Is it possible to print full SIP packet in logs using Irule

Firstly, I would strongly recommend against logging locally for this, and I would apply such an iRule only for debugging. If you really want the entire content of each SIP packet, you could simply log the contents of each TCP segment (since SIP metadata is text and the body is generally text), as in (untested!):

when CLIENT_ACCEPTED {
   if { [catch { HSL::open -publisher some_log_publisher } hsl] } {
       log local0.warn "Failed to open HSL to publisher (some_log_publisher): $hsl"
   } else {
       TCP::collect
   }
}


when CLIENT_DATA {
    set data [TCP::payload]

    TCP::release
    TCP::collect
    
    HSL::send $hsl $data
}