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RELAYD.CONF(5) File Formats Manual RELAYD.CONF(5)

relayd.conf
relay daemon configuration file

TABLE OF CONTENTS

relayd.conf is the configuration file for the relay daemon, relayd(8).

relayd.conf is divided into seven main sections:
Macros
User-defined variables may be defined and used later, simplifying the configuration file.
Global Configuration
Global settings for relayd(8). Do note that the config file allows global settings to be added after defining tables in the config file, but those tables will use the built-in defaults instead of the global settings below them.
Tables
Table definitions describe a list of hosts, in a similar fashion to pf(4) tables. They are used for relay, redirection, and router target selection with the described options and health checking on the host they contain.
Redirections
Redirections are translated to pf(4) rdr-to rules for stateful forwarding to a target host from a health-checked table on layer 3.
Relays
Relays allow application layer load balancing, SSL acceleration, and general purpose TCP proxying on layer 7.
Protocols
Protocols are predefined protocol handlers and settings for relays.
Routers
Routers are used to insert routes with health-checked gateways for (WAN) link balancing.

Within the sections, a host address can be specified by IPv4 address, IPv6 address, interface name, interface group, or DNS hostname. If the address is an interface name, relayd(8) will look up the first IPv4 address and any other IPv4 and IPv6 addresses of the specified network interface. A port can be specified by number or name. The port name to number mappings are found in the file /etc/services; see services(5) for details.

The current line can be extended over multiple lines using a backslash (‘\’). Comments can be put anywhere in the file using a hash mark (‘#’), and extend to the end of the current line. Care should be taken when commenting out multi-line text: the comment is effective until the end of the entire block.

Additional configuration files can be included with the include keyword, for example:

include "/etc/relayd.conf.local"

Macros can be defined that will later be expanded in context. Macro names must start with a letter, and may contain letters, digits, and underscores. Macro names may not be reserved words (for example, table, relay, or timeout). Macros are not expanded inside quotes.

For example:

www1="10.0.0.1"
www2="10.0.0.2"
table <webhosts> {
	$www1
	$www2
}

Here are the settings that can be set globally:
number
Set the interval in seconds at which the hosts will be checked. The default interval is 10 seconds.
(updates|all)
Log state notifications after completed host checks. Either only log the updates to new states or log all state notifications, even if the state didn't change. The host state can be up (the health check completed successfully), down (the host is down or didn't match the check criteria), or unknown (the host is disabled or has not been checked yet).
number
When using relays, run the specified number of processes to handle relayed connections. This increases the performance and prevents delays when connecting to a relay. relayd(8) runs 5 relay processes by default and every process will handle all configured relays.
Send an SNMP trap when the state of a host changes. relayd(8) will try to connect to snmpd(8) and request it send a trap to the registered trap receivers; see snmpd.conf(5) for more information about the configuration.
number
Set the global timeout in milliseconds for checks. This can be overridden by the timeout value in the table definitions. The default interval is 200 milliseconds and it must not exceed the global interval. Please note that the default value is optimized for checks within the same collision domain – use a higher timeout, such as 1000 milliseconds, for checks of hosts in other subnets. If this option is to be set, it should be placed before overrides in tables.

Tables are used to group a set of hosts as the target for redirections or relays; they will be mapped to a pf(4) table for redirections. Tables may be defined with the following attribute:
Start the table disabled – no hosts will be checked in this table. The table can be later enabled through relayctl(8).

Each table must contain at least one host address; multiple hosts are separated by newline, comma, or whitespace. Host entries may be defined with the following attributes:

number
Change the default time-to-live value in the IP headers for host checks.
number
The optional parent option inherits the state from a parent host with the specified identifier. The check will be skipped for this host and copied from the parent host. This can be used to prevent multiple checks on hosts with multiple IP addresses for the same service. The host identifiers are sequentially assigned to the configured hosts starting with 1; it can be shown with the relayctl(8) show summary commands.
number
Change the route priority used when adding a route. If not specified, the kernel will set a priority of 8 (RTP_STATIC). In ordinary use, a fallback route should be added statically with a very high (e.g. 52) priority. Unused in all other modes.
number
The optional retry option adds a tolerance for failed host checks; the check will be retried for number more times before setting the host state to down. If this table is used by a relay, it will also specify the number of retries for outgoing connection attempts.

