[syslog-ng] [PATCH]: Experimental SMTP destination

[Gergely Nagy]

Hi!

I've had a little free time, and started toying with the idea of
implementing an SMTP destination for syslog-ng. So far, it's progressing
nicely, but there are a few shortcomings, as I will explain later.

For anyone interested, it can be found on the 'work/modules/afsmtp'
branch of my syslog-ng-3.3 tree:

  git://git.balabit.hu/algernon/syslog-ng-3.3.git

Or, one can browse the branch on the web:

  http://git.balabit.hu/?p=algernon/syslog-ng-3.3.git;a=shortlog;h=work/modules/afsmtp

One will need the libesmtp library installed for the module to work. It
should be available in most distributions, but if one doesn't have it,
it can be downloaded from http://www.stafford.uklinux.net/libesmtp/
(although, as of this writing, the site seems to be down).

The usage is something like this:

        destination d_smtp {
          smtp(
            host("localhost")
            port(25)
            mail_from("syslog-ng alert service <noreply at example.com>")
            rcpt_to("Admin #1 <admin at example.com>")
            rcpt_to("Admin #2 <admin2 at example.com>")
            subject("[ALERT] $LEVEL condition in $PROGRAM!")
            header("X-Program" "$PROGRAM")
            header("X-Facility" "$FACILITY")
            body("Hi!\nThe syslog-ng alerting service thinks you might be interested in the following message:\n $MSG\n-- \nsyslog-ng\n")
          );
        };

One can specify any number of recipients, and the mail will be sent to
all of them. Custom headers can also be specified, but at this time, a
selected few headers do not work as one would expect, due to libesmtp
handling them specially.

These are: Date, From, To, Cc, Bcc, Reply-To - trying to set either of
these will result in unspecified behaviour (ranging from mangled headers
to crashes, in case of Date). I will fix these at a later point. They
will probably be need to set via their own statements (header_date,
header_from, etc, or something along those lines).

Specifying mail_from or subject multiple times will override any
previous values. Adding the same custom header multiple times will only
add the first (though, plans include changing that, so that one can
include the same header multiple times, with different values - if I can
find a use-case for that).

There are also a few other minor issues here and there, but nothing
major, as far as I could check.

Further plans include authentication & starttls support. libesmtp
supports both, I just didn't have time to write the neccessary glue code
yet.

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