Enforces the use of the NetScaler Client IP insertion protocol over any
connection accepted by any of the TCP sockets declared on the same line. The
NetScaler Client IP insertion protocol dictates the layer 3/4 addresses of
the incoming connection to be used everywhere an address is used, with the
only exception of "" rules which will only see the
real connection address. Logs will reflect the addresses indicated in the
protocol, unless it is violated, in which case the real  address will still
be used. This keyword combined with support from external components can be
used as an efficient and reliable alternative to the X-Forwarded-For
mechanism which is not always reliable and not even always usable. See also
"tcp-request connection expect-netscaler-cip" for a finer-grained setting of
which client is allowed to use the protocol.

accept-proxy

Enforces the use of the PROXY protocol over any connection accepted by any of
the sockets declared on the same line. Versions 1 and 2 of the PROXY protocol
are supported and correctly detected. The PROXY protocol dictates the layer
3/4 addresses of the incoming connection to be used everywhere an address is
used, with the only exception of "" rules which will
only see the real connection address. Logs will reflect the addresses
indicated in the protocol, unless it is violated, in which case the real
address will still be used. This keyword combined with support from external
components can be used as an efficient and reliable alternative to the
X-Forwarded-For mechanism which is not always reliable and not even always
usable. See also "tcp-request connection expect-proxy" for a finer-grained
setting of which client is allowed to use the protocol.

allow-0rtt

Allow receiving early data when using TLSv1.3. This is disabled by default,
due to security considerations. Because it is vulnerable to replay attacks,
you should only allow if for requests that are safe to replay, i.e. requests
that are idempotent. You can use the "wait-for-handshake" action for any
request that wouldn't be safe with early data.

This enables the TLS ALPN extension and advertises the specified protocol
list as supported on top of ALPN. The protocol list consists in a comma-
delimited list of protocol names, for instance: "http/1.1,http/1.0" (without
quotes). This requires that the SSL library is built with support for TLS
extensions enabled (check with haproxy -vv). The ALPN extension replaces the
initial NPN extension. ALPN is required to enable HTTP/2 on an HTTP frontend.
Versions of OpenSSL prior to 1.0.2 didn't support ALPN and only supposed the
now obsolete NPN extension. At the time of writing this, most browsers still
support both ALPN and NPN for HTTP/2 so a fallback to NPN may still work for
a while. But ALPN must be used whenever possible. If both HTTP/2 and HTTP/1.1
are expected to be supported, both versions can be advertised, in order of
preference, like below :
 
     bind :443 ssl crt pub.pem alpn h2,http/1.1

backlog

Sets the socket's backlog to this value. If unspecified or 0, the frontend's
backlog is used instead, which generally defaults to the maxconn value.

This setting is only available when support for OpenSSL was built in. It sets
the string describing the list of elliptic curves algorithms ("curve suite")
that are negotiated during the SSL/TLS handshake with ECDHE. The format of the
string is a colon-delimited list of curve name.

Example:

"X25519:P-256" (without quote)

ecdhe

This setting is only available when support for OpenSSL was built in. It sets
the named curve (RFC 4492) used to generate ECDH ephemeral keys. By default,
used named curve is prime256v1.

This setting is only available when support for OpenSSL was built in. It
designates a PEM file from which to load CA certificates used to verify
client's certificate.

ca-ignore-err [all|,…]

This setting is only available when support for OpenSSL was built in.
Sets a comma separated list of errorIDs to ignore during verify at depth > 0.
If set to 'all', all errors are ignored. SSL handshake is not aborted if an
error is ignored.

This setting is only available when support for OpenSSL was built in. It
designates a PEM file containing both the CA certificate and the CA private
key used to create and sign server's certificates. This is a mandatory
setting when the dynamic generation of certificates is enabled. See
'generate-certificates' for details.

ca-sign-pass

This setting is only available when support for OpenSSL was built in. It is
the CA private key passphrase. This setting is optional and used only when
the dynamic generation of certificates is enabled. See
'generate-certificates' for details.

This setting is only available when support for OpenSSL was built in. It sets
the string describing the list of cipher algorithms ("cipher suite") that are
negotiated during the SSL/TLS handshake up to TLSv1.2. The format of the
string is defined in "man 1 ciphers" from OpenSSL man pages. For background
information and recommendations see e.g.
(https://wiki.mozilla.org/Security/Server_Side_TLS) and
(https://mozilla.github.io/server-side-tls/ssl-config-generator/). For TLSv1.3
cipher configuration, please check the "ciphersuites
This keyword is available in sections :
Server and default-server options
" keyword.