For example:

table <service> { 192.168.1.1, 192.168.1.2, 192.168.2.3 }
table <fallback> disable { 10.1.5.1 retry 2 }

redirect "www" {
	listen on www.example.com port 80
	forward to <service> check http "/" code 200
	forward to <fallback> check http "/" code 200
}

Tables are used by forward to directives in redirections or relays with a set of general options, health-checking rules, and timings; see the REDIRECTIONS and RELAYS sections for more information about the forward context. Table specific configuration directives are described below. Multiple options can be appended to forward to directives, separated by whitespaces.

The following options will configure the health-checking method for the table, and is mandatory for redirections:

path [host hostname] code number
For each host in the table, verify that retrieving the URL path gives the HTTP return code number. If hostname is specified, it is used as the “Host:” header to query a specific hostname at the target host. To validate the HTTP return code, use this shell command:
$ echo -n "HEAD <path> HTTP/1.0\r\n\r\n" | \
	nc <host> <port> | head -n1
    

This prints the status header including the actual return code:

HTTP/1.1 200 OK
    
path [host hostname] code number
This has the same effect as above but wraps the HTTP request in SSL.
path [host hostname] digest string
For each host in the table, verify that retrieving the URL path produces non-binary content whose message digest matches the defined string. The algorithm used is determined by the string length of the digest argument, either SHA1 (40 characters) or MD5 (32 characters). If hostname is specified, it is used as the “Host:” header to query a specific hostname at the target host. The digest does not take the HTTP headers into account. Do not specify a binary object (such as a graphic) as the target of the request, as relayd.conf expects the data returned to be a string. To compute the digest, use this simple command:
$ ftp -o - http://host[:port]/path | sha1
    

This gives a digest that can be used as-is in a digest statement:

a9993e36476816aba3e25717850c26c9cd0d89d
    
path [host hostname] digest string
This has the same effect as above but wraps the HTTP request in SSL.
Ping hosts in this table to determine whether they are up or not. This method will automatically use ICMP or ICMPV6 depending on the address family of each host.
path
Execute an external program to check the host state. The program will be executed for each host by specifying the hostname on the command line:
/usr/local/bin/checkload.pl front-www1.private.example.com
    

relayd(8) expects a positive return value on success and zero on failure. Note that the script will be executed with the privileges of the “_relayd” user and terminated after timeout milliseconds.

data expect pattern [ssl]
For each host in the table, a TCP connection is established on the port specified, then data is sent. Incoming data is then read and is expected to match against pattern using shell globbing rules. If data is an empty string or nothing then nothing is sent on the connection and data is immediately read. This can be useful with protocols that output a banner like SMTP, NNTP, and FTP. If the ssl keyword is present, the transaction will occur in an SSL tunnel.
Perform a complete SSL handshake with each host to check their availability.
Use a simple TCP connect to check that hosts are up.

The following general table options are available:

group
Enable the per-table carp(4) demotion option. This will increment the carp demotion counter for the specified interface group if all hosts in the table are down. For more information on interface groups, see the group keyword in ifconfig(8).
number
Override the global interval and specify one for this table. It must be a multiple of the global interval.
number
Set the timeout in milliseconds for each host that is checked using TCP as the transport. This will override the global timeout, which is 200 milliseconds by default.

The following options will set the scheduling algorithm to select a host from the specified table:

Balances the outgoing connections across the active hosts based on the hashed name of the table. Additional input can be fed into the hash by looking at HTTP headers and GET variables; see the PROTOCOLS section below. This mode is only supported by relays.
Balances the outgoing connections across the active hosts based on the hashed name of the table, the source and destination addresses, and the corresponding ports. This mode is only supported by relays.
Distributes the outgoing connections using a round-robin scheduler through all active hosts. This is the default mode and will be used if no option has been specified. This mode is supported by redirections and relays.

