Starting Point

If your Squid version is older than 2.6 is is very outdated. Many of the issues experienced in those versions are now fixed in 2.6 and later.

Your first point of troubleshooting should be to test with a newer supported release and resolve any remaining issues with that install.

Current releases can be retrieved from http://www.squid-cache.org/Versions or your operating system distributor.

• RHEL users will need to use an unofficial package or build their own. Due to RedHat update policies.

Why am I getting "Proxy Access Denied?"

You may need to set up the http_access option to allow requests from your IP addresses. Please see ../SquidAcl for information about that.

Alternately, you may have misconfigured one of your ACLs. Check the access.log and squid.conf files for clues.

Connection Refused when reaching a sibling

I get Connection Refused when the cache tries to retrieve an object located on a sibling, even though the sibling thinks it delivered the object to my cache.

If the HTTP port number is wrong but the ICP port is correct you will send ICP queries correctly and the ICP replies will fool your cache into thinking the configuration is correct but large objects will fail since you don't have the correct HTTP port for the sibling in your squid.conf file. If your sibling changed their http_port, you could have this problem for some time before noticing.

Running out of filedescriptors

If you see the Too many open files error message, you are most likely running out of file descriptors. This may be due to running Squid on an operating system with a low filedescriptor limit. This limit is often configurable in the kernel or with other system tuning tools. There are two ways to run out of file descriptors: first, you can hit the per-process limit on file descriptors. Second, you can hit the system limit on total file descriptors for all processes.

Linux

• This information is outdated, and may no longer be relevant.

Linux kernel 2.2.12 and later supports "unlimited" number of open files without patching. So does most of glibc-2.1.1 and later (all areas touched by Squid is safe from what I can tell, even more so in later glibc releases). But you still need to take some actions as the kernel defaults to only allow processes to use up to 1024 filedescriptors, and Squid picks up the limit at build time.

• Before configuring Squid run "ulimit -HSn ####" (where #### is the number of filedescriptors you need to support). Be sure to run "make clean" before configure if you have already run configure as the script might otherwise have cached the prior result.

• Configure, build and install Squid as usual

• Make sure your script for starting Squid contains the above ulimit command to raise the filedescriptor limit. You may also need to allow a larger port span for outgoing connections (set in /proc/sys/net/ipv4/, like in "echo 1024 32768 > /proc/sys/net/ipv4/ip_local_port_range")

Alternatively you can

• Run configure with your needed configure options
• edit include/autoconf.h and define SQUID_MAXFD to your desired limit. Make sure to make it a nice and clean modulo 64 value (multiple of 64) to avoid various bugs in the libc headers.
• build and install Squid as usual
• Set the runtime ulimit as described above when starting Squid.

If running things as root is not an option then get your sysadmin to install a the needed ulimit command in /etc/inittscript (see man initscript), install a patched kernel where INR_OPEN in include/linux/fs.h is changed to at least the amount you need or have them install a small suid program which sets the limit (see link below).

More information can be found from Henriks How to get many filedescriptors on Linux 2.2.X and later page.

Solaris

• This information is outdated, and may no longer be relevant.

Add the following to your /etc/system file and reboot to increase your maximum file descriptors per process:

set rlim_fd_max = 4096

Next you should re-run the configure script in the top directory so that it finds the new value. If it does not find the new limit, then you might try editing include/autoconf.h and setting #define DEFAULT_FD_SETSIZE by hand. Note that include/autoconf.h is created from autoconf.h.in every time you run configure. Thus, if you edit it by hand, you might lose your changes later on.

Jens-S. Voeckler advises that you should NOT change the default soft limit (rlim_fd_cur) to anything larger than 256. It will break other programs, such as the license manager needed for the SUN workshop compiler. Jens-S. also says that it should be safe to raise the limit for the Squid process as high as 16,384 except that there may be problems duruing reconfigure or logrotate if all of the lower 256 filedescriptors are in use at the time or rotate/reconfigure.

FreeBSD

• This information is outdated, and may no longer be relevant.

by Torsten Sturm

• How do I check my maximum filedescriptors?

  • Do sysctl -a and look for the value of kern.maxfilesperproc.

• How do I increase them?

sysctl -w kern.maxfiles=XXXX
sysctl -w kern.maxfilesperproc=XXXX

• What is the upper limit?
  • I don't think there is a formal upper limit inside the kernel. All the data structures are dynamically allocated. In practice there might be unintended metaphenomena (kernel spending too much time searching tables, for example).

General BSD

• This information is outdated, and may no longer be relevant.

For most BSD-derived systems (SunOS, 4.4BSD, OpenBSD, FreeBSD, NetBSD, BSD/OS, 386BSD, Ultrix) you can also use the "brute force" method to increase these values in the kernel (requires a kernel rebuild):

• How do I check my maximum filedescriptors?

  • Do pstat -T and look for the files value, typically expressed as the ratio of currentmaximum.

• How do I increase them the easy way?

  • One way is to increase the value of the maxusers variable in the kernel configuration file and build a new kernel. This method is quick and easy but also has the effect of increasing a wide variety of other variables that you may not need or want increased.

• Is there a more precise method?

