commit 9b0dc3f61345b941d137cfe76b3f8585dfcd77b6
Author: J. Fernando Sánchez <balkian@gmail.com>
Date:   Tue Oct 20 12:44:55 2015 +0200

diff --git a/dns.py b/dns.py
new file mode 100644
index 0000000..a694787
--- /dev/null
+++ b/dns.py
@@ -0,0 +1,114 @@
+# -*- coding: utf-8 -*-
+
+from __future__ import print_function
+
+try:
+    from subprocess import getoutput
+except ImportError:
+    from commands import getoutput
+
+from dnslib import RR,QTYPE,RCODE,A,parse_time
+from dnslib.label import DNSLabel
+from dnslib.server import DNSServer,DNSHandler,BaseResolver,DNSLogger
+from docker import Client, errors
+
+class DockerResolver(BaseResolver):
+    """
+
+    """
+    def __init__(self, docker='unix://var/run/docker.sock',
+                 origin='docker', ttl='60s'):
+        self.client = Client(base_url=docker)
+        self.origin = DNSLabel(origin)
+        self.ttl = parse_time(ttl)
+
+    def resolve(self,request,handler):
+        reply = request.reply()
+        qname = request.q.qname
+        print("Queried: %s" % qname)
+        print("Label: %s" % self.origin)
+        found = False
+        if not qname.matchSuffix(self.origin):
+            print("Not the %s domain" % self.origin)
+            return reply
+        cname = "/" + str(qname.stripSuffix(self.origin))[:-1].replace("/", "_")
+        try:
+            for c in self.client.containers():
+                if cname in c["Names"]:
+                    container = self.client.inspect_container(c["Id"])
+                    ns = container.get("NetworkSettings", {})
+                    if ns:
+                        address = ns.get("IPAddress", None)
+                        print("Found %s [%s]" % (cname, address))
+                        if address:
+                            reply.add_answer(RR(qname,QTYPE.A,ttl=self.ttl,
+                                                rdata=A(address)))
+                    else:
+                        print("Found %s - NO IP" % cname)
+                    found = True
+                    break
+            if not found:
+                print("Container not found: %s" % cname)
+        except Exception as ex:
+            print("Error occurred querying [%s]: %s" % (cname, ex))
+        return reply
+
+if __name__ == '__main__':
+
+    import argparse,sys,time
+
+    p = argparse.ArgumentParser(description="Docker DNS Resolver")
+    p.add_argument("--docker","-d",default="unix://var/run/docker.sock",
+                   metavar="<url>",
+                   help="Docker Socket/URL (default: unix://var/run/docker.sock)")
+    p.add_argument("--origin","-o",default="docker",
+                    metavar="<origin>",
+                    help="Origin domain label (default: .)")
+    p.add_argument("--ttl","-t",default="60s",
+                    metavar="<ttl>",
+                    help="Response TTL (default: 60s)")
+    p.add_argument("--port","-p",type=int,default=53,
+                    metavar="<port>",
+                   help="Server port (default:53)")
+    p.add_argument("--address","-a",default="",
+                   metavar="<address>",
+                   help="Listen address (default:all)")
+    p.add_argument("--udplen","-u",type=int,default=0,
+                   metavar="<udplen>",
+                   help="Max UDP packet length (default:0)")
+    p.add_argument("--tcp",action='store_true',default=False,
+                   help="TCP server (default: UDP only)")
+    p.add_argument("--log",default="request,reply,truncated,error",
+                   help="Log hooks to enable (default: +request,+reply,+truncated,+error,-recv,-send,-data)")
+    p.add_argument("--log-prefix",action='store_true',default=False,
+                   help="Log prefix (timestamp/handler/resolver) (default: False)")
+    args = p.parse_args()
+
+    resolver = DockerResolver(docker=args.docker, origin=args.origin, ttl=args.ttl)
+    logger = DNSLogger(args.log,args.log_prefix)
+
+    print("Starting Docker Resolver for %s (%s:%d) [%s]" % (
+                        args.docker,
+                        args.address or "*",
+                        args.port,
+                        "UDP/TCP" if args.tcp else "UDP"))
+
+    if args.udplen:
+        DNSHandler.udplen = args.udplen
+
+    udp_server = DNSServer(resolver,
+                           port=args.port,
+                           address=args.address,
+                           logger=logger)
+    udp_server.start_thread()
+
+    if args.tcp:
+        tcp_server = DNSServer(resolver,
+                               port=args.port,
+                               address=args.address,
+                               tcp=True,
+                               logger=logger)
+        tcp_server.start_thread()
+
+    while udp_server.isAlive():
+        time.sleep(1)