I am getting ICMP type 3 messages from my gateway machine and they are being dropped by iptables. My questions are...

1. Is this correct behaviour to send ICMP type 3 messages from gateway machine, with source IP of that gateway machine, as opposed to sending it with the source IP of the non-local machine I am trying to access.

2. If it is correct behaviour, why aren't these matched by RELATED target.

3. Is there anything else wrong with these packets?

IN=eth0 OUT= MAC=hexes-here SRC=gateway-ip DST=my-ip LEN=56 TOS=0x00 PREC=0x00 TTL=64 ID=54386 DF PROTO=ICMP TYPE=3 CODE=1 [SRC=my-ip DST=non-local-ip LEN=40 TOS=0x00 PREC=0x00 TTL=64 ID=28066 DF PROTO=TCP INCOMPLETE [8 bytes] ]