kern/60729: incosistent st_ino from the first stat(2) on a socket

["uwe%stderr.spb.ru@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60729
>Category:       kern
>Synopsis:       incosistent st_ino from the first stat(2) on a socket
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Sep 14 22:30:00 +0000 2026
>Originator:     Valery Ushakov
>Release:        NetBSD 11.99
>Organization:
>Environment:
>Description:
Came across this blog post on lobsters:

https://yuvalino.com/how-can-you-not-be-romantic-about-unix-domain-sockets

The absolutely first call of stat(2) on a socket returns st_ino of zero.
The next call of stat(2) on the same socket will return a different st_ino.
>How-To-Repeat:
# cat sockino.c
#include <sys/socket.h>
#include <sys/stat.h>

#include <err.h>
#include <stdio.h>
#include <stdlib.h>


int
main()
{
    int status;

    int sock[2];
    status = socketpair(PF_UNIX, SOCK_DGRAM, 0, sock);
    if (status < 0)
	err(EXIT_FAILURE, "socketpair");

    struct stat st;

    status = fstat(sock[0], &st);
    if (status < 0)
	err(EXIT_FAILURE, "fstat");

    printf("%lld/%llu\n",
	   (signed long long)st.st_dev,
	   (unsigned long long)st.st_ino);

    status = fstat(sock[0], &st);
    if (status < 0)
	err(EXIT_FAILURE, "fstat");

    printf("%lld/%llu\n",
	   (signed long long)st.st_dev,
	   (unsigned long long)st.st_ino);

    return 0;
}
# ./sockino 
-1/0
-1/1
# ./sockino 
-1/2
-1/2

>Fix:
A comment on lobsters

https://lobste.rs/s/uauns9/how_can_you_not_be_romantic_about_unix

pointed to

https://cgit.freebsd.org/src/commit/sys/kern/uipc_usrreq.c?id=6f782c4636672e40c45ef9c9f17635e6c110d290
https://cgit.freebsd.org/src/commit/sys/kern/uipc_usrreq.c?id=f218ac5087c7697321d3866d68c037cc88b0b005