# Squid 3.1.10 release notes

## Squid Developers

This document contains the release notes for version 3.1 of Squid. Squid is a WWW Cache application developed by the National Laboratory for Applied Network Research and members of the Web Caching community.

## 1. Notice

- 1.1 Known issues
- 1.2 Changes since earlier releases of Squid-3.1

## 2. Major new features since Squid-3.0

- 2.1 New Version Numbering System
- 2.2 Minimal squid.conf improvements
- 2.3 Internet Protocol version 6 (IPv6)
- 2.4 Error Page Localization
- 2.5 Connection Pinning (for NTLM Auth Passthrough)
- 2.6 Quality of Service (QoS) Flow support
- 2.7 SSL Bump (for HTTPS Filtering and Adaptation)
- 2.8 eCAP Adaptation Module support
- 2.9 ICAP Bypass and Retry enhancements
- 2.10 ICY streaming protocol support

## 3. Changes to squid.conf since Squid-3.0

- 3.1 New tags
- 3.2 Changes to existing tags
- 3.3 Removed tags

## 4. Changes to ./configure options since Squid-3.0

- 4.1 New options
- 4.2 Changes to existing options
- 4.3 Removed options

## 5. Options Removed since Squid-2

- 5.1 Removed squid.conf options since Squid-2.7
- 5.2 Removed squid.conf options since Squid-2.6
- 5.3 Removed ./configure options since Squid-2.7

## 6. Regressions since Squid-2.7

- 6.1 Missing squid.conf options available in Squid-2.7
- 6.2 Missing ./configure options available in Squid-2.7

## 1. Notice

The Squid Team are pleased to announce the release of Squid-3.1.10

This new release is available for download from http://www.squid-cache.org/Versions/v3/3.1/ or the mirrors.

A large number of the show-stopper bugs have been fixed along with general improvements to the ICAP support. While this release is not fully bug-free we believe it is ready for use in production on many systems.

We welcome feedback and bug reports. If you find a new bug, please see http://wiki.squid-cache.org/SquidFaq/BugReporting for how to submit a report with a stack trace and other required details. Additional information is also very welcome on other open bugs.

## 1.1 Known issues

Although this release is deemed good enough for use in many setups, please note the existence of open bugs against Squid-3.1.

Some issues to note as currently known in this release which are not able to be fixed in the 3.1 series are:

- The lack of some features available in Squid-2.x series. See the regression sections below for full details.
- CVE-2009-0801 : NAT interception vulnerability to malicious clients.

Currently known issues which only depends on available developer time and may still be resolved in a future 3.1 release are:

- Windows support is still largely missing.
- AIX support for building with the IBM compiler is broken.

## 1.2 Changes since earlier releases of Squid-3.1

The 3.1 change history can be viewed here.

## 2. Major new features since Squid-3.0

Squid 3.1 represents a new feature release above 3.0.

The most important of these new features are:

- New Version Numbering System
- Minimal squid.conf improvements
- Native IPv6 Support
- Error Page Localization
- Connection Pinning (for NTLM Auth Passthrough)
- Quality of Service (QoS) Flow support
- SSL Bump (for HTTPS Filtering and Adaptation)
- eCAP Adaptation Module support
- ICAP Bypass and Retry enhancements
- ICY streaming protocol support

Most user-facing changes are reflected in squid.conf (see below).

## 2.1 New Version Numbering System

Begining with 3.1 the Squid Developers are using a new release numbering system.

We have decided, based on input from interested users to drop the Squid-2 terminology of (DEVEL, PRE, RC, and STABLE) from the release package names. These are replaced with a simpler 3-tier system based around the natural code development cycle.

Daily generated snapshots of all current versions are provided as testing (old DEVEL) and bug-fix releases. These are numbered from their last release with a date appended. Snapshots generated from 3.HEAD continue to be highly volatile.

Regular feature releases from Squid-3 will be branched out as sub-versions. Such as this Squid-3.1.

All this is previous policy you should be accustomed to. Now we get to the new numbering change.

Initial branch packages will be generated with a 3.X.0.Z version as beta testing packages. Packages and Snapshots generated with these 3-dot numbers are expected to be relatively stable regarding feature behaviors. Suitable for testing, but without any guarantees under production loads. This replaces both the old PRE and RC packages.

If a large number of bugs are found several *.0.Z packages may be attempted before any is fully frozen for production use. To be frozen as stable the code must be compiling well and have passed a period of 14 days with no new bugs reported against the new code added in that release.

When one of these Squid-3.X.0.Z packages passes those criteria a 3.X.Y numbered release will be made.

We can only hope enough testing has been done to consider these ready for production use. As always we are fully dependent on people testing the previous packages and reporting all bugs.

In support of all this are several squid-dev process changes which have been worked out over the last year.

- We no longer accept new features into branches. Those are reserved for the next feature release. The cycle for major releases is hoped to be fast enough to suit some peoples needs for new features and others need for stability in the branched releases.
- We now audit and vote on all feature and major code additions. Requiring at least two sets of developer eyes on any new features before they are committed to 3.HEAD. Vastly reducing the number of bugs in all code.
- We have implemented and continue to add more testing infrastructure.

## 2.2 Minimal squid.conf improvements

squid.conf has undergone a facelift.

Don't worry, few operational changes have been made. Older configs from Squid 2.x and 3.0 are still expected to run in 3.1 with only the usual minor changes seen between major release. Details on those are listed below.

New users will be relieved to see a very short squid.conf on clean installs. Many of the options have reasonable defaults but had previously needed them explicitly configured! These are now proper built-in defaults and no longer need to be in squid.conf unless changed.

All of the option documentation has been offloaded to another file squid.conf.documented which contains a fully documented set of available options previously cluttering up squid.conf itself.

Package maintainers are provided with a second file squid.conf.default which as always contains the default config options provided on a clean install.

We are also providing online copies of configuration documentation. Updated live to match the latest release of each Squid series, and a combined global version. This is available on the Squid website

## 2.3 Internet Protocol version 6 (IPv6)

Squid 3.1 supports IPv6. Details in The Squid wiki

### New Features for IPv6

Squid handles localhost values seperately. For the purpose of ACLs and also external connections ::1 is considered a seperate IP from 127.0.0.1. This means all ACL which define behaviour for localhost may need ::1/128 included.

Pinger has been upgraded to perform both ICMP and ICMPv6 as required. As a result of this and due to a change in the binary protocol format between them, new builds of Squid are no longer backwards-compatible with old pinger binaries. You will need to perform "make install-pinger" again after installing Squid.

Peer and Client SNMP tables have been altered to handle IPv6 addresses. As a side effect of this the long-missing fix to show seperate named peers on one IP has been integrated. Making the SNMP peer table now produce correct output. The table structure change is identical for both IPv4-only and Dual modes but with IPv4-only simply not including any IPv6 entries. This means any third-party SNMP software which hard coded the MIB paths needs to be upgraded for this Squid release. Details can be found in the wiki SNMP feature page.

### Limitations of IPv6 Support

In this release there is incomplete split-stack support. This means that OS which do not provide IP stacks based on the KAME stack with Hybrid extensions to do IPv4-mapping cannot use full IPv6 with Squid. From 3.1.6 the automatic capability detection will enable these abilities:

- open both IPv4 and IPv6 versions of http_port for client connections where applicable.
- perform DNS to both IPv4 and IPv6 DNS servers.
- permit IPv6-only snmp_incoming_address and snmp_outgoing_address to be configured.
- permit IPv6 server connection provided tcp_outgoing_address has been configured (see below).

