Fix tests for existing PR-312 (#337)

* use addrtype match to return the LOCAL trafik

* Add assertion for the new LOCAL firewall rule added in PR 312.

* Fix linter complaints

sshuttle/client.py

@@ -602,8 +602,13 @@ def main(listenip_v6, listenip_v4,
         except KeyError:
             raise Fatal("User %s does not exist." % user)
 
-    required.ipv6 = len(subnets_v6) > 0 or listenip_v6 is not None
-    required.ipv4 = len(subnets_v4) > 0 or listenip_v4 is not None
+    if fw.method.name != 'nat':
+        required.ipv6 = len(subnets_v6) > 0 or listenip_v6 is not None
+        required.ipv4 = len(subnets_v4) > 0 or listenip_v4 is not None
+    else:
+        required.ipv6 = None
+        required.ipv4 = None
+
     required.udp = avail.udp
     required.dns = len(nslist) > 0
     required.user = False if user is None else True

sshuttle/methods/nat.py

@@ -50,6 +50,12 @@ class Method(BaseMethod):
         _ipt('-I', 'OUTPUT', '1', *args)
         _ipt('-I', 'PREROUTING', '1', *args)
 
+        # Firstly we always skip all LOCAL addtrype address, i.e. avoid
+        # tunnelling the traffic designated to all local TCP/IP addresses.
+        _ipt('-A', chain, '-j', 'RETURN',
+             '-m', 'addrtype',
+             '--dst-type', 'LOCAL')
+
         # create new subnet entries.
         for _, swidth, sexclude, snet, fport, lport \
                 in sorted(subnets, key=subnet_weight, reverse=True):

tests/client/test_methods_nat.py

@@ -139,6 +139,8 @@ def test_setup_firewall(mock_ipt_chain_exists, mock_ipt_ttl, mock_ipt):
         call(AF_INET, 'nat', '-F', 'sshuttle-1025'),
         call(AF_INET, 'nat', '-I', 'OUTPUT', '1', '-j', 'sshuttle-1025'),
         call(AF_INET, 'nat', '-I', 'PREROUTING', '1', '-j', 'sshuttle-1025'),
+        call(AF_INET, 'nat', '-A', 'sshuttle-1025', '-j', 'RETURN',
+             '-m', 'addrtype', '--dst-type', 'LOCAL'),
         call(AF_INET, 'nat', '-A', 'sshuttle-1025', '-j', 'RETURN',
              '--dest', u'1.2.3.66/32', '-p', 'tcp', '--dport', '8080:8080')
     ]