def buildResponse(req, packet, serverMac, serverIp, **kwargs):
resp = None
typ = extractMsgType(packet)
if typ == Dhcp.DISCOVER_MSG:
dhcpPkt = buildOfferMsg(packet, **kwargs)
elif typ == Dhcp.REQUEST_MSG:
dhcpPkt = buildAckMsg(packet, **kwargs)
else:
return None
udpPkt = udp.buildUdpResponse(req, dhcpPkt)
ipKwargs = {}
ipKwargs['srcip'] = serverIp
if (isinstance(dhcpPkt.yiaddr, (int, long))):
ipKwargs['dstip'] = IPAddr(dhcpPkt.yiaddr)
else:
ipKwargs['dstip'] = dhcpPkt.yiaddr
ipKwargs['protocol'] = Ipv4.UDP_PROTOCOL
ipPkt = ipv4.buildIpResponse(req, udpPkt, **ipKwargs)
udpPkt.csum = udp.checksum(udpPkt)
resp = ethernet.buildResponse(req, ipPkt, src=serverMac)
return resp
def buildUnreachResp(req, packet, unreachCode):
icmpPkt = Icmp()
icmpPkt.type = TYPE_DEST_UNREACH
icmpPkt.code = unreachCode
icmpPkt.set_payload(packet)
icmpPkt.parsed = True
ipPkt = ipv4.buildIpResponse(req, icmpPkt, protocol=Ipv4.ICMP_PROTOCOL, tos=0xC0)
dummy = DummyHdr("\x00\x00\x00\x00")
icmpPkt.set_payload(dummy)
dummy.set_payload(packet)
ipLen = 0
a = ipPkt
while a is not None:
m = getattr(a, "hdr", None)
if m:
n = len(a.hdr())
else:
n = len(a)
ipLen += n
a = getattr(a, "next", None)
ipPkt.iplen = ipLen
icmpPkt.prev = ipPkt
ethPkt = ethernet.buildResponse(req, ipPkt)
icmpPkt.csum = 0
icmpPkt.csum = checksum(icmpPkt)
return ethPkt
def buildResponse(req, packet, typ):
resp = None
if typ == Echo:
icmpPkt = _buildEcho(packet)
else:
return None
if icmpPkt is None:
return None
ipPkt = ipv4.buildIpResponse(req, icmpPkt, protocol=Ipv4.ICMP_PROTOCOL)
resp = ethernet.buildResponse(req, ipPkt)
return resp
def buildStandardTcpResponse(req, tcpPkt, payload="", ipId=None):
tcpPkt.next = payload
offres = 20 * 4 # header length = 20
tcpPkt.off = offres >> 4
tcpPkt.res = offres & 0x0F
tcpPkt.parsed = True
hdr = tcpPkt.hdr(payload, calc_checksum=False)
tcpPkt.arr = hdr
tcpPkt.tcplen = len(hdr)
kwargs = {}
if ipId is None and isSyn(tcpPkt) and isAck(tcpPkt):
kwargs["id"] = 0
kwargs["protocol"] = Ipv4.TCP_PROTOCOL
ipPkt = ipv4.buildIpResponse(req, tcpPkt, **kwargs)
if ipId is not None:
ipPkt.id = ipId
ipPkt.iplen = len(hdr) + tcpPkt.tcplen
tcpPkt.csum = tcpPkt.checksum()
resp = ethernet.buildResponse(req, ipPkt)
return resp