This setting is only available when support for OpenSSL was built in and
OpenSSL 1.1.1 or later was used to build HAProxy. It sets the string describing
the list of cipher algorithms ("cipher suite") that are negotiated during the
TLSv1.3 handshake. The format of the string is defined in "man 1 ciphers" from
OpenSSL man pages under the "ciphersuites
This keyword is available in sections :
Server and default-server options
" section. For cipher configuration
for TLSv1.2 and earlier, please check the "
This keyword is available in sections :
Bind options
" keyword.

crl-file

This setting is only available when support for OpenSSL was built in. It
designates a PEM file from which to load certificate revocation list used
to verify client's certificate.

This setting is only available when support for OpenSSL was built in. It
designates a PEM file containing both the required certificates and any
associated private keys. This file can be built by concatenating multiple
PEM files into one (e.g. cat cert.pem key.pem > combined.pem). If your CA
requires an intermediate certificate, this can also be concatenated into this
file.
 
If the OpenSSL used supports Diffie-Hellman, parameters present in this file
are loaded.
 
If a directory name is used instead of a PEM file, then all files found in
that directory will be loaded in alphabetic order unless their name ends with
'.issuer', '.ocsp' or '.sctl' (reserved extensions). This directive may be
specified multiple times in order to load certificates from multiple files or
directories. The certificates will be presented to clients who provide a
valid TLS Server Name Indication field matching one of their CN or alt
subjects. Wildcards are supported, where a wildcard character '*' is used
instead of the first hostname component (e.g. *.example.org matches
www.example.org but not www.sub.example.org).
 
If no SNI is provided by the client or if the SSL library does not support
TLS extensions, or if the client provides an SNI hostname which does not
match any certificate, then the first loaded certificate will be presented.
This means that when loading certificates from a directory, it is highly
recommended to load the default one first as a file or to ensure that it will
always be the first one in the directory.
 
Note that the same cert may be loaded multiple times without side effects.
 
Some CAs (such as GoDaddy) offer a drop down list of server types that do not
include HAProxy when obtaining a certificate. If this happens be sure to
choose a web server that the CA believes requires an intermediate CA (for
GoDaddy, selection Apache Tomcat will get the correct bundle, but many
others, e.g. nginx, result in a wrong bundle that will not work for some
clients).
 
For each PEM file, haproxy checks for the presence of file at the same path
suffixed by ".ocsp". If such file is found, support for the TLS Certificate
Status Request extension (also known as "OCSP stapling") is automatically
enabled. The content of this file is optional. If not empty, it must contain
a valid OCSP Response in DER format. In order to be valid an OCSP Response
must comply with the following rules: it has to indicate a good status,
it has to be a single response for the certificate of the PEM file, and it
has to be valid at the moment of addition. If these rules are not respected
the OCSP Response is ignored and a warning is emitted. In order to  identify
which certificate an OCSP Response applies to, the issuer's certificate is
necessary. If the issuer's certificate is not found in the PEM file, it will
be loaded from a file at the same path as the PEM file suffixed by ".issuer"
if it exists otherwise it will fail with an error.
 
For each PEM file, haproxy also checks for the presence of file at the same
path suffixed by ".sctl". If such file is found, support for Certificate
Transparency (RFC6962) TLS extension is enabled. The file must contain a
valid Signed Certificate Timestamp List, as described in RFC. File is parsed
to check basic syntax, but no signatures are verified.
 
There are cases where it is desirable to support multiple key types, e.g. RSA
and ECDSA in the cipher suites offered to the clients. This allows clients
that support EC certificates to be able to use EC ciphers, while
simultaneously supporting older, RSA only clients.
 
In order to provide this functionality, multiple PEM files, each with a
different key type, are required. To associate these PEM files into a
"cert bundle" that is recognized by haproxy, they must be named in the
following way: All PEM files that are to be bundled must have the same base
name, with a suffix indicating the key type. Currently, three suffixes are
supported: rsa, dsa and ecdsa. For example, if www.example.com has two PEM
files, an RSA file and an ECDSA file, they must be named: "example.pem.rsa"
and "example.pem.ecdsa". The first part of the filename is arbitrary; only the
suffix matters. To load this bundle into haproxy, specify the base name only:

Example :

bind :8443 ssl crt example.pem

Note that the suffix is not given to haproxy; this tells haproxy to look for
a cert bundle.
 
