qemu when started with -net tap is crashing on tap_open on 
NetBSD-current, I had to apply the following patch to get it to work

alpine# diff --from-file /tmp/vl.c  vl.c
50,51d49
< #include <net/if.h>
< #include <net/if_tap.h>
2054c2052
<     struct ifreq ifinfo;
---
 >     struct stat s;
2062,2063c2060,2062
<     ioctl(fd,TAPGIFNAME, &ifinfo);
<     pstrcpy(ifname, ifname_size, ifinfo.ifr_name);
---
 >     fstat(fd, &s);
 >     dev = devname(s.st_rdev, S_IFCHR);
 >     pstrcpy(ifname, ifname_size, dev);
alpine#