NOTE: ICAP, SNMP, ICP and HTCP are not yet opening double ports so they will only run as IPv4-only or IPv6-only.

Specify a specific tcp_outgoing_address and the clients who match its ACL are limited to the IPv4 or IPv6 network that address belongs to. They are not permitted over the IPv4-IPv6 boundary. Some ACL voodoo can however be applied to explicitly route the IPv6/IPv4 bound traffic (DIRECT access) out an appropriate interface. See the squid.conf documentation for further details.

WCCP is not available (neither version 1 or 2). It remains built into Squid for use with IPv4 traffic but IPv6 cannot use it.

Pseudo-Transparent Interception is done via NAT at the OS level and is not available in IPv6. Squid will ensure that any port set with transparent or intercept options be an IPv4-only listening address. Wildcard can still be used but will not open as an IPv6. To ensure that Squid can accept IPv6 traffic on its default port, an alternative should be chosen to handle transparently intercepted traffic.

       http_port 3128
       http_port 8080 intercept

Real transparent Interception (TPROXY) may be able to perform IPv6 interception. However this currently still needs patching of kernels older than 2.6.37. Squid will attempt to discover support on startup and may permit or deny IPv6 wildcard for tproxy flagged ports depending on your system.

The bundled NTLM Auth helper is IPv4-native between itself and the NTLM server. A new one will be needed for IPv6 traffic between the helper and server.

The bundled RADIUS Auth helper is IPv4-native, both in traffic between and data storage with the RADIUS server. A new helper will be needed for IPv6 RADIUS protocol.

## 2.4 Error Page Localization

Details in The Squid wiki

### Localization

The error pages presented by Squid may now be localized per-request to match the visitors local preferred language.

The error_directory option in squid.conf needs to be removed.

For best coverage of languages, using the latest language pack of error files is recommended. Updates can be downloaded from www.squid-cache.org/Versions/langpack/

The Squid developers are interested in making Squid available in a wide variety of languages. Contribution of new languages is encouraged.

### CSS Stylesheet controls

To further enhance the visitor experience all new translations have embeded CSS hooks for scalable per-site localization of the display.

CSS display is controlled by updating the errorpage.css file installed into Squids configuration directory or the err_page_stylesheet option in squid.conf.

Custom error pages can also embed the CSS content by adding the %l tag to their headers.

## 2.5 Connection Pinning (for NTLM Auth Passthrough)

Details in The Squid wiki

Squid 3.1 includes the much asked for Connection Pinning feature from Squid 2.6.

This feature is often called 'NTLM Passthru' since it is a giant workaround which permits Web servers to use Microsoft NTLM Authentication instead of HTTP standard authentication through a web proxy.

## 2.6 Quality of Service (QoS) Flow support

Details in The Squid wiki

Zero Penalty Hit created a patch to set QoS markers on outgoing traffic.

- Allows you to select a TOS/Diffserv value to mark local hits.
- Allows you to select a TOS/Diffserv value to mark peer hits.
- Allows you to selectively mark only sibling or parent requests
- Allows any HTTP response towards clients to have the TOS value of the response coming from the remote server preserved. For this to work correctly, you will need to patch your linux kernel with the TOS preserving ZPH patch. The kernel patch can be downloaded from http://zph.bratcheda.org
- Allows you to mask certain bits in the TOS received from the remote server, before copying the value to the TOS send towards clients.

### Squid Configuration

Squid 3.1 needs to be configured with --enable-zph-qos for the ZPH QoS controls to be available.

The configuration options for Squid 2.7 and 3.1 are based on different ZPH patches. The two releases configuration differs and only the TOS mode settings are directly translatable.

- qos_flows local-hit=0xff Responses found as a HIT in the local cache
- qos_flows sibling-hit=0xff Responses found as a HIT in a sibling peer
- qos_flows parent-hit=0xff Responses found as a HIT in a parent peer

The lines above are separated for documentation. qos_flows may be configured with all options on one line, or separated as shown. Also options may be repeated as many times as desired. Only the final configured value for any option will be used.

The legacy Option and Priority modes available in Squid-2.7 are no longer supported.

## 2.7 SSL Bump (for HTTPS Filtering and Adaptation)

Details in The Squid wiki

Squid-in-the-middle decryption and encryption of CONNECT tunneled SSL traffic, using configurable client- and server-side certificates. While decrypted, the traffic can be inspected using ICAP.

Squid 3.1 releases limit SSL Bump to CONNECT requests and requires that clients are configured to explicitly use the proxy in their browser settings or via WPAD/PAC configuration. Use of interception for port 443 is not officially supported, despite being known to work under certain limited networking circumstances.

## 2.8 eCAP Adaptation Module support

Details in The Squid wiki

eCAP provides a way to integrate CAP modules directly into Squid without the need for a c-icap server wrapper. This enables faster processing.

Currently known and available eCAP modules are listed in the wiki feature page on eCAP.

## 2.9 ICAP Bypass and Retry enhancements

Details in The Squid wiki

ICAP is now extended with full bypass and dynamic chain routing to handle multiple adaptation services.

### ICAP Adaptation Service Sets and Chains

An adaptation service set contains similar, interchangeable services. No more than one service is successfully applied. If one service is down or fails, Squid can use another service. Think "hot standby" or "spare" ICAP servers.

Sets may seem similar to the existing "service bypass" feature, but they allow the failed adaptation to be retried and succeed if a replacement service is available. The services in a set may be all optional or all essential, depending on whether ignoring the entire set is acceptable. The mixture of optional and essential services in a set is supported, but yields results that may be difficult for a human to anticipate or interpret. Squid warns when it detects such a mixture.

When performing adaptations with a set, failures at a service (optional or essential, does not matter) are retried with a different service if possible. If there are no more replacement services left to try, the failure is treated depending on whether the last service tried was optional or essential: Squid either tries to ignore the failure and proceed or terminates the master transaction.

An adaptation chain is a list of different services applied one after another, forming an adaptation pipeline. Services in a chain may be optional or essential. When performing adaptations, failures at an optional service are ignored as if the service did not exist in the chain.

Request satisfaction terminates the adaptation chain.

When forming a set or chain for a given transaction, optional down services are ignored as if they did not exist.

ICAP and eCAP services can be mixed and matched in an adaptation set or chain.

### Dynamically form adaptation chains based on the ICAP X-Next-Services header.

If an ICAP service with the routing=1 option in squid.conf returns an ICAP X-Next-Services response header during a successful REQMOD or RESPMOD transaction, Squid abandons the original adaptation plan and forms a new adaptation chain consisting of services identified in the X-Next-Services header value (using a comma-separated list of adaptation service names from squid.conf). The dynamically created chain is destroyed once the new plan is completed or replaced.

This feature is useful when a custom adaptation service knows which other services are applicable to the message being adapted.

Limit adaptation iterations to adaptation_service_iteration_limit to protect Squid from infinite adaptation loops caused by ICAP services constantly including themselves in the dynamic adaptation chain they request. When the limit is exceeded, the master transaction fails. The default limit of 16 should be large enough to not require an explicit configuration in most environments yet may be small enough to limit side-effects of loops.

