[2647] in linux-net channel archive
port reuse problem with ftp
daemon@ATHENA.MIT.EDU (Raul Miller)
Thu Apr 25 11:11:08 1996
Date: 24 Apr 1996 19:34:45 GMT
From: Raul Miller <rdm@tad.micro.umn.edu>
To: linux-kernel@vger.rutgers.edu
Cc: Linus.Torvalds@vger.rutgers.edu, linux-net@vger.rutgers.edu
I think this problem has been in the kernel for a while, but this is a
problem I see in 1.3.94:
If I use /usr/bin/ftp with any frequency, I some file transfers start
failing with status messages like:
425 Can't build data connection: Cannot assign requested address.
I think this is the port-reuse issue (where a port can not be reused
"for security reasons").
If the current behavior of /usr/bin/ftp is considered a bug in ftp,
I'd like a pointer to a version that doesn't have this problem. [And,
can I reasonably expect that arbitrary browser software won't be hit
by this problem?]
Also, I think I should point out that the rfcs which define tcp ports
suggest that a mechanism exists to reserve ports before a program
begins servicing them. [My impression of what the rfc would mean for
unix is a syscall mechanism where a port can be associated with a
process and all it's children, with a companion mechanism for
discarding the association, and that a reserved port would be
unavailable to a process that didn't have a reservation for it. Yes,
I know bind() currently does something like this, but in a very
limited fashion.]
Anyways, ftp ought to work reliably. [And, personally, I dislike
"security mechanisms" which make utility code less portable.]
[Then again, maybe I'm wrong about what I think is causing this?]
--
Raul
