Roman,

(1) How did you confirm that nscd is not listening on a datagram socket?

(2) How did you determine that nscd is not inheriting the listening socket from the parent?

Cheers,
Carlos.

> (1) How did you confirm that nscd is not listening on a datagram socket?

1)
# sudo ss -lpx |grep nscd
u_dgr  UNCONN     0      0      /var/run/nscd/socket 15662     * 0       users:(("systemd",1,49))
u_str  LISTEN     0      0      /var/run/nscd/socket 16779     * 0       users:(("nscd",580,15))
u_dgr  UNCONN     0      0                    * 16392 * 7598    users:(("nscd",580,4))

2) by code inspection:
# grep -F F_UNIX nscd/*
nscd/connections.c:      sock = socket (AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
nscd/connections.c:    sock = socket (AF_UNIX, SOCK_STREAM, 0);
nscd/connections.c:  sock_addr.sun_family = AF_UNIX;
nscd/nscd.c:  sock = socket (PF_UNIX, SOCK_STREAM, 0);
nscd/nscd.c:  addr.sun_family = AF_UNIX;
nscd/nscd_helper.c:      sock = __socket (PF_UNIX, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
nscd/nscd_helper.c:    sock = __socket (PF_UNIX, SOCK_STREAM, 0);
nscd/nscd_helper.c:  sun.sun_family = AF_UNIX;

> (2) How did you determine that nscd is not inheriting the listening socket from
> the parent?

1) by modifying nscd.socket to use stream socket, and observing that
the first name lookup (which causes nscd activation) times out, and
that afterwards the activated nscd listens on a different socket than
systemd

2) by code inspection: nscd unconditionally creates a listening socket
regardless of whether it was started the socket passed to it from the
parent or not:

 532 void
 533 nscd_init (void)
 534 {
...
 850   /* Create the socket.  */
 851 #ifndef __ASSUME_SOCK_CLOEXEC
 852   sock = -1;
 853   if (have_sock_cloexec >= 0)
 854 #endif
 855     {
 856       sock = socket (AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
 857 #ifndef __ASSUME_SOCK_CLOEXEC
 858       if (have_sock_cloexec == 0)
 859         have_sock_cloexec = sock != -1 || errno != EINVAL ? 1 : -1;
 860 #endif
 861     }
 862 #ifndef __ASSUME_SOCK_CLOEXEC
 863   if (have_sock_cloexec < 0)
 864     sock = socket (AF_UNIX, SOCK_STREAM, 0);
 865 #endif
 866   if (sock < 0)
 867     {
 868       dbg_log (_("cannot open socket: %s"), strerror (errno));
 869       exit (errno == EACCES ? 4 : 1);
 870     }

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