Hello,
when giving lessons about Exim it's always not easy to differentiate
between the generic and the private options in the driver instance
configuration blocks.
Let me demonstrate this using the modified default config
begin routers
dnslookup:
driver = dnslookup
check_srv = yes
domains = !+local_domains
transport = remote_smtp
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
no_more
Nobody can tell on the first sight, which of these options is a generic
router option and which one is private to dnslookup. "check_srv" -
generic or private. (Of course, if you're familiar with DNS and with
Exim you can tell, but not everybody is…)
One aproach could be to re-order the options, putting the generic
options first, then the driver and then the private options.
But it doesn't help a lot, since it somehow obfuscates the
information flow (ignore_target_hosts is evaluated when the driver *did*
its job):
dnslookup:
domains = !+local_domains
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
driver = dnslookup
transport = remote_smtp
no_more
check_srv = yes
Re-ordering in another way
dnslookup:
domains = !+local_domains
driver = dnslookup
check_srv = yes
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
transport = remote_smtp
no_more
… cures a bit only, because now again nobody sees if
"ignore_target_hosts" is private or generic.
What about adding some syntactic sugar, some decorations,
to the private options. Either this way
dnslookup:
driver = dnslookup
_check_srv = yes
domains = !+local_domains
transport = remote_smtp
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
no_more
… or even more verbose:
dnslookup:
driver = dnslookup
dnslookup.check_srv = yes
domains = !+local_domains
transport = remote_smtp
ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
no_more
What do you think? It's kind of a change, but with sensible coding it
could be made compatible with all existing configurations.
Best regards from Dresden/Germany
Viele Grüße aus Dresden
Heiko Schlittermann
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