1.\" $OpenBSD: viornd.4,v 1.2 2015/02/17 16:29:16 bentley Exp $ 2.\" 3.\" Copyright (c) 2014 Stefan Fritsch <sf@sfritsch.de> 4.\" 5.\" Permission to use, copy, modify, and distribute this software for any 6.\" purpose with or without fee is hereby granted, provided that the above 7.\" copyright notice and this permission notice appear in all copies. 8.\" 9.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16.\" 17.Dd $Mdocdate: February 17 2015 $ 18.Dt VIORND 4 19.Os 20.Sh NAME 21.Nm viornd 22.Nd VirtIO random number device 23.Sh SYNOPSIS 24.Cd "viornd* at virtio? flags 0x00" 25.Sh DESCRIPTION 26The 27.Nm 28driver provides a virtual random number generator using a 29.Xr virtio 4 30entropy device provided by QEMU 1.3 and later, and possibly by other 31hypervisors. 32.Pp 33As there is currently no way for 34.Nm 35to determine how much entropy is needed, the second byte of the flags value 36can be used to configure how often it should request more entropy from the 37host. 38If the second lowest byte of the flags has a value from 1 to 15, 39.Nm 40will ask for 16 bytes of entropy every 15 * (1 << value) seconds. 41For example, flags == 0x100 means an interval of 30 seconds, 420x500 means 8 minutes, 0xa00 means 256 minutes, and 0xf00 means about 6 days. 43For flags == 0, a default value will be used (currently 8 minutes). 44If the bit 0x1000 is set in the flags, 45.Nm 46will only request entropy from the host once during system boot. 47.Sh SEE ALSO 48.Xr intro 4 , 49.Xr virtio 4 50.Sh HISTORY 51The 52.Nm 53driver first appeared in 54.Ox 5.5 . 55.Sh AUTHORS 56.An -nosplit 57The 58.Nm 59driver was written by 60.An Stefan Fritsch Aq Mt sf@sfritsch.de . 61