struct buffer *rxbuf;
struct buffer *txbuf;
struct poll_waiter *tx_waiter;
+
+ /* rx_want and tx_want record the result of the last call to SSL_read()
+ * and SSL_write(), respectively:
+ *
+ * - If the call reported that data needed to be read from the file
+ * descriptor, the corresponding member is set to SSL_READING.
+ *
+ * - If the call reported that data needed to be written to the file
+ * descriptor, the corresponding member is set to SSL_WRITING.
+ *
+ * - Otherwise, the member is set to SSL_NOTHING, indicating that the
+ * call completed successfully (or with an error) and that there is no
+ * need to block.
+ *
+ * These are needed because there is no way to ask OpenSSL what a data read
+ * or write would require without giving it a buffer to receive into or
+ * data to send, respectively. (Note that the SSL_want() status is
+ * overwritten by each SSL_read() or SSL_write() call, so we can't rely on
+ * its value.)
+ *
+ * A single call to SSL_read() or SSL_write() can perform both reading
+ * and writing and thus invalidate not one of these values but actually
+ * both. Consider this situation, for example:
+ *
+ * - SSL_write() blocks on a read, so tx_want gets SSL_READING.
+ *
+ * - SSL_read() laters succeeds reading from 'fd' and clears out the
+ * whole receive buffer, so rx_want gets SSL_READING.
+ *
+ * - Client calls vconn_wait(WAIT_RECV) and vconn_wait(WAIT_SEND) and
+ * blocks.
+ *
+ * - Now we're stuck blocking until the peer sends us data, even though
+ * SSL_write() could now succeed, which could easily be a deadlock
+ * condition.
+ *
+ * On the other hand, we can't reset both tx_want and rx_want on every call
+ * to SSL_read() or SSL_write(), because that would produce livelock,
+ * e.g. in this situation:
+ *
+ * - SSL_write() blocks, so tx_want gets SSL_READING or SSL_WRITING.
+ *
+ * - SSL_read() blocks, so rx_want gets SSL_READING or SSL_WRITING,
+ * but tx_want gets reset to SSL_NOTHING.
+ *
+ * - Client calls vconn_wait(WAIT_RECV) and vconn_wait(WAIT_SEND) and
+ * blocks.
+ *
+ * - Client wakes up immediately since SSL_NOTHING in tx_want indicates
+ * that no blocking is necessary.
+ *
+ * The solution we adopt here is to set tx_want to SSL_NOTHING after
+ * calling SSL_read() only if the SSL state of the connection changed,
+ * which indicates that an SSL-level renegotiation made some progress, and
+ * similarly for rx_want and SSL_write(). This prevents both the
+ * deadlock and livelock situations above.
+ */
+ int rx_want, tx_want;
};
/* SSL context created by ssl_init(). */
static int do_ssl_init(void);
static bool ssl_wants_io(int ssl_error);
static void ssl_close(struct vconn *);
-static int interpret_ssl_error(const char *function, int ret, int error);
-static void ssl_do_tx(int fd, short int revents, void *vconn_);
+static int interpret_ssl_error(const char *function, int ret, int error,
+ int *want);
+static void ssl_tx_poll_callback(int fd, short int revents, void *vconn_);
static DH *tmp_dh_callback(SSL *ssl, int is_export UNUSED, int keylength);
+short int
+want_to_poll_events(int want)
