+/**
+ * tcp_vu_data_from_sock() - Handle new data from socket, queue to vhost-user,
+ * in window
+ * @c: Execution context
+ * @conn: Connection pointer
+ *
+ * Return: Negative on connection reset, 0 otherwise
+ */
+int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
+{
+ uint32_t wnd_scaled = conn->wnd_from_tap << conn->ws_from_tap;
+ struct vu_dev *vdev = c->vdev;
+ struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
+ const struct flowside *tapside = TAPFLOW(conn);
+ uint16_t mss = MSS_GET(conn);
+ size_t l2_hdrlen, fillsize;
+ int i, iov_cnt, iov_used;
+ int v4 = CONN_V4(conn);
+ uint32_t already_sent = 0;
+ const uint16_t *check;
+ struct iovec *first;
+ int frame_size;
+ int num_buffers;
+ ssize_t len;
+
+ if (!vu_queue_enabled(vq) || !vu_queue_started(vq)) {
+ flow_err(conn,
+ "Got packet, but RX virtqueue not usable yet");
+ return 0;
+ }
+
+ already_sent = conn->seq_to_tap - conn->seq_ack_from_tap;
+
+ if (SEQ_LT(already_sent, 0)) {
+ /* RFC 761, section 2.1. */
+ flow_trace(conn, "ACK sequence gap: ACK for %u, sent: %u",
+ conn->seq_ack_from_tap, conn->seq_to_tap);
+ conn->seq_to_tap = conn->seq_ack_from_tap;
+ already_sent = 0;
+ }
+
+ if (!wnd_scaled || already_sent >= wnd_scaled) {
+ conn_flag(c, conn, STALLED);
+ conn_flag(c, conn, ACK_FROM_TAP_DUE);
+ return 0;
+ }
+
+ /* Set up buffer descriptors we'll fill completely and partially. */
+
+ fillsize = wnd_scaled;
+
+ if (peek_offset_cap)
+ already_sent = 0;
+
+ iov_vu[0].iov_base = tcp_buf_discard;
+ iov_vu[0].iov_len = already_sent;
+ fillsize -= already_sent;
+
+ /* collect the buffers from vhost-user and fill them with the
+ * data from the socket
+ */
+ iov_cnt = tcp_vu_sock_recv(c, conn, v4, fillsize, &len);
+ if (iov_cnt <= 0)
+ return iov_cnt;
+
+ len -= already_sent;
+ if (len <= 0) {
+ conn_flag(c, conn, STALLED);
+ vu_queue_rewind(vq, iov_cnt);
+ return 0;
+ }
+
+ conn_flag(c, conn, ~STALLED);
+
+ /* Likely, some new data was acked too. */
+ tcp_update_seqack_wnd(c, conn, 0, NULL);
+
+ /* initialize headers */
+ l2_hdrlen = tcp_vu_l2_hdrlen(!v4);
+ iov_used = 0;
+ num_buffers = 0;
+ check = NULL;
+ frame_size = 0;
+
+ /* iov_vu is an array of buffers and the buffer size can be
+ * smaller than the frame size we want to use but with
+ * num_buffer we can merge several virtio iov buffers in one packet
+ * we need only to set the packet headers in the first iov and
+ * num_buffer to the number of iov entries
...this part is clear to me, what I
don't understand is if we still
have a way to guarantee that the sum of several buffers is big enough
to fit frame_size bytes.
We don't have this garantee. But I think it's the same for the socket version?
Thanks,
Laurent