## 2.10 ICY streaming protocol support

Squid-3.1 adds native support for streaming protocol ICY. Also commonly known as SHOUTcast multimedia streams.

This protocol uses port 80 and violates RFC 2616 by using an HTTP/1.1 compliant request and non-HTTP reply to start the stream transaction. If the reply is handled according to HTTP/1.1 RFC-compliance requirements the audio stream becomes jerky and contains regular 'popping' sounds.

Squid now processes the ICY replies natively according to the ICY requirements, not HTTP/1.1 requirements. The streamed data is not cacheable. All processing and access controls may be applied the same as for HTTP.

### squid.conf change

Squid-2 contained a hack using the update_http0.9 squid.conf option to work around the unusual replies. This option is now obsolete.

The proto ACL type only matches ICY once the reply has been received, before that the processing is only aware on an HTTP request. So the ACL will match HTTP in http_access and ICY in http_reply_access.

## 3. Changes to squid.conf since Squid-3.0

There have been changes to Squid's configuration file since Squid-3.0.

This section gives a thorough account of those changes in three categories:

- New tags
- Changes to existing tags
- Removed tags

## 3.1 New tags

acl_uses_indirect_client

  Whether to use any result found by follow_x_forwarded_for in further ACL processing. Default: ON

              Controls whether the indirect client address
              (see follow_x_forwarded_for) is used instead of the
              direct client address in acl matching.

adaptation_access

  Sends an HTTP transaction to an ICAP or eCAP adaptation service.

              adaptation_access service_name allow|deny [!]aclname...
              adaptation_access set_name     allow|deny [!]aclname...

              At each supported vectoring point, the adaptation_access
              statements are processed in the order they appear in this
              configuration file. Statements pointing to the following services
              are ignored (i.e., skipped without checking their ACL):

                  - services serving different vectoring points
                  - "broken-but-bypassable" services
                  - "up" services configured to ignore such transactions
                     (e.g., based on the ICAP Transfer-Ignore header).

              When a set_name is used, all services in the set are checked
              using the same rules, to find the first applicable one. See
              adaptation_service_set for details.

              If an access list is checked and there is a match, the
              processing stops: For an "allow" rule, the corresponding
              adaptation service is used for the transaction. For a "deny"
              rule, no adaptation service is activated.

              It is currently not possible to apply more than one adaptation
              service at the same vectoring point to the same HTTP transaction.

adaptation_masterx_shared_names

              For each master transaction (i.e., the HTTP request and response
              sequence, including all related ICAP and eCAP exchanges), Squid
              maintains a table of metadata. The table entries are (name, value)
              pairs shared among eCAP and ICAP exchanges. The table is destroyed
              with the master transaction.

              This option specifies the table entry names that Squid must accept
              from and forward to the adaptation transactions.

              An ICAP REQMOD or RESPMOD transaction may set an entry in the
              shared table by returning an ICAP header field with a name
              specified in adaptation_masterx_shared_names. Squid will store
              and forward that ICAP header field to subsequent ICAP
              transactions within the same master transaction scope.

              Only one shared entry name is supported at this time.

adaptation_service_chain

              Configures a list of complementary services that will be applied
              one-by-one, forming an adaptation chain or pipeline. This is useful
              when Squid must perform different adaptations on the same message.

                  adaptation_service_chain chain_name service_name1 svc_name2 ...

              The named services are used in the chain declaration order. The first
              applicable adaptation service from the chain is used first. The next
              applicable service is applied to the successful adaptation results of
              the previous service in the chain.

              When adaptation starts, broken services are ignored as if they were
              not a part of the chain. A broken service is a down optional service.

              Request satisfaction terminates the adaptation chain because Squid
              does not currently allow declaration of RESPMOD services at the
              "reqmod_precache" vectoring point (see icap_service or ecap_service).

              The services in a chain must be attached to the same vectoring point
              (e.g., pre-cache) and use the same adaptation method (e.g., REQMOD).

              A chain may contain a mix of optional and essential services. If an
              essential adaptation fails (or the failure cannot be bypassed for
              other reasons), the master transaction fails. Otherwise, the failure
              is bypassed as if the failed adaptation service was not in the chain.

adaptation_service_iteration_limit

              Limits the number of iterations allowed when applying adaptation
              services to a message. If your longest adaptation set or chain
              may have more than 16 services, increase the limit beyond its
              default value of 16. If detecting infinite iteration loops sooner
              is critical, make the iteration limit match the actual number
              of services in your longest adaptation set or chain.

              Infinite adaptation loops are most likely with routing services.

adaptation_service_set

              Configures an ordered set of similar, redundant services. This is
              useful when hot standby or backup adaptation servers are available.

                  adaptation_service_set set_name service_name1 service_name2 ...

              The named services are used in the set declaration order. The first
              applicable adaptation service from the set is used first. The next
              applicable service is tried if and only if the transaction with the
              previous service fails and the message waiting to be adapted is still
              intact.

              When adaptation starts, broken services are ignored as if they were
              not a part of the set. A broken service is a down optional service.

              The services in a set must be attached to the same vectoring point
              (e.g., pre-cache) and use the same adaptation method (e.g., REQMOD).

              If all services in a set are optional then adaptation failures are
              bypassable. If all services in the set are essential, then a
              transaction failure with one service may still be retried using
              another service from the set, but when all services fail, the master
              transaction fails as well.

              A set may contain a mix of optional and essential services, but that
              is likely to lead to surprising results because broken services become
              ignored (see above), making previously bypassable failures fatal.
              Technically, it is the bypassability of the last failed service that
              matters.

adapted_http_access

  New name for http_access2. This form includes access control of ICAP and eCAP adaptations as well as the URL-rewriter alterations.

chunked_request_body_max_size

  New option to enable handing of broken HTTP/1.1 clients sending chunk requests.

              A broken or confused HTTP/1.1 client may send a chunked HTTP
              request to Squid. Squid does not have full support for that
              feature yet. To cope with such requests, Squid buffers the
              entire request and then dechunks request body to create a
              plain HTTP/1.0 request with a known content length. The plain
              request is then used by the rest of Squid code as usual.

              The option value specifies the maximum size of the buffer used
              to hold the request before the conversion. If the chunked
              request size exceeds the specified limit, the conversion
              fails, and the client receives an "unsupported request" error,
              as if dechunking was disabled.

              Dechunking is enabled by default. To disable conversion of
              chunked requests, set the maximum to zero.

              Request dechunking feature and this option in particular are a
              temporary hack. When chunking requests and responses are fully
              supported, there will be no need to buffer a chunked request.

delay_pool_uses_indirect_client

  Whether to use any result found by follow_x_forwarded_for in delay_pool assignment. Default: ON

              Controls whether the indirect client address
              (see follow_x_forwarded_for) is used instead of the
              direct client address in delay pools.

client_request_buffer_max_size

  New directive added with squid-3.1.10 to set limits on the amount of buffer space allocated for receiving upload and request data from clients.

dns_v4_fallback

  New option to prevent Squid from always looking up IPv4 regardless of whether IPv6 addresses are found. Squid will follow a policy of prefering IPv6 links, keeping the IPv4 only as a safety net behind IPv6.

