Created attachment 16638 [details]
samba logs

When unix_nss_info = yes and the network connection is switched to a new interface, winbind fails to respond to some queries :
wbinfo --uid-info XXX
finish with a timeout error :
failed to call wbcGetpwuid: WBC_ERR_WINBIND_NOT_AVAILABLE
Could not get info for uid XXX

I get similar results with :
wbinfo --user-info XXX
wbinfo --user-sidinfo XXX

As a result, applications that depend on winbind for user authentication are almost no longer usable. Even opening a new terminal or a sudo is impacted.

Environment:
dc.test.lan (DC) and ubuntu01.test.lan (guest) : Ubuntu 20.04
Samba version : 4.11.6
See smb.conf of ubuntu01 is below.
Guest has 2 NIC, enp0s3 and enp0s8. 

Tests (time refers to log timestamp) :
enp0s3 is up, enp0s8 is down.
winbind service start [11:50], DC can be ping (wbinfo -P) [11:52] and wbinfo --uid-info successfully answers [11:53].

Now [11:54], switch network interface : enp0s3 is down, enp0s8 is up.
wbinfo -P successed [11:59], but wbinfo --uid-info 20100 finish with a timeout error [12:00] :

failed to call wbcGetpwuid: WBC_ERR_WINBIND_NOT_AVAILABLE
Could not get info for uid 20100

Also, 
wbinfo --user-info sn1a fails [12:02]


wbinfo --uid-to-sid 20100 success [12:04]

wbinfo --user-sidinfo fails [12:06]


Note :
The problem also appears when the network connection(s) are disabled. In this case, if unix_nss_info = no the request succeeds (with obviously cached data), but if unix_nss_info = no the request fails. 


smb.conf of ubunut01 for this test :
# Global parameters
[global]
	log level = 10
	debug pid = true
	max log size = 0

        workgroup = TEST
        realm = TEST.LAN
        netbios name = ubuntu01
        security = ADS

        idmap config TEST:backend = ad
        idmap config TEST:schema_mode = rfc2307
        idmap config TEST:range = 10000-29999
        idmap config TEST:unix_nss_info = yes

        idmap config *:backend = tdb
        idmap config *:range = 30000-39999

        winbind use default domain = yes
        winbind enum users = yes
        winbind enum groups = yes
        winbind refresh tickets = yes

        winbind expand groups = 1

        kerberos method = system keytab

        winbind offline logon = yes