[CentOS] squid transparent proxy problem

Hüvely Balázs balazs.huvely at gmail.com
Sat Jan 21 22:33:33 UTC 2012


Greetings,

I installed a squid 3.1.10.i686 squid to a centos 6.2i686. The proxy is 
working fine with the default config.
After I decided to use it as a transparent proxy, I added two lines to 
config: http_proxy 10.0.5.1:3128 transparent, always_direct allow all

http_port 10.0.5.1:3128 transparent
#
# Recommended minimum configuration:
#
acl manager proto cache_object
#acl localhost src 127.0.0.1/32 ::1
acl localhost src 127.0.0.1/32
#acl to_localhost dst 127.0.0.0/8 0.0.0.0/32 ::1
acl to_localhost dst 127.0.0.0/8 0.0.0.0/32

# Example rule allowing access from your local networks.
# Adapt to list your (internal) IP networks from where browsing
# should be allowed
acl localnet src 10.0.0.0/8     # RFC1918 possible internal network
#acl localnet src 172.16.0.0/12 # RFC1918 possible internal network
#acl localnet src 192.168.0.0/16        # RFC1918 possible internal network
#acl localnet src fc00::/7       # RFC 4193 local private network range
#acl localnet src fe80::/10      # RFC 4291 link-local (directly 
plugged) machines

acl SSL_ports port 443
acl Safe_ports port 80          # http
acl Safe_ports port 21          # ftp
acl Safe_ports port 443         # https
acl Safe_ports port 70          # gopher
acl Safe_ports port 210         # wais
acl Safe_ports port 1025-65535  # unregistered ports
acl Safe_ports port 280         # http-mgmt
acl Safe_ports port 488         # gss-http
acl Safe_ports port 591         # filemaker
acl Safe_ports port 777         # multiling http
acl CONNECT method CONNECT

#
# Recommended minimum Access Permission configuration:
#
# Only allow cachemgr access from localhost
http_access allow manager localhost
http_access deny manager

# Deny requests to certain unsafe ports
http_access deny !Safe_ports

# Deny CONNECT to other than secure SSL ports
http_access deny CONNECT !SSL_ports

# We strongly recommend the following be uncommented to protect innocent
# web applications running on the proxy server who think the only
# one who can access services on "localhost" is a local user
#http_access deny to_localhost

#
# INSERT YOUR OWN RULE(S) HERE TO ALLOW ACCESS FROM YOUR CLIENTS
#

# Example rule allowing access from your local networks.
# Adapt localnet in the ACL section to list your (internal) IP networks
# from where browsing should be allowed
http_access allow localnet
http_access allow localhost

# And finally deny all other access to this proxy
http_access deny all

# Squid normally listens to port 3128
http_port 3128

# We recommend you to use at least the following line.
hierarchy_stoplist cgi-bin ?

# Uncomment and adjust the following to add a disk cache directory.
#cache_dir ufs /var/spool/squid 100 16 256

# Leave coredumps in the first cache dir
coredump_dir /var/spool/squid

# Add any of your own refresh_pattern entries above these.
refresh_pattern ^ftp:           1440    20%     10080
refresh_pattern ^gopher:        1440    0%      1440
refresh_pattern -i (/cgi-bin/|\?) 0     0%      0
refresh_pattern .               0       20%     4320

always_direct allow all

There are 2 iptables rule too:
-A PREROUTING -i lo -p tcp -m tcp --dport 80 -j REDIRECT --to-ports 3128
-A PREROUTING -i eth0 -p tcp -m tcp --dport 80 -j REDIRECT --to-ports 3128

eth0 is the local NIC, eth1 is for internet.
ipv4_forward is enabled.

[root at atom squid]# iptables -S -t nat
-P PREROUTING ACCEPT
-P POSTROUTING ACCEPT
-P OUTPUT ACCEPT
-A PREROUTING -i lo -p tcp -m tcp --dport 80 -j REDIRECT --to-ports 3128
-A PREROUTING -i eth0 -p tcp -m tcp --dport 80 -j REDIRECT --to-ports 3128
-A POSTROUTING -o eth1 -j MASQUERADE

[root at atom squid]# iptables -S
-P INPUT DROP
-P FORWARD ACCEPT
-P OUTPUT ACCEPT
-A INPUT -i eth1 -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p udp -m udp --dport 53 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 53 -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -i tun+ -j ACCEPT
-A INPUT -i eth0 -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -j DROP
-A FORWARD -j ACCEPT
-A OUTPUT -j ACCEPT

The cache.log tells me about strange errors:
2012/01/22 00:23:51| Starting Squid Cache version 3.1.4 for 
i386-koji-linux-gnu...
2012/01/22 00:23:51| Process ID 4981
2012/01/22 00:23:51| With 1024 file descriptors available
2012/01/22 00:23:51| Initializing IP Cache...
2012/01/22 00:23:51| DNS Socket created at [::], FD 7
2012/01/22 00:23:51| Adding nameserver 192.168.4.254 from /etc/resolv.conf
2012/01/22 00:23:51| Adding nameserver 192.168.5.254 from /etc/resolv.conf
2012/01/22 00:23:51| User-Agent logging is disabled.
2012/01/22 00:23:51| Referer logging is disabled.
2012/01/22 00:23:51| Unlinkd pipe opened on FD 12
2012/01/22 00:23:51| Local cache digest enabled; rebuild/rewrite every 
3600/3600 sec
2012/01/22 00:23:51| Store logging disabled
2012/01/22 00:23:51| Swap maxSize 0 + 262144 KB, estimated 20164 objects
2012/01/22 00:23:51| Target number of buckets: 1008
2012/01/22 00:23:51| Using 8192 Store buckets
2012/01/22 00:23:51| Max Mem  size: 262144 KB
2012/01/22 00:23:51| Max Swap size: 0 KB
2012/01/22 00:23:51| Using Least Load store dir selection
2012/01/22 00:23:51| Set Current Directory to /var/spool/squid
2012/01/22 00:23:51| Loaded Icons.
2012/01/22 00:23:51| Accepting  HTTP connections at [::]:3128, FD 13.
2012/01/22 00:23:51| HTCP Disabled.
2012/01/22 00:23:51| Squid modules loaded: 0
2012/01/22 00:23:51| Adaptation support is off.
2012/01/22 00:23:51| Ready to serve requests.
2012/01/22 00:23:52| storeLateRelease: released 0 objects
2012/01/22 00:23:56| idnsGrokReply: Malformed DNS response
2012/01/22 00:24:01| idnsGrokReply: Malformed DNS response
2012/01/22 00:24:02| idnsGrokReply: Malformed DNS response
2012/01/22 00:24:06| idnsGrokReply: Malformed DNS response
2012/01/22 00:24:08| idnsGrokReply: Malformed DNS response
2012/01/22 00:24:13| idnsGrokReply: Malformed DNS response
2012/01/22 00:24:16| idnsGrokReply: Malformed DNS response
2012/01/22 00:24:23| idnsGrokReply: Malformed DNS response

I tried to get another verision of squid, but 3.1.4, and 3.1.10 makes 
the same error.

On a fedora 16 x86_64, with the same config as above, there is no error, 
and works perfectly, with the same iptables rule.

Any idea, how can I fix it, or what I may configured wrong?

Thanks Balazs



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