Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!decwrl!labrea!rutgers!uwvax!oddjob!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.mail.sendmail
Subject: Re: sendmail generates bogus error messages
Keywords: errno fprintf error ENOTTY network host
Message-ID: <13864@mimsy.UUCP>
Date: 4 Oct 88 19:41:53 GMT
References: <3153@hermes.ai.mit.edu> <30999@uunet.UU.NET>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 36

-In article <3153@hermes.ai.mit.edu> wisner@zug.AI.MIT.EDU (Bill Wisner) writes:
->... I should be seeing error messages like
->  Deferred: Connection timed out during user open with basel.ai.mit.edu
->Instead, I get this:
->  Deferred: Not a typewriter

In article <30999@uunet.UU.NET> dsc@izimbra.CSS.GOV
(card carrying aclu member) writes:
-i believe the problem you are seeing is that errno gets clobbered
-during a fprintf() call in usersmtp.c.  look in smtpinit() for the
-fprintf() call where one of the arguments is errstring(errno) and add
-two assignments to save & restore errno before calling fprintf, ala
-
-				r = errno;
-  				fprintf(CurEnv->e_xfp,
-  					"421 %s.%s... Deferred: %s\n",
-  					pvp[1], m->m_name, errstring(errno));
-				errno = r;

This will work, but there are other fixes.

-of course, why errno is getting set to ENOTTY or some other value by
-fprintf is in itself an interesting question ...

fprintf calls isatty when printing the first character to a FILE.
isatty calls ioctl(fd, TIOCGETP) and checks for errors.  TIOCGETP
succeeds only on terminals.  The error, of course, is ENOTTY.

I fixed(?) this by changing the C library routine isatty() to itself
save and restore errno; but a proper program should never check errno
except immediately after a failing system call.  A better fix to
sendmail itself (with or without the change in the C library) is to
have it retain the error number (or string) in the envelope structure.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris