def ICMPPortUnreachable(version, srcaddr, dstaddr, packet):
if version == 4:
# Linux hardcodes the ToS on ICMP errors to 0xc0 or greater because of
# RFC 1812 4.3.2.5 (!).
return ("ICMPv4 port unreachable",
scapy.IP(src=srcaddr, dst=dstaddr, proto=1, tos=0xc0) /
scapy.ICMPerror(type=3, code=3) / packet)
else:
return ("ICMPv6 port unreachable",
scapy.IPv6(src=srcaddr, dst=dstaddr) /
scapy.ICMPv6DestUnreach(code=4) / packet)
def ICMPPacketTooBig(version, srcaddr, dstaddr, packet):
if version == 4:
return ("ICMPv4 fragmentation needed",
scapy.IP(src=srcaddr, dst=dstaddr, proto=1) /
scapy.ICMPerror(type=3, code=4, unused=1280) / str(packet)[:64])
else:
udp = packet.getlayer("UDP")
udp.payload = str(udp.payload)[:1280-40-8]
return ("ICMPv6 Packet Too Big",
scapy.IPv6(src=srcaddr, dst=dstaddr) /
scapy.ICMPv6PacketTooBig() / str(packet)[:1232])
def ICMPPacketTooBig(version, srcaddr, dstaddr, packet):
if version == 4:
desc = "ICMPv4 fragmentation needed"
pkt = (scapy.IP(src=srcaddr, dst=dstaddr, proto=1) /
scapy.ICMPerror(type=3, code=4) / str(packet)[:64])
# Only newer versions of scapy understand that since RFC 1191, the last two
# bytes of a fragmentation needed ICMP error contain the MTU.
if hasattr(scapy.ICMP, "nexthopmtu"):
pkt[scapy.ICMPerror].nexthopmtu = PTB_MTU
else:
pkt[scapy.ICMPerror].unused = PTB_MTU
return desc, pkt
else:
return ("ICMPv6 Packet Too Big", scapy.IPv6(src=srcaddr, dst=dstaddr) /
scapy.ICMPv6PacketTooBig(mtu=PTB_MTU) / str(packet)[:1232])