[tor-commits] [ooni-probe/master] Refactor logic for importing scapy related functions

[art at torproject.org]

commit b32d6fd187e78539e2f9c4415f478a2da80d7a0f
Author: Arturo Filastò <art at fuffa.org>
Date:   Wed Feb 27 15:57:35 2013 +0100

    Refactor logic for importing scapy related functions
    
    * Make scapy related requirements less strict
    * Always print out a useful error message when something goes wrong
    (cherry picked from commit 77b2f6e7206f5a1bb1531fb2416eaf36675b098b)
---
 ooni/utils/net.py     |    2 +-
 ooni/utils/txscapy.py |   54 ++++++++++++++++++++++++++++++++++++------------
 2 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/ooni/utils/net.py b/ooni/utils/net.py
index 49f9998..67a98c2 100644
--- a/ooni/utils/net.py
+++ b/ooni/utils/net.py
@@ -7,7 +7,7 @@ from twisted.internet import protocol, defer
 from twisted.internet import threads, reactor
 from twisted.web.iweb import IBodyProducer
 
-from ooni.utils import log, txscapy
+from ooni.utils import log
 
 #if sys.platform.system() == 'Windows':
 #    import _winreg as winreg
diff --git a/ooni/utils/txscapy.py b/ooni/utils/txscapy.py
index 0e805e7..84e69a6 100644
--- a/ooni/utils/txscapy.py
+++ b/ooni/utils/txscapy.py
@@ -14,24 +14,50 @@ from scapy.config import conf
 from ooni.utils import log
 from ooni import config
 
-try:
-    conf.use_pcap = True
-    conf.use_dnet = True
+class LibraryNotInstalledError(Exception):
+    pass
 
-    from scapy.all import PcapWriter
-    from scapy.arch import pcapdnet
+def pcapdnet_installed():
+    """
+    Checks to see if libdnet or libpcap are installed and set the according
+    variables.
 
-    config.pcap_dnet = True
-    from scapy.all import Gen, SetGen, MTU
+    Returns:
 
-except ImportError, e:
-    log.err("pypcap or dnet not installed. "
-            "Certain tests may not work.")
+        True
+            if pypcap and libdnet are installed
 
-    config.pcap_dnet = False
-    conf.use_pcap = False
-    conf.use_dnet = False
+        False
+            if one of the two is absent
+    """
+    try:
+        conf.use_pcap = True
+        conf.use_dnet = True
+        from scapy.arch import pcapdnet
+
+        config.pcap_dnet = True
+
+    except ImportError:
+        log.err("pypcap or dnet not installed. "
+                "Certain tests may not work.")
+
+        config.pcap_dnet = False
+        conf.use_pcap = False
+        conf.use_dnet = False
+
+    # This is required for unix systems that are different than linux (OSX for
+    # example) since scapy explicitly wants pcap and libdnet installed for it
+    # to work.
+    try:
+        from scapy.arch import pcapdnet
+    except ImportError:
+        log.err("Your platform requires to having libdnet and libpcap installed.")
+        raise LibraryNotInstalledError
+
+if pcapdnet_installed():
+    from scapy.all import PcapWriter
 
+else:
     class DummyPcapWriter:
         def __init__(self, pcap_filename, *arg, **kw):
             log.err("Initializing DummyPcapWriter. We will not actually write to a pcapfile")
@@ -41,7 +67,7 @@ except ImportError, e:
 
     PcapWriter = DummyPcapWriter
 
-    from scapy.all import Gen, SetGen, MTU
+from scapy.all import Gen, SetGen, MTU
 
 def getNetworksFromRoutes():
     """ Return a list of networks from the routing table """