              Standard practice with DNS is to lookup either A or AAAA records
              and use the results if it succeeds. Only looking up the other if
              the first attempt fails or otherwise produces no results.

              That policy however will cause Squid to produce error pages for some
              servers that advertise AAAA but are unreachable over IPv6.

              If this is ON  Squid will always lookup both AAAA and A, using both.
              If this is OFF Squid will lookup AAAA and only try A if none found.

              WARNING: There are some possibly unwanted side-effects with this on:
                      *) Doubles the load placed by Squid on the DNS network.
                      *) May negatively impact connection delay times.

ecap_enable

  Controls whether eCAP support is enabled. Default: OFF

ecap_service

  Defines a single eCAP service

              ecap_service servicename vectoring_point bypass service_url

              vectoring_point = reqmod_precache|reqmod_postcache|respmod_precache|respmod_postcache
                      This specifies at which point of transaction processing the
                      eCAP service should be activated. *_postcache vectoring points
                      are not yet supported.

              bypass = 1|0
                      If set to 1, the eCAP service is treated as optional. If the
                      service cannot be reached or malfunctions, Squid will try to
                      ignore any errors and process the message as if the service
                      was not enabled. No all eCAP errors can be bypassed.
                      If set to 0, the eCAP service is treated as essential and all
                      eCAP errors will result in an error page returned to the
                      HTTP client.

              service_url = ecap://vendor/service_name?custom&cgi=style&parameters=optional

              Example:
                    ecap_service service_1 reqmod_precache 0 ecap://filters-R-us/leakDetector?on_error=block
                    ecap_service service_2 respmod_precache 1 icap://filters-R-us/virusFilter?config=/etc/vf.cfg

err_page_stylesheet

  New option to configure location for CSS stylesheet controlling error page display.

error_default_language

  New option to replace the old configure option --enable-default-err-language New translations can be downloaded from http://www.squid-cache.org/Versions/langpack/

              Set the default language which Squid will send error pages in
              if no existing translation matches the clients language
              preferences.

              If unset (default) generic English will be used.

error_log_languages

              Log to cache.log what languages users are attempting to
              auto-negotiate for translations.

              Successful negotiations are not logged. Only failures
              have meaning to indicate that Squid may need an upgrade
              of its error page translations.

follow_x_forwarded_for

  Enable processing of the X-Forwarded-for header for various administration tasks.

              Allowing or Denying the X-Forwarded-For header to be followed to
              find the original source of a request.

              Requests may pass through a chain of several other proxies
              before reaching us.  The X-Forwarded-For header will contain a
              comma-separated list of the IP addresses in the chain, with the
              rightmost address being the most recent.

              If a request reaches us from a source that is allowed by this
              configuration item, then we consult the X-Forwarded-For header
              to see where that host received the request from.  If the
              X-Forwarded-For header contains multiple addresses, and if
              acl_uses_indirect_client is on, then we continue backtracking
              until we reach an address for which we are not allowed to
              follow the X-Forwarded-For header, or until we reach the first
              address in the list.  (If acl_uses_indirect_client is off, then
              it's impossible to backtrack through more than one level of
              X-Forwarded-For addresses.)

              The end result of this process is an IP address that we will
              refer to as the indirect client address.  This address may
              be treated as the client address for access control, delay
              pools and logging, depending on the acl_uses_indirect_client,
              delay_pool_uses_indirect_client and log_uses_indirect_client
              options.

              SECURITY CONSIDERATIONS:
                      Any host for which we follow the X-Forwarded-For header
                      can place incorrect information in the header, and Squid
                      will use the incorrect information as if it were the
                      source address of the request.  This may enable remote
                      hosts to bypass any access control restrictions that are
                      based on the client's source addresses.

              For example:

                      acl localhost src 127.0.0.1
                      acl my_other_proxy srcdomain .proxy.example.com
                      follow_x_forwarded_for allow localhost
                      follow_x_forwarded_for allow my_other_proxy

ftp_epsv

              FTP Protocol extensions permit the use of a special "EPSV" command.

              NATs may be able to put the connection on a "fast path" through the
              translator using EPSV, as the EPRT command will never be used and therefore,
              translation of the data portion of the segments will never be needed.

              Turning this OFF will prevent EPSV being attempted.

              WARNING: Doing so will convert Squid back to the old behavior with all
              the related problems with external NAT devices/layers.

              Requires ftp_passive to be ON (default) for any effect.

ftp_epsv_all

              FTP Protocol extensions permit the use of a special "EPSV ALL" command.

              NATs may be able to put the connection on a "fast path" through the
              translator, as the EPRT command will never be used and therefore,
              translation of the data portion of the segments will never be needed.

              When a client only expects to do two-way FTP transfers this may be useful.
              If Squid finds that it must do a three-way FTP transfer after issuing
              an EPSV ALL command, the FTP session will fail.

              If you have any doubts about this option do not use it.
              Squid will nicely attempt all other connection methods.

              Requires ftp_passive to be ON (default)

forward_max_tries

  Controls how many different forward paths Squid will try before giving up. Default: 10

icap_log

  New option to write ICAP log files record ICAP transaction summaries, one line per transaction. Similar to access.log.

              The icap_log option format is:
                      icap_log <filepath> [<logformat name> [acl acl ...]]
                      icap_log none [acl acl ...]]

              Please see access_log option documentation for details. The two
              kinds of logs share the overall configuration approach and many
              features.

              ICAP processing of a single HTTP message or transaction may
              require multiple ICAP transactions.  In such cases, multiple
              ICAP transaction log lines will correspond to a single access
              log line.

              ICAP log uses logformat codes that make sense for an ICAP
              transaction. Header-related codes are applied to the HTTP header
              embedded in an ICAP server response, with the following caveats:
              For REQMOD, there is no HTTP response header unless the ICAP
              server performed request satisfaction. For RESPMOD, the HTTP
              request header is the header sent to the ICAP server. For
              OPTIONS, there are no HTTP headers.

              The following format codes are also available for ICAP logs:

                      icap::<A     ICAP server IP address. Similar to <A.

                      icap::<service_name  ICAP service name from the icap_service
                                      option in Squid configuration file.

                      icap::ru        ICAP Request-URI. Similar to ru.

                      icap::rm        ICAP request method (REQMOD, RESPMOD, or
                                      OPTIONS). Similar to existing rm.

                      icap::>st       Bytes sent to the ICAP server (TCP payload
                                      only; i.e., what Squid writes to the socket).

                      icap::<st    Bytes received from the ICAP server (TCP
                                      payload only; i.e., what Squid reads from
                                      the socket).

                      icap::tr        Transaction response time (in
                                      milliseconds).  The timer starts when
                                      the ICAP transaction is created and
                                      stops when the transaction is completed.
                                      Similar to tr.

                      icap::tio       Transaction I/O time (in milliseconds). The
                                      timer starts when the first ICAP request
                                      byte is scheduled for sending. The timers
                                      stops when the last byte of the ICAP response
                                      is received.

                      icap::to        Transaction outcome: ICAP_ERR* for all
                                      transaction errors, ICAP_OPT for OPTION
                                      transactions, ICAP_ECHO for 204
                                      responses, ICAP_MOD for message
                                      modification, and ICAP_SAT for request
                                      satisfaction. Similar to Ss.

                      icap::Hs        ICAP response status code. Similar to Hs.

                      icap::>h        ICAP request header(s). Similar to >h.

                      icap::<h     ICAP response header(s). Similar to <h.