  • Another way is to find the param.c file in your kernel build area and change the arithmetic behind the relationship between maxusers and the maximum number of open files.

Here are a few examples which should lead you in the right direction:

SunOS

• This information is outdated, and may no longer be relevant.

Change the value of nfile in 'usr/kvm/sys/conf.common/param.c/tt> by altering this equation:

Where NPROC is defined by:

#define NPROC (10 + 16 * MAXUSERS)

FreeBSD (from the 2.1.6 kernel)

• This information is outdated, and may no longer be relevant.

Very similar to SunOS, edit /usr/src/sys/conf/param.c and alter the relationship between maxusers and the maxfiles and maxfilesperproc variables:

int     maxfiles = NPROC*2;
int     maxfilesperproc = NPROC*2;

Where NPROC is defined by: #define NPROC (20 + 16 * MAXUSERS) The per-process limit can also be adjusted directly in the kernel configuration file with the following directive: options OPEN_MAX=128

BSD/OS (from the 2.1 kernel)

• This information is outdated, and may no longer be relevant.

Edit /usr/src/sys/conf/param.c and adjust the maxfiles math here:

int     maxfiles = 3 * (NPROC + MAXUSERS) + 80;

Where NPROC is defined by: #define NPROC (20 + 16 * MAXUSERS) You should also set the OPEN_MAX value in your kernel configuration file to change the per-process limit.

Reconfigure afterwards

• This information is outdated, and may no longer be relevant.

After you rebuild/reconfigure your kernel with more filedescriptors, you must then recompile Squid. Squid's configure script determines how many filedescriptors are available, so you must make sure the configure script runs again as well. For example:

cd squid-1.1.x
make realclean
./configure --prefix=/usr/local/squid
make

What are these strange lines about removing objects?

For example:

97/01/23 22:31:10| Removed 1 of 9 objects from bucket 3913
97/01/23 22:33:10| Removed 1 of 5 objects from bucket 4315
97/01/23 22:35:40| Removed 1 of 14 objects from bucket 6391

These log entries are normal, and do not indicate that squid has reached cache_swap_high.

Consult your cache information page in cachemgr.cgi for a line like this:

Storage LRU Expiration Age:     364.01 days

Objects which have not been used for that amount of time are removed as a part of the regular maintenance. You can set an upper limit on the LRU Expiration Age value with reference_age in the config file.

Can I change a Windows NT FTP server to list directories in Unix format?

Why, yes you can! Select the following menus:

• Start
• Programs
• Microsoft Internet Server (Common)
• Internet Service Manager

This will bring up a box with icons for your various services. One of them should be a little ftp "folder." Double click on this.

You will then have to select the server (there should only be one) Select that and then choose "Properties" from the menu and choose the "directories" tab along the top.

There will be an option at the bottom saying "Directory listing style." Choose the "Unix" type, not the "MS-DOS" type.

by Oskar Pearson

Why am I getting "Ignoring MISS from non-peer x.x.x.x?"

You are receiving ICP MISSes (via UDP) from a parent or sibling cache whose IP address your cache does not know about. This may happen in two situations.

If the peer is multihomed, it is sending packets out an interface which is not advertised in the DNS. Unfortunately, this is a configuration problem at the peer site. You can tell them to either add the IP address interface to their DNS, or use Squid's "udp_outgoing_address" option to force the replies out a specific interface. For example: on your parent squid.conf:

udp_outgoing_address proxy.parent.com

on your squid.conf:

cache_peer proxy.parent.com parent 3128 3130

You can also see this warning when sending ICP queries to multicast addresses. For security reasons, Squid requires your configuration to list all other caches listening on the multicast group address. If an unknown cache listens to that address and sends replies, your cache will log the warning message. To fix this situation, either tell the unknown cache to stop listening on the multicast address, or if they are legitimate, add them to your configuration file.

DNS lookups for domain names with underscores (_) always fail.

The standards for naming hosts ( RFC 952 and RFC 1101) do not allow underscores in domain names:

A "name" (Net, Host, Gateway, or Domain name) is a text string up to 24 characters drawn from the alphabet (A-Z), digits (0-9), minus sign (-), and period (.).

The resolver library that ships with recent versions of BIND enforces this restriction, returning an error for any host with underscore in the hostname. The best solution is to complain to the hostmaster of the offending site, and ask them to rename their host.

See also the comp.protocols.tcp-ip.domains FAQ.

Some people have noticed that RFC 1033 implies that underscores are allowed. However, this is an informational RFC with a poorly chosen example, and not a standard by any means.

Why does Squid say: "Illegal character in hostname; underscores are not allowed?'

See the above question. The underscore character is not valid for hostnames.

Some DNS resolvers allow the underscore, so yes, the hostname might work fine when you don't use Squid.

To make Squid allow underscores in hostnames:

• 	Squid 2.x	Re-build with --enable-underscores configure option
  	Squid-3.x	add to squid.conf: enable_underscores on

Why am I getting access denied from a sibling cache?

The answer to this is somewhat complicated, so please hold on.

