On Thu, Mar 25, 2010 at 2:30 PM, Sai Pullabhotla <sai.pullabho...@jmethods.com> wrote: > I've not looked at the patch that supports concurrent data connections > on a single passive port, but I've some serious doubts as to if it is > even legitimate to have such support and if we can gracefully handle > such scenario.
I think most FTP servers support concurrent use of the same port. > Here is an example scenario - > > 1. Client A has more than one session (for this example let us say > two) open with the FTP server. > 2. Session 1 issues PASV command. > 3. Server replies back asking to connect on port 2000. > 4. About the same time, Session 2 issues PASV command > 5. Server replies back asking to connect on port 2000. > 6. Both session 1 and session 2 connect to port 2000 almost at the same time. > 7. How do we distinguish which data connection belongs to which > control session? > > Would we possibly be sending/receiving incorrect data on session 1/2? Step 5 must not be allowed. That is, we should not have two waiting passive ports from the same IP. In this case (if only port 2000 is used for passive ports), step 5 should be returning a 4XX reply. Would that work? All considered, adding support for this will require quite some work when it comes to testing. /niklas
