Well, first of all, I'm not sure you really want to pass all HTTP traffic to the LTM log, unless it's for a short period of testing or something to that effect.
Second, you can send any information you want to the log, but there isn't a command to generate a standardized log formatted entry.
So, you can create your own logging string, and have it fire for every HTTP_REQUEST event if that's what you're trying to track (like most webservers do).
This would simply be something like:
when HTTP_REQUEST {
log local0. "[IP::client_addr] - [clock format $time_now -format {%d/%m/%Y:%H:%M:%S}] [HTTP::request]"
}
Of course you'd want to configure the logging string to fit your needs.
Colin