Send TCP SYN over IPv6 using Python

Question

I have a Python project that I need to send a simple TCP SYN message to IPv6 and use a raw socket. My script could be executed without errors, but the syn packet was not sent. I'm not sure about my IPv6 script header, TCP header, or the original IPv6 socket that did the wrong thing. The network was configured for IPv6, so network problems can be eliminated.

Here is my script, I am using Python 2.4 on RHEL 5:

import socket, sys from struct import * # checksum functions needed for calculation checksum def checksum(msg): s = 0 # loop taking 2 characters at a time for i in range(0, len(msg), 2): w = (ord(msg[i]) << 8) + (ord(msg[i+1]) ) s = s + w s = (s>>16) + (s & 0xffff); s = ~s & 0xffff return s def init_tcp_syn_packet_v6(source_port,dest_port, source_ip, dest_ip): packet = ''; # ip header fields version = 6 #4 bit traffic_class = 0 #8 bit flow_level = 1 #20 bit payload_len = 20 #not true lenght, I just selected a random value #16 bit next_header = socket.IPPROTO_TCP #8 bit hop_limit = 255 #8 bit saddr = socket.inet_pton ( socket.AF_INET6, source_ip ) #128 bit daddr = socket.inet_pton ( socket.AF_INET6, dest_ip ) #128 bit ver_traff_flow = (version << 8) + traffic_class ver_traff_flow = (ver_traff_flow << 20) + flow_level ip_header = pack( '!IHBB', ver_traff_flow, payload_len, next_header, hop_limit) ip_header = ip_header + saddr + daddr # tcp header fields seq = 0 ack_seq = 0 doff = 5 #4 bit field, size of tcp header, 5*4 = 20 bytes #tcp flags fin = 0 syn = 1 rst = 0 psh = 0 ack = 0 urg = 0 window = socket.htons (5840) #maximum allowed window size check = 0 urg_ptr = 0 offset_res = (doff << 4) + 0 tcp_flags = fin + (syn << 1) + (rst << 2) + (psh <<3) + (ack << 4) + (urg << 5) tcp_header = pack('!HHLLBBHHH' , source_port, dest_port, seq, ack_seq, offset_res, tcp_flags, window, check, urg_ptr) source_address = socket.inet_pton( socket.AF_INET6, source_ip ) dest_address = socket.inet_pton( socket.AF_INET6, dest_ip ) placeholder = 0 protocol = socket.IPPROTO_TCP tcp_length = len(tcp_header) psh = source_address + dest_address + pack('!BBH' , placeholder , protocol , tcp_length); psh = psh + tcp_header; tcp_checksum = checksum(psh) # make the tcp header again and fill the correct checksum tcp_header = pack('!HHLLBBHHH' , source_port, dest_port, seq, ack_seq, offset_res, tcp_flags, window, tcp_checksum , urg_ptr) packet = ip_header + tcp_header return packet #main #create raw socket v6 s = socket.socket(socket.AF_INET6, socket.SOCK_RAW, socket.IPPROTO_TCP) s.setsockopt(socket.IPPROTO_IPV6, socket.IP_HDRINCL, 1) #send syn packet packet = init_tcp_syn_packet_v6( 1235, 80, '2001:172:22:5::31','2014:2008:0:c::284a:78a4')