• Most of this text is taken from ICP and the Squid Web Cache

An ICP query does not include any parent or sibling designation, so the receiver really has no indication of how the peer cache is configured to use it. This issue becomes important when a cache is willing to serve cache hits to anyone, but only handle cache misses for its paying users or customers. In other words, whether or not to allow the request depends on if the result is a hit or a miss. To accomplish this, Squid acquired the miss_access feature in October of 1996.

The necessity of "miss access" makes life a little bit complicated, and not only because it was awkward to implement. Miss access means that the ICP query reply must be an extremely accurate prediction of the result of a subsequent HTTP request. Ascertaining this result is actually very hard, if not impossible to do, since the ICP request cannot convey the full HTTP request. Additionally, there are more types of HTTP request results than there are for ICP. The ICP query reply will either be a hit or miss. However, the HTTP request might result in a "304 Not Modified" reply sent from the origin server. Such a reply is not strictly a hit since the peer needed to forward a conditional request to the source. At the same time, its not strictly a miss either since the local object data is still valid, and the Not-Modified reply is quite small.

One serious problem for cache hierarchies is mismatched freshness parameters. Consider a cache C using "strict" freshness parameters so its users get maximally current data. C has a sibling S with less strict freshness parameters. When an object is requested at C, C might find that S already has the object via an ICP query and ICP HIT response. C then retrieves the object from S.

In an HTTP/1.0 world, C (and Cs client) will receive an object that was never subject to its local freshness rules. Neither HTTP/1.0 nor ICP provides any way to ask only for objects less than a certain age. If the retrieved object is stale by Cs rules, it will be removed from Cs cache, but it will subsequently be fetched from S so long as it remains fresh there. This configuration miscoupling problem is a significant deterrent to establishing both parent and sibling relationships.

HTTP/1.1 provides numerous request headers to specify freshness requirements, which actually introduces a different problem for cache hierarchies: ICP still does not include any age information, neither in query nor reply. So S may return an ICP HIT if its copy of the object is fresh by its configuration parameters, but the subsequent HTTP request may result in a cache miss due to any Cache-control: headers originated by C or by C 's client. Situations now emerge where the ICP reply no longer matches the HTTP request result.

In the end, the fundamental problem is that the ICP query does not provide enough information to accurately predict whether the HTTP request will be a hit or miss. In fact, the current ICP Internet Draft is very vague on this subject. What does ICP HIT really mean? Does it mean "I know a little about that URL and have some copy of the object?" Or does it mean "I have a valid copy of that object and you are allowed to get it from me?"

So, what can be done about this problem? We really need to change ICP so that freshness parameters are included. Until that happens, the members of a cache hierarchy have only two options to totally eliminate the "access denied" messages from sibling caches:

• Make sure all members have the same refresh_rules parameters.

• Do not use miss_access at all. Promise your sibling cache administrator that your cache is properly configured and that you will not abuse their generosity. The sibling cache administrator can check his log files to make sure you are keeping your word.

If neither of these is realistic, then the sibling relationship should not exist.

Cannot bind socket FD NN to *:8080 (125) Address already in use

This means that another processes is already listening on port 8080 (or whatever you're using). It could mean that you have a Squid process already running, or it could be from another program. To verify, use the netstat command:

netstat -antup | grep 8080

• Windows Users need to use netstat -ant and manually find the entry.

If you find that some process has bound to your port, but you're not sure which process it is, you might be able to use the excellent lsof program. It will show you which processes own every open file descriptor on your system.

icpDetectClientClose: ERROR xxx.xxx.xxx.xxx: (32) Broken pipe

This means that the client socket was closed by the client before Squid was finished sending data to it. Squid detects this by trying to read(2) some data from the socket. If the read(2) call fails, then Squid konws the socket has been closed. Normally the read(2) call returns ECONNRESET: Connection reset by peer and these are NOT logged. Any other error messages (such as EPIPE: Broken pipe are logged to cache.log. See the "intro" of section 2 of your Unix manual for a list of all error codes.

icpDetectClientClose: FD 135, 255 unexpected bytes

These are caused by misbehaving Web clients attempting to use persistent connections.

Does Squid work with NTLM Authentication?

Yes, Squid supports Microsoft NTLM authentication to authenticate users accessing the proxy server itself (be it in a forward or reverse setup). See ../ProxyAuthentication for further details

Squid 2.6+ and 3.1+ also support the kind of infrastructure that's needed to properly allow an user to authenticate against an NTLM-enabled webserver.

As NTLM authentication backends go, the real work is usually done by Samba on squid's behalf. That being the case, Squid supports any authentication backend supported by Samba, including Samba itself and MS Windows 3.51 and onwards Domain Controllers.

NTLM for HTTP is, however, an horrible example of an authentication protocol, and we recommend to avoid using it in favour of saner and standard-sanctioned alternatives such as Digest.

"Hotmail" complains about: Intrusion Logged. Access denied.

Hotmail is proxy-unfriendly and requires all requests to come from the same IP address.

My Squid becomes very slow after it has been running for some time.

This is most likely because Squid is using more memory than it should be for your system. When the Squid process becomes large, it experiences a lot of paging. This will very rapidly degrade the performance of Squid. Memory usage is a complicated problem. There are a number of things to consider.

