stealth firewall problem

[George Petre <glpetre@bitdefender.com>]

Hello!
I have a server using 3 network cards, 2 of them used as a bridge with 
the folowing script:

INTERIOR_IFACE=eth2
EXTERIOR_IFACE=eth1
BRIDGE_IFACE=br0

brctl addbr $BRIDGE_IFACE
ifconfig $INTERIOR_IFACE 0.0.0.0 promisc up -arp
ifconfig $EXTERIOR_IFACE 0.0.0.0 promisc up -arp
brctl addif $BRIDGE_IFACE $INTERIOR_IFACE
brctl addif $BRIDGE_IFACE $EXTERIOR_IFACE
ifconfig $BRIDGE_IFACE 0.0.0.0 up -arp


I want to limit the number of the tcp connections/hour, so i am using 
the folowing script:

iptables -N tcpHandler

EXTERIOR_IFACE="eth1"
INTERIOR_IFACE="eth2"


SCALE="hour"            # second, minute, hour, etc.
TCPRATE="20"             # Number of TCP connections per $SCALE


/sbin/depmod -a
/sbin/modprobe ipt_LOG

echo "1" > /proc/sys/net/ipv4/ip_forward

iptables -A FORWARD -i $EXTERIOR_IFACE -p tcp -m state --state NEW -j 
LOG --log-prefix "INBOUND TCP: "
iptables -A FORWARD -i $EXTERIOR_IFACE -p tcp -m state --state NEW -j 
ACCEPT

iptables -A FORWARD -p tcp -i $INTERIOR_IFACE -m state --state NEW -m 
limit --limit $TCPRATE/$SCALE --limit-burst $TCPRATE -j tcpHandler
iptables -A FORWARD -p tcp -i $INTERIOR_IFACE -m state --state NEW -m 
limit --limit 1/$SCALE --limit-burst 1 -j LOG --log-prefix "Drop TCP 
after $TCPRATE conn"
iptables -A FORWARD -p tcp -i $INTERIOR_IFACE -m state --state NEW -j DROP
iptables -A tcpHandler -p tcp -j ACCEPT


The problem is that i made a lot of connections from the computer 
connected on eth2 but the firewall seems to not exist. Even more, 
somethimes i get the "kernel panic" message with some errors on the 
bridge kernel module. This is happening on the 2.6.8-2-386 kernel that 
comes with debian Sarge.

I tried to update to 2.6.15 included in debian testing and then to 
2.6.16 from the kernel.org ftp server, to be sure that i compiled 
correctly the bridge support. After that, the klogd jumped to 99% of cpu 
and my machine freozed many times. Surprisingly, klogd didn't log anything.
Then, i gave a "strace -f klogd" and, after a few seconds this message 
was looping:

read(0, "", 4095)                       = 0
read(0, "", 4095)                       = 0
read(0, "", 4095)                       = 0
read(0, "", 4095)                       = 0

I also tried with a virtual machine to be sure that the hardware was ok, 
and i got the same result.
I googled it and i found that i need a symbolic link from 
System.map.2.6.16 to /boot/System.map for klogd. After i did this the 
klogd is still keeping my cpu at 100%. I also see that there are some 
problems with reiserfs, so i tried with ext3, but i got the same result. 
I also observed that when i log on the other interface, the logging is 
working without problems, but when i log the packets that pass the 
bridge, nothing's happening.

here is the kernel config part where i set the networking support:

----------------------START HERE-------------------


# Networking
#
CONFIG_NET=y

#
# Networking options
#
# CONFIG_NETDEBUG is not set
CONFIG_PACKET=m
CONFIG_PACKET_MMAP=y
CONFIG_UNIX=m
CONFIG_XFRM=y
CONFIG_XFRM_USER=m
CONFIG_NET_KEY=m
CONFIG_INET=y
CONFIG_IP_MULTICAST=y
CONFIG_IP_ADVANCED_ROUTER=y
CONFIG_ASK_IP_FIB_HASH=y
# CONFIG_IP_FIB_TRIE is not set
CONFIG_IP_FIB_HASH=y
CONFIG_IP_MULTIPLE_TABLES=y
CONFIG_IP_ROUTE_FWMARK=y
CONFIG_IP_ROUTE_MULTIPATH=y
# CONFIG_IP_ROUTE_MULTIPATH_CACHED is not set
CONFIG_IP_ROUTE_VERBOSE=y
# CONFIG_IP_PNP is not set
CONFIG_NET_IPIP=m
CONFIG_NET_IPGRE=m
CONFIG_NET_IPGRE_BROADCAST=y
CONFIG_IP_MROUTE=y
CONFIG_IP_PIMSM_V1=y
CONFIG_IP_PIMSM_V2=y
# CONFIG_ARPD is not set
CONFIG_SYN_COOKIES=y
CONFIG_INET_AH=m
CONFIG_INET_ESP=m
CONFIG_INET_IPCOMP=m
CONFIG_INET_TUNNEL=m
CONFIG_INET_DIAG=y
CONFIG_INET_TCP_DIAG=y
# CONFIG_TCP_CONG_ADVANCED is not set
CONFIG_TCP_CONG_BIC=y