Redirections represent a pf(4) rdr-to rule. They are used for stateful redirections to the hosts in the specified tables. pf(4) rewrites the target IP addresses and ports of the incoming connections, operating on layer 3. The configuration directives that are valid in the redirect context are described below:
The redirection is initially disabled. It can be later enabled through relayctl(8).
table⟩ [port number] options ...
Specify the tables of target hosts to be used; see the TABLES section above for information about table options. If the port option is not specified, the first port from the listen on directive will be used. This directive can be specified twice – the second entry will be used as the backup table if all hosts in the main table are down. At least one entry for the main table is mandatory.
address [ip-proto] port port [interface name]
Specify an address and a port to listen on. pf(4) will redirect incoming connections for the specified target to the hosts in the main or backup table. The port argument can optionally specify a port range instead of a single port; the format is min-port:max-port. The optional argument ip-proto can be used to specify an IP protocol like tcp or udp; it defaults to tcp. The rule can be optionally restricted to a given interface name.
table⟩ [port number] options ...
Like the forward to directive, but directly routes the packets to the target host without modifying the target address using a pf(4) route-to rule. This can be used for “direct server return” to force the target host to respond via a different gateway. Note that hosts have to accept sessions for the same address as the gateway, which is typically done by configuring a loopback interface on the host with this address.
seconds
Specify the inactivity timeout in seconds for established redirections. The default timeout is 600 seconds (10 minutes).
This has the same effect as specifying sticky-address for an rdr-to rule in pf.conf(5). It will ensure that multiple connections from the same source are mapped to the same redirection address.
[match] tag name
Automatically tag packets passing through the pf(4) rdr-to rule with the name supplied. This allows simpler filter rules. The optional match keyword will change the default rule action from pass in quick to match in to allow further evaluation in the pf ruleset using the tagged name rule option.

Relays will forward traffic between a client and a target server. In contrast to redirections and IP forwarding in the network stack, a relay will accept incoming connections from remote clients as a server, open an outgoing connection to a target host, and forward any traffic between the target host and the remote client, operating on layer 7. A relay is also called an application layer gateway or layer 7 proxy.

The main purpose of a relay is to provide advanced load balancing functionality based on specified protocol characteristics, such as HTTP headers, to provide SSL acceleration and to allow basic handling of the underlying application protocol.

The relay configuration directives are described below:

Start the relay but immediately close any accepted connections.
[transparent] forward [with ssl] to address [port port] options ...
Specify the address and port of the target host to connect to. If the port option is not specified, the port from the listen on directive will be used. Use the transparent keyword to enable fully-transparent mode; the source address of the client will be retained in this case.

The with ssl directive enables client-side SSL mode to connect to the remote host. Verification of server certificates can be enabled by setting the ca file option in the protocol section.

The following options may be specified for forward directives:

number
The optional host retry option will be used as a tolerance for failed host connections; the connection will be retried for number more times.
If the requested destination is an IPv6 address, relayd(8) will forward the connection to an IPv4 address which is determined by the last 4 octets of the original IPv6 destination. For example, if the original IPv6 destination address is 2001:db8:7395:ffff::a01:101, the session is relayed to the IPv4 address 10.1.1.1 (a01:101).
address-prefix
If the requested destination is an IPv4 address, relayd(8) will forward the connection to an IPv6 address which is determined by setting the last 4 octets of the specified IPv6 address-prefix to the 4 octets of the original IPv4 destination. For example, if the original IPv4 destination address is 10.1.1.1 and the specified address prefix is 2001:db8:7395:ffff::, the session is relayed to the IPv6 address 2001:db8:7395:ffff::a01:101.
table⟩ [port port] options ...
Like the previous directive, but connect to a host from the specified table; see the TABLES section above for information about table options. This directive can be specified twice – the second entry will be used as the backup table if all hosts in the main table are down. At least one entry for the main table is mandatory.
destination options ...
When redirecting connections with a divert-to rule in pf.conf(5) to a relay listening on localhost, this directive will look up the real destination address of the intended target host, allowing the relay to be run as a transparent proxy. If an additional forward to directive to a specified address or table is present, it will be used as a backup if the lookup failed.
nat lookup options ...
Like the previous directive, but for redirections with rdr-to in pf.conf(5).
address [port port] [ssl]
Specify the address and port for the relay to listen on. The relay will accept incoming connections to the specified address. If the port option is not specified, the port from the listen on directive will be used.