              The default ICAP log format, which can be used without an explicit
              definition, is called icap_squid:

      logformat icap_squid %ts.%03tu %6icap::tr %>a %icap::to/%03icap::Hs %icap::<size %icap::rm %icap::ru% %un -/%icap::<A -

icap_retry

  New option to determine which retriable ICAP transactions are retried.

              Transactions that received a complete ICAP response
              and did not have to consume or produce HTTP bodies to receive
              that response are usually retriable.

                      icap_retry allow|deny [!]aclname ...

              Squid automatically retries some ICAP I/O timeouts and errors
              due to persistent connection race conditions.

icap_retry_limit

              Limits the number of retries allowed. When set to zero (default),
              no retries are allowed.

              Communication errors due to persistent connection race
              conditions are unavoidable, automatically retried, and do not
              count against this limit.

ignore_expect_100

  Ported from 2.7. Requires --enable-http-violations Prevents 417 errors being sent to broken HTTP/1.1 non-compliant clients.

include

  New option to import entire secondary configuration files into squid.conf.

              Squid will follow the files immediately and insert all their content
              as if it was at that position in squid.conf. As per squid.conf some
              options are order-specific within the config as a whole.

              A few layers of include are allowed, but too many are confusing and
              Squid will enforce an include depth of 16 files.

              Syntax:
                      include /path/to/file1 /path/to/file2

loadable_modules

  Instructs Squid to load the specified dynamic module(s) or activate preloaded module(s).

              Example:
                    loadable_modules @DEFAULT_PREFIX@/lib/MinimalAdapter.so

log_icap aclname [aclname ...]

              This options allows you to control which requests get logged
              to icap.log. See the icap_log directive for ICAP log details.

log_uses_indirect_client

  Whether to use any result found by follow_x_forwarded_for in access.log. Default: ON

              Controls whether the indirect client address
              (see follow_x_forwarded_for) is used instead of the
              direct client address in the access log.

max_filedescriptors

  Ported from 2.7.

netdb_filename

              A filename where Squid stores it's netdb state between restarts.
              To disable, enter "none".

pinger_enable

  New option to enable/disable the ICMP pinger helper with a reconfigure instead of a full rebuild.

              Control whether the pinger is active at run-time.
              Enables turning ICMP pinger on and off with a simple squid -k reconfigure.
              default is off when --enable-icmp is compiled in.

ssl_bump

  New Access control for which CONNECT requests to an http_port marked with an ssl-bump flag are actually "bumped". Please see the ssl-bump flag of an http_port option for more details about decoding proxied SSL connections. DEFAULT: No requests are bumped.

      NOCOMMENT_START
      # Example: Bump all requests except those originating from localhost and
      # those going to webax.com or example.com sites.
      #
      # acl broken_sites dstdomain .webax.com
      # acl broken_sites dstdomain .example.com
      # ssl_bump deny localhost
      # ssl_bump deny broken_sites
      # ssl_bump allow all

sslproxy_cert_error

  New Access Control to selectively bypass server certificate validation errors. DEFAULT: None bypassed.

              For example, the following lines will bypass all validation errors
              when talking to servers located at 172.16.0.0/16. All other
              validation errors will result in ERR_SECURE_CONNECT_FAIL error.

                      acl BrokenServersAtTrustedIP dst 172.16.0.0/16
                      sslproxy_cert_error allow BrokenServersAtTrustedIP
                      sslproxy_cert_error deny all

              This option must use fast ACL expressions only. Expressions that use
              external lookups or communication result in unpredictable behavior or
              crashes.

              Without this option, all server certificate validation errors
              terminate the transaction. Bypassing validation errors is dangerous
              because an error usually implies that the server cannot be trusted and
              the connection may be insecure.

qos_flows local-hit= sibling-hit= parent-hit=

              Allows you to select a TOS/DSCP value to mark outgoing
              connections with, based on where the reply was sourced.

              TOS values really only have local significance - so you should
              know what you're specifying. For more information, see RFC2474,
              RFC2475, and RFC3260.

              The TOS/DSCP byte must be exactly that - octet value 0x00-0xFF.
              Note that in practice often only values up to 0x3F are usable
              as the two highest bits have been redefined for use by ECN
              (RFC3168).

              This setting is configured by setting the source TOS values:

              local-hit=0xFF          Value to mark local cache hits.

              sibling-hit=0xFF        Value to mark hits from sibling peers.

              parent-hit=0xFF         Value to mark hits from parent peers.

              NOTE: 'miss' preserve feature is only possible on Linux at this time.

              For the following to work correctly, you will need to patch your
              linux kernel with the TOS preserving ZPH patch.
              The kernel patch can be downloaded from http://zph.bratcheda.org

              disable-preserve-miss
                      If set, any HTTP response towards clients will
                      have the TOS value of the response comming from the
                      remote server masked with the value of miss-mask.
              miss-mask=0xFF
                      Allows you to mask certain bits in the TOS received from the
                      remote server, before copying the value to the TOS sent
                      towards clients.
                      Default: 0xFF (TOS from server is not changed).

## 3.2 Changes to existing tags

acl

  New preset ipv6 available in the src and dst ACL matching all of the public IPv6 network space.

  New preset ipv4 available in the src and dst ACL matching all of IPv4 network space.

  New acl type myportname, matching the name of the http_port or https_port where the request was accepted.

  New acl type tag, matching the tag= returned from the external_acl_type helper.

  New acl type peername, matching against a named cache_peer entry where the request will be attempted first. NP: peername currently is limited to only match the first peer possible.

              acl aclname dst ipv6                    # request for IPv6-enabled site
              acl aclname src ipv6                    # request from IPv6 address
              acl aclname dst ipv4                    # request for IPv4 site
              acl aclname src ipv4                    # request from IPv4 address
              acl aclname myportname 3128 ...         # http(s)_port name
              acl aclname peername myPeer ...         # cache_peer ... name=myPeer
              acl aclname tag value ...               # tag= option from external ACL

auth_param ntlm, basic, digest

  BASIC, DIGEST: New parameter option utf8 on|off to permit helpers to selectively process UTF-8 characters even though HTTP accepts only ISO-8859-1.

  NTLM: The helper binary bundled with Squid under the name ntlm_auth has been renamed to accurately reflect its real behavior and to prevent confusion with the more useful Samba helper using the same name.

  Despite being used for NTLM, the helper does not in fact provide true NTLM function. What it does provide is SMB LanManager authentication through the NTLM interface without the need for a domain controller. Thus the new name is ntlm_smb_lm_auth.

  WARNING: due to the name clash with Samba helper, admin should be careful to only update their squid.conf if the Squid bundled binary is used and needed. If the Samba helper is in use, the squid.conf should not be altered.

balance_on_multiple_ip

  The previous default behavour (rotate per-request) of this setting causes failover clashes with IPv6 built-in mechanisms. It has thus been turned off by default. Making the 'best choice' IP continue in use for any hostname until it encounters a connection failure and failover drops to the next known IP.