WARNING: Failed to start 'dnsserver'

• All current Squid now contain an optimized internal DNS engine. Which is much faster and responsive that then the dnsserver helper. That should be used by preference.

This could be a permission problem. Does the Squid userid have permission to execute the dnsserver program?

Sending bug reports to the Squid team

Bug reports for Squid should be registered in our bug database. Any bug report must include

• The Squid release version
• Your Operating System type and version
• A clear description of the bug symptoms.
• If your Squid crashes the report must include a coredumps stack trace as described below

Please note that bug reports are only processed if they can be reproduced or identified in the current STABLE or development versions of Squid. If you are running an older version of Squid the first response will be to ask you to upgrade unless the developer who looks at your bug report immediately can identify that the bug also exists in the current versions. It should also be noted that any patches provided by the Squid developer team will be to the current STABLE version even if you run an older version.

crashes and core dumps

There are two conditions under which squid will exit abnormally and generate a coredump. First, a SIGSEGV or SIGBUS signal will cause Squid to exit and dump core. Second, many functions include consistency checks. If one of those checks fail, Squid calls abort() to generate a core dump.

If you have a core dump file then use gdb to extract a stack trace from the core as follows:

% gdb /usr/local/squid/sbin/squid core
gdb> backtrace

Many people report that Squid doesn't leave a coredump anywhere. This may be due to one of the following reasons:

• Resource Limits
  • The shell has limits on the size of a coredump file. You may need to increase the limit using ulimit or a similar command (see below)
• sysctl options
  • On FreeBSD, you won't get a coredump from programs that call setuid() and/or setgid() (like Squid sometimes does) unless you enable this option:

# sysctl -w kern.sugid_coredump=1

• No debugging symbols
  • The Squid binary must have debugging symbols in order to get a meaningful coredump. The debugging traces we need look something like this:

Core was generated by `(squid) -D'.
Program terminated with signal 6, Aborted.

(gdb) bt
#0  0x006ad7a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2
#1  0x006ed7a5 in raise () from /lib/tls/libc.so.6
#2  0x006ef209 in abort () from /lib/tls/libc.so.6
#3  0x0806b987 in xassert (msg=Could not find the frame base for "xassert".
) at debug.c:514
#4  0x0808170b in httpBuildRequestHeader (request=0x10791f40,
orig_request=0x10791f40, entry=0xfc6ba30, hdr_out=0xbfed04f0, flags=
      {proxying = 0, keepalive = 1, only_if_cached = 0, keepalive_broken = 0,
abuse_detected = 0, request_sent = 0, front_end_https = 0, originpeer = 0}) at
http.c:1195
...

• Threads and Linux
  • On Linux, threaded applications do not generate core dumps. When you use the aufs cache_dir type, it uses threads and you can't get a coredump.
• It did leave a coredump file, you just can't find it.

Resource Limits

These limits can usually be changed in shell scripts. The command to change the resource limits is usually either ulimit or limits. Sometimes it is a shell-builtin function, and sometimes it is a regular program. Also note that you can set resource limits in the /etc/login.conf file on FreeBSD and maybe other systems.

To change the coredumpsize limit you might use a command like:

limits coredump unlimited

Debugging Symbols

To see if your Squid binary has debugging symbols, use this command:

% nm /usr/local/squid/bin/squid | head

The binary has debugging symbols if you see gobbledegook like this:

0812abec B AS_tree_head
080a7540 D AclMatchedName
080a73fc D ActionTable
080908a4 r B_BYTES_STR
080908bc r B_GBYTES_STR
080908ac r B_KBYTES_STR
080908b4 r B_MBYTES_STR
080a7550 D Biggest_FD
08097c0c R CacheDigestHashFuncCount
08098f00 r CcAttrs

There are no debugging symbols if you see this instead:

/usr/local/squid/bin/squid: no symbols

Debugging symbols may have been removed by your install program. If you look at the squid binary from the source directory, then it might have the debugging symbols.

Coredump Location

The core dump file will be left in one of the following locations:

1. The coredump_dir directory, if you set that option.

2. The first cache_dir directory if you have used the cache_effective_user option.

3. The current directory when Squid was started

Recent versions of Squid report their current directory after starting, so look there first:

2000/03/14 00:12:36| Set Current Directory to /usr/local/squid/cache

If you cannot find a core file, then either Squid does not have permission to write in its current directory, or perhaps your shell limits are preventing the core file from being written.

Often you can get a coredump if you run Squid from the command line like this (csh shells and clones):

% limit core un
% /usr/local/squid/bin/squid -NCd1

Once you have located the core dump file, use a debugger such as dbx or gdb to generate a stack trace:

% gdb /usr/local/squid/sbin/squid core
gdb> backtrace

If possible, you might keep the coredump file around for a day or two. It is often helpful if we can ask you to send additional debugger output, such as the contents of some variables. But please note that a core file is only useful if paired with the exact same binary as generated the corefile. If you recompile Squid then any coredumps from previous versions will be useless unless you have saved the corresponding Squid binaries, and any attempts to analyze such coredumps will most certainly give misleading information about the cause to the crash.