If the ssl keyword is present, the relay will accept connections using the encrypted SSL protocol. The relay will look up a private key in /etc/ssl/private/address.key and a public certificate in /etc/ssl/address.crt, where address is the specified IP address of the relay to listen on. See ssl(8) for details about SSL server certificates.

name
Use the specified protocol definition for the relay. The generic TCP protocol options will be used by default; see the PROTOCOLS section below.
seconds
Specify the inactivity timeout in seconds for accepted sessions. The default timeout is 600 seconds (10 minutes).

Protocols are templates defining actions and settings for relays. They allow setting generic TCP options, SSL settings, and actions specific to the selected application layer protocol.

The protocol directive is available for a number of different application layer protocols. There is no generic handler for UDP-based protocols because it is a stateless datagram-based protocol which has to look into the application layer protocol to find any possible state information.

(UDP) Domain Name System (DNS) protocol. The requested IDs in the DNS header will be used to match the state. relayd(8) replaces these IDs with random values to compensate for predictable values generated by some hosts.
Handle the HyperText Transfer Protocol (HTTP, or "HTTPS" if encapsulated in an SSL tunnel).
[tcp] protocol
Generic handler for TCP-based protocols. This is the default.

The available configuration directives are described below:

[direction] [type] action [marked id] [log]
Define an action for the selected entity. The optional log keyword will log the entity name and the value and the optional marked keyword requires that the session has been marked with a given identifier in order to execute the action. The actions are dependent on the underlying application protocol.

[direction] may be one of:

Handle the data stream from the client to the relay, like HTTP requests. This is the default if the direction directive is omitted.
Handle the data stream from the target host to the relay, like HTTP server replies.

[type] may be one of:

Look up the entity as a value in the Cookie header when using the http protocol. This type is only available with the direction request.
Look up the entity in the application protocol headers, like HTTP headers in http mode.
Look up the entity as a value in the URL path when using the http protocol. This type is only available with the direction request. The key will match the path of the requested URL without the hostname and query and the value will match the complete query, for example:
request path filter "/index.html"
request path filter "foo=bar*" from "/cgi-bin/t.cgi"
    
Look up the entity as a query variable in the URL when using the http protocol. This type is only available with the direction request, for example:
# Will match /cgi-bin/example.pl?foo=bar&ok=yes
request query expect "bar" from "foo"
    
Look up the entity as a URL suffix/prefix expression consisting of a canonicalized hostname without port or suffix and a path name or prefix when using the http protocol. This type is only available with the direction request, for example:
request url filter "example.com/index.html"
request url filter "example.com/test.cgi?val=1"
    

relayd(8) will match the full URL and different possible suffix/prefix combinations by stripping subdomains and path components (up to 5 levels), and the query string. For example, the following lookups will be done for http://www.example.com:81/1/2/3/4/5.html?query=yes:

www.example.com/1/2/3/4/5.html?query=yes
www.example.com/1/2/3/4/5.html
www.example.com/
www.example.com/1/
www.example.com/1/2/
www.example.com/1/2/3/
example.com/1/2/3/4/5.html?query=yes
example.com/1/2/3/4/5.html
example.com/
example.com/1/
example.com/1/2/
example.com/1/2/3/
    

[action] may be one of:

value to key
Append the specified value to a protocol entity with the selected name. When using the http protocol, key will indicate a specified HTTP header. If key does not exist in the request, it will be created with the value set to value.

The value string may contain predefined macros that will be expanded at runtime:

The IP address of the connected client.
The TCP source port of the connected client.
The configured IP address of the relay.
The configured TCP server port of the relay.
The server software name of relayd(8).
The configured session timeout of the relay.
key to value
Like the append directive above, but change the contents of the specified entity. If key does not exist in the request, it will be created with the value set to value.

The value string may contain predefined macros that will be expanded at runtime, as detailed for the append directive above.

value from key
Expect an entity key and match against value using shell globbing rules. If the entity is not present or the value doesn't match, the connection will be dropped.
[digest] key
Expect an entity key with any possible value. This is the short form of expect * from key.

