rng: add request queue support to rng-random
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>
diff --git a/backends/rng-random.c b/backends/rng-random.c
index 8cdad6a..a6cb385 100644
--- a/backends/rng-random.c
+++ b/backends/rng-random.c
@@ -22,10 +22,6 @@
int fd;
char *filename;
-
- EntropyReceiveFunc *receive_func;
- void *opaque;
- size_t size;
};
/**
@@ -38,36 +34,35 @@
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)
