Hi Corinna, Corinna Vinschen wrote: > > On Aug 5 22:35, D. Boland wrote: > > Corinna Vinschen wrote: > > > > > > Can you produce another strace for the overwriting case (non-R/O aliases) > > > for comparison? Also, can you do the same strace with no syslogd running? > > > > > > It might be necessary to create a few test versions of Cygwin with more > > > debug output, but let's please see these straces first. > > > > I attached all three of them in a zipped file. > > Thanks. I got it now. AFAICS it's a bug in sendmail. Take a look > into your newaliases.strace.txt file. Start at line 260 (stripping > off timestamp, thread and process info): > > 260: normalize_posix_path: src /dev/log > > Here the syslog() function tries to open a connection to a syslogd > listening on /dev/log. > > 282: cygwin_socket: 3 = socket(1, 2 (flags 0x0), 0) > > Socket created, file descriptor is 3. > > 296: connect_syslogd: found /dev/log, fd = 3, type = DGRAM > > Yes, there's a listener on /dev/log. Now Cygwin stores the info that fd > 3 is the connection to the syslog daemon. > > 332: close: close(3) > > And at line 332, a file descriptor close orgy starts. sendmail closes > all descriptors from 3 to 255. This obviously closes fd 3, but how's > Cygwin's syslog() function to know? > > 2263: open: 3 = open(/etc/mail/aliases, 0x8000) > > Uh oh! Now fd 3 is reused for the aliases file. Things certainly go > downhill. > > 2651: writev: -1 = writev(3, 0x2287F0, 2), errno 9 > > This is syslog trying to write the log to the descriptor it knows > is connected to /dev/log. Fortunately the aliases file is R/O at > this point, but it's pretty much working as designed. Syslog() > doesn't know the application broke its connection to the syslog > daemon. It dutyfully writes to the syslog descriptor it knows > about. > > As for using a file descriptor inside of syslog, that's perfectly > valid behaviour, see > http://pubs.opengroup.org/onlinepubs/9699919799/functions/closelog.html: > > "The openlog() and syslog() functions may allocate a file descriptor." > > Without looking into the sources, I'd assume there's a closelog() > call missing prior to the descriptor close orgy. This closelog() > call should fix the problem.
It is exactly as you say. I found the close() orgy and put a closelog() prior to it. Now it works perfectly without corrupting the aliases file (writable to sendmail). I'm asking myself if this closing of 253 file descriptors is a sensible thing to do. What would Sendmail be trying to accomplish there? It comments "Be shure we have enough file descriptors". And: "in 4.4BSD, the table ([of fd's]) can be huge; impose a reasonable limit". Bizarre. Could it be that incoming e-mail is such a volatile process that previous opened file descriptors are not closed quick enough? This feels like a crude hack. Can you give your opinion on this? Thanks for the quick response & the time you put into this. Daniel -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