If the digest keyword is specified, compare the message digest of the entity against the defined string. The algorithm used is determined by the string length of the key argument, either SHA1 (40 characters) or MD5 (32 characters). To compute the digest, use this simple command:

$ echo -n "example.com/path/?args" | sha1
    
path
Like the directive above, but load the non-digest keys from an external file with the specified path containing one key per line. Lines will be stripped at the first whitespace or newline character. Any empty lines or lines beginning with a hash mark (‘#’) will be ignored.
value from key
Like the expect .. from directive above, but drop any connections with the specified entity key and a matching value.
[digest] key
Like the expect directive above, but drop any connections with the specified entity key and any possible value. This is the short form of filter * from key.
path
Like the directive above, but load the non-digest keys from path. See expect file path for more information.
key
Feed the value of the selected entity into the load balancing hash to select the target host. See the table keyword in the RELAYS section above.
key
Log the name and the value of the entity.
path
Like the directive above, but load the keys from path. See expect file path for more information.
[value from] key with id
Mark the session with the specified identifier (a positive number between 1 and 65535) if the specified condition matches. Note that the mark action does not accept the marked option (see above).
string
Add a label to subsequently added actions. The label will be printed as part of the error message if the return error option is set and may contain HTML tags, for example:
label "<a href='http://example.com/advisory.pl?id=7359'>\
	Advisory provided by example.com</a>"
url filter digest 5c1e03f58f8ce0b457474ffb371fd1ef
url filter digest 80c1a7b8337462093ef8359c57b4d56a
no label
    
Do not set a label for subsequently added actions; this is the default.
key
Remove the entity with the selected name.
path
Like the directive above, but load the keys from path. See expect file path for more information.
[option]
Return an error response to the client if an internal operation or the forward connection to the client failed. By default, the connection will be silently dropped. The effect of this option depends on the protocol: HTTP will send an error header and page to the client before closing the connection. Additional valid options are:
string
Specify a Cascading Style Sheet (CSS) to be used for the returned HTTP error pages, for example:
body { background: #a00000; color: white; }
        
option
Set the SSL options and session settings. This is only used if SSL is enabled in the relay. Valid options are:
path
This option enables CA verification in SSL client mode. The daemon will load the CA (Certificate Authority) certificates from the specified path to verify the server certificates. OpenBSD provides a default CA bundle in /etc/ssl/cert.pem.
string
Set the string defining the SSL cipher suite. If not specified, the default value HIGH:!ADH will be used (strong crypto cipher suites without anonymous DH). See the CIPHERS section of openssl(1) for information about SSL cipher suites and preference lists.
value
Set the maximum size of the SSL session cache. If the value is zero, the default size defined by the SSL library will be used. A positive number will set the maximum size in bytes and the keyword disable will disable the SSL session cache.
[no] sslv2
Enable the SSLv2 protocol; disabled by default.
[no] sslv3
Disable the SSLv3 protocol; enabled by default.
[no] tlsv1
Disable the TLSv1/SSLv3.1 protocol; enabled by default.
option
Enable or disable the specified TCP/IP options; see tcp(4) and ip(4) for more information about the options. Valid options are:
number
Set the maximum length the queue of pending connections may grow to. The backlog option is 10 by default and is limited by the kern.somaxconn sysctl(8) variable.
number
This option for the underlying IP connection may be used to discard packets with a TTL lower than the specified value. This can be used to implement the Generalized TTL Security Mechanism (GTSM) according to RFC 3682.
number
Change the default time-to-live value in the IP headers.
[no] nodelay
Enable the TCP NODELAY option for this connection. This is recommended to avoid delays in the relayed data stream, e.g. for SSH connections.
[no] sack
Use selective acknowledgements for this connection.
number
Set the socket-level buffer size for input and output for this connection. This will affect the TCP window size.
[no] splice
Use socket splicing for zero-copy data transfer. This option is enabled by default.

Routers represent routing table entries in the kernel forwarding database, see route(4), and a table of associated gateways. They are used to dynamically insert or remove routes with gateways based on their availability and health-check results. A router can include multiple network statements and a single forward statement with a table of one or more gateways. All entries in a single router directive must match the same address family, either IPv4 or IPv6.

