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diff --git a/docs/gettingstarted/developers/binary_api_support.rst b/docs/gettingstarted/developers/binary_api_support.rst deleted file mode 100644 index 732ce978daa..00000000000 --- a/docs/gettingstarted/developers/binary_api_support.rst +++ /dev/null @@ -1,486 +0,0 @@ -.. _binary_api_support: - -.. toctree:: - -Binary API Support -================== - -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 80 api -files, with more arriving as folks add programmable features. The API -file compiler sources reside in src/tools/vppapigen. - -From `src/vnet/interface.api -<https://docs.fd.io/vpp/18.11/de/d75/interface_8api.html>`_, here's a -typical request/response message definition: - -.. code-block:: console - - 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 -*vpp/build-root/install-vpp_debug-native/vpp/include/vnet/interface.api.h* -as follows: - -.. code-block:: 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 - #ifndef defined_sw_interface_set_flags - #define defined_sw_interface_set_flags - 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; - #endif - - #ifndef defined_sw_interface_set_flags_reply - #define defined_sw_interface_set_flags_reply - 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 - ... - #endif /* vl_typedefs */ - -To change the admin state of an interface, a binary api client sends a -`vl_api_sw_interface_set_flags_t -<https://docs.fd.io/vpp/18.11/dc/da3/structvl__api__sw__interface__set__flags__t.html>`_ -to VPP, which will respond with a -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 straightforward 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 `src/vlibmemory/memory_shared.c -<https://docs.fd.io/vpp/18.11/dd/d0d/memory__shared_8c.html>`_ -`vl_msg_api_alloc_internal() -<https://docs.fd.io/vpp/18.11/dd/d0d/memory__shared_8c.html#ac6b6797850e1a53bc68b206e6b8413fb>`_. - -Regardless of transport, binary api messages always follow a `msgbuf_t <https://docs.fd.io/vpp/18.11/d9/d65/structmsgbuf__.html>`_ header: - -.. code-block:: C - - /** Message header structure */ - typedef struct msgbuf_ - { - svm_queue_t *q; /**< message allocated in this shmem ring */ - u32 data_len; /**< message length not including header */ - u32 gc_mark_timestamp; /**< message garbage collector mark TS */ - u8 data[0]; /**< actual message begins here */ - } msgbuf_t; - -This structure makes it easy to trace messages without having to -decode them - simply save data_len bytes - and allows -`vl_msg_api_free() -<https://docs.fd.io/vpp/18.11/d6/d1b/api__common_8h.html#aff61e777fe5df789121d8e78134867e6>`_ -to rapidly dispose of message buffers: - -.. code-block:: C - - void - vl_msg_api_free (void *a) - { - msgbuf_t *rv; - void *oldheap; - 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; - <more code...> - return; - } - <more code...> - } - -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 `src/vlibmemory/memory_vlib::c -<https://docs.fd.io/vpp/18.11/dd/d3e/vpp__get__metrics_8c.html#a7c3855ed3c45b48ff92a7e881bfede73>`_ -`vl_msg_api_process_file() -<https://docs.fd.io/vpp/18.11/d0/d5b/vlib__api__cli_8c.html#a60194e3e91c0dc6a75906ea06f4ec113>`_, -and `src/vlibapi/api_shared.c -<https://docs.fd.io/vpp/18.11/d6/dd1/api__shared_8c.html>`_. See also -the debug CLI command "api trace" - -API trace replay caveats -________________________ - -The vpp instance which replays a binary API trace must have the same -message-ID numbering space as the vpp instance which captured the -trace. The replay instance **must** load the same set of plugins as -the capture instance. Otherwise, API messages will be processed by the -**wrong** API message handlers! - -Always start vpp with command-line arguments which include an -"api-trace on" stanza, so vpp will start tracing binary API messages -from the beginning: - -.. code-block:: console - - api-trace { - on - } - -Given a binary api trace in /tmp/api_trace, do the following to work -out the set of plugins: - -.. code-block:: console - - DBGvpp# api trace custom-dump /tmp/api_trace - vl_api_trace_plugin_msg_ids: abf_54307ba2 first 846 last 855 - vl_api_trace_plugin_msg_ids: acl_0d7265b0 first 856 last 893 - vl_api_trace_plugin_msg_ids: cdp_8f707b96 first 894 last 895 - vl_api_trace_plugin_msg_ids: flowprobe_f2f0286c first 898 last 901 - <etc> - -Here, we see the "abf," "acl," "cdp," and "flowprobe" plugins. Use the -list of plugins to construct a matching "plugins" command-line argument -stanza: - -.. code-block:: console - - plugins { - ## Disable all plugins, selectively enable specific plugins - plugin default { disable } - plugin abf_plugin.so { enable } - plugin acl_plugin.so { enable } - plugin cdp_plugin.so { enable } - plugin flowprobe_plugin.so { enable } - } - -To begin with, use the same vpp image that captured a trace to replay -it. It's perfectly fair to rebuild the vpp replay instance, to add -scaffolding to facilitate setting gdb breakpoints on complex -conditions or similar. - -API trace interface issues -__________________________ - -Along the same lines, it may be necessary to manufacture [simulated] -physical interfaces so that an API trace will replay correctly. "show -interface" on the trace origin system can help. An API trace -"custom-dump" as shown above may make it obvious how many loopback -interfaces to create. If you see vhost interfaces being created and -then configured, the first such configuration message in the trace -will tell you how many physical interfaces were involved. - -.. code-block:: console - - SCRIPT: create_vhost_user_if socket /tmp/foosock server - SCRIPT: sw_interface_set_flags sw_if_index 3 admin-up - -In this case, it's fair to guess that one needs to create two loopback -interfaces to "help" the trace replay correctly. - -These issues can be mitigated to a certain extent by replaying the -trace on the system which created it, but in a field debug case that's -not a realistic. - -Client connection details -_________________________ - -Establishing a binary API connection to VPP from a C-language client is easy: - -.. code-block:: 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. The -VPP-side binary API message handlers are very fast. So, when sending -asynchronous messages, make sure to scrape the binary API rx ring with -some enthusiasm! - -**Binary API message RX pthread** - -Calling `vl_client_connect_to_vlib -<https://docs.fd.io/vpp/18.11/da/d25/memory__client_8h.html#a6654b42c91be33bfb6a4b4bfd2327920>`_ -spins up a binary API message RX pthread: - -.. code-block:: C - - static void * - rx_thread_fn (void *arg) - { - svm_queue_t *q; - memory_client_main_t *mm = &memory_client_main; - api_main_t *am = &api_main; - int i; - - 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; - /* - * Find an unused slot in the per-cpu-mheaps array, - * and grab it for this thread. We need to be able to - * push/pop the thread heap without affecting other thread(s). - */ - if (__os_thread_index == 0) - { - for (i = 0; i < ARRAY_LEN (clib_per_cpu_mheaps); i++) - { - if (clib_per_cpu_mheaps[i] == 0) - { - /* Copy the main thread mheap pointer */ - clib_per_cpu_mheaps[i] = clib_per_cpu_mheaps[0]; - __os_thread_index = i; - break; - } - } - ASSERT (__os_thread_index > 0); - } - while (1) - vl_msg_api_queue_handler (q); - } - pthread_exit (0); - } - -To handle the binary API message queue yourself, use -`vl_client_connect_to_vlib_no_rx_pthread -<https://docs.fd.io/vpp/18.11/da/d25/memory__client_8h.html#a11b9577297106c57c0783b96ab190c36>`_. - -**Queue non-empty signalling** - -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 `vl_client_disconnect_from_vlib -<https://docs.fd.io/vpp/18.11/da/d25/memory__client_8h.html#a82c9ba6e7ead8362ae2175eefcf2fd12>`_. 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: - -.. code-block:: 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 `vl_msg_api_alloc <https://docs.fd.io/vpp/18.11/dc/d5a/memory__shared_8h.html#a109ff1e95ebb2c968d43c100c4a1c55a>`_ 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 `api_main <https://docs.fd.io/vpp/18.11/d6/dd1/api__shared_8c.html#af58e3e46b569573e9622b826b2f47a22>`_ 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 -`vl_client_connect_to_vlib_no_rx_pthread -<https://docs.fd.io/vpp/18.11/da/d25/memory__client_8h.html#a11b9577297106c57c0783b96ab190c36>`_), -*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: - -.. code-block:: 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 -`vl_msg_api_set_handlers -<https://docs.fd.io/vpp/18.11/d6/dd1/api__shared_8c.html#aa8a8e1f3876ec1a02f283c1862ecdb7a>`_ -, which sets values in multiple parallel vectors in the `api_main_t -<https://docs.fd.io/vpp/18.11/dd/db2/structapi__main__t.html>`_ -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: - -.. code-block:: 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; - -API message numbering in plugins --------------------------------- - -Binary API message numbering in plugins relies on vpp to issue a block -of message-ID's for the plugin to use: - -.. code-block:: C - - static clib_error_t * - my_init (vlib_main_t * vm) - { - my_main_t *mm = &my_main; - - name = format (0, "myplugin_%08x%c", api_version, 0); - - /* Ask for a correctly-sized block of API message decode slots */ - mm->msg_id_base = vl_msg_api_get_msg_ids - ((char *) name, VL_MSG_FIRST_AVAILABLE); - - } - -Control-plane codes use the vl_client_get_first_plugin_msg_id (...) api -to recover the message ID block base: - -.. code-block:: C - - /* Ask the vpp engine for the first assigned message-id */ - name = format (0, "myplugin_%08x%c", api_version, 0); - sm->msg_id_base = vl_client_get_first_plugin_msg_id ((char *) name); - -It's a fairly common error to forget to add msg_id_base when -registering message handlers, or when sending messages. Using macros -from .../src/vlibapi/api_helper_macros.h can automate the process, but -remember to #define REPLY_MSG_ID_BASE before #including the file: - -.. code-block:: C - - #define REPLY_MSG_ID_BASE mm->msg_id_base - #include <vlibapi/api_helper_macros.h> |