docs: convert vpp doc md->rst

Type: improvement

Change-Id: If453321785b04f9c16e8cea36fb1910efaeb2c59
Signed-off-by: Nathan Skrzypczak <nathan.skrzypczak@gmail.com>

1 files changed, 0 insertions, 352 deletions

diff --git a/src/vlibapi/api_doc.md b/src/vlibapi/api_doc.md
deleted file mode 100644
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--- a/src/vlibapi/api_doc.md
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-# Binary API support    {#api_doc}
-
-VPP provides a binary API scheme to allow a wide variety of client codes to
-program data-plane tables. As of this writing, there are hundreds of binary
-APIs.
-
-Messages are defined in `*.api` files. Today, there are about 50 api files,
-with more arriving as folks add programmable features.  The API file compiler
-sources reside in @ref src/tools/vppapigen.
-
-From @ref src/vnet/interface.api, here's a typical request/response message
-definition:
-
-```{.c}
-     autoreply define sw_interface_set_flags
-     {
-       u32 client_index;
-       u32 context;
-       u32 sw_if_index;
-       /* 1 = up, 0 = down */
-       u8 admin_up_down;
-     };
-```
-
-To a first approximation, the API compiler renders this definition into
-`build-root/.../vpp/include/vnet/interface.api.h` as follows:
-
-```{.c}
-    /****** Message ID / handler enum ******/
-    #ifdef vl_msg_id
-    vl_msg_id(VL_API_SW_INTERFACE_SET_FLAGS, vl_api_sw_interface_set_flags_t_handler)
-    vl_msg_id(VL_API_SW_INTERFACE_SET_FLAGS_REPLY, vl_api_sw_interface_set_flags_reply_t_handler)
-    #endif	
-
-    /****** Message names ******/
-    #ifdef vl_msg_name
-    vl_msg_name(vl_api_sw_interface_set_flags_t, 1)
-    vl_msg_name(vl_api_sw_interface_set_flags_reply_t, 1)
-    #endif	
-
-    /****** Message name, crc list ******/
-    #ifdef vl_msg_name_crc_list
-    #define foreach_vl_msg_name_crc_interface \
-    _(VL_API_SW_INTERFACE_SET_FLAGS, sw_interface_set_flags, f890584a) \
-    _(VL_API_SW_INTERFACE_SET_FLAGS_REPLY, sw_interface_set_flags_reply, dfbf3afa) \
-    #endif	
-
-    /****** Typedefs *****/
-    #ifdef vl_typedefs
-    typedef VL_API_PACKED(struct _vl_api_sw_interface_set_flags {
-        u16 _vl_msg_id;
-        u32 client_index;
-        u32 context;
-        u32 sw_if_index;
-        u8 admin_up_down;
-    }) vl_api_sw_interface_set_flags_t;
-
-    typedef VL_API_PACKED(struct _vl_api_sw_interface_set_flags_reply {
-        u16 _vl_msg_id;
-        u32 context;
-        i32 retval;
-    }) vl_api_sw_interface_set_flags_reply_t;
-
-    ...
-    #endif /* vl_typedefs */
-```
-
-To change the admin state of an interface, a binary api client sends a
-@ref vl_api_sw_interface_set_flags_t to VPP, which will respond  with a
-@ref vl_api_sw_interface_set_flags_reply_t message.
-
-Multiple layers of software, transport types, and shared libraries
-implement a variety of features:
-
-* API message allocation, tracing, pretty-printing, and replay.
-* Message transport via global shared memory, pairwise/private shared
-  memory, and sockets.
-* Barrier synchronization of worker threads across thread-unsafe
-  message handlers.
-    
-Correctly-coded message handlers know nothing about the transport used to
-deliver messages to/from VPP. It's reasonably straighforward to use multiple
-API message transport types simultaneously.
-
-For historical reasons, binary api messages are (putatively) sent in network
-byte order. As of this writing, we're seriously considering whether that
-choice makes sense.
-
-
-## Message Allocation
-
-Since binary API messages are always processed in order, we allocate messages
-using a ring allocator whenever possible. This scheme is extremely fast when
-compared with a traditional memory allocator, and doesn't cause heap
-fragmentation. See
-@ref src/vlibmemory/memory_shared.c @ref vl_msg_api_alloc_internal().