The kernel supports multipath routing when multiple gateways exist to the same destination address. The multipath routing behaviour can be changed globally using the sysctl(8) variables net.inet.ip.multipath and net.inet6.ip6.multipath. With the default setting of 0, the first route selected will be used for subsequent packets to that destination regardless of source. Setting it to 1 will enable load balancing based on the packet source address across gateways; multiple routes with the same priority are used equally. The kernel will also check the link state of the related network interface and try a different route if it is not active.

The configuration directives that are valid in the routers context are described below:

tableport number options ...
Specify the table of target gateways to be used; see the TABLES section above for information about table options. This entry is mandatory and must be specified once.
address/prefix
Specify the network address and prefix length of a route destination that is reachable via the active gateways. This entry must be specified at least once in a router directive.
id
Add the routes to the kernel routing table with the specified id.
label
Add the routes with the specified label to the kernel routing table.

/etc/relayd.conf
relayd(8) configuration file.

/etc/services
Service name database.

/etc/ssl/address.crt
 
/etc/ssl/private/address.key
Location of the relay SSL server certificates, where address is the configured IP address of the relay.
/etc/ssl/cert.pem
Default location of the CA bundle that can be used with relayd(8).

This configuration file would create a redirection service “www” which load balances four hosts and falls back to one host containing a “sorry page”:
www1=front-www1.private.example.com
www2=front-www2.private.example.com
www3=front-www3.private.example.com
www4=front-www4.private.example.com

interval 5

table <phphosts> { $www1, $www2, $www3, $www4 }
table <sorryhost> disable { sorryhost.private.example.com }

redirect "www" {
	listen on www.example.com port 8080 interface trunk0
	listen on www6.example.com port 80 interface trunk0

	tag REDIRECTED

	forward to <phphosts> port 8080 timeout 300 \
		check http "/" digest "630aa3c2f..."
	forward to <sorryhost> port 8080 timeout 300 check icmp
}

It is possible to specify multiple listen directives with different IP protocols in a single redirection configuration:

redirect "dns" {
	listen on dns.example.com tcp port 53
	listen on dns.example.com udp port 53

	forward to <dnshosts> port 53 check tcp
}

The following configuration would add a relay to forward secure HTTPS connections to a pool of HTTP webservers using the loadbalance mode (SSL acceleration and layer 7 load balancing). The HTTP protocol definition will add two HTTP headers containing address information of the client and the server, set the “Keep-Alive” header value to the configured session timeout, and include the “sessid” variable in the hash to calculate the target host:

http protocol "http_ssl" {
	header append "$REMOTE_ADDR" to "X-Forwarded-For"
	header append "$SERVER_ADDR:$SERVER_PORT" to "X-Forwarded-By"
	header change "Keep-Alive" to "$TIMEOUT"
	query hash "sessid"
	cookie hash "sessid"
	path filter "*command=*" from "/cgi-bin/index.cgi"

	ssl { sslv2, ciphers "MEDIUM:HIGH" }
}

relay "sslaccel" {
	listen on www.example.com port 443 ssl
	protocol "http_ssl"
	forward to <phphosts> port 8080 mode loadbalance check tcp
}

The second relay example will accept incoming connections to port 2222 and forward them to a remote SSH server. The TCP nodelay option will allow a “smooth” SSH session without delays between keystrokes or displayed output on the terminal:

protocol "myssh" {
        tcp { nodelay, socket buffer 65536 }
}

relay "sshforward" {
        listen on www.example.com port 2222
	protocol "myssh"
	forward to shell.example.com port 22
}

The next simple router configuration example can be used to run redundant, health-checked WAN links:

table <gateways> { $gw1 ip ttl 1, $gw2 ip ttl 1 }
router "uplinks" {
	route 0.0.0.0/0
	forward to <gateways> check icmp
}

relayctl(8), relayd(8), snmpd(8), ssl(8)

The relayd.conf file format, formerly known as hoststated.conf, first appeared in OpenBSD 4.1. It was renamed to relayd.conf in OpenBSD 4.3.

The relayd(8) program was written by Pierre-Yves Ritschard ⟨pyr@openbsd.org⟩ and Reyk Floeter ⟨reyk@openbsd.org⟩.

relayd(8) Verification of SSL server certificates is based on a static CA bundle and relayd(8) currently does not support CRLs (Certificate Revocation Lists).
January 20, 2012 OpenBSD-5.1