arping(): handle scanning on a unknown IP (#4856)

Author: gpotter2

scapy/interfaces.py

@@ -293,8 +293,11 @@ def dev_from_index(self, if_index):
                 return self.dev_from_networkname(conf.loopback_name)
             raise ValueError("Unknown network interface index %r" % if_index)
 
-    def _add_fake_iface(self, ifname, mac="00:00:00:00:00:00"):
-        # type: (str, str) -> None
+    def _add_fake_iface(self,
+                        ifname,
+                        mac="00:00:00:00:00:00",
+                        ips=["127.0.0.1", "::"]):
+        # type: (str, str, List[str]) -> None
         """Internal function used for a testing purpose"""
         data = {
             'name': ifname,
@@ -304,7 +307,7 @@ def _add_fake_iface(self, ifname, mac="00:00:00:00:00:00"):
             'dummy': True,
             'mac': mac,
             'flags': 0,
-            'ips': ["127.0.0.1", "::"],
+            'ips': ips,
             # Windows only
             'guid': "{%s}" % uuid.uuid1(),
             'ipv4_metric': 0,

scapy/layers/l2.py

@@ -1071,17 +1071,17 @@ def arping(net: str,
         hint = net[0]
     else:
         hint = str(net)
-    psrc = conf.route.route(hint, verbose=False)[1]
-    if psrc == "0.0.0.0":
-        if "iface" in kargs:
-            psrc = get_if_addr(kargs["iface"])
-        else:
-            warning(
-                "No route found for IPv4 destination %s. "
-                "Using conf.iface. Please provide an 'iface' !" % hint)
-            psrc = get_if_addr(conf.iface)
-            hwaddr = get_if_hwaddr(conf.iface)
-            kargs["iface"] = conf.iface
+    psrc = conf.route.route(
+        hint,
+        dev=kargs.get("iface", None),
+        verbose=False,
+        _internal=True,  # Do not follow default routes.
+    )[1]
+    if psrc == "0.0.0.0" and "iface" not in kargs:
+        warning(
+            "Could not find the interface for destination %s based on the routes. "
+            "Using conf.iface. Please provide an 'iface' !" % hint
+        )
 
     ans, unans = srp(
         Ether(dst="ff:ff:ff:ff:ff:ff", src=hwaddr) / ARP(

test/scapy/layers/l2.uts

@@ -17,6 +17,40 @@ def _test():
 
 retry_test(_test)
 
+= Arping - interface that has no ip
+~ mock
+
+from unittest import mock
+
+_old_routes = conf.route.routes
+_old_ifaces = conf.ifaces.data.copy()
+
+try:
+    conf.route.routes = [
+        (180996905, 4294967295, '0.0.0.0', 'eth0', '10.201.203.41', 0),
+        (180997119, 4294967295, '0.0.0.0', 'eth0', '10.201.203.41', 0),
+        (0, 0, '10.201.203.254', 'eth0', '0.0.0.0', 0),
+        (180996864, 4294967040, '0.0.0.0', 'eth0', '10.201.203.41', 0),
+        (3758096384, 4026531840, '0.0.0.0', 'eth0', '10.201.203.41', 250)
+    ]
+    conf.ifaces._add_fake_iface("toto", mac="11:22:33:aa:bb:cc", ips=[])
+
+    def dummy_srp(pkts, **kwargs):
+        assert pkts.dst == "ff:ff:ff:ff:ff:ff"
+        assert pkts.src == "11:22:33:aa:bb:cc"
+        assert pkts[ARP].psrc == "0.0.0.0"
+        assert pkts[ARP].pdst == Net("192.168.0.1/24")
+        assert pkts[ARP].hwsrc == "11:22:33:aa:bb:cc"
+        # No results, we don't care.
+        return SndRcvList([]), PacketList(pkts)
+
+    with mock.patch("scapy.layers.l2.srp", side_effect=dummy_srp):
+        arping("192.168.0.1/24", iface="toto")
+
+finally:
+    conf.route.routes = _old_routes
+    conf.ifaces.data = _old_ifaces
+
 = Test ARPingResult output
 ~ manufdb