HAProxy will load all PEM files in the bundle at the same time to try to
support multiple key types. PEM files are combined based on Common Name
(CN) and Subject Alternative Name (SAN) to support SNI lookups. This means
that even if you give haproxy a cert bundle, if there are no shared CN/SAN
entries in the certificates in that bundle, haproxy will not be able to
provide multi-cert support.
 
Assuming bundle in the example above contained the following:

Users connecting with an SNI of "www.example.com" will be able
to use both RSA and ECDSA cipher suites. Users connecting with an SNI of
"rsa.example.com" will only be able to use RSA cipher suites, and users
connecting with "ecdsa.example.com" will only be able to use ECDSA cipher
suites. With BoringSSL and Openssl >= 1.1.1 multi-cert is natively supported,
no need to bundle certificates. ECDSA certificate will be preferred if client
support it.
 
If a directory name is given as the <cert> argument, haproxy will
automatically search and load bundled files in that directory.
 
OSCP files (.ocsp) and issuer files (.issuer) are supported with multi-cert
bundling. Each certificate can have its own .ocsp and .issuer file. At this
time, sctl is not supported in multi-certificate bundling.

crt-ignore-err

This setting is only available when support for OpenSSL was built in. Sets a
comma separated list of errorIDs to ignore during verify at depth == 0. If
set to 'all', all errors are ignored. SSL handshake is not aborted if an error
is ignored.

This setting is only available when support for OpenSSL was built in. It
designates a list of PEM file with an optional ssl configuration and a SNI
filter per certificate, with the following format for each line :
 
      <crtfile> [\[<sslbindconf> ...\]] [[!]<snifilter> ...]
 
sslbindconf support "npn
This keyword is available in sections :
Server and default-server options
", "
This keyword is available in sections :
Bind options
", "verify
This keyword is available in sections :
Server and default-server options
", "
This keyword is available in sections :
Bind options
", "",
crl-file", "ecdhe", "", "ciphers
This keyword is available in sections :
Server and default-server options
" configuration. With BoringSSL
and Openssl >= 1.1.1 "
This keyword is available in sections :
Bind options
" and "ssl-max-ver
This keyword is available in sections :
Server and default-server options
" are also supported.
It override the configuration set in bind line for the certificate.
 
Wildcards are supported in the SNI filter. Negative filter are also supported,
only useful in combination with a wildcard filter to exclude a particular SNI.
The certificates will be presented to clients who provide a valid TLS Server
Name Indication field matching one of the SNI filters. If no SNI filter is
specified, the CN and alt subjects are used. This directive may be specified
multiple times. See the "
This keyword is available in sections :
Bind options
" option for more information. The default
certificate is still needed to meet OpenSSL expectations. If it is not used,
the 'strict-sni' option may be used.
 
Multi-cert bundling (see "crt
This keyword is available in sections :
Server and default-server options
") is supported with crt-list, as long as only
the base name is given in the crt-list. SNI filter will do the same work on
all bundled certificates. With BoringSSL and Openssl >= 1.1.1 multi-cert is
natively supported, avoid multi-cert bundling. RSA and ECDSA certificates can
be declared in a row, and set different ssl and filter parameter.
 
crt-list file example:
      cert1.pem
      cert2.pem [alpn h2,http/1.1]
      certW.pem                   *.domain.tld !secure.domain.tld
      certS.pem [curves X25519:P-256 ciphers ECDHE-ECDSA-AES256-GCM-SHA384] secure.domain.tld

expose-fd listeners

This option is only usable with the stats socket. It gives your stats socket
the capability to pass listeners FD to another HAProxy process.
During a reload with the master-worker mode, the process is automatically
reexecuted adding -x and one of the stats socket with this option.
See also "-x" in the management guide.

