[Dovecot] Logging authentication failures when Dovecot's auth service used to authenticate postfix smtpd

[MV]

> in case of SASL postfix is talking via a unix socket so there is no connection IP dovecot knows about

I don't not where Dovecot get the client IP from, but having auth
socket in place, below is a redacted extract from my logs. As you can
see Dovecot does know the client's IP.

Dovecot config:
  auth_verbose = yes
  auth_debug = no

# Dovecot log after submission/smtpd AUTH successful
<nothing>

# Dovecot log after submission/smtpd AUTH failure
... auth: Info: passwd-file(joe at example.com,46.z.z.z): Password mismatch


Dovecot config:
  auth_verbose = yes
  auth_debug = yes

# Dovecot log after submission/smtpd AUTH successful
... auth: Debug: client in: AUTH  1  PLAIN  service=smtp  nologin
lip=212.x.x.x  rip=46.z.z.z secured resp=<hidden>
... auth: Debug: passwd-file(joe at example.com,46.z.z.z): lookup:
user=joe at example.com file=/etc/dovecot/virtual_users
... auth: Debug: client passdb out: OK  1  user=joe at example.com

# Dovecot log after submission/smtpd AUTH failure
... auth: Debug: client in: AUTH 2  PLAIN  service=smtp  nologin
lip=212.x.x.x  rip=46.z.z.z secured resp=<hidden>
... auth: Info: plain(?,46.z.z.z): invalid input
... auth: Debug: client passdb out: FAIL  2


And regardless of Docecot config, postfix always logs the same stuff

# Postfix log after submission/smtpd AUTH successful (QUIT after AUTH
without sending RCPT TO)
... postfix/smtpd[5678]: connect from host.client.foo.tld[46.z.z.z]
... postfix/smtpd[5678]: disconnect from host.client.foo.tld[46.z.z.z]

# Postfix log after submission/smtpd AUTH failure
... postfix/smtpd[1234]: connect from host.client.foo.tld[46.z.z.z]
... postfix/smtpd[1234]: warning: host.client.foo.tld[46.z.z.z]: SASL
PLAIN authentication failed:
... postfix/smtpd[1234]: disconnect from host.client.foo.tld[46.z.z.z]