+{
+ switch (want) {
+ case SSL_NOTHING:
+ NOT_REACHED();
+
+ case SSL_READING:
+ return POLLIN;
+
+ case SSL_WRITING:
+ return POLLOUT;
+
+ default:
+ NOT_REACHED();
+ }
+}
+
static int
new_ssl_vconn(const char *name, int fd, enum session_type type,
enum ssl_state state, struct vconn **vconnp)
sslv->rxbuf = NULL;
sslv->txbuf = NULL;
sslv->tx_waiter = NULL;
+ sslv->rx_want = sslv->tx_want = SSL_NOTHING;
*vconnp = &sslv->vconn;
return 0;
return EAGAIN;
} else {
interpret_ssl_error((sslv->type == CLIENT ? "SSL_connect"
- : "SSL_accept"), retval, error);
+ : "SSL_accept"), retval, error, NULL);
shutdown(sslv->fd, SHUT_RDWR);
return EPROTO;
}
}
static int
-interpret_ssl_error(const char *function, int ret, int error)
+interpret_ssl_error(const char *function, int ret, int error,
+ int *want)
{
+ *want = SSL_NOTHING;
+
switch (error) {
case SSL_ERROR_NONE:
VLOG_ERR("%s: unexpected SSL_ERROR_NONE", function);
break;
case SSL_ERROR_WANT_READ:
+ *want = SSL_READING;
+ return EAGAIN;
+
case SSL_ERROR_WANT_WRITE:
+ *want = SSL_WRITING;
return EAGAIN;
case SSL_ERROR_WANT_CONNECT:
struct ssl_vconn *sslv = ssl_vconn_cast(vconn);
struct buffer *rx;
size_t want_bytes;
+ int old_state;
ssize_t ret;
if (sslv->rxbuf == NULL) {
/* Behavior of zero-byte SSL_read is poorly defined. */
assert(want_bytes > 0);
+ old_state = SSL_get_state(sslv->ssl);
ret = SSL_read(sslv->ssl, buffer_tail(rx), want_bytes);
+ if (old_state != SSL_get_state(sslv->ssl)) {
+ sslv->tx_want = SSL_NOTHING;
+ if (sslv->tx_waiter) {
+ poll_cancel(sslv->tx_waiter);
+ ssl_tx_poll_callback(sslv->fd, POLLIN, vconn);
+ }
+ }
+ sslv->rx_want = SSL_NOTHING;
+
if (ret > 0) {
rx->size += ret;
if (ret == want_bytes) {
return EOF;
}
} else {
- return interpret_ssl_error("SSL_read", ret, error);
+ return interpret_ssl_error("SSL_read", ret, error, &sslv->rx_want);
}
}
}
}
static void
-ssl_register_tx_waiter(struct vconn *vconn)
+ssl_register_tx_waiter(struct vconn *vconn)
{
struct ssl_vconn *sslv = ssl_vconn_cast(vconn);
- short int events = SSL_want_read(sslv->ssl) ? POLLIN : POLLOUT;
- sslv->tx_waiter = poll_fd_callback(sslv->fd, events, ssl_do_tx, vconn);
+ sslv->tx_waiter = poll_fd_callback(sslv->fd,
+ want_to_poll_events(sslv->tx_want),
+ ssl_tx_poll_callback, vconn);
+}
+
+static int
+ssl_do_tx(struct vconn *vconn)
+{
+ struct ssl_vconn *sslv = ssl_vconn_cast(vconn);
+
+ for (;;) {
+ int old_state = SSL_get_state(sslv->ssl);
+ int ret = SSL_write(sslv->ssl, sslv->txbuf->data, sslv->txbuf->size);
+ if (old_state != SSL_get_state(sslv->ssl)) {
+ sslv->rx_want = SSL_NOTHING;
+ }
+ sslv->tx_want = SSL_NOTHING;
+ if (ret > 0) {
+ buffer_pull(sslv->txbuf, ret);
+ if (sslv->txbuf->size == 0) {
+ return 0;
+ }
+ } else {
+ int ssl_error = SSL_get_error(sslv->ssl, ret);
+ if (ssl_error == SSL_ERROR_ZERO_RETURN) {
+ VLOG_WARN("SSL_write: connection closed");
+ return EPIPE;
+ } else {
+ return interpret_ssl_error("SSL_write", ret, ssl_error,
+ &sslv->tx_want);
+ }
+ }
+ }
}
static void
-ssl_do_tx(int fd UNUSED, short int revents UNUSED, void *vconn_)
+ssl_tx_poll_callback(int fd UNUSED, short int revents UNUSED, void *vconn_)
