Date: Wed, 7 Feb 2001 18:30:02 -0800 (PST) From: Peter Wemm <peter@netplex.com.au> To: freebsd-bugs@FreeBSD.org Subject: Re: misc/24942: tftp client timeout failure Message-ID: <200102080230.f182U2r62479@freefall.freebsd.org>
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The following reply was made to PR misc/24942; it has been noted by GNATS.
From: Peter Wemm <peter@netplex.com.au>
To: yxiao@cisco.com
Cc: freebsd-gnats-submit@FreeBSD.ORG
Subject: Re: misc/24942: tftp client timeout failure
Date: Wed, 07 Feb 2001 18:20:54 -0800
yxiao@cisco.com wrote:
[..]
> >Release: $FreeBSD: src/usr.bin/tftp/tftp.c,v 1.5 1999/08/28 01:06:24
peter Exp
> >Environment:
> Linux dhcp-171-70-93-24.cisco.com 2.2.14-5.0 #1 Tue Mar 7 21:07:39 EST 2000 i
686 unknown
Are you running our tftpd under Linux? Or is that just the send-pr
environment?
> >Description:
> Alarm clock can only fired once. Problem: SIGALRM blocked.
The patch below has a couple of problems:
> >Fix:
> change timer function:
> --- tftp.c 2000/08/01 20:38:08 1.2
> +++ tftp.c 2001/02/07 16:18:03
> @@ -455,9 +455,15 @@
> timer(sig)
> int sig;
> {
> + sigset_t sigset;
> + int error;
>
> + //signal(SIGALRM, timer);
> + error = sigemptyset(&sigset);
> + error |= sigdelset(&sigset, SIGALRM);
> + error |= sigprocmask(SIG_SETMASK, &sigset, NULL);
> timeout += rexmtval;
> - if (timeout >= maxtimeout) {
> + if (timeout >= maxtimeout || error) {
> printf("Transfer timed out.\n");
> global_errno = ETIMEDOUT;
> longjmp(toplevel, -1);
sigdelset() to delete a signal from an already empty set is a NOP.
It might as well be:
error = sigemptyset(&sigset);
error |= sigprocmask(SIG_SETMASK, &sigset, NULL);
There is also a problem.. if sigemptyset() returned an error, sigset would
have undefined contents. And yet you call sigprocmask() anyway.
I think a more correct fix would be to use sigsetjmp()/siglongjmp()
to save/restore the mask.. However, according to the man pages, that
shouldn't be necessary:
The setjmp()/longjmp() pairs save and restore the signal mask while
_setjmp()/_longjmp() pairs save and restore only the register set and the
stack. (See sigprocmask(2).)
The sigsetjmp()/siglongjmp() function pairs save and restore the signal
mask if the argument savemask is non-zero, otherwise only the register
set and the stack are saved.
Cheers,
-Peter
--
Peter Wemm - peter@FreeBSD.org; peter@yahoo-inc.com; peter@netplex.com.au
"All of this is for nothing if we don't go to the stars" - JMS/B5
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