[Bug 247201] stat()'ing /dev/tap results in a new interface

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=247201

            Bug ID: 247201
           Summary: stat()'ing /dev/tap results in a new interface
           Product: Base System
           Version: CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: bugs at FreeBSD.org
          Reporter: fk at fabiankeil.de

stat()'ing /dev/tap (with "stat" or "ls -l") results in a new interface:

# uname -a
FreeBSD  13.0-CURRENT FreeBSD 13.0-CURRENT #0 r361779: Thu Jun  4 05:01:54 UTC
2020     root at releng1.nyi.freebsd.org:/usr/obj/usr/src/amd64.amd64/sys/GENERIC 
amd64
# ifconfig | grep ^tap
# stat /dev/tap
1895890688 93 crw------- 1 uucp dialer 93 0 "Jun 12 12:25:33 2020" "Jun 12
12:25:33 2020" "Jun 12 12:25:33 2020" "Dec 31 23:59:59 1969" 4096 0 0 /dev/tap
# ifconfig | grep ^tap
tap0: flags=8802<BROADCAST,SIMPLEX,MULTICAST> metric 0 mtu 1500

The issue is also present in earlier versions such as 11/stable where dtrace
shows the following stack:

fk at t520 ~ $sudo dtrace -n "fbt:if_tap:tapcreate:entry {stack()}"
dtrace: description 'fbt:if_tap:tapcreate:entry ' matched 1 probe
CPU     ID                    FUNCTION:NAME
  1  44398                  tapcreate:entry 
              if_tap.ko`tap_clone_create+0x71
              kernel`if_clone_createif+0xb3
              if_tap.ko`tapclone+0x1af
              kernel`devfs_lookup+0x59e
              kernel`VOP_LOOKUP_APV+0x7a
              kernel`lookup+0x6d1
              kernel`namei+0x455
              kernel`kern_statat+0x9a
              kernel`sys_lstat+0x30
              kernel`amd64_syscall+0xa86
              kernel`0xffffffff8085cd40

^C

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