Question regarding FLOCK or POSIX with Sendmail 8.13.x and MailScanner.

[Scott Silva]

Duncan, Brian M. spake the following on 11/2/2006 6:05 AM:
>> Earlier this year, there was an internal inconsistency within
> 
>> MS which I spotted at 4.54.6 .
>>
> 
>> In "MailScanner.conf" the comments describing the default "Lock Type"
>> (i.e. left blank) behaviour said 'it defaults to "posix"',
> 
>> but the actual behaviour (when left blank) was to set it to "flock".
>>
> 
>> That is, the comments said MS would behave one way but its
> 
>> actual behaviour was the opposite.
>>
> 
>> See threads starting at:
>>   
> 
>> http://lists.mailscanner.info/pipermail/mailscanner/2006-June/
>> 061887.html
>> and Julian's acknowledgement and fix at:
>>   
> 
>> http://lists.mailscanner.info/pipermail/mailscanner/2006-June/
>> 061974.html
>>
> 
> 
>> So either upgrade to a more recent version (than 4.54.6) or
> 
>> if you need to stay back at 4.54.6 then explicitly state
> 
>> which lock type you want.
>>
> 
>> Hope that helps.
> 
> Thank you for the information.  I found those this morning when doing
> further searches.
> 
> I am hesitant to turn posix on, on my main server that has been using
> Sendmail 8.13.x and flock for months now without issue.
> 
> I am starting with a lower load box first.  I am afraid that it will
> cause a duplication issue.  It seems to with some sendmail 8.12.x users,
> and when they show their compiled options I don't see flock listed.
> 
> Here is one posting from a recent person with the duplicating message
> issue that was using Sendmail 8.12.11:
> 
>> Yes I'm using sendmail.
>>
>> 8.12.11-4.6
>>
>> # sendmail -d0.1
>> Version 8.12.11
>> Compiled with: DNSMAP HESIOD HES_GETMAILHOST LDAPMAP LOG MAP_REGEX
> MATCHGECOS MILTER MIME7TO8 MIME8TO7 NAMED_BIND NETINET
>> NETINET6 NETUNIX NEWDB NIS PIPELINING SASLv2 SCANF STARTTLS TCPWRAPPERS
> USERDB USE_LDAP_INIT
>> Duncan
> 
> 
> Since he does not have FLOCK shown in his compiled options, shouldn't of
> Posix worked for him? (Everything was ok when he switched to flock) - I
> looked at an older box I have here with sendmail 8.12 on it and I don't
> have flock shown as a compiled option.  I thought it was supposed to
> show you if flock support is compiled into sendmail.
> 
> Can someone please explain to me how it is determined that with Sendmail
> 8.13.x + versions you have to use posix? Is there any way to determine
> 100% that your sendmail compile is already using Posix and NOT flock?
> Looking for flock in the compiled options does not look to be accurate
> based on the above post I included. (He had to switch to flock to make
> his work, yet flock does NOT show up in his compiled options)
> 
> Thanks
This note was posted with sendmail 8.12.5 in the announce;
		NOTE: Linux appears to have broken flock() again.  Unless
			the bug is fixed before sendmail 8.13 is shipped,
			8.13 will change the default locking method to
			fcntl() for Linux kernel 2.4 and later.  You may
			want to do this in 8.12 by compiling with
			-DHASFLOCK=0.  Be sure to update other sendmail
			related programs to match locking techniques.
( see http://www.sendmail.org/releases/8.12.5.html)

I can't tell you why your version is different, maybe a custom compiled
version to get around the Flock exploit that was posted about the time 8.12.11
came out. The consensus so far has been ;
Linux and sendmail 8.12 = flock
Linux and sendmail 8.13 = posix
Also note that there have been some problems with dovecot if it is set to a
different locking.

I am still curious as to how you have been so lucky with no problems!
Are you running on a filesystem other than ext2/ext3?
Maybe Core 4 has a kernel that doesn't have the locking problem that the
enterprise distros lack because of the conservative patching that is done.



-- 

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You hope everybody uses it, and
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