Adds python IP utility library

Changes include:
 - IP utility library in python 3 that supports both IPv4 and IPv6
   address generation. This library currently includes a single
   function of generating IP ranges or single IP for a given CIDR.
   More functionality will be added at a later time to support
   features such as IP address calculation.
 - Updated common-function.sh to use python library to generate IP
   ranges. All existing bash functions are preserved, so any
   callers will get identical IP ranges as before.
 - Add dependency to python3 for opnfv-apex-common package.
 - Add python dependency to build.sh

No change is made to interface related functions.

Change-Id: Idc6998754f9f3c7a3868ec5b5768f3bb5f78cd90
Signed-off-by: Feng Pan <fpan@redhat.com>

2 files changed, 63 insertions, 0 deletions

diff --git a/lib/python/apex/__init__.py b/lib/python/apex/__init__.py
new file mode 100644
index 00000000..0c0ae6c6
--- /dev/null
+++ b/lib/python/apex/__init__.py
@@ -0,0 +1,9 @@
+##############################################################################
+# Copyright (c) 2016 Feng Pan (fpan@redhat.com) and others.
+#
+# All rights reserved. This program and the accompanying materials
+# are made available under the terms of the Apache License, Version 2.0
+# which accompanies this distribution, and is available at
+# http://www.apache.org/licenses/LICENSE-2.0
+##############################################################################
+
diff --git a/lib/python/apex/ip_utils.py b/lib/python/apex/ip_utils.py
new file mode 100644
index 00000000..680ce7e0
--- /dev/null
+++ b/lib/python/apex/ip_utils.py
@@ -0,0 +1,54 @@
+
+##############################################################################
+# Copyright (c) 2016 Feng Pan (fpan@redhat.com) and others.
+#
+# All rights reserved. This program and the accompanying materials
+# are made available under the terms of the Apache License, Version 2.0
+# which accompanies this distribution, and is available at
+# http://www.apache.org/licenses/LICENSE-2.0
+##############################################################################
+
+
+import ipaddress
+
+
+def generate_ip_range(args):
+    """
+    Generate IP range in string format for given CIDR.
+    This function works for both IPv4 and IPv6.
+
+    args is expected to contain the following members:
+    CIDR: any valid CIDR representation.
+    start_position: starting index, default to first address in subnet (1)
+    end_position:  ending index, default to last address in subnet (-1)
+
+    Returns IP range in string format. A single IP is returned if start and end IPs are identical.
+    """
+    cidr = ipaddress.ip_network(args.CIDR)
+    (start_index, end_index) = (args.start_position, args.end_position)
+    if cidr[start_index] == cidr[end_index]:
+        return str(cidr[start_index])
+    else:
+        return ','.join(sorted([str(cidr[start_index]), str(cidr[end_index])]))
+
+
+def main():
+    import argparse
+    import sys
+
+    parser = argparse.ArgumentParser()
+    subparsers = parser.add_subparsers()
+
+    parser_gen_ip_range = subparsers.add_parser('generate_ip_range', help='Generate IP Range given CIDR')
+    parser_gen_ip_range.add_argument('CIDR', help='Network in CIDR notation')
+    parser_gen_ip_range.add_argument('start_position', type=int, help='Starting index')
+    parser_gen_ip_range.add_argument('end_position', type=int, help='Ending index')
+    parser_gen_ip_range.set_defaults(func=generate_ip_range)
+
+    args = parser.parse_args(sys.argv[1:])
+    print(args.func(args))
+
+
+if __name__ == '__main__':
+    main()
+