On Wed, 27 Apr 2016 11:59:50 +0300, Jukka Rissanen wrote:

Signed-off-by: Jukka Rissanen <jukka.rissanen(a)linux.intel.com>
---
Hi,

current network application APIs in Zephyr are synchronous and a
bit of awkward to use in TCP. Because of these things, I propose
couple of new functions that are asynchronous and easier to use
by the application. These APIs require net_buf fragmentation support
that I sent earlier.

Cheers,
Jukka


include/net/net_socket.h | 141 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 141 insertions(+)

diff --git a/include/net/net_socket.h b/include/net/net_socket.h
index 88073b1..2451de3 100644
--- a/include/net/net_socket.h
+++ b/include/net/net_socket.h
@@ -143,6 +143,147 @@ int net_reply(struct net_context *context, struct net_buf *buf);
struct simple_udp_connection *
net_context_get_udp_connection(struct net_context *context);

+/**
+ * @brief Callback that is called when there is something received from
+ * the network.
+ *
+ * @details It is callback responsibility to release the net_buf when the
+ * data is no longer needed. The callback is called in fiber context.
+ *
+ * @param context Network context
+ * @param status 0 if ok, <0 if there is an error
+ * @param iov List of net_buf that contain data
+ * @param user_data User supplied data
+ */
+typedef void (*net_readv_cb_t)(struct net_context *context,
+ int status,
+ struct net_buf *iov,
+ void *user_data);

I receive a list of net_buf, based on what criteria? A list of packets
or a single packet split in several buffers? If the latter, then you are
relegating to the application developer the job of putting it all
together, which in many cases will be required. Unless we expect that
every single higher level protocol will work with non-continuous chunks
of memory.

+
+/**
+ * @brief Register a receiver to get data from network.
+ *
+ * @details Application uses this to get data from network connection.
+ * Caller needs to specify a callback function that is called when data
+ * is received by the socket. When the IP stack has received data, it then
+ * calls user specified callback and it is callback responsibility to
+ * release the net_buf when the data is no longer needed.
+ * This function will return immediately as it only sets a callback to be
+ * called when new data is received. Application can remove the registered
+ * callback by calling the function with same context and setting cb to NULL.
+ *
+ * @param context Network context
+ * @param cb User supplied callback function
+ * @param user_data User supplied data
+ *
+ * @return 0 if cb registration was ok, <0 otherwise
+ */
+int net_readv(struct net_context *context,
+ net_readv_cb_t cb,
+ void *user_data);
+
+/**
+ * @brief Callback that is called when user can send
+ * data to the network.
+ *
+ * @details The first call to this function will set *status to 0 and
+ * bytes_sent to 0. Application can then prepare the data to be sent
+ * in net_buf fragment list. The data to be sent is returned to the
+ * caller of the function. If application does not wish to send anything
+ * it can just return NULL. In this case the caller will deallocate the
+ * iov list. Application should set the *status to <0 to indicate more
+ * detailed reason for the error if NULL is returned.
+ *
+ * For successfully sent UDP data, the IP stack will call this
+ * callback again with status set to 0 and bytes_sent telling how many bytes
+ * were sent. If the UDP data was not sent for some reason, then *status
+ * will have value < 0 and bytes_sent is set to 0.
+ *
+ * For TCP, the callback is called when the network connection has been
+ * established. In this case the *status is 0 and bytes_sent is 0.
+ * If there is a connection timeout, the status code will be -ETIMEDOUT
+ * and bytes_sent is set to 0. Other error codes are also possible in
+ * which case the *status < 0 and bytes_sent will tell how many bytes were
+ * successfully sent. If the *status is set to 0 then bytes_sent will tell
+ * how many bytes were sent to the peer.
+ *
+ * The iov fragment list does not contain data that has been successfully
+ * sent. Also the iov->frags->data of the first data fragment will point to
+ * first byte that has not yet been sent. If all the data was sent
+ * successfully, then the first item of iov list will have its frags pointer
+ * set to NULL. Application can send more data if it wishes by returning
+ * a new list of data fragments.
+ *
+ * The callback is called in fiber context.
+ *
+ * @param context Network context
+ * @param status 0 if ok, <0 if there is an error in stack side
+ * Application can return error code if needed via this pointer.
+ * @param bytes_sent How many bytes were sent.
+ * @param iov List of net_buf that contain data. If this is NULL, then
+ * allocate the buf and fill it with data. If non-NULL, then the protocol
+ * headers are already there and you can append the data.
+ * @param user_data User supplied data
+ *
+ * @return A valid net_buf that needs to be sent,
+ * NULL if user is not able to send anything.
+ */
+typedef struct net_buf *(*net_writev_cb_t)(struct net_context *context,
+ int *status,
+ int bytes_sent,
+ struct net_buf *iov,
+ void *user_data);

So the way to use this is:
- I have data to send, I call net_writev() and set my callback.
- When data can be sent, callback is called, *status and bytes_sent = 0
- I allocate a net_buf, put my data in it, and return it.
* What's the iov received here? Only for error cases or the callback
can be called multiple times to send the remaining data? In that
case, the idea is that I receive a list of unsent data that I need
to return and that's it?
- When all data was sent, the callback is called again with *status 0
and bytes_sent sent to the total of bytes sent... since the last time
the function was called? Since the first?

The thing with the fragment list, I'm understanding is meant to work as
an iovec, so let's say I have a CoAP server that wants to notify three
different clients of a change in a resource, it would make sense to have
a single buffer with the payload and change the one with the header. If
I understand this correctly, when data was sent successfully, I will not
have access to the net_buf with the payload anymore, so I would need to
recreate it, correct? In this case, there's no gain (and maybe even a
little loss) in doing a list of fragments, when I can just use a single
buffer and copy both header and payload to it.

+
+/**
+ * @brief Send data to network.
+ *
+ * @details Application uses this to send data to a network connection.
+ * Caller needs to specify a callback function that is called when data
+ * is ready to be sent. The function will return immediately, the timeout
+ * is only used when calling the user callback. For UDP, the timeout is
+ * ignored. For TCP the callback is called after the TCP connection is
+ * established and user is able to send data, or if there is an error
+ * creating a connection or if the connection timeouts.
+ *

This means that every time I call net_writev(), the TCP connection is
established? Or is that only the first time? If it's only the first, why
not add a connect() function? And if it's established every time, what's
the point of that?

+ * @param context Network context
+ * @param timeout How long to wait until user can send data. This is only
+ * used in TCP.
+ * @param cb User supplied callback function
+ * @param user_data User supplied data
+ *
+ * @return 0 if cb registration was ok, <0 otherwise
+ */
+int net_writev(struct net_context *context,
+ int32_t timeout,
+ net_writev_cb_t cb,
+ void *user_data);
+
+/**
+ * @brief Reply data to sender.
+ *
+ * @details This is a helper that will help user to reply data to the
+ * sender. Application can use this function to reply data it received
+ * via net_readv().
+ *
+ * @param context Network context
+ * @param timeout How long to wait until user can send data. This is only
+ * used in TCP.
+ * @param iov Data to be sent
+ * @param cb User supplied callback function
+ * @param user_data User supplied data
+ *
+ * @return 0 if cb registration was ok, <0 otherwise
+ */
+int net_replyv(struct net_context *context,
+ int32_t timeout,
+ struct net_buf *iov,
+ net_writev_cb_t cb,
+ void *user_data);
+

Is there really no way to get rid of this? Why can't we just have a
'send' function that works for all cases? If the problem is getting the
address to send to, just add a helper function to put this in the
net_buf before sending.

#ifdef __cplusplus
}
#endif
--
2.5.5