iptables slows down access to httpd server

[Tony Nelson]

At 9:31 AM -0600 11/1/07, Steve Lindemann wrote:
>This, strictly speaking, isn't a Fedora problem, but I'm hoping someone
>out there can help.
>
>system config:
>dell poweredge 2950
>kernel: 2.6.22.9-61.fc6
>apache: 2.2.6
>
>problem summary:  when iptables is turned on, web pages (graphics in
>particular) served up from the box are *extremely* slow to load,
>sometimes timing out.  when iptables is turned off, web pages served up
>from the box load normally.  I've compared my /etc/sysconfig/iptables
>file to another (fc6) server and they are effectively the same, *but*
>I've never had a problem with page loads from the other box.
>
>I'm assuming (yes, I know 8^) that the problem lies with iptables, but
>I'm running out of places to look for answers.  Should I be looking
>somewhere other than the firewall?  Has anyone else seen this?  I'd
>really appreciate any help anyone out there could give.
>
>((beware of line wrapping))
># Firewall configuration written by system-config-securitylevel
># Manual customization of this file is not recommended.
>*filter
>:INPUT ACCEPT [0:0]
>:FORWARD ACCEPT [0:0]
>:OUTPUT ACCEPT [0:0]
>:RH-Firewall-1-INPUT - [0:0]
>-A INPUT -j RH-Firewall-1-INPUT
>-A FORWARD -j RH-Firewall-1-INPUT
>-A RH-Firewall-1-INPUT -i lo -j ACCEPT
>-A RH-Firewall-1-INPUT -p icmp --icmp-type any -j ACCEPT
>-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
>-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
>-A RH-Firewall-1-INPUT -p udp --dport 5353 -d 224.0.0.251 -j ACCEPT
>-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT
>-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 631 -j ACCEPT
>-A RH-Firewall-1-INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
>-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j
>ACCEPT
>-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j
>ACCEPT
>-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited
>COMMIT
>
>...ok I did manually edit the file to add the http rule, but up until
>now I've not had any problems doing that sort of thing.  Iptables does
>drive me just a bit crazy, but I do know enough to to that successfully
>(up until now that is).  Help!  ...and thanks!

Use `iptables -L` to see what the rules really are.  `iptables -vL` with
counts.  `iptables -vnL` for numbers instead of names.

Use `iptables -vL` before and after trying to get an uncached web page.
See which counts went up.

If that doesn't do it, use tcpdump and look for ports that you didn't open.
-- 
____________________________________________________________________
TonyN.:'                       <mailto:tonynelson at georgeanelson.com>
      '                              <http://www.georgeanelson.com/>