Scapy - crafted ICMP replies being ignored by sender - python-3.x

Question

I have wrote a small app to respond to ICMP, however it seems that the sender is ignoring the ICMP replies. Inspecting the packets in Wireshark they are missing the timestamp fields, and working ICMP replies from actual devices contain the timestamp fields, is it just a case I'm missing them in mine?
I've poisoned the ARP cache so it has a correct ARP mapping in the ARP table.
I've confirmed using TCPDump that the ICMP replies are at least hitting the interface, not sure if they are being processed beyond that - if anyone has any advice on where to check for that, it would be appreciated
def respond_to_icmp(self, icmp_packet):
if icmp_packet["IP"].dst == self.ip: # if this is my IP
eth = Ether(dst=icmp_packet["Ether"].src, src=self.mac)
ip = IP(src=icmp_packet["IP"].dst, dst=icmp_packet["IP"].src)
icmp = ICMP(type=0, id=icmp_packet['ICMP'].id, seq=icmp_packet['ICMP'].seq)
icmp_reply = eth/ip/icmp
sendp(icmp_reply, iface=self.interface) # eth0 (on which it is received)
ICMP Reply Packet
###[ Ethernet ]###
dst = de:ad:be:ef:ee:ff
src = aa:bb:cc:dd:ee:ff
type = IPv4
###[ IP ]###
version = 4
ihl = None
tos = 0x0
len = None
id = 1
flags =
frag = 0
ttl = 64
proto = icmp
chksum = None
src = 192.168.3.46
dst = 192.168.3.1
\options \
###[ ICMP ]###
type = echo-reply
code = 0
chksum = None
id = 0x6b86
seq = 0x19f
ICMP activity from sender
21:14:06.487711 IP 192.168.3.46 > 192.168.3.1: ICMP echo reply, id 0, seq 0, length 8
21:14:07.417939 IP 192.168.3.1 > 192.168.3.46: ICMP echo request, id 27526, seq 52, length 64
21:14:07.487494 IP 192.168.3.46 > 192.168.3.1: ICMP echo reply, id 0, seq 0, length 8
21:14:08.441948 IP 192.168.3.1 > 192.168.3.46: ICMP echo request, id 27526, seq 53, length 64
21:14:08.548995 IP 192.168.3.46 > 192.168.3.1: ICMP echo reply, id 0, seq 0, length 8
Actual ICMP Result
From 192.168.3.1 icmp_seq=368 Destination Host Unreachable
From 192.168.3.1 icmp_seq=369 Destination Host Unreachable
From 192.168.3.1 icmp_seq=370 Destination Host Unreachable
From 192.168.3.1 icmp_seq=458 Destination Host Unreachable
From 192.168.3.1 icmp_seq=459 Destination Host Unreachable
From 192.168.3.1 icmp_seq=460 Destination Host Unreachable

Answer 1

Turns out when Linux is responsible for ICMP, it includes a nice little data payload, without adding this payload to the reply, Linux must think that there was an error or malformation of packet.
def respond_to_icmp(self, icmp_packet):
if icmp_packet["IP"].dst == self.ip:
eth = Ether(dst=icmp_packet["Ether"].src, src=icmp_packet["Ether"].dst)
ip = IP(src=icmp_packet["IP"].dst, dst=icmp_packet["IP"].src)
icmp = ICMP(type=0, id=icmp_packet['ICMP'].id, seq=icmp_packet['ICMP'].seq)
raw = Raw(load=icmp_packet["Raw"].load)
icmp_reply = eth/ip/icmp/raw
sendp(icmp_reply, iface=self.interface)