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Re: Abort data transfer?

2009-10-21 10:10:40

David MacQuigg wrote:

I would just continue accepting the message, and throw away the data,
then give a 'message too big' error at the end.


This doesn't deal with the case where the data never stops.

What would be the criteria?

That is why our server, once upon a time, had a block transfer count check against local policy size limits with the drop idea as well.

But it was pulled due to retransmissions and mostly seen from legitimate users. We want the client MUA to see a normal server response to this and have it popup the dialog to the user hopefully showing the server response text. The odds are good nor should we expect the MUA to read some forced DATA abort server text from the server. At best we can expect the client to be modeled as followed in a client/server state machine fashion:

DATA state:

      read data
      err = send data
      if err is socket closed then
         // RFC 2821/5321 says assume 451
         close resources
         return false
      end if
    wait 5 mins (default) for server response

We can't assume that for an socket error that it will exit the loop and capture some legacy transmission data remaining in the socket buffers. It MAY be there, but we can't assume this.

      read data
      err = send data
      if err is not successful then
         // see if there is any buffered data in input stream
         exit loop
      end if
    wait 5 mins (default) for server response

We have one rule left related to this on the server's data transfer loop and outside the loop. If the detected extended SMTP sender provided MAIL SIZE info and it exceeded the size in the transfer, then this is trapped and the sender info is recorded. But we don't drop the line anymore. I can't tell you off hand if we have any logs on this.

So I would lean towards Levine's point, that it is rare to see this, and probably simply because that it would be trapped under normal circumstances after the data transfer is complete. Sure, a pain in the butt - but they are not defeating your server.


Hector Santos

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