[tests/wr_arp] Migrate warm reboot mgmt plane script ferret to py3 (s…

…onic-net#12898)

What is the motivation for this PR?
The warm reboot test scripts have been migrated to Python 3. The ferret script still runs in Python 2 environment. This PR migrates that to Py3.

How did you do it?
Run 2to3
Modified script as struct packing handles bytes instead of str.
Modified other affected parts to handle bytes directly

How did you verify/test it?
Ran warm reboot and warm reboot advanced tests on Dell S6100. Tests have passed successfully.

tests/arp/files/ferret.conf.j2

@@ -1,5 +1,5 @@
 [program:ferret]
-command=/usr/bin/python /opt/ferret.py {{ ferret_args }}
+command=/root/env-python3/bin/python3 /opt/ferret.py {{ ferret_args }}
 process_name=ferret
 stdout_logfile=/tmp/ferret.out.log
 stderr_logfile=/tmp/ferret.err.log

tests/arp/files/ferret.py

@@ -2,11 +2,10 @@
 
 # python t.py -f /tmp/vxlan_decap.json -s 192.168.8.1
 
-import SocketServer
+import socketserver
 import select
-import shutil
 import json
-import BaseHTTPServer
+import http.server
 import time
 import socket
 import ctypes
@@ -16,7 +15,7 @@
 import argparse
 import os
 
-from cStringIO import StringIO
+from io import StringIO
 from collections import namedtuple
 
 
@@ -26,7 +25,7 @@
 ASIC_TYPE = None
 
 
-class Ferret(BaseHTTPServer.BaseHTTPRequestHandler):
+class Ferret(http.server.BaseHTTPRequestHandler):
     server_version = "FerretHTTP/0.1"
 
     def do_POST(self):
@@ -38,7 +37,7 @@ def do_POST(self):
             self.send_resp(info)
 
     def extract_info(self):
-        c_len = int(self.headers.getheader('content-length', 0))
+        c_len = int(self.headers['content-length'])
         body = self.rfile.read(c_len)
         j = json.loads(body)
         return j
@@ -79,7 +78,7 @@ def send_resp(self, info):
         self.send_header("Content-Length", str(line))
         self.send_header("Last-Modified", self.date_time_string())
         self.end_headers()
-        shutil.copyfileobj(f, self.wfile)
+        self.wfile.write(bytes(f.read(), encoding='utf-8'))
         f.close()
         return
 
@@ -95,8 +94,8 @@ class RestAPI(object):
     PORT = 448
 
     def __init__(self, obj, db, src_ip):
-        SocketServer.TCPServer.allow_reuse_address = True
-        self.httpd = SocketServer.TCPServer(("", self.PORT), obj)
+        socketserver.TCPServer.allow_reuse_address = True
+        self.httpd = socketserver.TCPServer(("", self.PORT), obj)
         self.context = ssl.SSLContext(ssl.PROTOCOL_TLS)
         self.context.verify_mode = ssl.CERT_NONE
         self.context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
@@ -126,8 +125,10 @@ def __init__(self, iface, bpf_src):
         self.socket = socket.socket(
             socket.AF_PACKET, socket.SOCK_RAW, socket.htons(self.ETH_P_ALL))
         if bpf_src is not None:
-            blob = ctypes.create_string_buffer(
-                ''.join(struct.pack("HBBI", *e) for e in bpf_src))
+            bpf_bytes = bytearray()
+            for e in bpf_src:
+                bpf_bytes.extend(struct.pack("HBBI", *e))
+            blob = ctypes.create_string_buffer(bytes(bpf_bytes))
             address = ctypes.addressof(blob)
             bpf = struct.pack('HL', len(bpf_src), address)
             self.socket.setsockopt(
@@ -156,7 +157,7 @@ def __init__(self, httpd, interfaces, responder):
         self.httpd = httpd
 
     def poll(self):
-        handlers = self.mapping.keys() + [self.httpd.handler()]
+        handlers = list(self.mapping.keys()) + [self.httpd.handler()]
         while True:
             (rdlist, _, _) = select.select(handlers, [], [])
             for handler in rdlist:
@@ -178,11 +179,10 @@ def __init__(self, db, vxlan_port):
         self.vxlan_port = vxlan_port
 
     def hexdump(self, data):
-        print((" ".join("%02x" % ord(d) for d in data)))
+        print(' '.join(str(i) for i in list(data)))
 
     def action(self, interface):
         data = interface.recv()
-
         ext_dst_mac = data[0x00:0x06]
         ext_src_mac = data[0x06:0x0c]
         ext_eth_type = data[0x0c:0x0e]
@@ -243,11 +243,11 @@ def action(self, interface):
             return
 
         if r.family == 'ipv4':
-            new_pkt = ext_src_mac + ext_dst_mac + ext_eth_type  # outer eth frame
+            new_pkt = bytearray(ext_src_mac + ext_dst_mac + ext_eth_type)  # outer eth frame
             ipv4 = binascii.unhexlify(
                 '45000060977e400040110000') + dst_ip + src_ip  # ip
             crc = self.calculate_header_crc(ipv4)
-            ipv4 = ipv4[0:10] + crc + ipv4[12:]
+            ipv4 = bytearray(ipv4[0:10] + crc + ipv4[12:])
             new_pkt += ipv4
             if self.vxlan_port:
                 # udp
@@ -272,9 +272,7 @@ def action(self, interface):
     def calculate_header_crc(self, ipv4):
         s = 0
         for left, right in zip(ipv4[::2], ipv4[1::2]):
-            l_u = struct.unpack("B", left)[0]
-            r_u = struct.unpack("B", right)[0]
-            s += (l_u << 8) + r_u
+            s += (left << 8) + right
 
         c = s >> 16
         s = s & 0xffff
@@ -285,18 +283,17 @@ def calculate_header_crc(self, ipv4):
             s = s & 0xffff
 
         s = 0xffff - s
-
         return binascii.unhexlify("%x" % s)
 
     def extract_arp_info(self, data):
-        vlan_id = ord(data[14]) * 256 + ord(data[15])
+        vlan_id = data[14] * 256 + data[15]
         if vlan_id == 1:
             offset = 0
         else:
             offset = 4
         # vlan_id, remote_mac, remote_ip, request_ip, op_type
         return vlan_id, data[6:12], data[offset+28:offset+32], data[offset+38:offset+42], \
-            (ord(data[offset+20]) * 256 + ord(data[offset+21]))
+            (data[offset+20] * 256 + data[offset+21])
 
     def generate_arp_reply(self, local_mac, remote_mac, local_ip, remote_ip, vlan_id):
         eth_hdr = remote_mac + local_mac
@@ -328,7 +325,7 @@ def extract_iface_names(config_file):
         graph = json.load(fp)
 
     net_ports = []
-    for name, val in graph['minigraph_portchannels'].items():
+    for name, val in list(graph['minigraph_portchannels'].items()):
         members = ['eth%d' % graph['minigraph_port_indices'][member]
                    for member in val['members']]
         net_ports.extend(members)