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|
#!/usr/bin/env python
import os
import sys
import pwd
try:
import asyncore
except:
import py_asyncore as asyncore
import socket
import errno
from struct import unpack
import time
from exabgp.util.od import od
class BGPHandler(asyncore.dispatcher_with_send):
wire = not not os.environ.get('wire', '')
update = True
keepalive = chr(0xFF) * 16 + chr(0x0) + chr(0x13) + chr(0x4)
_name = {
chr(1): 'OPEN',
chr(2): 'UPDATE',
chr(3): 'NOTIFICATION',
chr(4): 'KEEPALIVE',
}
def isupdate(self, header):
return header[18] == chr(2)
def name(self, header):
return self._name.get(header[18], 'SOME WEIRD RFC PACKET')
def routes(self, body):
len_w = unpack('!H', body[0:2])[0]
prefixes = [ord(_) for _ in body[2 : 2 + len_w :]]
if not prefixes:
yield 'no ipv4 withdrawal'
while prefixes:
l = prefixes.pop(0)
r = [0, 0, 0, 0]
for index in range(4):
if index * 8 >= l:
break
r[index] = prefixes.pop(0)
yield 'withdraw ' + '.'.join(str(_) for _ in r) + '/' + str(l)
len_a = unpack('!H', body[2 + len_w : 2 + len_w + 2])[0]
prefixes = [ord(_) for _ in body[2 + len_w + 2 + len_a :]]
if not prefixes:
yield 'no ipv4 announcement'
while prefixes:
l = prefixes.pop(0)
r = [0, 0, 0, 0]
for index in range(4):
if index * 8 >= l:
break
r[index] = prefixes.pop(0)
yield 'announce ' + '.'.join(str(_) for _ in r) + '/' + str(l)
def announce(self, *args):
print self.ip, self.port, ' '.join(str(_) for _ in args) if len(args) > 1 else args[0]
def setup(self, record, ip, port):
self.ip = ip
self.port = port
now = time.strftime("%a-%d-%b-%Y-%H:%M:%S", time.gmtime())
self.record = open("%s-%s" % ('bgp', now), 'w') if record else None
self.handle_read = self.handle_open
self.update_count = 0
self.time = time.time()
return self
def read_message(self):
header = ''
while len(header) != 19:
try:
left = 19 - len(header)
header += self.recv(left)
if self.wire:
self.announce("HEADER ", od(header))
if self.wire and len(header) != 19:
self.announce("left", 19 - len(header))
if left == 19 - len(header): # ugly
# the TCP session is gone.
self.announce("TCP connection closed")
self.close()
return None, None
except socket.error, exc:
if exc.args[0] in (errno.EWOULDBLOCK, errno.EAGAIN):
continue
raise exc
self.announce("read", self.name(header))
length = unpack('!H', header[16:18])[0] - 19
if self.wire:
self.announce("waiting for", length, "bytes")
if length > 4096 - 19:
print "packet"
print od(header)
print "Invalid length for packet", length
sys.exit(1)
body = ''
left = length
while len(body) != length:
try:
body += self.recv(left)
left = length - len(body)
if self.wire:
self.announce("BODY ", od(body))
if self.wire and left:
self.announce("missing", left)
except socket.error, exc:
if exc.args[0] in (errno.EWOULDBLOCK, errno.EAGAIN):
continue
raise exc
self.update_count += 1
if self.record:
self.record.write(header + body)
elif self.isupdate(header):
self.announce(
"received %-6d updates (%6d/sec) " % (self.update_count, self.update_count / (time.time() - self.time)),
', '.join(self.routes(body)),
)
return header, body
def handle_open(self):
# reply with a IBGP response with the same capability (just changing routerID)
header, body = self.read_message()
routerid = chr((ord(body[8]) + 1) & 0xFF)
o = header + body[:8] + routerid + body[9:]
self.announce("sending open")
self.send(o)
self.announce("sending keepalive")
self.send(self.keepalive)
self.handle_read = self.handle_keepalive
def handle_keepalive(self):
header, body = self.read_message()
if header is not None:
self.announce("sending keepalive")
self.send(self.keepalive)
class BGPServer(asyncore.dispatcher):
def __init__(self, host, port, record):
self.record = record
asyncore.dispatcher.__init__(self)
self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
self.set_reuse_addr()
self.bind((host, port))
self.listen(5)
def handle_accept(self):
pair = self.accept()
if pair is not None:
# The if prevent invalid unpacking
sock, addr = pair # pylint: disable=W0633
print "new BGP connection from", addr
BGPHandler(sock).setup(self.record, *addr)
def drop():
uid = os.getuid()
gid = os.getgid()
if uid and gid:
return
for name in [
'nobody',
]:
try:
user = pwd.getpwnam(name)
nuid = int(user.pw_uid)
ngid = int(user.pw_uid)
except KeyError:
pass
if not gid:
os.setgid(ngid)
if not uid:
os.setuid(nuid)
try:
if os.environ.get('exabgp.tcp.port', '').isdigit():
port = int(os.environ.get('exabgp.tcp.port'))
elif os.environ.get('exabgp_tcp_port', '').isdigit():
port = int(os.environ.get('exabgp_tcp_port'))
else:
port = 179
bind = os.environ.get('exabgp.tcp.bind', os.environ.get('exabgp_tcp_bind', 'localhost'))
record = bool(os.environ.get('exabgp.wire.record', os.environ.get('exabgp.wire.record', False)))
server = BGPServer(bind, port, record)
drop()
asyncore.loop()
except socket.error:
print 'need root right to bind to port 179'
|
