Add new option for overriding destination DNS server.

sshuttle/assembler.py

@@ -34,4 +34,4 @@ sshuttle.helpers.verbose = verbosity
 
 import sshuttle.cmdline_options as options
 from sshuttle.server import main
-main(options.latency_control, options.auto_hosts)
+main(options.latency_control, options.auto_hosts, options.to_nameserver)

sshuttle/client.py

@@ -415,7 +415,8 @@ def ondns(listener, method, mux, handlers):
 
 def _main(tcp_listener, udp_listener, fw, ssh_cmd, remotename,
           python, latency_control,
-          dns_listener, seed_hosts, auto_hosts, auto_nets, daemon):
+          dns_listener, seed_hosts, auto_hosts, auto_nets, daemon,
+          to_nameserver):
 
     debug1('Starting client with Python version %s\n'
            % platform.python_version())
@@ -434,7 +435,8 @@ def _main(tcp_listener, udp_listener, fw, ssh_cmd, remotename,
             ssh_cmd, remotename, python,
             stderr=ssyslog._p and ssyslog._p.stdin,
             options=dict(latency_control=latency_control,
-                auto_hosts=auto_hosts))
+                         auto_hosts=auto_hosts,
+                         to_nameserver=to_nameserver))
     except socket.error as e:
         if e.args[0] == errno.EPIPE:
             raise Fatal("failed to establish ssh session (1)")
@@ -534,7 +536,7 @@ def _main(tcp_listener, udp_listener, fw, ssh_cmd, remotename,
 def main(listenip_v6, listenip_v4,
          ssh_cmd, remotename, python, latency_control, dns, nslist,
          method_name, seed_hosts, auto_hosts, auto_nets,
-         subnets_include, subnets_exclude, daemon, pidfile):
+         subnets_include, subnets_exclude, daemon, to_nameserver, pidfile):
 
     if daemon:
         try:
@@ -549,6 +551,8 @@ def main(listenip_v6, listenip_v4,
     # Get family specific subnet lists
     if dns:
         nslist += resolvconf_nameservers()
+        if to_nameserver is not None:
+            to_nameserver = "%s@%s" % tuple(to_nameserver[1:])
 
     subnets = subnets_include + subnets_exclude  # we don't care here
     subnets_v6 = [i for i in subnets if i[0] == socket.AF_INET6]
@@ -741,7 +745,7 @@ def main(listenip_v6, listenip_v4,
     try:
         return _main(tcp_listener, udp_listener, fw, ssh_cmd, remotename,
                      python, latency_control, dns_listener,
-                     seed_hosts, auto_hosts, auto_nets, daemon)
+                     seed_hosts, auto_hosts, auto_nets, daemon, to_nameserver)
     finally:
         try:
             if daemon:

sshuttle/cmdline.py

@@ -73,7 +73,9 @@ def main():
                                       opt.auto_nets,
                                       includes,
                                       excludes,
-                                      opt.daemon, opt.pidfile)
+                                      opt.daemon,
+                                      opt.to_ns,
+                                      opt.pidfile)
 
             if return_code == 0:
                 log('Normal exit code, exiting...')

sshuttle/options.py

@@ -146,6 +146,15 @@ parser.add_argument(
     capture and forward DNS requests made to the following servers
     """
 )
+parser.add_argument(
+    "--to-ns",
+    metavar="IP[:PORT]",
+    type=parse_ipport,
+    help="""
+    the DNS server to forward requests to; defaults to servers in /etc/resolv.conf on remote side if not given.
+    """
+)
+
 parser.add_argument(
     "--method",
     choices=["auto", "nat", "tproxy", "pf", "ipfw"],

sshuttle/server.py

@@ -160,7 +160,7 @@ class Hostwatch:
 
 class DnsProxy(Handler):
 
-    def __init__(self, mux, chan, request):
+    def __init__(self, mux, chan, request, to_nameserver):
         Handler.__init__(self, [])
         self.timeout = time.time() + 30
         self.mux = mux
@@ -168,6 +168,15 @@ class DnsProxy(Handler):
         self.tries = 0
         self.request = request
         self.peers = {}
+        if to_nameserver is None:
+            self.to_nameserver = None
+        else:
+            peer, port = to_nameserver.split("@")
+            port = int(port)
+            if port == 0:
+                port = 53
+            family = socket.AF_INET6 if ":" in peer else socket.AF_INET
+            self.to_nameserver = family, peer, port
         self.try_send()
 
     def try_send(self):
@@ -175,18 +184,19 @@ class DnsProxy(Handler):
             return
         self.tries += 1
 
+        if self.to_nameserver is None:
             family, peer = resolvconf_random_nameserver()
+            port = 53
+        else:
+            family, peer, port = self.to_nameserver
 
         sock = socket.socket(family, socket.SOCK_DGRAM)
         sock.setsockopt(socket.SOL_IP, socket.IP_TTL, 42)
-        # Connect to custom DNS server running in the Telepresence pod:
-        # XXX eventually this should be configured via command-line
-        # option and submitted to upstream as improvement.
-        sock.connect(('127.0.0.1', 9053))
+        sock.connect((peer, port))
 
         self.peers[sock] = peer
 
-        debug2('DNS: sending to %r (try %d)\n' % (peer, self.tries))
+        debug2('DNS: sending to %r:%d (try %d)\n' % (peer, port, self.tries))
         try:
             sock.send(self.request)
             self.socks.append(sock)
@@ -261,7 +271,7 @@ class UdpProxy(Handler):
         self.mux.send(self.chan, ssnet.CMD_UDP_DATA, hdr + data)
 
 
-def main(latency_control, auto_hosts):
+def main(latency_control, auto_hosts, to_nameserver):
     debug1('Starting server with Python version %s\n'
            % platform.python_version())
 
@@ -335,7 +345,7 @@ def main(latency_control, auto_hosts):
 
     def dns_req(channel, data):
         debug2('Incoming DNS request channel=%d.\n' % channel)
-        h = DnsProxy(mux, channel, data)
+        h = DnsProxy(mux, channel, data, to_nameserver)
         handlers.append(h)
         dnshandlers[channel] = h
     mux.got_dns_req = dns_req