{
struct vconn *vconn = vconn_;
struct ssl_vconn *sslv = ssl_vconn_cast(vconn);
- int ret = SSL_write(sslv->ssl, sslv->txbuf->data, sslv->txbuf->size);
- if (ret > 0) {
- buffer_pull(sslv->txbuf, ret);
- if (sslv->txbuf->size == 0) {
- ssl_clear_txbuf(sslv);
- return;
- }
+ int error = ssl_do_tx(vconn);
+ if (error != EAGAIN) {
+ ssl_clear_txbuf(sslv);
} else {
- int error = SSL_get_error(sslv->ssl, ret);
- if (error == SSL_ERROR_ZERO_RETURN) {
- /* Connection closed (EOF). */
- VLOG_WARN("SSL_write: connection close");
- } else if (interpret_ssl_error("SSL_write", ret, error) != EAGAIN) {
- ssl_clear_txbuf(sslv);
- return;
- }
+ ssl_register_tx_waiter(vconn);
}
- ssl_register_tx_waiter(vconn);
}
static int
ssl_send(struct vconn *vconn, struct buffer *buffer)
{
struct ssl_vconn *sslv = ssl_vconn_cast(vconn);
- ssize_t ret;
if (sslv->txbuf) {
return EAGAIN;
- }
+ } else {
+ int error;
- ret = SSL_write(sslv->ssl, buffer->data, buffer->size);
- if (ret > 0) {
- if (ret == buffer->size) {
- buffer_delete(buffer);
- } else {
- sslv->txbuf = buffer;
- buffer_pull(buffer, ret);
+ sslv->txbuf = buffer;
+ error = ssl_do_tx(vconn);
+ switch (error) {
+ case 0:
+ ssl_clear_txbuf(sslv);
+ return 0;
+ case EAGAIN:
ssl_register_tx_waiter(vconn);
+ return 0;
+ default:
+ sslv->txbuf = NULL;
+ return error;
}
- return 0;
- } else {
- int error = SSL_get_error(sslv->ssl, ret);
- if (error == SSL_ERROR_ZERO_RETURN) {
- /* Connection closed (EOF). */
- VLOG_WARN("SSL_write: connection close");
- return EPIPE;
- } else {
- return interpret_ssl_error("SSL_write", ret, error);
- }
- }
-}
-
-static bool
-ssl_needs_wait(struct ssl_vconn *sslv)
-{
- if (SSL_want_read(sslv->ssl)) {
- poll_fd_wait(sslv->fd, POLLIN);
- return true;
- } else if (SSL_want_write(sslv->ssl)) {
- poll_fd_wait(sslv->fd, POLLOUT);
- return true;
- } else {
- return false;
}
}
case WAIT_CONNECT:
if (vconn_connect(vconn) != EAGAIN) {
poll_immediate_wake();
- } else if (sslv->state == STATE_TCP_CONNECTING) {
- poll_fd_wait(sslv->fd, POLLOUT);
- } else if (!ssl_needs_wait(sslv)) {
- NOT_REACHED();
+ } else {
+ switch (sslv->state) {
+ case STATE_TCP_CONNECTING:
+ poll_fd_wait(sslv->fd, POLLOUT);
+ break;
+
+ case STATE_SSL_CONNECTING:
+ /* ssl_connect() called SSL_accept() or SSL_connect(), which
+ * set up the status that we test here. */
+ poll_fd_wait(sslv->fd,
+ want_to_poll_events(SSL_want(sslv->ssl)));
+ break;
+
+ default:
+ NOT_REACHED();
+ }
}
break;
case WAIT_RECV:
- if (!ssl_needs_wait(sslv)) {
- if (SSL_pending(sslv->ssl)) {
- poll_immediate_wake();
- } else {
- poll_fd_wait(sslv->fd, POLLIN);
- }
+ if (sslv->rx_want != SSL_NOTHING) {
+ poll_fd_wait(sslv->fd, want_to_poll_events(sslv->rx_want));
+ } else {
+ poll_immediate_wake();
}
break;
case WAIT_SEND:
- if (!sslv->txbuf && !ssl_needs_wait(sslv)) {
- poll_fd_wait(sslv->fd, POLLOUT);
+ if (!sslv->txbuf) {
+ /* We have room in our tx queue. */
+ poll_immediate_wake();
+ } else {
+ /* The call to ssl_tx_poll_callback() will wake us up. */
}
break;
projects / openvswitch / commitdiff