HTTP::header

Description

Queries or modifies HTTP headers. This command replaces the BIG-IP 4.X variable http_header.
The header name is not case sensitive, so for example, ‘HTTP::header value HEADER_NAME’ will match a header with the name HeAdEr_NaMe.

Syntax

HTTP::header [value] <name>
HTTP::header values <name>
HTTP::header names
HTTP::header count <name>
HTTP::header at <index>
HTTP::header exists <name>
HTTP::header insert ["lws"] [<name> <value>]+
HTTP::header lws
HTTP::header is_keepalive
HTTP::header is_redirect
HTTP::header replace <name> [<string>]
HTTP::header remove <name>
HTTP::header insert_modssl_fields <addr port | addr addr addr | port port port>
HTTP::header sanitize [header name]+

HTTP::header [value] <name>

  • Returns the value of the HTTP header named <name>.
  • Returns a null string if the HTTP header named <name> does not exist.
  • Note that the command will operate on the value of the last header if there are multiple headers with the same name.
  • You may omit the value argument if the header name does not collide with any of the HTTP::header subcommands.

HTTP::header values <name>

  • Returns a list of value(s) of the HTTP header named <name>. Note that the command will return the values all of the headers as a Tcl list if there are multiple headers with the same name. If there is a single value for the HTTP header, that value will be returned.
  • (This subcommand was added in v9.4.0)

Note: There is an issue where HTTP::header values can remove colons in the header values it returns. The actual header values are unchanged. This issue is tracked as CR98328 and has been fixed in 10.0.

HTTP::header names

  • Returns a list of all the headers present in the request or response.
  • In v9.4.0 and higher, multiple headers with the same name will be listed multiple times.

HTTP::header count <name>

  • Returns the number of HTTP headers present in the request or response. If is supplied, returns the number of HTTP headers present in the request or response with that name.
  • In v9.4.0 and higher, multiple headers with the same name will be counted multiple times.

Note: Due to a bug described in CR114612, HTTP::header count doesn’t count the last header, so it is unintentionally zero-index based. This was an issue at least in 9.4.x and possibly earlier (and later?). This has been fixed in 9.4.8 and 10.0.0.

HTTP::header at <index>

  • Returns the HTTP header name that the system finds at the zero-based index value.

HTTP::header exists <name>

  • Returns true if the named header is present and not empty on the request or response.

HTTP::header insert [“lws”] [<name> <value>]+

  • Inserts the named HTTP header(s) and value(s) onto the end of the HTTP request or response. The input can be a single header name and value, or a list containing name value pairs [list name1 value1 name2 value2].
  • If you specify ‘“lws”’, the system adds linear white space to long header values.
  • If this command is executed after issuing the HTTP::redirect or HTTP::respond command, the F5 will become confused, generate an “Operation Not Supported” TCL error and reset the connection.

HTTP::header lws

  • Returns 1 if a header was encountered that had linear white space, and 0 otherwise. See RFC2616 for more information on lws and HTTP headers.

HTTP::header is_keepalive


HTTP::header is_redirect


HTTP::header replace <name> [<string>]

  • Replaces the value of the last occurrence of the header named <name> with the string <string>. This command performs a header insertion if the header was not present. If there are multiple instances of the header, only the last instance is replaced.
  • If this command is executed after issuing the HTTP::redirect or HTTP::respond command, the F5 will become confused, generate an “Operation Not Supported” TCL error and reset the connection.

HTTP::header remove <name>

  • Removes all headers names with the name <name>.

HTTP::header insert_modssl_fields <addr port | addr addr addr | port port port>

  • If “addr port” is specified, inserts the HTTP header ClientIPAddress with the client IP and port as the value.
  • If “addr addr addr” is specified, inserts the HTTP header ClientIPAddress with the client IP only as the value.
  • if “port port port” is specified, insertd the HTTP header ClientTCPService with the client port as the value.
  • This documents the implementation in v9.4.0 (and possibly earlier versions), which is slightly buggy. The corrected syntax should be: HTTP::header insert_modssl_fields [addr] [service | port] and should behave intuitively.
  • Note that this command is only for HTTP requests, not responses.

HTTP::header sanitize [header name]+

  • Removes all headers except the ones you specify and the following: Connection, Content-Encoding, Content-Length, Content-Type, Proxy-Connection, Set-Cookie, Set-Cookie2, and Transfer-Encoding.
  • Note that the Host header (required by HTTP/1.1) is removed unless explicitly specified.
  • This command can be used in the client-side or server-side context, depending on whether you want to sanitize request and/or response headers.
  • If you are using the command in the server-side context, you may want to consider adding Location to the list of retained headers if your application requires they be sent to clients.
  • If you are using the command in the client-side context, you may want to consider adding Cookie, Accept, and Accept-Encoding to the list of retained headers.

Examples

when HTTP_REQUEST {
  if { [HTTP::header "Host"] starts_with "uat" }  {
    pool uat_pool
  } else {
    pool main_pool
  }
}


when HTTP_RESPONSE {
   # loop through and remove all instances of the unwanted
   # headers from the server response
   # (Server, X-Powered-By in this example)
   foreach header {Server X-Powered-By} {
      log local0. "Removing $header: [HTTP::header value $header]"
      HTTP::header remove $header
   }
}


when HTTP_RESPONSE {
   # test the new (as of 9.4.0) command, HTTP::header values <name>
   #    for retrieving the values of multiple, identically named headers
   HTTP::header insert header_1 value_1
   HTTP::header insert header_1 value_2
   HTTP::header insert header_1 value_3

   log local0. "\[HTTP::header header_1\]: [HTTP::header header_1]"
   log local0. "\[HTTP::header value header_1\]: [HTTP::header value header_1]"
   log local0. "\[HTTP::header values header_1\]: [HTTP::header values header_1]"
}

Logs:

   [HTTP::header header_1]: value_3
   [HTTP::header value header_1]: value_3
   [HTTP::header values header_1]: value_1 value_2 value_3