If you CANNOT get Squid to leave a core file for you then one of the following approaches can be used

First alternative is to start Squid under the contol of GDB

% gdb /path/to/squid
handle SIGPIPE pass nostop noprint
run -DNYCd3
[wait for crash]
backtrace
quit

The drawback from the above is that it isn't really suitable to run on a production system as Squid then won't restart automatically if it crashes. The good news is that it is fully possible to automate the process above to automatically get the stack trace and then restart Squid. Here is a short automated script that should work:

trap "rm -f $$.gdb" 0
cat <<EOF >$$.gdb
handle SIGPIPE pass nostop noprint
run -DNYCd3
backtrace
quit
EOF
while sleep 2; do
  gdb -x $$.gdb /path/to/squid 2>&1 | tee -a squid.out
done

Other options if the above cannot be done is to:

1. Build Squid with the --enable-stacktraces option, if support exists for your OS (exists for Linux glibc on Intel, and Solaris with some extra libraries which seems rather impossible to find these days..)
2. Run Squid using the "catchsegv" tool. (Linux glibc Intel)

   these approaches do not by far provide as much details as using gdb.

Debugging Squid

If you believe you have found a non-fatal bug (such as incorrect HTTP processing) please send us a section of your cache.log with debugging to demonstrate the problem. The cache.log file can become very large, so alternatively, you may want to copy it to an FTP or HTTP server where we can download it.

It is very simple to enable full debugging on a running squid process.

squid -k debug

This causes every debug() statement in the source code to write a line in the cache.log file. You also use the same command to restore Squid to normal debugging level.

To enable selective debugging (e.g. for one source file only), you need to edit squid.conf and add to the debug_options line. Every Squid source file is assigned a different debugging section. The debugging section assignments can be found by looking at the top of individual source files, or by reading the file debug-sections.txt . You also specify the debugging level to control the amount of debugging. Higher levels result in more debugging messages. For example, to enable full debugging of Access Control functions, you would use:

debug_options 28,9

Then you have to restart or reconfigure Squid.

Once you have the debugging captured to cache.log, take a look at it yourself and see if you can make sense of the behaviour which you see. If not, please feel free to send your debugging output to the squid-users or squid-bugs mailing lists.

FATAL: ipcache_init: DNS name lookup tests failed

• This issue is now permanently resolved in Squid 3.1 and later.

Squid normally tests your system's DNS configuration before it starts server requests. Squid tries to resolve some common DNS names, as defined in the dns_testnames configuration directive. If Squid cannot resolve these names, it could mean:

• your DNS nameserver is unreachable or not running.
• your System is in the process of booting
• your /etc/resolv.conf file may contain incorrect information.
• your /etc/resolv.conf file may have incorrect permissions, and may be unreadable by Squid.

To disable this feature, use the -D command line option. Due to this issue displaying on Boot. Is is highly recommended that OS startup scripts for Squid earlier than 3.1 use this option to disable tests.

Note, Squid does NOT use the dnsservers to test the DNS. The test is performed internally, before the dnsservers start. '

FATAL: Failed to make swap directory /var/spool/cache: (13) Permission denied

Starting with version 1.1.15, we have required that you first run

squid -z

to create the swap directories on your filesystem.

Squid basic default is user nobody. This can be overridden in packages with the --with-default-user option when building or in squid.conf with the cache_effective_user option.

The Squid process takes on the given userid before making the directories. If the cache_dir directory (e.g. /var/spool/cache) does not exist, and the Squid userid does not have permission to create it, then you will get the "permission denied" error. This can be simply fixed by manually creating the cache directory.

Alternatively, if the directory already exists, then your operating system may be returning "Permission Denied" instead of "File Exists" on the mkdir() system call.

FATAL: Cannot open HTTP Port

Either

1. the Squid userid does not have permission to bind to the port, or
2. some other process has bound itself to the port

   Remember that root privileges are required to open port numbers less than 1024. If you see this message when using a high port number, or even when starting Squid as root, then the port has already been opened by another process.

   SELinux can also deny squid access to port 80, even if you are starting squid as root. Configure SELinux to allow squid to open port 80 or disable SELinux in this case.

   Maybe you are running in the HTTP Accelerator mode and there is already a HTTP server running on port 80? If you're really stuck, install the way cool lsof utility to show you which process has your port in use.

FATAL: All redirectors have exited!

This is explained in ../SquidRedirectors.

FATAL: Cannot open /usr/local/squid/logs/access.log: (13) Permission denied

In Unix, things like processes and files have an owner. For Squid, the process owner and file owner should be the same. If they are not the same, you may get messages like "permission denied."

To find out who owns a file, use the command:

ls -l

A process is normally owned by the user who starts it. However, Unix sometimes allows a process to change its owner. If you specified a value for the cache_effective_user option in squid.conf, then that will be the process owner. The files must be owned by this same userid.

If all this is confusing, then you probably should not be running Squid until you learn some more about Unix. As a reference, I suggest Learning the UNIX Operating System, 4th Edition.

pingerOpen: icmp_sock: (13) Permission denied

This means your pinger helper program does not have root priveleges.

You should either do this when building Squid:

make install pinger

or

# chown root /usr/local/squid/bin/pinger
# chmod 4755 /usr/local/squid/bin/pinger

• location of the pinger binary may vary. I recommend searching for it first:

locate bin/pinger

What is a forwarding loop?

