lists+post...@sad.lv:
> Hello !
>
> I met an issue with milter when multiple messages pushed within single
> smtp session (using pipelining indeed):
> warning: milter unix:/run/t.socket: unexpected filter response
> SMFIR_ADDHEADER after event SMFIC_MAIL
>
> It looks similar for
> https://www.mail-archive.com/postfix-users@postfix.org/msg13652.html
This was caused by a bug in Sendmail::PMilter.
Background: the SMTP protocol supports multiple MAIL transactions
per SMTP connection. After each successful or unsuccessful MAIL
transaction, Postfix sends an SMFIC_ABORT command to all Milters,
to ensure that they are in a knwn state for the next MAIL transaction.
The Sendmail::PMilter code comes with a description of the Milter
protocol that says:
COMMAND CODES
...
'A' SMFIC_ABORT Abort current filter checks
Expected response: NONE
...
Yet, when the Sendmail::PMilter receives SMFIC_ABORT, it sends a
response (SMFIR_CONTINUE). Evidence from PMilter logging:
Fri Dec 9 20:14:15 2022 PID=13886 Context.pm(215): main(eval): got command=[A]
Fri Dec 9 20:14:15 2022 PID=13886 Context.pm(508): call_hooks: (non-existent
callback=[abort])
write =>c<= ><
The command=[A] is SMFIC_ABORT, and the =>c<= response is SMFIR_CONTINUE.
Because of this "extra" response, Postfix and Sendmail::PMilter are
now out of step, and eventually Postfix complains about a protocol error.
Wietse
