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Re: mail.local NSS awareness

On Tue, Apr 29, 2008 at 09:16:06AM +0000, Emmanuel Dreyfus wrote:
  | Hello
  | mail.local assumes that if getpwnam(3) returns NULL, that means the 
  | recipient does not exists, and the message shall be dropped. Hence it
  | returns code EX_OK to the MTA.
  | This behaviour does not take NSS into account. NSS source others than 
  | file may fail, and they may fail for a temporary condition. In that 
  | situation, mail.local should exit with a status code different than
  | EX_OK, so that the MTA understands that delivery should be retried
  | at a later time.
  | As I understand, sendmail expects EX_OK, EX_TEMPFAIL, or EX_UNAVAILABLE,
  | so I propose the patch included below. I don't know how well that cope
  | with other MTA, or if there are other errno like EAGAIN and ETIMEDOUT
  | that should cause EX_TEMPFAIL (temporary failure) instead of EX_UNAVAILABLE
  | (permanent failure). Opinions?

POSIX doesn't document that getpwnam() can fail with EAGAIN or ETIMEDOUT;
I think you'd be relying upon implementation-specific values.

Arguably the retry after temporary failure could be dealt with via
the nsswitch.conf interface, although the NetBSD implementation
doesn't support that at this time.

NetBSD's nsswitch implementation was inspired by early Solaris 2.x
(2.3? 2.4?) behaviour; it appears that Solaris 8 (2.8?) now supports
which could be used to force retries on temporary failures "forever"
or for "n" retries.

Until now there hasn't been a big demand for the "tryagain=(forever|<n>)"
semantics in NetBSD; if you think it would be useful for you, submit
a PR so we don't forget about it.


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