Good call Randall... Were these in place for popper v3.0.2?
Regards,
Gregory Hicks
> Date: Tue, 25 Sep 2001 15:32:36 -0700
> To: "Dan Harkless" <[EMAIL PROTECTED]>, Subscribers of Qpopper
<[EMAIL PROTECTED]>
> From: Randall Gellens <[EMAIL PROTECTED]>
> Subject: Re: I lose email when our server crashes due to lack of O_EXCL use
>
> At 8:31 PM -0700 9/24/01, Dan Harkless wrote:
>
> >It looks to me like what's happening is that my scripts do a POP3 connect
> >(which I do more often than anyone else, explaining why only _I_ have
> >noticed mail loss), my spool is emptied out of /var/mail/<user> into
> >/var/mail/.<user>.pop, the machine crashes, and then after the machine's
> >back up again, my spool is zero-length and the temp_drop is overwritten by
> >the first check.
> >
> >I didn't pore through the code exhaustively, but I couldn't find any code
> >that would prevent this. Shouldn't there be code that would check for the
> >pre-existence of the temp_drop file and merge its messages back into the
> >spool before doing anything else??
>
> There is such code, and has been for as long as I can recall. I've
> hit it many times in testing.
>
> An popper/pop_dropcopy.c:1532, we revert to non-server mode if the
> temp drop isn't empty:
>
> /*
> * If the temporary popdrop is not empty, revert to regular mode.
> */
> if ( mybuf.st_size != 0 )
> p->server_mode = 0;
>
>
> Then at line 1604 we deal with any left-over mail in the temp drop:
>
> if ( mybuf.st_size != 0 ) { /* Mostly this is for regular mode. */
> DEBUG_LOG2 ( p, "Temp drop %s not empty (%u octets)",
> p->temp_drop, (unsigned) mybuf.st_size );
> if ( init_dropinfo ( p, p->temp_drop, p->drop, time(0) ) !=
POP_SUCCESS ) {
> /* Occurs on temp_drop corruption */
> flock ( dfd, LOCK_UN );
> close ( dfd );
> return ( POP_FAILURE );
> }
>
> At this point, the file pointer is at the end of the temp drop,
> following any left-over mail. We then lock the spool, append mail
> from it to the temp drop (after any left-over mail), zero the spool,
> and work out of the temp drop.
>
>
> >As I understand things, the only way to prevent any possibility of
> >overwriting an existing temp_drop file would be to do it atomically, with
> >O_EXCL specified along with O_CREAT on the open() call.
>
> I'm not sure why O_EXCL is needed. Qpopper always locks the temp
> drop before doing anything, to make sure only one Qpopper process is
> active for the user. It then checks if the file is non-empty, and
> processes any left-over mail.
>
> --
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Gregory Hicks | Principal Systems Engineer
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