system_filter issue "name too long in directory_make"

[Andrew McGlashan]

Hi,

I have a system_filter entry that does backups (for archival purposes)
of emails.  The path for storing the backup copy exceeds the buffer size
of 256 as per the source file [1].

Outside of exim, I can create the directory without any trouble, then
actual length for my test was 275 characters, this includes many path
components of smaller size, the total length of the path being 275.

Is there any reason why the code couldn't be adjusted to have a maximum
length of say, 512, 768 or even 1024 as 256 is too short for my use case
and there is no problem at the file system level with the actual
required path.


Here is the relevant part of my system_filter that expands out to the
super long path; this usually fails with salesforce emails and has done
for years, but now I'm hoping to get this fixed and have done the
further investigation.

   unseen save   
/backup/mail/other-domains/$sender_address_domain/$sender_host_address/${tr{$sender_address}{.,\040}{_}}/$1/${length_99:${tr{$recipients}{.,\040}{_--}}}/


I have a similar line for emails with a List-ID as follows (the path
would be longer) in this case.

   unseen save   
/backup/mail/other-domains-list-id-mail/$sender_address_domain/$sender_host_address/${tr{$sender_address}{.,\040}{_}}/$1/${length_99:${tr{$recipients}{.,\040}{_--}}}/


The message remains frozen in the mail queue.

If I create the directory at the file system level (ext4), then it
creates fine.  When I then run exim4 -M message_id ... the message
doesn't get saved, but it is removed from the mail queue and is no
longer frozen.

2017-12-20 14:37:39 [19932] cwd=/var/log/exim4 3 args: exim4 -M
1eRE4Y-00037m-IO
2017-12-20 14:37:39 [19932] 1eRE4Y-00037m-IO Unfrozen by forced delivery
2017-12-20 14:37:39 [19932] 1eRE4Y-00037m-IO Completed QT=18h17m13s


[1] https://github.com/Exim/exim/blob/master/src/src/directory.c

Kind Regards
AndrewM

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