On 06/22/2012 07:06 AM, Amit Shah wrote:
On (Wed) 20 Jun 2012 [16:29:22], Anthony Liguori wrote:
On 06/20/2012 01:59 AM, Amit Shah wrote:
The Linux kernel already has a virtio-rng driver, this is the device
implementation.
When the guest asks for entropy from the virtio hwrng, it puts a buffer
in the vq. We then put entropy into that buffer, and push it back to
the guest.
The chardev connected to this device is fed the data to be sent to the
guest.
Invocation is simple:
$ qemu ... -device virtio-rng-pci,chardev=foo
In the guest, we see
$ cat /sys/devices/virtual/misc/hw_random/rng_available
virtio
$ cat /sys/devices/virtual/misc/hw_random/rng_current
virtio
# cat /dev/hwrng
Simply feeding /dev/urandom from the host to the chardev is sufficient:
$ qemu ... -chardev socket,path=/tmp/foo,server,nowait,id=foo \
-device virtio-rng,chardev=foo
$ nc -U /tmp/foo< /dev/urandom
A QMP event is sent for interested apps to monitor activity and send the
appropriate number of bytes that get asked by the guest:
{"timestamp": {"seconds": 1337966878, "microseconds": 517009}, \
"event": "ENTROPY_NEEDED", "data": {"bytes": 64}}
Nack.
Use a protocol.
How does one write a program on Linux to get random numbers?
He uses /dev/random, of course.
You could also use the nss freebl crypto library that provides a random
number generator that for example seeds itself from /dev/urandom and
then uses hash operations on the seed before it goes back to getting
random numbers from /dev/urandom again. So, another idea: call
RNG_GenerateGlobalRandomBytes() to get the entropy.
Stefan
