Workaround to ignore interfaces name truncated by netstat

When interface names are longer than 7 characters, netstat will truncate
them to the first 7 chars which leads to looking up an invalid interface
name.
We attempt to guess the name of the interface based on the output of
ifconfig -l. If there is only one candidate we consider it, otherwise we
ignore it.

scapy/arch/unix.py

@@ -7,6 +7,8 @@
 Common customizations for all Unix-like operating systems other than Linux
 """
 
+from __future__ import with_statement
+
 import sys,os,struct,socket,time
 from fcntl import ioctl
 import socket
@@ -24,6 +26,21 @@
 ## Routes stuff ##
 ##################
 
+def _guess_iface_name(netif):
+    """
+    We attempt to guess the name of interfaces that are truncated from the
+    output of ifconfig -l.
+    If there is only one possible candidate matching the interface name then we
+    return it.
+    If there are none or more, then we return None.
+    """
+    with os.popen('%s -l' % conf.prog.ifconfig) as fdesc:
+        ifaces = fdesc.readline().strip().split(' ')
+    matches = [iface for iface in ifaces if iface.startswith(netif)]
+    if len(matches) == 1:
+        return matches[0]
+    return None
+
 
 def read_routes():
     if scapy.arch.SOLARIS:
@@ -81,8 +98,22 @@ def read_routes():
         if not "G" in flg:
             gw = '0.0.0.0'
         if netif is not None:
-            ifaddr = scapy.arch.get_if_addr(netif)
-            routes.append((dest,netmask,gw,netif,ifaddr))
+            try:
+                ifaddr = scapy.arch.get_if_addr(netif)
+                routes.append((dest,netmask,gw,netif,ifaddr))
+            except OSError as exc:
+                if exc.message == 'Device not configured':
+                    # This means the interface name is probably truncated by
+                    # netstat -nr. We attempt to guess it's name and if not we
+                    # ignore it.
+                    guessed_netif = _guess_iface_name(netif)
+                    if guessed_netif is not None:
+                        ifaddr = scapy.arch.get_if_addr(guessed_netif)
+                        routes.append((dest, netmask, gw, guessed_netif, ifaddr))
+                    else:
+                        warning("Could not guess partial interface name: %s" % netif)
+                else:
+                    raise
         else:
             pending_if.append((dest,netmask,gw))
     f.close()

test/regression.uts

@@ -4554,6 +4554,62 @@ assert isinstance(pkt, UDP) and pkt.dport == 5353
 pkt = pkt.payload
 assert isinstance(pkt, DNS) and isinstance(pkt.payload, NoPayload)
 
++ Mocked read_routes() calls
+
+= Truncated netstat -rn output on OS X
+
+import mock
+import StringIO
+
+@mock.patch("scapy.arch.get_if_addr")
+@mock.patch("scapy.arch.unix.os")
+def test_osx_netstat_truncated(mock_os, mock_get_if_addr):
+    """Test read_routes() on OS X 10.? with a long interface name"""
+    # netstat & ifconfig outputs from https://github.com/secdev/scapy/pull/119
+    netstat_output = """
+Routing tables
+
+Internet:
+Destination        Gateway            Flags        Refs      Use   Netif Expire
+default            192.168.1.1        UGSc          460        0     en1
+default            link#11            UCSI            1        0 bridge1
+127                127.0.0.1          UCS             1        0     lo0
+127.0.0.1          127.0.0.1          UH             10  2012351     lo0
+"""
+    ifconfig_output = "lo0 en1 bridge10\n"
+    # Mocked file descriptors
+    def se_popen(command):
+        """Perform specific side effects"""
+        if command == "netstat -rn":
+	    return StringIO.StringIO(netstat_output)
+        elif command == "ifconfig -l":
+	    ret = StringIO.StringIO(ifconfig_output)
+	    def unit():
+		return ret
+	    ret.__call__ = unit
+	    ret.__enter__ = unit
+	    ret.__exit__ = lambda x,y,z: None
+	    return ret
+	raise Exception("Command not mocked: %s" % command)
+    mock_os.popen.side_effect = se_popen
+    # Mocked get_if_addr() behavior
+    def se_get_if_addr(iface):
+        """Perform specific side effects"""
+        if iface == "bridge1":
+	    oserror_exc = OSError()
+	    oserror_exc.message = "Device not configured"
+	    raise oserror_exc
+	return "1.2.3.4"
+    mock_get_if_addr.side_effect = se_get_if_addr
+    # Test the function
+    from scapy.arch.unix import read_routes
+    routes = read_routes()
+    assert(len(routes) == 4)
+    assert([r for r in routes if r[3] == "bridge10"])
+
+
+test_osx_netstat_truncated()
+
 + Mocked read_routes6() calls
 
 = Preliminary definitions