#
# IP: Virtual Server Configuration
#
# CONFIG_IP_VS is not set
# CONFIG_IPV6 is not set
CONFIG_NETFILTER=y
# CONFIG_NETFILTER_DEBUG is not set
CONFIG_BRIDGE_NETFILTER=y

#
# Core Netfilter Configuration
#
CONFIG_NETFILTER_NETLINK=m
CONFIG_NETFILTER_NETLINK_QUEUE=m
CONFIG_NETFILTER_NETLINK_LOG=m
CONFIG_NETFILTER_XTABLES=m
CONFIG_NETFILTER_XT_TARGET_CLASSIFY=m
# CONFIG_NETFILTER_XT_TARGET_CONNMARK is not set
CONFIG_NETFILTER_XT_TARGET_MARK=m
CONFIG_NETFILTER_XT_TARGET_NFQUEUE=m
# CONFIG_NETFILTER_XT_TARGET_NOTRACK is not set
CONFIG_NETFILTER_XT_MATCH_COMMENT=m
CONFIG_NETFILTER_XT_MATCH_CONNBYTES=m
CONFIG_NETFILTER_XT_MATCH_CONNMARK=m
CONFIG_NETFILTER_XT_MATCH_CONNTRACK=m
CONFIG_NETFILTER_XT_MATCH_DCCP=m
CONFIG_NETFILTER_XT_MATCH_HELPER=m
CONFIG_NETFILTER_XT_MATCH_LENGTH=m
CONFIG_NETFILTER_XT_MATCH_LIMIT=m
CONFIG_NETFILTER_XT_MATCH_MAC=m
CONFIG_NETFILTER_XT_MATCH_MARK=m
CONFIG_NETFILTER_XT_MATCH_PHYSDEV=m
CONFIG_NETFILTER_XT_MATCH_PKTTYPE=m
CONFIG_NETFILTER_XT_MATCH_REALM=m
CONFIG_NETFILTER_XT_MATCH_SCTP=m
CONFIG_NETFILTER_XT_MATCH_STATE=m
CONFIG_NETFILTER_XT_MATCH_STRING=m
CONFIG_NETFILTER_XT_MATCH_TCPMSS=m

#
# IP: Netfilter Configuration
#
CONFIG_IP_NF_CONNTRACK=m
CONFIG_IP_NF_CT_ACCT=y
CONFIG_IP_NF_CONNTRACK_MARK=y
CONFIG_IP_NF_CONNTRACK_EVENTS=y
CONFIG_IP_NF_CONNTRACK_NETLINK=m
CONFIG_IP_NF_CT_PROTO_SCTP=m
CONFIG_IP_NF_FTP=m
CONFIG_IP_NF_IRC=m
CONFIG_IP_NF_NETBIOS_NS=m
CONFIG_IP_NF_TFTP=m
CONFIG_IP_NF_AMANDA=m
# CONFIG_IP_NF_PPTP is not set
CONFIG_IP_NF_QUEUE=m
CONFIG_IP_NF_IPTABLES=m
CONFIG_IP_NF_MATCH_IPRANGE=m
CONFIG_IP_NF_MATCH_MULTIPORT=m
CONFIG_IP_NF_MATCH_TOS=m
CONFIG_IP_NF_MATCH_RECENT=m
CONFIG_IP_NF_MATCH_ECN=m
CONFIG_IP_NF_MATCH_DSCP=m
CONFIG_IP_NF_MATCH_AH_ESP=m
CONFIG_IP_NF_MATCH_TTL=m
CONFIG_IP_NF_MATCH_OWNER=m
CONFIG_IP_NF_MATCH_ADDRTYPE=m
CONFIG_IP_NF_MATCH_HASHLIMIT=m
CONFIG_IP_NF_MATCH_POLICY=m
CONFIG_IP_NF_FILTER=m
CONFIG_IP_NF_TARGET_REJECT=m
CONFIG_IP_NF_TARGET_LOG=m
CONFIG_IP_NF_TARGET_ULOG=m
CONFIG_IP_NF_TARGET_TCPMSS=m
CONFIG_IP_NF_NAT=m
CONFIG_IP_NF_NAT_NEEDED=y
CONFIG_IP_NF_TARGET_MASQUERADE=m
CONFIG_IP_NF_TARGET_REDIRECT=m
CONFIG_IP_NF_TARGET_NETMAP=m
CONFIG_IP_NF_TARGET_SAME=m
CONFIG_IP_NF_NAT_SNMP_BASIC=m
CONFIG_IP_NF_NAT_IRC=m
CONFIG_IP_NF_NAT_FTP=m
CONFIG_IP_NF_NAT_TFTP=m
CONFIG_IP_NF_NAT_AMANDA=m
CONFIG_IP_NF_MANGLE=m
CONFIG_IP_NF_TARGET_TOS=m
CONFIG_IP_NF_TARGET_ECN=m
CONFIG_IP_NF_TARGET_DSCP=m
CONFIG_IP_NF_TARGET_TTL=m
CONFIG_IP_NF_TARGET_CLUSTERIP=m
CONFIG_IP_NF_RAW=m
CONFIG_IP_NF_ARPTABLES=m
CONFIG_IP_NF_ARPFILTER=m
CONFIG_IP_NF_ARP_MANGLE=m

