[Samba] nmb.service fails on pure IPv6 system

[Tim Hoke]

I have an IPv6 only system (no IPv4 addresses) and nmb.service goes into a
failed state saying:

Status: "nmbd: No local IPv4 non-loopback interfaces available, waiting for
interface ..."

I've seen several references to a previous bug where the service wasn't
waiting
for networking to be ready. That's _not_ my case here. Instead, I have no
IPv4
addresses, so I think it's stuck in the loop looking for non-loopback IPv4
addresses.

Here's some information:

$ ip -4 addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group
default qlen 1000
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
[appadmin at eagappnbu479p2v6 ~]$ ip -6 addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 state UNKNOWN qlen 1000
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0 at if29: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP
    inet6 2620:128:f021:900f::8f/64 scope global
       valid_lft forever preferred_lft forever
    inet6 fe80::8017:a4ff:fe70:5386/64 scope link
       valid_lft forever preferred_lft forever

$ ifconfig -a
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet6 2620:128:f021:900f::8f  prefixlen 64  scopeid 0x0<global>
        inet6 fe80::8017:a4ff:fe70:5386  prefixlen 64  scopeid 0x20<link>
        ether 82:17:a4:70:53:86  txqueuelen 0  (Ethernet)
        RX packets 1597463  bytes 177662026 (169.4 MiB)
        RX errors 0  dropped 86683  overruns 0  frame 0
        TX packets 103658  bytes 46092995 (43.9 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 276013  bytes 563801450 (537.6 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 276013  bytes 563801450 (537.6 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

$ systemctl status nmb.service
● nmb.service - Samba NMB Daemon
   Loaded: loaded (/usr/lib/systemd/system/nmb.service; disabled; vendor
preset: disabled)
   Active: activating (start) since Wed 2023-07-26 17:50:13 UTC; 1min 24s
ago
     Docs: man:nmbd(8)
           man:samba(7)
           man:smb.conf(5)
 Main PID: 51521 (nmbd)
   Status: "nmbd: No local IPv4 non-loopback interfaces available, waiting
for interface ..."
   CGroup:
/machine.slice/libpod-89fe3c9994aaa42ca8be5f92402d6da6e22f55f53cfad850d7561b9f51e77f52.scope/system.slice/nmb.service
           └─51521 /usr/sbin/nmbd --foreground --no-process-group

Jul 26 17:50:13 server.example.com systemd[1]: Starting Samba NMB Daemon...

After some time, (90 seconds?), the unit will go to a failed state:

$ systemctl status nmb.service
● nmb.service - Samba NMB Daemon
   Loaded: loaded (/usr/lib/systemd/system/nmb.service; disabled; vendor
preset: disabled)
   Active: failed (Result: timeout) since Wed 2023-07-26 17:51:43 UTC; 11s
ago
     Docs: man:nmbd(8)
           man:samba(7)
           man:smb.conf(5)
  Process: 51521 ExecStart=/usr/sbin/nmbd --foreground --no-process-group
$NMBDOPTIONS (code=killed, signal=TERM)
 Main PID: 51521 (code=killed, signal=TERM)
   Status: "nmbd: No local IPv4 non-loopback interfaces available, waiting
for interface ..."

Jul 26 17:50:13 eagappnbu479p2v6.engba.veritas.com systemd[1]: Starting
Samba NMB Daemon...
Jul 26 17:51:43 eagappnbu479p2v6.engba.veritas.com systemd[1]: nmb.service:
start operation timed out. Terminating.
Jul 26 17:51:43 eagappnbu479p2v6.engba.veritas.com systemd[1]: nmb.service:
Failed with result 'timeout'.
Jul 26 17:51:43 eagappnbu479p2v6.engba.veritas.com systemd[1]: Failed to
start Samba NMB Daemon.

I've tried explicitly listing `interfaces = eth0` in smb.conf, but that
doesn't have an impact.

Thanks,
-Tim