-
-Regardless of transport, binary api messages always follow a @ref msgbuf_t
-header:
-
-```{.c}
-    typedef struct msgbuf_
-    {
-      unix_shared_memory_queue_t *q;
-      u32 data_len;
-      u32 gc_mark_timestamp;
-      u8 data[0];
-    } msgbuf_t;
-```
-
-This structure makes it easy to trace messages without having to
-decode them - simply save data_len bytes - and allows
-@ref vl_msg_api_free() to rapidly dispose of message buffers:
-
-```{.c}
-    void
-    vl_msg_api_free (void *a)
-    {
-      msgbuf_t *rv;
-      api_main_t *am = &api_main;
-
-      rv = (msgbuf_t *) (((u8 *) a) - offsetof (msgbuf_t, data));
-
-      /*
-       * Here's the beauty of the scheme.  Only one proc/thread has
-       * control of a given message buffer. To free a buffer, we just 
-       * clear the queue field, and leave. No locks, no hits, no errors...
-       */
-      if (rv->q)
-        {
-          rv->q = 0;
-          rv->gc_mark_timestamp = 0;
-          return;
-        }
-      <snip>
-    }
-```
-
-## Message Tracing and Replay
-
-It's extremely important that VPP can capture and replay sizeable binary API
-traces. System-level issues involving hundreds of thousands of API
-transactions can be re-run in a second or less. Partial replay allows one to
-binary-search for the point where the wheels fall off. One can add scaffolding
-to the data plane, to trigger when complex conditions obtain.
-
-With binary API trace, print, and replay, system-level bug reports of the form
-"after 300,000 API transactions, the VPP data-plane stopped forwarding
-traffic, FIX IT!" can be solved offline.
-
-More often than not, one discovers that a control-plane client
-misprograms the data plane after a long time or under complex
-circumstances. Without direct evidence, "it's a data-plane problem!"
-
-See @ref src/vlibmemory/memory_vlib.c @ref vl_msg_api_process_file(),
-and @ref src/vlibapi/api_shared.c. See also the debug CLI command "api trace"
-
-## Client connection details
-
-Establishing a binary API connection to VPP from a C-language client
-is easy:
-
-```{.c}
-        int
-        connect_to_vpe (char *client_name, int client_message_queue_length)
-        {
-          vat_main_t *vam = &vat_main;
-          api_main_t *am = &api_main;
-
-          if (vl_client_connect_to_vlib ("/vpe-api", client_name, 
-                                    	client_message_queue_length) < 0)
-            return -1;
-
-          /* Memorize vpp's binary API message input queue address */
-          vam->vl_input_queue = am->shmem_hdr->vl_input_queue;
-          /* And our client index */
-          vam->my_client_index = am->my_client_index;
-          return 0;
-        }       
-```
-
-32 is a typical value for client_message_queue_length. VPP cannot
-block when it needs to send an API message to a binary API client, and
-the VPP-side binary API message handlers are very fast. When sending
-asynchronous messages, make sure to scrape the binary API rx ring with
-some enthusiasm.
-
-### binary API message RX pthread
-
-Calling @ref vl_client_connect_to_vlib spins up a binary API message RX
-pthread:
-
-```{.c}
-        static void *
-        rx_thread_fn (void *arg)
-        {
-          unix_shared_memory_queue_t *q;
-          memory_client_main_t *mm = &memory_client_main;
-          api_main_t *am = &api_main;
-
-          q = am->vl_input_queue;
-
-          /* So we can make the rx thread terminate cleanly */
-          if (setjmp (mm->rx_thread_jmpbuf) == 0)
-            {
-              mm->rx_thread_jmpbuf_valid = 1;
-              while (1)
-        	{
-        	  vl_msg_api_queue_handler (q);
-        	}
-            }
-          pthread_exit (0);
-        }       
-```
-
-To handle the binary API message queue yourself, use
-@ref vl_client_connect_to_vlib_no_rx_pthread.
-
-In turn, vl_msg_api_queue_handler(...) uses mutex/condvar signalling
-to wake up, process VPP -> client traffic, then sleep. VPP supplies a
-condvar broadcast when the VPP -> client API message queue transitions
-from empty to nonempty.
