iRule

Components

Using TCL language, http://tmml.sourceforge.net/doc/tcl/index.html Operators: https://clouddocs.f5.com/api/irules/Operators.html Functions: https://clouddocs.f5.com/api/irules/Functions.html Statements: https://clouddocs.f5.com/api/irules/Statements.html Commands: https://clouddocs.f5.com/api/irules/Commands.html Disabled commands: https://clouddocs.f5.com/api/irules/DisabledTclCommands.html Events: Between the time when a connection flows into TMOS, and out the other side, there are a series of internal states that are reached by that connection. Each of these states equate to an event in the iRule language. State can be: Global such as CLIENT_ACCEPTED Profile specific such as HTTP_REQUEST, CLIENTSSL_CLIENTCERT, RTSP_RESPONSE, and so on when EVENT_NAME { TCL-CODE } List of Events: https://clouddocs.f5.com/api/irules/Events.html

iRules Syntax

Variables

set msg "Hello, World!" # Local Variable
set ::myGlobal "Hello, World!" # Global variable, REMEMBER to unset
unset msg
unset msg r vbl

set r [expr rand()]
set vbl in[expr {rand() >= 0.5}]
set reqArray([IP::client_addr]) [getfield [string tolower [HTTP::uri]] "?" 2]

# append data to variable
set var 0
for {set i 1} {$i<=10} {incr i} {
   append var "," $i
}
puts $var # Prints 0,1,2,3,4,5,6,7,8,9,10

#Join values
concat " a b {c   " d "  e} f"
will return "a b {c d e} f" as its result.

# Increase values
Add one to the contents of the variable x:
  incr x

Add 42 to the contents of the variable x:
  incr x 42

Switch command

# -exact: Use exact matching when comparing string to a pattern. This is the default.
switch [HTTP::uri] {
  "/foo" {
    # do something...
  }
  "/bar" - # means OR
  "/foobar" {
    # do something else...
  }
  default {
    # don't do anything...
  }
}

# glob: use glob-style matching (i.e. the same as implemented by the string match command).
switch -glob [HTTP::uri] {
  "/foo*" {
    # this will match on any string that starts with "/foo"
  }
  "*bar" {
    # this will match on any string that ends with "bar"
  }
  "/foobar[a-zA-Z]" {
    # This will match with any string that starts with "/foobar" followed by any case character from a-z.
  }
  "/foo?bar" {
    # this will match any string that starts with "/foo", followed by any character, and followed by and ending with "bar".
  }
}

Some iRule Samples

when HTTP_REQUEST { 
if { [HTTP::uri] starts_with "/foobar" } { 
  switch -glob [HTTP::uri] { 
    "*[0-9].jpg" { pool numbers_pool } 
    default { 
      if { [string length [substr [HTTP::uri] 0 "?"]] > 0 } { 
        HTTP::respond 200 content "<html><head><title>Where's the number?</title></head></body><h1>Where's the number?</h1></body></html>" } 
    } 
  } 
}
} 

when HTTP_RESPONSE { 
if { [HTTP::header Content-Length] > 100 } { 
  log local0. "too much data requested." drop } 
}

iRule Event

CLIENT_ACCEPTED: triggered when a client has established a connection

Reference

iRules 101: https://community.f5.com/t5/technical-articles/irules-101-01-introduction-to-irules/ta-p/283452
CLIENT_ACCEPTED: https://clouddocs.f5.com/api/irules/CLIENT_ACCEPTED.html

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Last updated 2 years ago