One SSL profile for different pool members

Before you've decrypted the traffic, there's no "URL" to look at. The best you can do is to rely on the Server Name Indication (SNI) value in the client's ClientHello TLS handshake message.

The trick here is that if you want to switch the client SSL profile, you have to do it before the client SSL profile engages, in a layer 4 (TCP) event. And at layer 4, you don't yet have access to any SSL:: commands to help you grab the ClientHello SNI value, so that too has to be done at layer 4...in binary.

There are a ton of versions of this iRule floating around, but I've found it makes code more manageable to shove all of the binary SNI code into a proc and call it remotely. So create a new iRule to use for your external procedures:

Proc rule: library-rule

proc getSNI { payload } {
    set detect_handshake 1

    binary scan ${payload} H* orig
    if { [binary scan [TCP::payload] cSS tls_xacttype tls_version tls_recordlen] < 3 } {
        reject
        return
    }

     768 SSLv3.0
     769 TLSv1.0
     770 TLSv1.1
     771 TLSv1.2
    switch $tls_version {
        "769" -
        "770" -
        "771" {
            if { ($tls_xacttype == 22) } {
                binary scan ${payload} @5c tls_action
                if { not (($tls_action == 1) && ([string length ${payload}] > $tls_recordlen)) } {
                    set detect_handshake 0
                }
            }
        }
        "768" {
            set detect_handshake 0
        }
        default {
            set detect_handshake 0
        }
    }

    if { ($detect_handshake) } {
         skip past the session id
        set record_offset 43
        binary scan ${payload} @${record_offset}c tls_sessidlen
        set record_offset [expr {$record_offset + 1 + $tls_sessidlen}]

         skip past the cipher list
        binary scan ${payload} @${record_offset}S tls_ciphlen
        set record_offset [expr {$record_offset + 2 + $tls_ciphlen}]

         skip past the compression list
        binary scan ${payload} @${record_offset}c tls_complen
        set record_offset [expr {$record_offset + 1 + $tls_complen}]

         check for the existence of ssl extensions
        if { ([string length ${payload}] > $record_offset) } {
             skip to the start of the first extension
            binary scan ${payload} @${record_offset}S tls_extenlen
            set record_offset [expr {$record_offset + 2}]
             read all the extensions into a variable
            binary scan ${payload} @${record_offset}a* tls_extensions

             for each extension
            for { set ext_offset 0 } { $ext_offset < $tls_extenlen } { incr ext_offset 4 } {
                binary scan $tls_extensions @${ext_offset}SS etype elen
                if { ($etype == 0) } {
                     if it's a servername extension read the servername
                    set grabstart [expr {$ext_offset + 9}]
                    set grabend [expr {$elen - 5}]
                    binary scan $tls_extensions @${grabstart}A${grabend} tls_servername_orig
                    set tls_servername [string tolower ${tls_servername_orig}]
                    set ext_offset [expr {$ext_offset + $elen}]
                    break
                } else {
                     skip over other extensions
                    set ext_offset [expr {$ext_offset + $elen}]
                }
            }
        }
    }

    if { ![info exists tls_servername] } {
         This isn't TLS so we can't decrypt it anyway
        return "null"
    } else {
        return ${tls_servername}
    }
    TCP::release
}

And then you can create a very simply iRule, attached to the VIP, to switch between client SSL profiles based on the SNI value in the ClientHello:

when CLIENT_ACCEPTED {
    TCP::collect
}
when CLIENT_DATA {
     call the external procedure
    set sni [call library-rule::getSNI [TCP::payload]]    
    log local0. "sni = $sni"

    if { ${sni} equals "www2.site.com" } {
        set newprof "SSL::profile www2.site.com-clientssl"
        catch { eval ${newprof} }
    }

    TCP::release
}

The above calls the procedure to get the SNI, then if the SNI equals "www2.site.com", you use an eval command to switch the client SSL profile.

Easy-Peasy 😉