A forwarding loop is when a request passes through one proxy more than once. You can get a forwarding loop if

• a cache forwards requests to itself. This might happen with interception caching (or server acceleration) configurations.
• a pair or group of caches forward requests to each other. This can happen when Squid uses ICP, Cache Digests, or the ICMP RTT database to select a next-hop cache.

Forwarding loops are detected by examining the Via request header. Each cache which "touches" a request must add its hostname to the Via header. If a cache notices its own hostname in this header for an incoming request, it knows there is a forwarding loop somewhere.

• Squid may report a forwarding loop if a request goes through two caches that have the same visible_hostname value. If you want to have multiple machines with the same visible_hostname then you must give each machine a different unique_hostname so that forwarding loops are correctly detected.

When Squid detects a forwarding loop, it is logged to the cache.log file with the recieved Via header. From this header you can determine which cache (the last in the list) forwarded the request to you.

• One way to reduce forwarding loops is to change a parent relationship to a sibling relationship.

  Another way is to use cache_peer_access rules.

accept failure: (71) Protocol error

This error message is seen mostly on Solaris systems. Mark Kennedy gives a great explanation:

Error 71 [EPROTO] is an obscure way of reporting that clients made it onto your
server's TCP incoming connection queue but the client tore down the
connection before the server could accept it.  I.e.  your server ignored
its clients for too long.  We've seen this happen when we ran out of
file descriptors.  I guess it could also happen if something made squid
block for a long time.

storeSwapInFileOpened: ... Size mismatch

Got these messages in my cache.log - I guess it means that the index contents do not match the contents on disk.

What does Squid do in this case?

These happen when Squid reads an object from disk for a cache hit. After it opens the file, Squid checks to see if the size is what it expects it should be. If the size doesn't match, the error is printed. In this case, Squid does not send the wrong object to the client. It will re-fetch the object from the source.

Why do I get ''fwdDispatch: Cannot retrieve 'https://www.buy.com/corp/ordertracking.asp' ''

These messages are caused by buggy clients, mostly Netscape Navigator. What happens is, Netscape sends an HTTPS/SSL request over a persistent HTTP connection. Normally, when Squid gets an SSL request, it looks like this:

CONNECT www.buy.com:443 HTTP/1.0

Then Squid opens a TCP connection to the destination host and port, and the real request is sent encrypted over this connection. Thats the whole point of SSL, that all of the information must be sent encrypted.

With this client bug, however, Squid receives a request like this:

CONNECT https://www.buy.com/corp/ordertracking.asp HTTP/1.0

Now, all of the headers, and the message body have been sent, unencrypted to Squid. There is no way for Squid to somehow turn this into an SSL request. The only thing we can do is return the error message.

• This browser bug does represent a security risk because the browser is sending sensitive information unencrypted over the network.

Squid can't access URLs like http://3626046468/ab2/cybercards/moreinfo.html

by Dave J Woolley (DJW at bts dot co dot uk)

• These are illegal URLs, generally only used by illegal sites; typically the web site that supports a spammer and is expected to survive a few hours longer than the spamming account.

Their intention is to:

• confuse content filtering rules on proxies, and possibly some browsers' idea of whether they are trusted sites on the local intranet;
• confuse whois (?);
• make people think they are not IP addresses and unknown domain names, in an attempt to stop them trying to locate and complain to the ISP.

Any browser or proxy that works with them should be considered a security risk.

RFC 1738 has this to say about the hostname part of a URL:

The fully qualified domain name of a network host, or its IP
address as a set of four decimal digit groups separated by
".". Fully qualified domain names take the form as described
in Section 3.5 of RFC 1034 [13] and Section 2.1 of RFC 1123
[5]: a sequence of domain labels separated by ".", each domain
label starting and ending with an alphanumerical character and
possibly also containing "-" characters. The rightmost domain
label will never start with a digit, though, which
syntactically distinguishes all domain names from the IP
addresses.

I get a lot of "URI has whitespace" error messages in my cache log, what should I do?

• Whitespace characters (space, tab, newline, carriage return) are not allowed in URI's and URL's.

Unfortunately, a number of web services generate URL's with whitespace. Of course your favorite browser silently accomodates these bad URL's. The servers (or people) that generate these URL's are in violation of Internet standards. The whitespace characters should be encoded.

If you want Squid to accept URL's with whitespace, you have to decide how to handle them. There are four choices that you can set with the uri_whitespace option in squid.conf:

• STRIP

  • This is the correct way to handle them. This is the default for Squid 3.x.

• DENY

  • The request is denied with an "Invalid Request" message. This is the default for Squid2.x.

• ALLOW

  • The request is allowed and the URL remains unchanged.

• ENCODE

  • The whitespace characters are encoded according to RFC 1738.

• CHOP

  • The URL is chopped at the first whitespace character and then processed normally.

