I have seen very similar results. I have my first rule as Established/Related then I allow out 80, 443, etc. (just a few ports)...and the web and other traffic dies. When I tcpdump, I notice that for some of this traffic the s-port and d-port are no longer matching (they are now high ports) and the established, related rules don't seem to pick this up. This is in my forwarding chain (there is a private network behind with 1 to 1 nats). I added a rule that allowed ALL out, since security is not a concern for that direction for me in this environment, but I shouldn't have had to do that. Let me know if you get anywhere with this Dave. Thanks. Jeff Ginter, CISSP Computer Associates Mid-Atlantic Consulting Manager tel: +1 908 874-9726 cell: +1 609 577-1494 jeff.ginter@xxxxxx -----Original Message----- From: netfilter-bounces@xxxxxxxxxxxxxxxxxxx [mailto:netfilter-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of David Busby Sent: Wednesday, June 08, 2005 7:32 PM To: netfilter@xxxxxxxxxxxxxxxxxxx Subject: Re: --policy DROP kills everything? Rob Sterenborg wrote: > > Add this on top of the other INPUT rules : > > -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT > Ok so I changed the rules to this: Chain INPUT (policy DROP) target prot opt source destination ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED ACCEPT all -- 127.0.0.0/8 0.0.0.0/0 ACCEPT udp -- 192.168.42.1 192.168.42.2 udp spt:53 ACCEPT tcp -- 0.0.0.0/0 192.168.42.2 tcp dpt:22 ACCEPT tcp -- 0.0.0.0/0 192.168.42.2 tcp dpt:80 LOG all -- 0.0.0.0/0 0.0.0.0/0 LOG level warning Chain FORWARD (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination But it won't accept new connections on port 80 or 22. The Established SSH conection is fine. I can see new connections to port 80 or 22 in my logs, see: IN=eth0 OUT= MAC=00:01:03:d2:db:0b:00:11:5b:50:ff:a4:08:00 SRC=192.168.42.34 DST=192.168.42.2 LEN=48 TOS=0x00 PREC=0x00 TTL=128 ID=18259 DF PROTO=TCP SPT=3704 DPT=80 WINDOW=65535 RES=0x00 SYN URGP=0 IN=eth0 OUT= MAC=00:01:03:d2:db:0b:00:11:5b:50:ff:a4:08:00 SRC=192.168.42.34 DST=192.168.42.2 LEN=48 TOS=0x00 PREC=0x00 TTL=128 ID=18526 DF PROTO=TCP SPT=3705 DPT=22 WINDOW=65535 RES=0x00 SYN URGP=0 Why they don't jump to accept? They match a rule. So then I adjusted #1 above to this ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state NEW,RELATED,ESTABLISHED Doesn't that now allow any new connection to any port on any protocol making my FW worthless? Then I tried moving the RELATED,ESTABLISHED to the last rule like this: imperium root # iptables -L INPUT -n Chain INPUT (policy DROP) target prot opt source destination ACCEPT all -- 127.0.0.0/8 0.0.0.0/0 ACCEPT udp -- 192.168.42.1 192.168.42.2 udp spt:53 ACCEPT tcp -- 0.0.0.0/0 192.168.42.2 tcp dpt:22 ACCEPT tcp -- 0.0.0.0/0 192.168.42.2 tcp dpt:80 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED LOG all -- 0.0.0.0/0 0.0.0.0/0 LOG flags 0 level 4 But I still cannot get new connections in and my estabilshed SSH is still OK. Should I not use policy DROP but add a last rule of DROP? Which is the "right" way? I guess I learned so far that I need to accept new and established. But I cannot seem to get the rules to work. I've been up and down the man page and samples but seem to be missing one more stupid little thing :( Please help. /djb
