Subject: fstat() and cloned devices
To: None <>
From: Klaus Heinz <>
List: tech-kern
Date: 10/07/2007 16:56:20

qemu does the following in vl.c:

  fd = open("/dev/tap", O_RDWR);
  fstat(fd, &s);
  dev = devname(s.st_rdev, S_IFCHR);

This fails on NetBSD 3 because fstat() returns -1 and most (all?)
members of struct stat are set to 0.

I have two questions:

- How can I get the name of the cloned interface (tap1, tap2, ...)?
- Can anyone please check whether there are any other undocumented
  errno values for fstat? If fstat() returns -1 errno is set to 45
  (EOPNOTSUPP) which is not listed on the man page for fstat().

  I tried to find the file where fstat is implemented but failed
  miserably. It looks like fstat in NetBSD 3 is really fstat13 with
  system call number 279, that's as far as I got.