When `CURLOPT_INTERFACE` (or the command line tool's `--interface` option) is set with one of the...

When CURLOPT_INTERFACE (or the command line tool's --interface option) is set with one of the documented prefixes (if!, host!, ifhost!), that binding is not part of the connection reuse key, so a later transfer asking for a different source can silently reuse an existing connection and go out from the earlier transfer's source address