Prevent import failure when /etc/protocols is unavailable.

Fixes #662.

* dns/rdtypes/IN/WKS.py: Wrap TCP and UDP protocol lookups in
try...except.

diff --git a/dns/rdtypes/IN/WKS.py b/dns/rdtypes/IN/WKS.py
index 0d36281788563e220c93ef5a5155c6b492a06fc2..e9bc33c511c84178b83387c3b2c8075d6e8adf92 100644 (file)
--- a/dns/rdtypes/IN/WKS.py
+++ b/dns/rdtypes/IN/WKS.py
@@ -22,9 +22,13 @@ import dns.ipv4
 import dns.immutable
 import dns.rdata
 
-_proto_tcp = socket.getprotobyname('tcp')
-_proto_udp = socket.getprotobyname('udp')
-
+try:
+    _proto_tcp = socket.getprotobyname('tcp')
+    _proto_udp = socket.getprotobyname('udp')
+except OSError:
+    # Fall back to defaults in case /etc/protocols is unavailable.
+    _proto_tcp = 6
+    _proto_udp = 17
 
 @dns.immutable.immutable
 class WKS(dns.rdata.Rdata):