              Modern IP resolvers in Squid sort lookup results by preferred access.
              By default Squid will use these IP in order and only rotates to
              the next listed when the most preffered fails.

              Some load balancing servers based on round robin DNS have been
              found not to preserve user session state across requests
              to different IP addresses.

              Enabling this directive Squid rotates IP's per request.

cache

  Removed the 'QUERY' acl and 'cache deny QUERY' entries. Replaced by new refresh_pattern instead.

cache_dir

  Default changed to 256MB in-memory cache. see cache_mem and maximum_object_size_in_memory for size parameters.

  'null' storage type dropped. In-memory cache is always present. Remove all cache_dir options to prevent on-disk caching.

cache_mem

  Default size increased to 256MB.

cache_peer htcp-no-clr htcp-no-purge-clr htcp-only-clr htcp-forward-clr connection-auth[=on|off|auto] connect-fail-limit=N multicast-siblings no-tproxy

  New Options.

              use 'htcp-no-clr' to send HTCP to the neighbor but without
              sending any CLR requests.  This cannot be used with
              htcp-only-clr.

              use 'htcp-no-purge-clr' to send HTCP to the neighbor
              including CLRs but only when they do not result from
              PURGE requests.

              use 'htcp-only-clr' to send HTCP to the neighbor but ONLY
              CLR requests.  This cannot be used with htcp-no-clr.

              use 'htcp-forward-clr' to forward any HTCP CLR requests
              this proxy receives to the peer.

              use 'connection-auth=off' to tell Squid that this peer does
              not support Microsoft connection oriented authentication,
              and any such challenges received from there should be
              ignored. Default is 'auto' to automatically determine the
              status of the peer.

              use 'connect-fail-limit=nn' to specify how many times
              connecting to a peer must fail before it is marked as
              down. Default is 10.

              use 'no-tproxy' to specify that requests passed to this peer
              are not to have the client IP spoofed. For use to prevent
              packet routing issues with a cluster of peers behind WCCPv2.

              multicast-siblings ported from 2.7

cache_store_log

  Default changed to OFF. Matching long-standing developer recommendations.

error_directory

  Now an optional entry in squid.conf. If present it will force all visitors to receive the error pages contained in the directory it points at. If absent, error page localization will be given a chance.

              If you wish to create your own versions of the default
              error files to customize them to suit your company COPY
              the error/template files to another directory and point
              this tag at them.

              WARNING: This option will disable multi-language support
                       on error pages if used.

debug_options rotate=

  New parameter rotate=N to control number of cache.log rotations independent of other logs.

external_acl_type

  New options 'ipv4' and 'ipv6' are added to set the IPv4/v6 protocol between Squid and its helpers. Please be aware of some limits to these options. These options only affet the transport protocol used to send data to and from the helpers. Squid in IPv6-mode may still send %SRC addresses in IPv4 or IPv6 format, so all helpers will need to be checked and converted to cope with such information cleanly.

                ipv4 / ipv6   IP-mode used to communicate to this helper.
                              For compatability with older configurations and helpers
                              the default is 'ipv4'.

  New header input format specifiers. To seperate Request and Reply headers when both passed back.

              %>{Header}        HTTP request header
              %>{Hdr:member}    HTTP request header list member
              %>{Hdr:;member}   HTTP request header list member using ; as
                                list separator. ; can be any non-alphanumeric
                                character.

              %<{Header}        HTTP reply header
              %<{Hdr:member}    HTTP reply header list member
              %<{Hdr:;member}   HTTP reply header list member using ; as
                                list separator. ; can be any non-alphanumeric
                                character.

forwarded_for

  New setting options. transparent, truncate, delete.

              If set to "transparent", Squid will not alter the
              X-Forwarded-For header in any way.

              If set to "delete", Squid will delete the entire
              X-Forwarded-For header.

              If set to "truncate", Squid will remove all existing
              X-Forwarded-For entries, and place itself as the sole entry.

http_port transparent intercept ssl-bump connection-auth[=on|off] ignore-cc

  Option 'transparent' is being deprecated in favour of 'intercept' which more clearly identifies what the option does. For now option 'tproxy' remains with old behaviour meaning fully-invisible proxy using TPROXY support.

  New port options

                 intercept    Rename of old 'transparent' option to indicate proper functionality.

                 allow-direct Allow direct forwarding in accelerator mode. Normally
                              accelerated requests are denied direct forwarding as if
                              never_direct was used.

                 connection-auth[=on|off]
                              use connection-auth=off to tell Squid to prevent
                              forwarding Microsoft connection oriented authentication
                              (NTLM, Negotiate and Kerberos)

                 keepalive[=idle,interval,timeout]
                              Enable TCP keepalive probes of idle connections
                              idle is the initial time before TCP starts probing
                              the connection, interval how often to probe, and
                              timeout the time before giving up.

                 ignore-cc    Ignore request Cache-Control headers.

                              Warning: This option violates HTTP specifications if
                              used in non-accelerator setups.

                 ssl-bump     Intercept each CONNECT request matching ssl_bump ACL,
                              establish secure connection with the client and with
                              the server, decrypt HTTP messages as they pass through
                              Squid, and treat them as unencrypted HTTP messages,
                              becoming the man-in-the-middle.

                              When this option is enabled, additional options become
                              available to specify SSL-related properties of the
                              client-side connection: cert, key, version, cipher,
                              options, clientca, cafile, capath, crlfile, dhparams,
                              sslflags, and sslcontext. See the https_port directive
                              for more information on these options.

                              The ssl_bump option is required to fully enable
                              the SSL Bump feature.

https_port intercept ssl-bump connection-auth[=on|off]

  New port options. see http_port.

icap_service bypass=on|off|1|0 routing=on|off|1|0 ipv6=on|off

  New options 'bypass=', 'routing=' and 'ipv6='.

              bypass=on|off|1|0
                      If set to 'on' or '1', the ICAP service is treated as
                      optional. If the service cannot be reached or malfunctions,
                      Squid will try to ignore any errors and process the message as
                      if the service was not enabled. No all ICAP errors can be
                      bypassed.  If set to 0, the ICAP service is treated as
                      essential and all ICAP errors will result in an error page
                      returned to the HTTP client.

                      Bypass is off by default: services are treated as essential.

              routing=on|off|1|0
                      If set to 'on' or '1', the ICAP service is allowed to
                      dynamically change the current message adaptation plan by
                      returning a chain of services to be used next. The services
                      are specified using the X-Next-Services ICAP response header
                      value, formatted as a comma-separated list of service names.
                      Each named service should be configured in squid.conf and
                      should have the same method and vectoring point as the current
                      ICAP transaction.  Services violating these rules are ignored.
                      An empty X-Next-Services value results in an empty plan which
                      ends the current adaptation.

