DHCPv6サーバーにIPv6 Prefixくれくれするスクリプト(注: まともなDHCPv6クライアントではないです．隔離環境で実行してください）

dhcp6c_pd_print.py

import ipaddress
import sys
import socket
import os


# ref 
# http://docs.python.jp/3/library/socket.html

def show_identifier(option):
        if option[1] == 1:
                print("client identifier DUID: ",end="")
        else:
                print("server identifier DUID: ",end="")
        # print DUID
        print("0x",end="")
        print("".join("%02x" % i for i in option[4:]))
        
        return

def show_prefix(option):
        iaid = int.from_bytes(option[4:8], byteorder="big", signed=False)
        T1 = int.from_bytes(option[8:12], byteorder="big", signed=False)
        T2 = int.from_bytes(option[12:16], byteorder="big", signed=False)
        # parse IA Prefix
        pdopt_type = int.from_bytes(option[16:18], byteorder="big", signed=False)
        if pdopt_type != 26:
                print("Prefix Delegation Option type: %d not supported" % pdopt_type)
                return
        pdopt_len = int.from_bytes(option[18:20], byteorder="big", signed=False)
        pereferred_lifetime = int.from_bytes(option[20:24], byteorder="big", signed=False)
        valid_lifetime = int.from_bytes(option[24:28], byteorder="big", signed=False)
        prefix_length = int.from_bytes(option[28:29], byteorder="big", signed=False)
        # print prefix
        prefix = option[29:]
        for i,x in enumerate(prefix):
                if i != 0 and i % 2 == 0:
                        print(":", end="")
                print("%02x" % x, end="")
        print("/%d" % prefix_length)
        return

dhv6_client = 546
dhv6_server = 547
BUF_MAX = 512
duid = [0x00,0x01,0x00,0x01,0x1c,0xfb,0x53,0xac,0x08,0x00,0x27,0x42,0xa9,0xd9]


s = None
s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
s.bind(("::1", dhv6_client))

# create dhcpv6 packet
# message type(8bit)
dhv6_mes = bytearray([1]) # Solicit
# transaction id(24bit)
dhv6_mes += os.urandom(1)
dhv6_mes += os.urandom(1)
dhv6_mes += os.urandom(1)

# Option: Client Identifier
# option code(16bit)
opt_cliident = bytearray([0,1])
# option length(16bit)
opt_cliident += bytearray([0,len(duid)])
# set client duid
opt_cliident += bytearray(duid)

# Option: Indentity Association for Prefix Delegation
iaid = [0x00] * 4
t1 = [0x00] * 4
t2 = [0x00] * 4
opt_iapd_val = iaid + t1 + t2
# option code(16bit)
opt_iapd = bytearray([0,25])
# option length(16bit)
opt_iapd += bytearray([0,len(opt_iapd_val)])
# set client duid
opt_iapd += bytearray(opt_iapd_val)

dhv6_mes += opt_cliident
dhv6_mes += opt_iapd


# send Solicit packet
s.sendto(dhv6_mes, ("ff02::1:2", dhv6_server))

# recv DHCPv6 packet from Server
recv = bytearray([0] * BUF_MAX)
r = s.recvfrom_into(recv)
rlen = r[0]

# split DHCPv6 options
dhv6_head = recv[:4]
dhv6_options = []
i = 4
while i < rlen:
        # get option length
        optlen = int.from_bytes(recv[i+2:i+4], byteorder="big", signed=False)
        # get value
        opt = recv[i:i+4+optlen]
        dhv6_options.append(opt)
        i += 4 + optlen

# parse DHCPv6
for option in dhv6_options:
        # check option type
        opt_type = int.from_bytes(option[:2], byteorder="big", signed=False)
        if opt_type in [1,2]:
                show_identifier(option)
                continue
#        if opt_type == 23:
#                show_dns(option)
#                continue
        if opt_type == 25:
                show_prefix(option)
                continue
        print("option code %d not supported" % opt_type)

s.close()