use netifaces for faster IPython.utils.localinterfaces

IPython/utils/localinterfaces.py

@@ -5,6 +5,8 b' LOCALHOST : The loopback interface, or the first interface that points to this'
             machine.  It will *almost* always be '127.0.0.1'
 
 LOCAL_IPS : A list of IP addresses, loopback first, that point to this machine.
+            This will include LOCALHOST, PUBLIC_IPS, and aliases for all hosts,
+            such as '0.0.0.0'.
 
 PUBLIC_IPS : A list of public IP addresses that point to this machine.
              Use these to tell remote clients where to find you.
@@ -31,7 +33,7 b' from .data import uniq_stable'
 LOCAL_IPS = []
 PUBLIC_IPS = []
 
-LOCALHOST = '127.0.0.1'
+LOCALHOST = ''
 
 def _only_once(f):
     """decorator to only run a function once"""
@@ -51,17 +53,45 b' def _requires_ips(f):'
         return f(*args, **kwargs)
     return ips_loaded
 
-@_only_once
-def _load_ips():
-    """load the IPs that point to this machine
+def _load_ips_netifaces():
+    """load ip addresses with netifaces"""
+    import netifaces
+    global LOCALHOST
+    local_ips = []
+    public_ips = []
+    
+    # list of iface names, 'lo0', 'eth0', etc.
+    for iface in netifaces.interfaces():
+        # list of ipv4 addrinfo dicts
+        ipv4s = netifaces.ifaddresses(iface).get(netifaces.AF_INET, [])
+        for entry in ipv4s:
+            addr = entry.get('addr')
+            if not addr:
+                continue
+            if not (iface.startswith('lo') or addr.startswith('127.')):
+                public_ips.append(addr)
+            elif not LOCALHOST:
+                LOCALHOST = addr
+            local_ips.append(addr)
+    if not LOCALHOST:
+        # we never found a loopback interface (can this ever happen?), assume common default
+        LOCALHOST = '127.0.0.1'
+        local_ips.insert(0, LOCALHOST)
+    local_ips.extend(['0.0.0.0', ''])
+    LOCAL_IPS[:] = uniq_stable(local_ips)
+    PUBLIC_IPS[:] = uniq_stable(public_ips)
     
-    This function will only ever be called once.
+def _load_ips_gethostbyname():
+    """load ip addresses with socket.gethostbyname_ex
+    
+    This can be slow.
     """
     global LOCALHOST
     try:
         LOCAL_IPS[:] = socket.gethostbyname_ex('localhost')[2]
     except socket.error:
-        pass
+        # assume common default
+        LOCAL_IPS[:] = ['127.0.0.1']
     
     try:
         hostname = socket.gethostname()
@@ -82,6 +112,32 b' def _load_ips():'
 
     LOCALHOST = LOCAL_IPS[0]
 
+def _load_ips_dumb():
+    """Fallback in case of unexpected failure"""
+    global LOCALHOST
+    LOCALHOST = '127.0.0.1'
+    LOCAL_IPS[:] = [LOCALHOST, '0.0.0.0', '']
+    PUBLIC_IPS[:] = []
+
+@_only_once
+def _load_ips():
+    """load the IPs that point to this machine
+    
+    This function will only ever be called once.
+    
+    It will use netifaces to do it quickly if available,
+    otherwise it will fallback on socket.gethostbyname_ex, which can be slow.
+    """
+    try:
+        try:
+            _load_ips_netifaces()
+        except ImportError:
+            _load_ips_gethostbyname()
+    except Exception:
+        # unexpected error shouldn't crash, load dumb default values instead.
+        _load_ips_dumb()
+
+
 @_requires_ips
 def local_ips():
     """return the IP addresses that point to this machine"""