns1",
+
+      "_detect-multiplier": "optional, defaults to 3",
+      "detect-multiplier": 3,
+
+      "_receive-interval": "optional, defaults to 300 milliseconds",
+      "receive-interval": 300,
+
+      "_transmit-interval": "optional, defaults to 300 milliseconds",
+      "transmit-interval": 300,
+
+      "_echo-interval": "optional, defaults to 50 milliseconds",
+      "echo-interval": 50,
+
+      "_echo-mode": "optional, defaults to false",
+      "echo-mode": false,
+
+      "_shutdown": "optional, defaults to false",
+      "shutdown": false
+    }
+  ],
+  "ipv6": [
+  ],
+  "label": [
+    {
+      "_label": "mandatory to identify the peer without addresses",
+      "_label-help": "peer must have been already created in ipv4 or ipv6",
+      "label": "peer1",
+    }
+  ]
+}