#
# DECnet: Netfilter Configuration
#
CONFIG_DECNET_NF_GRABULATOR=m

#
# Bridge: Netfilter Configuration
#
CONFIG_BRIDGE_NF_EBTABLES=m
CONFIG_BRIDGE_EBT_BROUTE=m
CONFIG_BRIDGE_EBT_T_FILTER=m
CONFIG_BRIDGE_EBT_T_NAT=m
CONFIG_BRIDGE_EBT_802_3=m
CONFIG_BRIDGE_EBT_AMONG=m
CONFIG_BRIDGE_EBT_ARP=m
CONFIG_BRIDGE_EBT_IP=m
CONFIG_BRIDGE_EBT_LIMIT=m
CONFIG_BRIDGE_EBT_MARK=m
CONFIG_BRIDGE_EBT_PKTTYPE=m
CONFIG_BRIDGE_EBT_STP=m
CONFIG_BRIDGE_EBT_VLAN=m
CONFIG_BRIDGE_EBT_ARPREPLY=m
CONFIG_BRIDGE_EBT_DNAT=m
CONFIG_BRIDGE_EBT_MARK_T=m
CONFIG_BRIDGE_EBT_REDIRECT=m
CONFIG_BRIDGE_EBT_SNAT=m
CONFIG_BRIDGE_EBT_LOG=m
CONFIG_BRIDGE_EBT_ULOG=m

#
# DCCP Configuration (EXPERIMENTAL)
#
# CONFIG_IP_DCCP is not set

#
# SCTP Configuration (EXPERIMENTAL)
#
# CONFIG_IP_SCTP is not set

#
# TIPC Configuration (EXPERIMENTAL)
#
# CONFIG_TIPC is not set
CONFIG_ATM=y
CONFIG_ATM_CLIP=y
# CONFIG_ATM_CLIP_NO_ICMP is not set
CONFIG_ATM_LANE=m
CONFIG_ATM_MPOA=m
CONFIG_ATM_BR2684=m
# CONFIG_ATM_BR2684_IPFILTER is not set
CONFIG_BRIDGE=m
CONFIG_VLAN_8021Q=m
CONFIG_DECNET=m
# CONFIG_DECNET_ROUTER is not set
CONFIG_LLC=m
CONFIG_LLC2=m
# CONFIG_IPX is not set
# CONFIG_ATALK is not set
CONFIG_X25=m
CONFIG_LAPB=m
# CONFIG_NET_DIVERT is not set
CONFIG_ECONET=m
CONFIG_ECONET_AUNUDP=y
CONFIG_ECONET_NATIVE=y
# CONFIG_WAN_ROUTER is not set

#
# QoS and/or fair queueing
#
CONFIG_NET_SCHED=y
CONFIG_NET_SCH_CLK_JIFFIES=y
# CONFIG_NET_SCH_CLK_GETTIMEOFDAY is not set
# CONFIG_NET_SCH_CLK_CPU is not set

#
# Queueing/Scheduling
#
CONFIG_NET_SCH_CBQ=m
CONFIG_NET_SCH_HTB=m
CONFIG_NET_SCH_HFSC=m
CONFIG_NET_SCH_ATM=m
CONFIG_NET_SCH_PRIO=m
CONFIG_NET_SCH_RED=m
CONFIG_NET_SCH_SFQ=m
CONFIG_NET_SCH_TEQL=m
CONFIG_NET_SCH_TBF=m
CONFIG_NET_SCH_GRED=m
CONFIG_NET_SCH_DSMARK=m
CONFIG_NET_SCH_NETEM=m
CONFIG_NET_SCH_INGRESS=m

#
# Classification
#
CONFIG_NET_CLS=y
# CONFIG_NET_CLS_BASIC is not set
CONFIG_NET_CLS_TCINDEX=m
CONFIG_NET_CLS_ROUTE4=m
CONFIG_NET_CLS_ROUTE=y
CONFIG_NET_CLS_FW=m
CONFIG_NET_CLS_U32=m
# CONFIG_CLS_U32_PERF is not set
# CONFIG_CLS_U32_MARK is not set
CONFIG_NET_CLS_RSVP=m
CONFIG_NET_CLS_RSVP6=m
# CONFIG_NET_EMATCH is not set
# CONFIG_NET_CLS_ACT is not set
CONFIG_NET_CLS_POLICE=y
# CONFIG_NET_CLS_IND is not set
CONFIG_NET_ESTIMATOR=y

#
# Network testing
#
CONFIG_NET_PKTGEN=m
# CONFIG_HAMRADIO is not set
# CONFIG_IRDA is not set
# CONFIG_BT is not set
# CONFIG_IEEE80211 is not set

----------------------STOP HERE-------------------


Can you help me?

Thanks in advice!
George


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