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rng: add request queue support to rng-random

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Requests are now created in the RngBackend parent class and the
code path is shared by both rng-egd and rng-random.

This commit fixes the rng-random implementation which processed
only one request at a time and simply discarded all but the most
recent one. In the guest this manifested as delayed completion
of reads from virtio-rng, i.e. a read was completed only after
another read was issued.

By switching rng-random to use the same request queue as rng-egd,
the unsafe stack-based allocation of the entropy buffer is
eliminated and replaced with g_malloc.

Signed-off-by: Ladi Prosek <lprosek@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Message-Id: <1456994238-9585-5-git-send-email-lprosek@redhat.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
This commit is contained in:
Ladi Prosek 2016-03-03 09:37:18 +01:00 • committed by Amit Shah
parent 9f14b0add1
commit 60253ed1e6
4 changed files with 34 additions and 41 deletions
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43
backends/rng-random.c
View file

@ -22,10 +22,6 @@ struct RndRandom
int fd;
char *filename;
EntropyReceiveFunc *receive_func;
void *opaque;
size_t size;
};
/**
@ -38,36 +34,35 @@ struct RndRandom
static void entropy_available(void *opaque)
{
RndRandom *s = RNG_RANDOM(opaque);
uint8_t buffer[s->size];
ssize_t len;
len = read(s->fd, buffer, s->size);
if (len < 0 && errno == EAGAIN) {
return;
while (s->parent.requests != NULL) {
RngRequest *req = s->parent.requests->data;
ssize_t len;
len = read(s->fd, req->data, req->size);
if (len < 0 && errno == EAGAIN) {
return;
}
g_assert(len != -1);
req->receive_entropy(req->opaque, req->data, len);
rng_backend_finalize_request(&s->parent, req);
}
g_assert(len != -1);
s->receive_func(s->opaque, buffer, len);
s->receive_func = NULL;
/* We've drained all requests, the fd handler can be reset. */
qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
}
static void rng_random_request_entropy(RngBackend *b, size_t size,
EntropyReceiveFunc *receive_entropy,
void *opaque)
static void rng_random_request_entropy(RngBackend *b, RngRequest *req)
{
RndRandom *s = RNG_RANDOM(b);
if (s->receive_func) {
s->receive_func(s->opaque, NULL, 0);
if (s->parent.requests == NULL) {
/* If there are no pending requests yet, we need to
* install our fd handler. */
qemu_set_fd_handler(s->fd, entropy_available, NULL, s);
}
s->receive_func = receive_entropy;
s->opaque = opaque;
s->size = size;
qemu_set_fd_handler(s->fd, entropy_available, NULL, s);
}
static void rng_random_opened(RngBackend *b, Error **errp)