-
-VPP checks its own binary API input queue at a very high rate.  VPP
-invokes message handlers in "process" context [aka cooperative
-multitasking thread context] at a variable rate, depending on
-data-plane packet processing requirements.
-
-## Client disconnection details
-
-To disconnect from VPP, call @ref vl_client_disconnect_from_vlib.
-Please arrange to call this function if the client application
-terminates abnormally. VPP makes every effort to hold a decent funeral
-for dead clients, but VPP can't guarantee to free leaked memory in the
-shared binary API segment.
-
-## Sending binary API messages to VPP
-
-The point of the exercise is to send binary API messages to VPP, and
-to receive replies from VPP. Many VPP binary APIs comprise a client
-request message, and a simple status reply. For example, to
-set the admin status of an interface, one codes:
-
-```{.c}
-    vl_api_sw_interface_set_flags_t *mp;
-
-    mp = vl_msg_api_alloc (sizeof (*mp));
-    memset (mp, 0, sizeof (*mp));
-    mp->_vl_msg_id = clib_host_to_net_u16 (VL_API_SW_INTERFACE_SET_FLAGS);
-    mp->client_index = api_main.my_client_index;
-    mp->sw_if_index = clib_host_to_net_u32 (<interface-sw-if-index>);
-    vl_msg_api_send (api_main.shmem_hdr->vl_input_queue, (u8 *)mp);
-```
-
-Key points:
-
-* Use @ref vl_msg_api_alloc to allocate message buffers
-
-* Allocated message buffers are not initialized, and must be presumed
-  to contain trash.
-
-* Don't forget to set the _vl_msg_id field!
-
-* As of this writing, binary API message IDs and data are sent in
-  network byte order
-
-* The client-library global data structure @ref api_main keeps track
-  of sufficient pointers and handles used to communicate with VPP
-
-## Receiving binary API messages from VPP
-
-Unless you've made other arrangements (see @ref
-vl_client_connect_to_vlib_no_rx_pthread), *messages are received on a
-separate rx pthread*. Synchronization with the client application main
-thread is the responsibility of the application!
-
-Set up message handlers about as follows:
-
-```{.c}
-    #define vl_typedefs		/* define message structures */
-    #include <vpp/api/vpe_all_api_h.h>
-    #undef vl_typedefs
-
-    /* declare message handlers for each api */
-
-    #define vl_endianfun		/* define message structures */
-    #include <vpp/api/vpe_all_api_h.h>
-    #undef vl_endianfun
-
-    /* instantiate all the print functions we know about */
-    #define vl_print(handle, ...)
-    #define vl_printfun
-    #include <vpp/api/vpe_all_api_h.h>
-    #undef vl_printfun
-
-    /* Define a list of all message that the client handles */
-    #define foreach_vpe_api_reply_msg                            \
-       _(SW_INTERFACE_SET_FLAGS_REPLY, sw_interface_set_flags_reply)           
-
-       static clib_error_t *
-       my_api_hookup (vlib_main_t * vm)
-       {
-         api_main_t *am = &api_main;
-
-       #define _(N,n)                                                  \
-           vl_msg_api_set_handlers(VL_API_##N, #n,                     \
-                                  vl_api_##n##_t_handler,              \
-                                  vl_noop_handler,                     \
-                                  vl_api_##n##_t_endian,               \
-                                  vl_api_##n##_t_print,                \
-                                  sizeof(vl_api_##n##_t), 1);
-         foreach_vpe_api_msg;
-       #undef _
-
-         return 0;
-        }
-```
-
-The key API used to establish message handlers is @ref
-vl_msg_api_set_handlers , which sets values in multiple parallel
-vectors in the @ref api_main_t structure. As of this writing: not all
-vector element values can be set through the API. You'll see sporadic
-API message registrations followed by minor adjustments of this form:
-
-```{.c}
-    /*
-     * Thread-safe API messages
-     */
-    am->is_mp_safe[VL_API_IP_ADD_DEL_ROUTE] = 1;
-    am->is_mp_safe[VL_API_GET_NODE_GRAPH] = 1;
-```
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