This option enforces use of SSLv3 only on SSL connections instantiated from
this listener. SSLv3 is generally less expensive than the TLS counterparts
for high connection rates. This option is also available on global statement
"". See also "ssl-min-ver
This keyword is available in sections :
Server and default-server options
" and "
This keyword is available in sections :
Bind options
".

force-tlsv10

This option enforces use of TLSv1.0 only on SSL connections instantiated from
this listener. This option is also available on global statement
"". See also "ssl-min-ver
This keyword is available in sections :
Server and default-server options
" and "
This keyword is available in sections :
Bind options
".

force-tlsv11

This option enforces use of TLSv1.1 only on SSL connections instantiated from
this listener. This option is also available on global statement
"". See also "ssl-min-ver
This keyword is available in sections :
Server and default-server options
" and "
This keyword is available in sections :
Bind options
".

force-tlsv12

This option enforces use of TLSv1.2 only on SSL connections instantiated from
this listener. This option is also available on global statement
"". See also "ssl-min-ver
This keyword is available in sections :
Server and default-server options
" and "
This keyword is available in sections :
Bind options
".

force-tlsv13

This option enforces use of TLSv1.3 only on SSL connections instantiated from
this listener. This option is also available on global statement
"". See also "ssl-min-ver
This keyword is available in sections :
Server and default-server options
" and "
This keyword is available in sections :
Bind options
".

generate-certificates

This setting is only available when support for OpenSSL was built in. It
enables the dynamic SSL certificates generation. A CA certificate and its
private key are necessary (see 'ca-sign-file'). When HAProxy is configured as
a transparent forward proxy, SSL requests generate errors because of a common
name mismatch on the certificate presented to the client. With this option
enabled, HAProxy will try to forge a certificate using the SNI hostname
indicated by the client. This is done only if no certificate matches the SNI
hostname (see 'crt-list'). If an error occurs, the default certificate is
used, else the 'strict-sni' option is set.
It can also be used when HAProxy is configured as a reverse proxy to ease the
deployment of an architecture with many backends.
 
Creating a SSL certificate is an expensive operation, so a LRU cache is used
to store forged certificates (see 'tune.ssl.ssl-ctx-cache-size'). It
increases the HAProxy's memory footprint to reduce latency when the same
certificate is used many times.

Sets the group of the UNIX sockets to the designated system gid. It can also
be set by default in the global section's "unix-bind" statement. Note that
some platforms simply ignore this. This setting is equivalent to the "
This keyword is available in sections :
Process management and security
Bind options
"
setting except that the group ID is used instead of its name. This setting is
ignored by non UNIX sockets.

Sets the group of the UNIX sockets to the designated system group. It can
also be set by default in the global section's "unix-bind" statement. Note
that some platforms simply ignore this. This setting is equivalent to the
"
This keyword is available in sections :
Process management and security
" setting except that the group name is used instead of its gid. This
setting is ignored by non UNIX sockets.

id

Fixes the socket ID. By default, socket IDs are automatically assigned, but
sometimes it is more convenient to fix them to ease monitoring. This value
must be strictly positive and unique within the listener/frontend. This
option can only be used when defining only a single socket.

Restricts the socket to a specific interface. When specified, only packets
received from that particular interface are processed by the socket. This is
currently only supported on Linux. The interface must be a primary system
interface, not an aliased interface. It is also possible to bind multiple
frontends to the same address if they are bound to different interfaces. Note
that binding to a network interface requires root privileges. This parameter
is only compatible with TCPv4/TCPv6 sockets. When specified, return traffic
uses the same interface as inbound traffic, and its associated routing table,
even if there are explicit routes through different interfaces configured.
This can prove useful to address asymmetric routing issues when the same
client IP addresses need to be able to reach frontends hosted on different
interfaces.

level

This setting is used with the stats sockets only to restrict the nature of
the commands that can be issued on the socket. It is ignored by other
sockets. <level> can be one of :
- "
This keyword is available in sections :
Process management and security
Bind options
" is the least privileged level; only non-sensitive stats can be
  read, and no change is allowed. It would make sense on systems where it
  is not easy to restrict access to the socket.
- "operator" is the default level and fits most common uses. All data can
  be read, and only non-sensitive changes are permitted (e.g. clear max
  counters).
- "admin" should be used with care, as everything is permitted (e.g. clear
  all counters).

