def _buildEcho(req):
if not isinstance(req, Icmp):
req = base.extract(req, Icmp)
if req is None:
return None
resp = Icmp()
resp.type = TYPE_ECHO_REPLY
resp.code = req.code
resp.set_payload(req.next)
resp.csum = 0
resp.csum = computeChecksum(resp.pack(), 0)
return resp
def checksumBak(packet):
if not isinstance(packet, Icmp):
packet = extract(packet)
if packet is None:
return 0
packet.csum = 0
icmpHdr = packet.hdr()
if packet.next is None:
nextHdr = ""
elif isinstance(packet.next, str):
nextHdr = packet.next
elif isinstance(packet.next, DummyHdr):
nextHdr = packet.next.hdr()
else:
nextHdr = packet.next.hdr()
s = "%s%s" % (icmpHdr, nextHdr)
icmpPkt = Icmp(arr=s, prev=packet.prev)
icmpPkt.next = nextHdr
return _checksum(icmpPkt)
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
