HTTP::respond and HTTP/1.0

In 11.2, an option was added to HTTP::respond which allows you to specify the response version:

https://devcentral.f5.com/wiki/iRules.http__respond.ashx

HTTP::respond < status code > [-version [1.0|1.1] ] [content < content value >] [noserver] [< header name > < header value >]+ 

Note: The -version flag was added in 11.2.0. It must immediately follow the status code and precede the content (if any) and any other flags.

You could check the client's HTTP version using [HTTP::version] in HTTP_REQUEST:

when HTTP_REQUEST {

   set version [HTTP::version]
}
when HTTP_RESPONSE {
   if {$some_condition == 1}{

       Use 1.0 unless the client version was 1.1
      if {$version ne "1.1"}{
         set version "1.0"
      }
       Send the response with the version set explicitly, no BIG-IP server header and some custom headers
      HTTP::respond 200 -version $version content "< html >Hi" noserver header1 value1 header2 value2
   }
}

Aaron