This setting is used with the stats sockets only to configure severity
level output prepended to informational feedback messages. Severity
level of messages can range between 0 and 7, conforming to syslog
rfc5424. Valid and successful socket commands requesting data
(i.e. "show map", "get acl foo" etc.) will never have a severity level
prepended. It is ignored by other sockets. <format> can be one of :
- "none" (default) no severity level is prepended to feedback messages.
- "number" severity level is prepended as a number.
- "string" severity level is prepended as a string following the
  rfc5424 convention.

maxconn

Limits the sockets to this number of concurrent connections. Extraneous
connections will remain in the system's backlog until a connection is
released. If unspecified, the limit will be the same as the frontend's
maxconn. Note that in case of port ranges or multiple addresses, the same
value will be applied to each socket. This setting enables different
limitations on expensive sockets, for instance SSL entries which may easily
eat all memory.

Sets the octal mode used to define access permissions on the UNIX socket. It
can also be set by default in the global section's "unix-bind" statement.
Note that some platforms simply ignore this. This setting is ignored by non
UNIX sockets.

Sets the TCP Maximum Segment Size (MSS) value to be advertised on incoming
connections. This can be used to force a lower MSS for certain specific
ports, for instance for connections passing through a VPN. Note that this
relies on a kernel feature which is theoretically supported under Linux but
was buggy in all versions prior to 2.6.28. It may or may not work on other
operating systems. It may also not change the advertised value but change the
effective size of outgoing segments. The commonly advertised value for TCPv4
over Ethernet networks is 1460 = 1500(MTU) - 40(IP+TCP). If this value is
positive, it will be used as the advertised MSS. If it is negative, it will
indicate by how much to reduce the incoming connection's advertised MSS for
outgoing segments. This parameter is only compatible with TCP v4/v6 sockets.

name

Sets an optional name for these sockets, which will be reported on the stats
page.

On Linux, it is possible to specify which network namespace a socket will
belong to. This directive makes it possible to explicitly bind a listener to
a namespace different from the default one. Please refer to your operating
system's documentation to find more details about network namespaces.

nice

Sets the 'niceness' of connections initiated from the socket. Value must be
in the range -1024..1024 inclusive, and defaults to zero. Positive values
means that such connections are more friendly to others and easily offer
their place in the scheduler. On the opposite, negative values mean that
connections want to run with a higher priority than others. The difference
only happens under high loads when the system is close to saturation.
Negative values are appropriate for low-latency or administration services,
and high values are generally recommended for CPU intensive tasks such as SSL
processing or bulk transfers which are less sensible to latency. For example,
it may make sense to use a positive value for an SMTP socket and a negative
one for an RDP socket.

This setting is only available when support for OpenSSL was built in. It
prevents from send CA names in server hello message when ca-file is used.

no-sslv3

This setting is only available when support for OpenSSL was built in. It
disables support for SSLv3 on any sockets instantiated from the listener when
SSL is supported. Note that SSLv2 is forced disabled in the code and cannot
be enabled using any configuration option. This option is also available on
global statement "". Use "ssl-min-ver
This keyword is available in sections :
Server and default-server options
" and

This setting is only available when support for OpenSSL was built in. It
disables support for TLSv1.0 on any sockets instantiated from the listener
when SSL is supported. Note that SSLv2 is forced disabled in the code and
cannot be enabled using any configuration option. This option is also
available on global statement "ssl-default-bind-options". Use "
This keyword is available in sections :
Bind options
"
and "ssl-max-ver
This keyword is available in sections :
Server and default-server options
" instead.

This setting is only available when support for OpenSSL was built in. It
disables support for TLSv1.1 on any sockets instantiated from the listener
when SSL is supported. Note that SSLv2 is forced disabled in the code and
cannot be enabled using any configuration option. This option is also
available on global statement "ssl-default-bind-options". Use "
This keyword is available in sections :
Bind options
"
and "ssl-max-ver
This keyword is available in sections :
Server and default-server options
" instead.

This setting is only available when support for OpenSSL was built in. It
disables support for TLSv1.2 on any sockets instantiated from the listener
when SSL is supported. Note that SSLv2 is forced disabled in the code and
cannot be enabled using any configuration option. This option is also
available on global statement "ssl-default-bind-options". Use "
This keyword is available in sections :
Bind options
"
and "ssl-max-ver
This keyword is available in sections :
Server and default-server options
" instead.

This setting is only available when support for OpenSSL was built in. It
disables support for TLSv1.3 on any sockets instantiated from the listener
when SSL is supported. Note that SSLv2 is forced disabled in the code and
cannot be enabled using any configuration option. This option is also
available on global statement "ssl-default-bind-options". Use "
This keyword is available in sections :
Bind options
"
and "ssl-max-ver
This keyword is available in sections :
Server and default-server options
" instead.

