api: provide api definition over api

This patch allows a client to bootstrap itself by downloading the
JSON API definitions over the API itself.

This patch enables it for Python (probably need a dynamic language).
Call VPPApiClient with the new bootstrapapi=True parameter.

Example (Python):

from vpp_papi import VPPApiClient
vpp = VPPApiClient(bootstrapapi=True)
rv = vpp.connect("foobar")
assert rv == 0
print(f'SHOW VERSION: {vpp.api.show_version()}')
vpp.disconnect()

Type: feature
Change-Id: Id903fdccc82b2e22aa1994331d2c150253f2ccae
Signed-off-by: Ole Troan <otroan@employees.org>

2 files changed, 50 insertions, 5 deletions

diff --git a/src/vlibmemory/memclnt.api b/src/vlibmemory/memclnt.api
index a8e7cfeaec0..dc0f4e1c8a7 100644
--- a/src/vlibmemory/memclnt.api
+++ b/src/vlibmemory/memclnt.api
@@ -27,7 +27,7 @@ service {
 };
 
 /*
- * Create a client registration 
+ * Create a client registration
  */
 define memclnt_create {
   option deprecated;
@@ -50,7 +50,7 @@ define memclnt_create_reply {
 };
 
 /*
- * Delete a client registration 
+ * Delete a client registration
  */
 define memclnt_delete {
     u32 index;                  /* index, used e.g. by API trace replay */
@@ -155,7 +155,7 @@ typedef message_table_entry
 };
 
 /*
- * Create a socket client registration. 
+ * Create a socket client registration.
  */
 define sockclnt_create {
     u32 context;                /* opaque value to be returned in the reply */
@@ -172,7 +172,7 @@ define sockclnt_create_reply {
 };
 
 /*
- * Delete a client registration 
+ * Delete a client registration
  */
 define sockclnt_delete {
     u32 client_index;
@@ -252,3 +252,14 @@ define memclnt_create_v2_reply {
     u32 index;                  /* index, used e.g. by API trace replay */
     u64 message_table;          /* serialized message table in shmem */
 };
+
+define get_api_json {
+    u32 client_index;
+    u32 context;
+};
+
+define get_api_json_reply {
+    u32 context;
+    i32 retval;
+    string json[];
+};
diff --git a/src/vlibmemory/memclnt_api.c b/src/vlibmemory/memclnt_api.c
index 7eb61fe7875..299e8d93f02 100644
--- a/src/vlibmemory/memclnt_api.c
+++ b/src/vlibmemory/memclnt_api.c
@@ -145,10 +145,44 @@ vl_api_control_ping_t_handler (vl_api_control_ping_t *mp)
 		({ rmp->vpe_pid = ntohl (getpid ()); }));
 }
 
+static void
+vl_api_get_api_json_t_handler (vl_api_get_api_json_t *mp)
+{
+  vl_api_get_api_json_reply_t *rmp;
+  api_main_t *am = vlibapi_get_main ();
+  int rv = 0, n = 0;
+  u8 *s = 0;
+
+  vl_api_registration_t *rp =
+    vl_api_client_index_to_registration (mp->client_index);
+  if (rp == 0)
+    return;
+
+  s = format (s, "[\n");
+  u8 **ptr;
+  vec_foreach (ptr, am->json_api_repr)
+    {
+      s = format (s, "%s,", ptr[0]);
+    }
+  s[vec_len (s) - 1] = ']'; // Replace last comma with a bracket
+  vec_terminate_c_string (s);
+  n = vec_len (s);
+
+done:
+  REPLY_MACRO3 (VL_API_GET_API_JSON_REPLY, n, ({
+		  if (rv == 0)
+		    {
+		      vl_api_c_string_to_api_string ((char *) s, &rmp->json);
+		    }
+		}));
+  vec_free (s);
+}
+
 #define foreach_vlib_api_msg                                                  \
   _ (GET_FIRST_MSG_ID, get_first_msg_id)                                      \
   _ (API_VERSIONS, api_versions)                                              \
-  _ (CONTROL_PING, control_ping)
+  _ (CONTROL_PING, control_ping)                                              \
+  _ (GET_API_JSON, get_api_json)
 
 /*
  * vl_api_init