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hosting-team_36's avatar
hosting-team_36
Icon for Nimbostratus rankNimbostratus
Oct 29, 2018

irule to extract single IP from X-Forwarded-for results with multiple IPs

I need an irule to split the IP::remote_addr and just set the first IP as theX-Forwarded-For when HTTP_REQUEST { HTTP::header insert X-Forwarded-For [IP::remote_addr] } https://devcentral.f5.com/...
application delivery
BIG-IP
devops
iRules
Kevin_Stewart's avatar
Kevin_Stewart
Icon for Employee rankEmployee
Oct 30, 2018

Ah, ok. Wasn't sure how [IP::remote_addr] was involved.

An X-Forwarded-For header with multiple IPs will be comma-delimited:

X-Forwarded-For: 10.10.0.1, 10.10.0.2, 10.10.0.3

So to grab the first one, you can do some simple list manipulation:

if { [HTTP::header "X-Forwarded-For"] ne "" } {
    if { [HTTP::header "X-Forwarded-For"] contains "," }{
        set ips [split [HTTP::header "X-Forwarded-For"] ","]
        set xff [lindex ${ips} 0]
    } else {
        set xff [HTTP::header "X-Forwarded-For"]
    }
} else {
    set xff [IP::remote_addr]
}