I'm having problems doing traceroute through my firewall.
It seems that the rule:
iptables -A OUTPUT -m state --state INVALID -j DROP
catches the ICMP error messages that is returned when TTL=0, and hence traceoute comes out showing "* * *" instead of the name of my firewall.
When logging the INVALID packets, this is entered in the system log:
May 25 22:38:42 debian kernel: INVALID:IN= OUT=eth1 SRC=10.0.0.254 DST=10.0.0.2 LEN=66 TOS=0x00 PREC=0xC0 TTL=64 ID=52226 PROTO=ICMP TYPE=11 CODE=0 [SRC=10.0.0.2 DST=130.225.76.31 LEN=38 TOS=0x00 PREC=0x00 TTL=1 ID=46519 PROTO=UDP SPT=46518 DPT=33435 LEN=18 ]
Is this a known problem, or is blocking outgoing invalid packets not recommended?
Regards Anders Fugmann
