zfs: Implement zfs_ioctl

The function zfs_ioctl was ported from FreeBSD code.

OSv port details:
1) Copyright was properly updated.
2) Added missing header bsd/sys/sys/filio.h from FreeBSD.
3) Solved conflicts.

Later on, lseek should be modified to take advantage of
this change, and add support for finding holes and data.

Signed-off-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>
Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
virtio::net: Don't use indirect buffers

This improve TCP Tx performance by about 10%.

Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
Signed-off-by: Avi Kivity <avi@cloudius-systems.com>
virtio-net:txq: Don't caclucate the sg length

Don't caclucate the sg length, use vqueue->_sg_vec.size() instead.

Signed-off-by: Vlad Zolotarov <vladz@cloudius-systems.com>
Signed-off-by: Avi Kivity <avi@cloudius-systems.com>