                      Routing is not allowed by default: the ICAP X-Next-Services
                      response header is ignored.

              ipv6=on|off
                      Only has effect on split-stack systems. The default on those systems
                      is to use IPv4-only connections. When set to 'on' this option will
                      make Squid use IPv6-only connections to contact this ICAP service.

logfile_rotate

  No longer controls cache.log rotation. Use debug_options rotate=N instead.

logformat

  New log format tag sets %icap::* %adapt::* for adaptation information. %Hs tag deprecated and replaced by request/reply specific >Hs and <Hs new %>ha option to log HTTP request headers after adaptation and redirection. HTTP request/reply format tags may now be optionally prefixed with http::. Old forms will be deprecated in some as yet undecided future release.

                      dt              Total time spent making DNS lookups (milliseconds)

                      [http::]>ha     The HTTP request headers after adaptation and redirection.
                      [http::]>Hs     HTTP status code sent to the client
                      [http::]<Hs  HTTP status code received from the next hop
                      [http::]>sh     Received HTTP request headers size
                      [http::]<sh  Sent HTTP reply headers size
                      [http::]<pt  Peer response time in milliseconds. The timer starts
                                      when the last request byte is sent to the next hop
                                      and stops when the last response byte is received.
                      [http::]<tt  Total server-side time in milliseconds. The timer
                                      starts with the first connect request (or write I/O)
                                      sent to the first selected peer. The timer stops
                                      with the last I/O with the last peer.

              If ICAP is enabled, the following two codes become available (as
              well as ICAP log codes documented with the icap_log option):

                      icap::tt        Total ICAP processing time for the HTTP
                                      transaction. The timer ticks when ICAP
                                      ACLs are checked and when ICAP
                                      transaction is in progress.

                      icap::<last_h        The header of the last ICAP response
                                      related to the HTTP transaction. Like
                                      <h, accepts an optional header name
                                      argument.  Will not change semantics
                                      when multiple ICAP transactions per HTTP
                                      transaction are supported.

              If adaptation is enabled the following two codes become available:

                      adapt::sum_trs Summed adaptation transaction response
                                      times recorded as a comma-separated list in
                                      the order of transaction start time. Each time
                                      value is recorded as an integer number,
                                      representing response time of one or more
                                      adaptation (ICAP or eCAP) transaction in
                                      milliseconds.  When a failed transaction is
                                      being retried or repeated, its time is not
                                      logged individually but added to the
                                      replacement (next) transaction.

                      adapt::all_trs All adaptation transaction response times.
                                      Same as adaptation_strs but response times of
                                      individual transactions are never added
                                      together. Instead, all transaction response
                                      times are recorded individually.

              You can prefix adapt::*_trs format codes with adaptation
              service name in curly braces to record response time(s) specific
              to that service. For example: %{my_service}adapt::sum_trs

maximum_object_size_in_memory

  Default size limit increased to 512KB.

memory_pools_limit

  Memory limits have been revised and corrected from 3.1.4 onwards.

  Please check and update your squid.conf to use the text none for no limit instead of the old 0 (zero).

  All users upgrading need to be aware that from Squid-3.3 setting this option to 0 (zero) will mean zero bytes of memory get pooled.

negative_ttl

  New default of 0 seconds. To prevent negative-caching of failure messages unless explicitly permitted by the message generating web server.

  Changing this is an RFC 2616 violation and now requires --enable-http-violations

refresh_pattern

  New option 'ignore-must-revalidate'.

              ignore-must-revalidate ignores any ``Cache-Control: must-revalidate``
              headers received from a server. Doing this VIOLATES
              the HTTP standard. Enabling this feature could make you
              liable for problems which it causes.

  New set of basic patterns. These should always be listed after any custom patterns. They ensure RFC compliance with certain protocol and request handling in the absence of accurate Cache-Control: and Expires: information.

      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

reply_header_max_size

  Default limit increased to 64KB for RFC 2616 compliance.

request_header_max_size

  Default limit increased to 64KB for RFC 2616 compliance.

tcp_outgoing_address

  This option causes some problems when bridging IPv4 and IPv6. A workaround has been provided.

              Squid is built with a capability of bridging the IPv4 and IPv6 internets.
              tcp_outgoing_address as previously used breaks this bridging by forcing
              all outbound traffic through a certain IPv4 which may be on the wrong
              side of the IPv4/IPv6 boundary.

              To operate with tcp_outgoing_address and keep the bridging benefits
              an additional ACL needs to be used which ensures the IPv6-bound traffic
              is never forced or permitted out the IPv4 interface.

              acl to_ipv6 dst ipv6
              http_access allow to_ipv6 !all

              tcp_outgoing_address 2002::c001 good_service_net to_ipv6
              tcp_outgoing_address 10.0.0.2 good_service_net !to_ipv6

              tcp_outgoing_address 2002::beef normal_service_net to_ipv6
              tcp_outgoing_address 10.0.0.1 normal_service_net !to_ipv6

              tcp_outgoing_address 2002::1 to_ipv6
              tcp_outgoing_address 10.0.0.3 !to_ipv6

wccp2_assignment_method hash mask

  Method names now accepted. Replacing the old magic numbers. '1' becomes 'hash' and '2' becomes 'mask'

wccp2_forwarding_method gre l2

  Method names now accepted. Replacing the old magic numbers. '1' becomes 'gre' and '2' becomes 'l2'

wccp2_return_method gre l2

  Method names now accepted. Replacing the old magic numbers. '1' becomes 'gre' and '2' becomes 'l2'

## 3.3 Removed tags

dns_testnames

  Obsolete. This feature is no longer relevant to modern networks and was causing boot problems. The -D command line option used previously to suppress these tests is also obsolete.

extension_methods

  Obsolete. All possible methods are now accepted and handled properly.

icap_class

  Replaced by adaptation_service_set.

icap_access

  Replaced by adaptation_access.

## 4. Changes to ./configure options since Squid-3.0

There have been some changes to Squid's build configuration since Squid-3.0.

This section gives an account of those changes in three categories:

- New options
- Changes to existing options
- Removed options

## 4.1 New options

--enable-ecap

  Build with support for loadable content adaptation modules. Cannot be used with --disable-loadable-modules.

--enable-follow-x-forwarded-for

  Support following the X-Forwarded-For HTTP header for determining the original or indirect client when a request has been forwarded through other proxies.

--enable-zph-qos

  Build with support for ZPH Quality of Service controls

--disable-auto-locale

  Disable error page localization for visitors.

  error_directory option is required if this option is used.

--disable-ipv6

  Build without IPv6 support. The default is to auto-detect system capabilities and use IPv6 when possible.

--disable-loadable-modules

  Build without support for loadable modules.

--disable-strict-error-checking

  Build Squid without advanced compiler error checking (without the -Werror option). This only affects the building process, enabling it to complete despite some possibly serious issues. Please do not use lightly, and please report the build issues which make it needed to the Squid developers before doing so.

--disable-translation

  Prevent Squid generating localized error page templates and manuals when built. Which is usually tried, but may not be needed.

  This is an optimization for building fast when localization is not needed or localization tools are not available.

  A copy of the latest translated files can instead be downloaded from http://www.squid-cache.org/Versions/langpack/

--with-dns-cname

  Enable CNAME recursion within the Internal DNS resolver stub squid uses. This has no effect on the external DNS helper.

  Please note this extension is still experimental and may encounter problems. To see if it is actually needed you can run squid without it for a period and check the CNAME-Only Requests statistics squid maintains.

  If it produces ongoing serious problems the external helper may be needed but please report the bugs anyway.

--with-libexpat / --without-libexpat

  Require libexpat XML parser to be built into Squid for ESI parsing. Build will fail if this option is used and the library is not present. Default is to auto-detect it when using ESI and ignore if not present. Use --without-libexpat to prevent it being auto-detected.