Only STRIP and DENY are the only approved ways of handling these URI. Others are technically violations and should not be performed. The broken web service should be fixed instead. It is breaking much more of the Internet than just your proxy.

commBind: Cannot bind socket FD 5 to 127.0.0.1:0: (49) Can't assign requested address

This likely means that your system does not have a loopback network device, or that device is not properly configured. All Unix systems should have a network device named lo0, and it should be configured with the address 127.0.0.1. If not, you may get the above error message. To check your system, run:

ifconfig

• Windows users must use: ipfconfig

The result should contain:

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host

If you use FreeBSD, see freebsd-no-lo0

What does "sslReadClient: FD 14: read failure: (104) Connection reset by peer" mean?

"Connection reset by peer" is an error code that Unix operating systems sometimes return for read, write, connect, and other system calls.

Connection reset means that the other host, the peer, sent us a RESET packet on a TCP connection. A host sends a RESET when it receives an unexpected packet for a nonexistent connection. For example, if one side sends data at the same time that the other side closes a connection, when the other side receives the data it may send a reset back.

The fact that these messages appear in Squid's log might indicate a problem, such as a broken origin server or parent cache. On the other hand, they might be "normal," especially since some applications are known to force connection resets rather than a proper close.

You probably don't need to worry about them, unless you receive a lot of user complaints relating to SSL sites.

Rick Jones notes that if the server is running a Microsoft TCP stack, clients receive RST segments whenever the listen queue overflows. In other words, if the server is really busy, new connections receive the reset message. This is contrary to rational behaviour, but is unlikely to change.

What does ''Connection refused'' mean?

This is an error message, generated by your operating system, in response to a connect() system call. It happens when there is no server at the other end listening on the port number that we tried to connect to.

It is quite easy to generate this error on your own. Simply telnet to a random, high numbered port:

telnet 12345

It happens because there is no server listening for connections on port 12345.

When you see this in response to a URL request, it probably means the origin server web site is temporarily down. It may also mean that your parent cache is down, if you have one.

squid: ERROR: no running copy

You may get this message when you run commands like squid -k rotate.

This error message usually means that the squid.pid file is missing. Since the PID file is normally present when squid is running, the absence of the PID file usually means Squid is not running. If you accidentally delete the PID file, Squid will continue running, and you won't be able to send it any signals.

• If you accidentally removed the PID file, there are two ways to get it back.

First locate the proces ID by running ps and find Squid. You'll probably see two processes, like this:

% ps ax | grep squid

  PID TTY      STAT   TIME COMMAND
 2267 ?        Ss     0:00 /usr/sbin/squid-ipv6 -D -sYC
 2735 pts/0    S+     0:00 grep squid
 8893 ?        Rl     2:57 (squid) -D -sYC
 8894 ?        Ss     0:17 /bin/bash /etc/squid3/helper/redirector.sh

You want the (squid) process id, 8893 in this case.

The first solution is to create the PID file yourself and put the process id number there. For example:

echo 8893 > /usr/local/squid/logs/squid.pid

• Be careful of file permissions. It's no use having a .pid file if squid can't update it when things change.

The second is to use the above technique to find the Squid process id. Then to send the process a HUP signal, which is the same as squid -k reconfigure:

kill -SIGHUP 8893

The reconfigure process creates a new PID file automatically.

FATAL: getgrnam failed to find groupid for effective group 'nogroup'

You are probably starting Squid as root. Squid is trying to find a group-id that doesn't have any special priveleges that it will run as. The default is nogroup, but this may not be defined on your system.

The best fix for this is to assign squid a low-privilege user-id and assign that uerid to a group-id. There is a good chance that nobody will work for you as part of group nogroup.

Alternatively in older Squid the cache_effective_group in squid.conf my be changed to the name of an unpriveledged group from /etc/group. There is a good chance that nobody will work for you.

Squid uses 100% CPU

There may be many causes for this.

Andrew Doroshenko reports that removing /dev/null, or mounting a filesystem with the nodev option, can cause Squid to use 100% of CPU. His suggested solution is to "touch /dev/null."

Webmin's ''cachemgr.cgi'' crashes the operating system

Mikael Andersson reports that clicking on Webmin's cachemgr.cgi link creates numerous instances of cachemgr.cgi that quickly consume all available memory and brings the system to its knees.

Joe Cooper reports this to be caused by SSL problems in some outdated browsers (mainly Netscape 6.x/Mozilla) if your Webmin is SSL enabled. Try with a more current browser or disable SSL encryption in Webmin.

Segment Violation at startup or upon first request

Some versions of GCC (notably 2.95.1 through 2.95.4 at least) have bugs with compiler optimization. These GCC bugs may cause NULL pointer accesses in Squid, resulting in a "FATAL: Received Segment Violation...dying" message and a core dump.

urlParse: Illegal character in hostname 'proxy.mydomain.com:8080proxy.mydomain.com'

By Yomler of fnac.net

A combination of a bad configuration of Internet Explorer and any application which use the cydoor DLLs will produce the entry in the log. See cydoor.com for a complete list.

The bad configuration of IE is the use of a active configuration script (proxy.pac) and an active or inactive, but filled proxy settings. IE will only use the proxy.pac. Cydoor aps will use both and will generate the errors.

Disabling the old proxy settings in IE is not enought, you should delete them completely and only use the proxy.pac for example.

Requests for international domain names do not work

by HenrikNordström.

