http://iptables-tutorial.frozentux.net/iptables-tutorial.html
"As a secondary note, if you use connection tracking you will not see
any fragmented packets, since they are dealt with before hitting any
chain or table in iptables."
PROBLEM:
root@p300:/etc/rc.d# iptables -t filter -I INPUT -f -j LOG --log-level 3
--log-prefix "FRAG: "
root@p300:/etc/rc.d# iptables -I INPUT -f -j LOG --log-level 3
--log-prefix "FRAG: "
root@p300:/etc/rc.d# iptables -I INPUT -f -j LOG --log-level 3
--log-prefix "FRAG: "
root@p300:/etc/rc.d# iptables -I INPUT -f -j DROP
I've tried all of these, each one by itself.
However, when I run tcpdump, I can clearly see these are not getting
dropped or logged by the kernel.
I like conn_track for DCC/FTP connections, however, to get logging &
dropping of fragmented packets working properly, I must recompile
without the conn_tracker's?
Wouldn't this be considered as a bug? Someone could be
pounding/scanning you with fragmented packets, and you would never see
it, as many people run the DCC and/or FTP connection trackers!
box1# nmap -sS -P0 -f -p 1-65535 box2.com
17:11:52.659286 box1.com > box2.com: (frag 2729:4@16)
17:11:52.661416 box1.com > box2.com: (frag 986:4@16)
17:11:52.663400 box1.com > box2.com: (frag 61814:4@16)
17:11:52.665398 box1.com > box2.com: (frag 30216:4@16)
17:11:52.667401 box1.com > box2.com: (frag 4100:4@16)
17:11:52.669392 box1.com > box2.com: (frag 61387:4@16)
947 packets received by filter
0 packets dropped by kernel
Is it possible in anyway to log/drop/match fragmented packets with
connection tracking turned on?