--with-libxml2 / --without-libxml2

  Require libxml2 XML parser to be built into Squid for ESI parsing. Build will fail if this option is used and the library is not present. Default is to auto-detect it when building with ESI. Use --without-libxml2 to prevent it being auto-detected.

--with-logdir=PATH

  Allow build-time configuration of Default location for Squid logs.

--with-pidfile=PATH

  Allow build-time configuration of Default location and name of squid.pid file.

--with-po2html=PATH

  Absolute path to po2html executable. Default is to automatically detect the binary.

--without-libcap

  Build without libcap support. The default is to auto-detect system capabilities and enable support when possible.

  NOTE: Disabling this or building without libcap support will break TPROXY support.

## 4.2 Changes to existing options

--enable-shared[=PKGS]

  Default changed to yes.

--enable-linux-netfilter

  This option now enables support for all three netfilter interception targets.

  Adding TPROXY version 4+ support to Squid through the netfilter TPROXY target. This options requires a linux kernel 2.6.25 or later for embeded netfilter TPROXY targets.

  Older REDIRECT and DNAT targets work as before on HTTP ports marked 'intercept'.

--enable-linux-tproxy

  Deprecated. Remains only to support old TPROXY version 2.2 installations. Scheduled for complete removal in Squid 3.2

--enable-ntlm-auth-helpers

  Helper previously built by SMB is now built by smb_lm. It also has a new squid.conf name for usage, see auth_param above for details.

--disable-internl-dns

  Better support for Linux using the external DNS helper. The helper will now compile and work with dns_nameservers on more variants of Linux than previously. It is still deprecated however and use of this option should be avoided as much as possible.

--with-aio

  Deprecated. POSIX AIO is now auto-detected and enabled. Use --without-aio to disable, but only if you really have to.

--with-pthreads

  Deprecated. pthreads library is now auto-detected and enabled. Use --without-pthreads to disable, but only if you really have to.

## 4.3 Removed options

--enable-default-err-language

  Replaced by error_default_language squid.conf option

--enable-err-languages

  Removed. All languages used now for error page localization.

--disable-carp

  Removed. CARP is required by several peering algoithms. Disabling is not useful.

--disable-mempools

  Replaced by memory_pools squid.conf option.

## 5. Options Removed since Squid-2

Some squid.conf and ./configure options which were available in Squid-2.6 and Squid-2.7 are made obsolete in Squid-3.1.

## 5.1 Removed squid.conf options since Squid-2.7

auth_param

  blankpassword option for basic scheme removed.

cache_peer

  http11 Obsolete.

external_acl_type

  Format tag %{Header} replaced by %>{Header}

  Format tag %{Header:member} replaced by %>{Header:member}

header_access

  Replaced by request_header_access and reply_header_access

http_access2

  Replaced by adapted_http_access

http_port

  no-connection-auth replaced by connection-auth=[on|off]. Default is ON.

  transparent option replaced by intercept

httpd_accel_no_pmtu_disc

  Replaced by http_port disable-pmtu-discovery= option

incoming_rate

  Obsolete.

redirector_bypass

  Replaced by url_rewrite_bypass

server_http11

  Obsolete.

upgrade_http0.9

  Obsolete. ICY protocol streaming support added natively.

zph_local

  Replaced by qos_flows local-hit=

zph_mode

  Obsolete.

zph_option

  Obsolete.

zph_parent

  Replaced by qos_flows parent-hit=

zph_sibling

  Replaced by qos_flows sibling-hit=

## 5.2 Removed squid.conf options since Squid-2.6

cache_dir

  read-only option replaced by no-store.

## 5.3 Removed ./configure options since Squid-2.7

--enable-coss-aio-ops

  Obsolete.

--enable-devpoll

  Replaced by automatic detection.

--enable-dlmalloc=LIB

  Obsolete.

--enable-epoll

  Replaced by automatic detection.

--enable-forward-log

  Obsolete.

--enable-heap-replacement

  Obsolete.

--enable-htcp

  Obsolete. Enabled by default.

--enable-large-cache-files

  Obsolete.

--enable-mempool-debug

  Obsolete.

--enable-multicast-miss

  Obsolete.

--enable-poll

  Replaced by automatic detection.

--enable-select

  Replaced by automatic detection.

--enable-select-simple

  Replaced by automatic detection.

--enable-snmp

  Obsolete. Enabled by default.

--enable-truncate

  Obsolete.

--disable-kqueue

  Obsolete. Disabled by default.

## 6. Regressions since Squid-2.7

Some squid.conf and ./configure options which were available in Squid-2.7 are not yet available in Squid-3.1

If you need something to do then porting one of these from Squid-2 to Squid-3 is most welcome.

## 6.1 Missing squid.conf options available in Squid-2.7

acl

  urllogin option not yet ported from 2.6

  urlgroup option not yet ported from 2.6

auth_param digest

  concurrency option not yet ported from Squid-2

authenticate_ip_shortcircuit_access

  Not yet ported from 2.7

authenticate_ip_shortcircuit_ttl

  Not yet ported from 2.7

broken_vary_encoding

  Not yet ported from 2.6

cache_dir

  min-size option not yet ported from Squid-2

  COSS storage type is lacking stability fixes from 2.6

  COSS overwrite-percent= option not yet ported from 2.6

  COSS max-stripe-waste= option not yet ported from 2.6

  COSS membufs= option not yet ported from 2.6

  COSS maxfullbufs= option not yet ported from 2.6

cache_peer

  idle= not yet ported from 2.7

  monitorinterval= not yet ported from 2.6

  monitorsize= not yet ported from 2.6

  monitortimeout= not yet ported from 2.6

  monitorurl= not yet ported from 2.6

cache_vary

  Not yet ported from 2.6

collapsed_forwarding

  Not yet ported from 2.6

error_map

  Not yet ported from 2.6

external_acl_type

  %ACL format tag not yet ported from 2.6

  %DATA format tag not yet ported from 2.6

external_refresh_check

  Not yet ported from 2.7

http_port

  act-as-origin not yet ported from 2.7

  http11 not yet ported from 2.7

  urlgroup= not yet ported from 2.6

ignore_ims_on_miss

  Not yet ported from 2.7

location_rewrite_access

  Not yet ported from 2.6

location_rewrite_children

  Not yet ported from 2.6

location_rewrite_concurrency

  Not yet ported from 2.6

location_rewrite_program

  Not yet ported from 2.6

logfile_daemon

  Not yet ported from 2.7.

logformat

  %oa tag not yet ported from 2.7

  %sn tag not yet ported from 2.7

max_stale

  Not yet ported from 2.7

refresh_pattern

  stale-while-revalidate= not yet ported from 2.7

  ignore-stale-while-revalidate= not yet ported from 2.7

  max-stale= not yet ported from 2.7

  negative-ttl= not yet ported from 2.7

refresh_stale_hit

  Not yet ported from 2.7

storeurl_access

  Not yet ported from 2.7

storeurl_rewrite_children

  Not yet ported from 2.7

storeurl_rewrite_concurrency

  Not yet ported from 2.7

storeurl_rewrite_program

  Not yet ported from 2.7

update_headers

  Not yet ported from 2.7

zero_buffers

  Not yet ported from 2.7

## 6.2 Missing ./configure options available in Squid-2.7

--without-system-md5