Some people have asked why requests for domain names using national symbols as "supported" by the certain domain registrars does not work in Squid. This is because there as of yet is no standard on how to manage national characters in the current Internet protocols such as HTTP or DNS. The current Internet standards is very strict on what is an acceptable hostname and only accepts A-Z a-z 0-9 and - in Internet hostname labels. Anything outside this is outside the current Internet standards and will cause interoperability issues such as the problems seen with such names and Squid.

When there is a consensus in the DNS and HTTP standardization groups on how to handle international domain names Squid will be changed to support this if any changes to Squid will be required.

If you are interested in the progress of the standardization process for international domain names please see the IETF IDN working group's dedicated page.

Why do I sometimes get "Zero Sized Reply"?

This happens when Squid makes a TCP connection to an origin server, but for some reason, the connection is closed before Squid reads any data. Depending on various factors, Squid may be able to retry the request again. If you see the "Zero Sized Reply" error message, it means that Squid was unable to retry, or that all retry attempts also failed.

What causes a connection to close prematurely? It could be a number of things, including:

• An overloaded origin server.

• TCP implementation/interoperability bugs. See the ../SystemWeirdnesses for details.

• Race conditions with HTTP persistent connections.
• Buggy or misconfigured NAT boxes, firewalls, and load-balancers.
• Denial of service attacks.

• Utilizing TCP blackholing on FreeBSD (check ../SystemWeirdnesses).

You may be able to use tcpdump to track down and observe the problem.

• Some users believe the problem is caused by very large cookies. One user reports that his Zero Sized Reply problem went away when he told Internet Explorer to not accept third-party cookies.

Here are some things you can try to reduce the occurance of the Zero Sized Reply error:

• Delete or rename your cookie file and configure your browser to prompt you before accepting any new cookies.

• Disable HTTP persistent connections with the server_persistent_connections and client_persistent_connections directives.

• Disable any advanced TCP features on the Squid system. Disable ECN on Linux with echo 0 > /proc/sys/net/ipv4/tcp_ecn/.

• Upgrade to Squid-2.6 or later to work around a Host header related bug in Cisco PIX HTTP inspection. The Cisco PIX firewall wrongly assumes the Host header can be found in the first packet of the request.

If this error causes serious problems for you and the above does not help, Squid developers would be happy to help you uncover the problem. However, we will require high-quality debugging information from you, such as tcpdump output, server IP addresses, operating system versions, and access.log entries with full HTTP headers.

If you want to make Squid give the Zero Sized error on demand, you can use a short C program. Simply compile and start the program on a system that doesn't already have a server running on port 80. Then try to connect to this fake server through Squid.

Why do I get "The request or reply is too large" errors?

by Grzegorz Janoszka

This error message appears when you try downloading large file using GET or uploading it using POST/PUT. There are three parameters to look for:

• request_body_max_size
• reply_body_max_size

These two are set to 0 by default, which means no limits at all. They should not be limited unless you really know how that affects your squid behavior. Or at all in standard proxy.

• request_header_max_size
• request_header_max_size

These two default to 64kB starting from 3.1. Earlier versions of Squid had defaults as low as 2 kB. In some rather rare circumstances even 64kB is too low, so you can increase this value.

Negative or very large numbers in Store Directory Statistics, or constant complaints about cache above limit

In some situations where swap.state has been corrupted Squid can be very confused about how much data it has in the cache. Such corruption may happen after a power failure or similar fatal event. To recover first stop Squid, then delete the swap.state files from each cache directory and then start Squid again. Squid will automatically rebuild the swap.state index from the cached files reasonably well.

If this does not work or causes too high load on your server due to the reindexing of the cache then delete the cache content as explained in ../OperatingSquid.

Squid problems with Windows Update v5

By Janno de Wit

There seems to be some problems with Microsoft Windows to access the Windows Update website. This is especially a problem when you block all traffic by a firewall and force your users to go through the Squid Cache.

Symptom: Windows Update gives error codes like 0x80072EFD and cannot update, automatic updates aren't working too.

Cause: In earlier Windows-versions Windows Update takes the proxy-settings from Internet Explorer. Since XP SP2 this is not sure. At my machine I ran Windows XP SP1 without Windows Update problems. When I upgraded to SP2 Windows Update started to give errors when searching updates etc.

The problem was that WU did not go through the proxy and tries to establish direct HTTP connections to Update-servers. Even when I set the proxy in IE again, it didn't help . It isn't Squid's problem that Windows Update doesn't work, but it is in Windows itself. The solution is to use the 'proxycfg' tool shipped with Windows XP. With this tool you can set the proxy for WinHTTP.

• Similar issues are found with other Microsoft products in the same Windows versions. The comands below often fix all Microsoft proxy issues at once.

Commands:

C:\> proxycfg
# gives information about the current connection type. Note: 'Direct Connection' does not force WU to bypass proxy
C:\> proxycfg -d
# Set Direct Connection
C:\> proxycfg -p wu-proxy.lan:8080
# Set Proxy to use with Windows Update to wu-proxy.lan, port 8080
c:\> proxycfg -u
# Set proxy to Internet Explorer settings.

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