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COREDNS-VIEW(7)			CoreDNS	Plugins		       COREDNS-VIEW(7)

NAME
       view  -	defines	 conditions  that  must	be met for a DNS request to be
       routed to the server block.

DESCRIPTION
       view defines an expression that must evaluate to	true for a DNS request
       to be routed to the server block.  This enables advanced	 server	 block
       routing functions such as split dns.

SYNTAX
	      view NAME	{
		expr EXPRESSION
	      }

       •   view	 NAME  -  The name of the view used by metrics and exported as
	   metadata for	requests that match the	view's expression

       •   expr	EXPRESSION - CoreDNS will only route incoming queries  to  the
	   enclosing server block if the EXPRESSION evaluates to true. See the
	   Expressions section for available variables and functions.  If mul-
	   tiple  instances  of	view are defined, all EXPRESSION must evaluate
	   to true for CoreDNS will only route incoming	queries	to the enclos-
	   ing server block.

       For expression syntax and examples, see the  Expressions	 and  Examples
       sections.

EXAMPLES
       Implement  CIDR	based split DNS	routing.  This will return a different
       answer for test.	depending on client's IP address.  It returns  ...   *
       test.  3600  IN	A  1.1.1.1,  for  queries  with	 a  source  address in
       127.0.0.0/24 * test. 3600 IN A 2.2.2.2, for queries with	a  source  ad-
       dress  in 192.168.0.0/16	* test.	3600 IN	AAAA 2001:0DB8::1, for queries
       with a source address in	2001:0DB8::/32 * test. 3600 IN A 3.3.3.3,  for
       all others

	      .	{
		view example1 {
		  expr incidr(client_ip(), '127.0.0.0/24')
		}
		hosts {
		  1.1.1.1 test
		}
	      }

	      .	{
		view example2 {
		  expr incidr(client_ip(), '192.168.0.0/16')
		}
		hosts {
		  2.2.2.2 test
		}
	      }

	      .	{
		view v6_example1 {
		  expr incidr(client_ip(), '2001:0DB8::/32')
		}
		hosts {
		  2001:0DB8::1 test
		}
	      }

	      }

	      .	{
		hosts {
		  3.3.3.3 test
		}
	      }

       Send  all  A  and  AAAA requests	to 10.0.0.6, and all other requests to
       10.0.0.1.

	      .	{
		view example {
		  expr type() in ['A', 'AAAA']
		}
		forward	. 10.0.0.6
	      }

	      .	{
		forward	. 10.0.0.1
	      }

       Send all	requests for abc.*.example.com (where *	can be any  number  of
       labels),	 to  10.0.0.2,	and all	other requests to 10.0.0.1.  Note that
       the regex pattern is enclosed in	single quotes, and backslashes are es-
       caped with backslashes.

	      .	{
		view example {
		  expr name() matches '^abc\\..*\\.example\\.com\\.$'
		}
		forward	. 10.0.0.2
	      }

	      .	{
		forward	. 10.0.0.1
	      }

EXPRESSIONS
       To  evaluate  expressions,  view	 uses  the  expr-lang/expr  package  (
       https://github.com/expr-lang/expr   <https://github.com/expr-lang/expr>
       ).  For example,	an expression could  look  like:  (type()  ==  'A'  &&
       name() == 'example.com.') || client_ip()	== '1.2.3.4'.

       All expressions should be written to evaluate to	a boolean value.

       See https://github.com/expr-lang/expr/blob/master/docs/Language-Defini-
       tion.md	 <https://github.com/expr-lang/expr/blob/master/docs/Language-
       Definition.md> as a detailed reference for valid	syntax.

   AVAILABLE EXPRESSION	FUNCTIONS
       In the context of the view plugin, expressions can reference DNS	 query
       information by using utility functions defined below.

   DNS QUERY FUNCTIONS
       •   bufsize() int: the EDNS0 buffer size	advertised in the query

       •   class() string: class of the	request	(IN, CH, ...)

       •   client_ip()	string:	 client's IP address, for IPv6 addresses these
	   are enclosed	in brackets: [::1]

       •   do()	bool: the EDNS0	DO (DNSSEC OK) bit set in the query

       •   id()	int: query ID

       •   name() string: name of the request (the domain name requested  end-
	   ing with a dot): example.com.

       •   opcode() int: query OPCODE

       •   port() string: client's port

       •   proto() string: protocol used (tcp or udp)

       •   server_ip()	string:	 server's IP address; for IPv6 addresses these
	   are enclosed	in brackets: [::1]

       •   server_port() string	: server's port

       •   size() int: request size in bytes

       •   type() string: type of the request (A, AAAA,	TXT, ...)

   UTILITY FUNCTIONS
       •   incidr(ip string, cidr string) bool:	returns	true if	ip  is	within
	   cidr

       •   metadata(label  string) - returns the value for the metadata	match-
	   ing label

METADATA
       The view	plugin will publish the	following metadata,  if	 the  metadata
       plugin is also enabled:

       •   view/name: the name of the view handling the	current	request

CoreDNS				   June	2025		       COREDNS-VIEW(7)

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