T1598: initial implementation of the hosts keeper daemon.

1 files changed, 254 insertions, 0 deletions

diff --git a/src/services/vyos-hostsd b/src/services/vyos-hostsd
new file mode 100755
index 000000000..972c2e3dc
--- /dev/null
+++ b/src/services/vyos-hostsd
@@ -0,0 +1,254 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2019 VyOS maintainers and contributors
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+#
+
+import os
+import sys
+import time
+import json
+import traceback
+
+import zmq
+
+import jinja2
+
+debug = True
+
+DATA_DIR = "/var/lib/vyos/"
+STATE_FILE = os.path.join(DATA_DIR, "hostsd.state")
+
+SOCKET_PATH = "ipc:///run/vyos-hostsd.sock"
+
+RESOLV_CONF_FILE = '/etc/resolv.conf'
+HOSTS_FILE = '/etc/hosts'
+
+hosts_tmpl_source = """
+### Autogenerated by VyOS ###
+127.0.0.1       localhost
+127.0.1.1       {{ host_name }}{% if domain_name %}.{{ domain_name }}{% endif %}
+
+# The following lines are desirable for IPv6 capable hosts
+::1             localhost ip6-localhost ip6-loopback
+fe00::0         ip6-localnet
+ff00::0         ip6-mcastprefix
+ff02::1         ip6-allnodes
+ff02::2         ip6-allrouters
+
+
+{%- if hosts %}
+{% for h in hosts -%}
+{{hosts[h]['address']}}\t{{h}}\t{% for a in hosts[h]['aliases'] %} {{a}} {% endfor %}
+{% endfor %}
+{%- endif %}
+"""
+
+hosts_tmpl = jinja2.Template(hosts_tmpl_source)
+
+resolv_tmpl_source = """
+### Autogenerated by VyOS ###
+{% for ns in name_servers -%}
+nameserver {{ns}}
+{% endfor -%}
+
+{%- if domain_name %}
+domain {{ domain_name }}
+{%- endif %}
+
+{%- if search_domains %}
+search {{ search_domains | join(" ") }}
+{%- endif %}
+
+"""
+
+resolv_tmpl = jinja2.Template(resolv_tmpl_source)
+
+# The state data includes a list of name servers
+# and a list of hosts entries.
+#
+# Name servers have the following structure:
+# {"server": {"tag": <str>}}
+#
+# Hosts entries are similar:
+# {"host": {"tag": <str>, "address": <str>}}
+#
+# The tag is either "static" or "dhcp-<intf>"
+# It's used to distinguish entries created
+# by different scripts so that they can be removed
+# and re-created without having to track what needs
+# to be changed
+STATE = {
+    "name_servers": {},
+    "hosts": {},
+    "host_name": "vyos",
+    "domain_name": "",
+    "search_domains": []}
+
+
+def make_resolv_conf(data):
+    resolv_conf = resolv_tmpl.render(data)
+    print("Writing /etc/resolv.conf")
+    with open(RESOLV_CONF_FILE, 'w') as f:
+        f.write(resolv_conf)
+
+def make_hosts_file(state):
+    print("Writing /etc/hosts")
+    hosts = hosts_tmpl.render(state)
+    with open(HOSTS_FILE, 'w') as f:
+        f.write(hosts)
+
+def add_hosts(data, entries, tag):
+    hosts = data['hosts']
+
+    if not entries:
+        return
+
+    for e in entries:
+        host = e['host']
+        hosts[host] = {}
+        hosts[host]['tag'] = tag
+        hosts[host]['address'] = e['address']
+        hosts[host]['aliases'] = e['aliases']
+
+def delete_hosts(data, tag):
+    hosts = data['hosts']
+    keys_for_deletion = []
+
+    # You can't delete items from a dict while iterating over it,
+    # so we build a list of doomed items first
+    for h in hosts:
+        if hosts[h]['tag'] == tag:
+            keys_for_deletion.append(h)
+
+    for k in keys_for_deletion:
+        del hosts[k]
+
+def add_name_servers(data, entries, tag):
+    name_servers = data['name_servers']
+
+    if not entries:
+        return
+
+    for e in entries:
+        name_servers[e] = {}
+        name_servers[e]['tag'] = tag
+
+def delete_name_servers(data, tag):
+    name_servers = data['name_servers']
+    keys_for_deletion = []
+
+    for ns in name_servers:
+      if name_servers[ns]['tag'] == tag:
+          keys_for_deletion.append(ns)
+
+    for k in keys_for_deletion:
+      del name_servers[k]
+
+def set_host_name(state, data):
+    if data['host_name']:
+        state['host_name'] = data['host_name']
+    if data['domain_name']:
+        state['domain_name'] = data['domain_name']
+    if data['search_domains']:
+        state['search_domains'] = data['search_domains']
+
+def get_option(msg, key):
+    if key in msg:
+        return msg[key]
+    else:
+        raise ValueError("Missing required option \"{0}\"".format(key))
+
+def handle_message(msg_json):
+    msg = json.loads(msg_json)
+
+    op = get_option(msg, 'op')
+    _type = get_option(msg, 'type')
+
+    if op == 'delete':
+        tag = get_option(msg, 'tag')
+
+        if _type == 'name_servers':
+            delete_name_servers(STATE, tag)
+        elif _type == 'hosts':
+            delete_hosts(STATE, tag)
+        else:
+            raise ValueError("Unknown message type {0}".format(_type))
+    elif op == 'add':
+        tag = get_option(msg, 'tag')
+        entries = get_option(msg, 'data')
+        if _type == 'name_servers':
+            add_name_servers(STATE, entries, tag)
+        elif _type == 'hosts':
+            add_hosts(STATE, entries, tag)
+        else:
+            raise ValueError("Unknown message type {0}".format(_type))
+    elif op == 'set':
+        # Host name/domain name/search domain are set without a tag,
+        # there can be only one anyway
+        data = get_option(msg, 'data')
+        if _type == 'host_name':
+            set_host_name(STATE, data)
+        else:
+            raise ValueError("Unknown message type {0}".format(_type))
+    else:
+        raise ValueError("Unknown operation {0}".format(op))
+
+    make_resolv_conf(STATE)
+    make_hosts_file(STATE)
+
+    print("Saving state to {0}".format(STATE_FILE))
+    with open(STATE_FILE, 'w') as f:
+        json.dump(STATE, f)
+
+
+if __name__ == '__main__':
+    # Create a directory for state checkpoints
+    os.makedirs(DATA_DIR, exist_ok=True)
+    if os.path.exists(STATE_FILE):
+        with open(STATE_FILE, 'r') as f:
+            try:
+                data = json.load(f)
+                STATE = data
+            except:
+                print(traceback.format_exc())
+                print("Failed to load the state file, using default")
+
+    context = zmq.Context()
+    socket = context.socket(zmq.REP)
+    socket.bind(SOCKET_PATH)
+
+    while True:
+        #  Wait for next request from client
+        message = socket.recv().decode()
+        print("Received a configuration change request")
+        if debug:
+            print("Request data: {0}".format(message))
+
+        resp = {}
+
+        try:
+            handle_message(message)
+        except ValueError as e:
+            resp['error'] = str(e)
+        except:
+            print(traceback.format_exc())
+            resp['error'] = "Internal error"
+
+        if debug:
+            print("Sent response: {0}".format(resp))
+
+        #  Send reply back to client
+        socket.send(json.dumps(resp).encode())