This enables the NPN TLS extension and advertises the specified protocol list
as supported on top of NPN. The protocol list consists in a comma-delimited
list of protocol names, for instance: "http/1.1,http/1.0" (without quotes).
This requires that the SSL library is built with support for TLS extensions
enabled (check with haproxy -vv). Note that the NPN extension has been
replaced with the ALPN extension (see the "alpn
This keyword is available in sections :
Server and default-server options
" keyword), though this one is
only available starting with OpenSSL 1.0.2. If HTTP/2 is desired on an older
version of OpenSSL, NPN might still be used as most clients still support it
at the time of writing this. It is possible to enable both NPN and ALPN
though it probably doesn't make any sense out of testing.

Use the client's preference when selecting the cipher suite, by default
the server's preference is enforced. This option is also available on
global statement "ssl-default-bind-options".
Note that with OpenSSL >= 1.1.1 ChaCha20-Poly1305 is reprioritized anyway
(without setting this option), if a ChaCha20-Poly1305 cipher is at the top of
the client cipher list.

[/]

This restricts the list of processes or threads on which this listener is
allowed to run. It does not enforce any process but eliminates those which do
not match. If the frontend uses a "bind-process" setting, the intersection
between the two is applied. If in the end the listener is not allowed to run
on any remaining process, a warning is emitted, and the listener will either
run on the first process of the listener if a single process was specified,
or on all of its processes if multiple processes were specified. If a thread
set is specified, it limits the threads allowed to process incoming
connections for this listener, for the the process set. If multiple processes
and threads are configured, a warning is emitted, as it either results from a
configuration error or a misunderstanding of these models. For the unlikely
case where several ranges are needed, this directive may be repeated.
<process-set> and <thread-set> must use the format
 
    all | odd | even | number[-[number]]
 
Ranges can be partially defined. The higher bound can be omitted. In such
case, it is replaced by the corresponding maximum value. The main purpose of
this directive is to be used with the stats sockets and have one different
socket per process. The second purpose is to have multiple bind lines sharing
the same IP:port but not the same process in a listener, so that the system
can distribute the incoming connections into multiple queues and allow a
smoother inter-process load balancing. Currently Linux 3.9 and above is known
for supporting this. See also "" and "nbproc
This keyword is available in sections :
Fetching samples from internal states
".

Forces the multiplexer's protocol to use for the incoming connections. It
must be compatible with the mode of the frontend (TCP or HTTP). It must also
be usable on the frontend side. The list of available protocols is reported
in haproxy -vv.
Idea behind this optipon is to bypass the selection of the best multiplexer's
protocol for all connections instantiated from this listening socket. For
instance, it is possible to force the http/2 on clear TCP by specifying "proto
h2" on the bind line.

ssl

This setting is only available when support for OpenSSL was built in. It
enables SSL deciphering on connections instantiated from this listener. A
certificate is necessary (see "
This keyword is available in sections :
Bind options
" above). All contents in the buffers will
appear in clear text, so that ACLs and HTTP processing will only have access
to deciphered contents. SSLv3 is disabled per default, use "ssl-min-ver SSLv3"
to enable it.

ssl-max-ver [ SSLv3 | TLSv1.0 | TLSv1.1 | TLSv1.2 | TLSv1.3 ]

This option enforces use of <version> or lower on SSL connections instantiated
from this listener. This option is also available on global statement
"". See also "ssl-min-ver
This keyword is available in sections :
Server and default-server options
".

[ SSLv3 | TLSv1.0 | TLSv1.1 | TLSv1.2 | TLSv1.3 ]

This option enforces use of <version> or upper on SSL connections instantiated
from this listener. This option is also available on global statement
"ssl-default-bind-options". See also "
This keyword is available in sections :
Bind options
".

strict-sni

This setting is only available when support for OpenSSL was built in. The
SSL/TLS negotiation is allow only if the client provided an SNI which match
a certificate. The default certificate is not used.
See the "
This keyword is available in sections :
Bind options
" option for more information.

tcp-ut

Sets the TCP User Timeout for all incoming connections instantiated from this
listening socket. This option is available on Linux since version 2.6.37. It
allows haproxy to configure a timeout for sockets which contain data not
receiving an acknowledgment for the configured delay. This is especially
useful on long-lived connections experiencing long idle periods such as
remote terminals or database connection pools, where the client and server
timeouts must remain high to allow a long period of idle, but where it is
important to detect that the client has disappeared in order to release all
resources associated with its connection (and the server's session). The
argument is a delay expressed in milliseconds by default. This only works
for regular TCP connections, and is ignored for other protocols.

Is an optional keyword which is supported only on Linux kernels >= 3.7. It
enables TCP Fast Open on the listening socket, which means that clients which
support this feature will be able to send a request and receive a response
during the 3-way handshake starting from second connection, thus saving one
round-trip after the first connection. This only makes sense with protocols
that use high connection rates and where each round trip matters. This can
possibly cause issues with many firewalls which do not accept data on SYN
packets, so this option should only be enabled once well tested. This option
is only supported on TCPv4/TCPv6 sockets and ignored by other ones. You may
need to build HAProxy with USE_TFO=1 if your libc doesn't define
TCP_FASTOPEN.

tls-ticket-keys

Sets the TLS ticket keys file to load the keys from. The keys need to be 48
or 80 bytes long, depending if aes128 or aes256 is used, encoded with base64
with one line per key (ex. openssl rand 80 | openssl base64 -A | xargs echo).
The first key determines the key length used for next keys: you can't mix
aes128 and aes256 keys. Number of keys is specified by the TLS_TICKETS_NO
build option (default 3) and at least as many keys need to be present in
the file. Last TLS_TICKETS_NO keys will be used for decryption and the
penultimate one for encryption. This enables easy key rotation by just
appending new key to the file and reloading the process.  Keys must be
periodically rotated (ex. every 12h) or Perfect Forward Secrecy is
compromised. It is also a good idea to keep the keys off any permanent
storage such as hard drives (hint: use tmpfs and don't swap those files).
Lifetime hint can be changed using tune.ssl.timeout.

Is an optional keyword which is supported only on certain Linux kernels. It
indicates that the addresses will be bound even if they do not belong to the
local machine, and that packets targeting any of these addresses will be
intercepted just as if the addresses were locally configured. This normally
requires that IP forwarding is enabled. Caution! do not use this with the
default address '*', as it would redirect any traffic for the specified port.
This keyword is available only when HAProxy is built with USE_LINUX_TPROXY=1.
This parameter is only compatible with TCPv4 and TCPv6 sockets, depending on
kernel version. Some distribution kernels include backports of the feature,
so check for support with your vendor.

v4v6

Is an optional keyword which is supported only on most recent systems
including Linux kernels >= 2.4.21. It is used to bind a socket to both IPv4
and IPv6 when it uses the default address. Doing so is sometimes necessary
on systems which bind to IPv6 only by default. It has no effect on non-IPv6
sockets, and is overridden by the "" option.

v6only

Is an optional keyword which is supported only on most recent systems
including Linux kernels >= 2.4.21. It is used to bind a socket to IPv6 only
when it uses the default address. Doing so is sometimes preferred to doing it
system-wide as it is per-listener. It has no effect on non-IPv6 sockets and
has precedence over the "" option.

uid

Sets the owner of the UNIX sockets to the designated system uid. It can also
be set by default in the global section's "" statement. Note that
some platforms simply ignore this. This setting is equivalent to the "user
This keyword is available in sections :
Userlists
"
setting except that the user numeric ID is used instead of its name. This
setting is ignored by non UNIX sockets.

user

Sets the owner of the UNIX sockets to the designated system user. It can also
be set by default in the global section's "" statement. Note that
some platforms simply ignore this. This setting is equivalent to the "uid
This keyword is available in sections :
Bind options
"
setting except that the user name is used instead of its uid. This setting is
ignored by non UNIX sockets.

[none|optional|required]

This setting is only available when support for OpenSSL was built in. If set
to 'none', client certificate is not requested. This is the default. In other
cases, a client certificate is requested. If the client does not provide a
certificate after the request and if 'verify' is set to 'required', then the
handshake is aborted, while it would have succeeded if set to 'optional'. The
certificate provided by the client is always verified using CAs from
'ca-file' and optional CRLs from 'crl-file'. On verify failure the handshake
is aborted, regardless of the 'verify' option, unless the error code exactly