api: enforce vla is last and fixed string type

Enforce that variable length fields are the last element of API messages.

Add a 'fixed' version of string type, since dealing with
multiple variable length strings turned out too painful
for the C language bindings.

The string type is now:
{
  string name[64]; // NUL terminated C-string. Essentially decays to u8 name[64]
  string name[];   // Variable length string with embedded len field (vl_api_string_t)
};

The latter notation could be made available to other types as well.
e.g.
{
  vl_api_address_t addresses[];
}
instead of

{
  u32 n_addr;
  vl_api_address_t addresses[n_addr];
};

Type: fix
Change-Id: I18fa17ef47227633752ab50453e8d20a652a9f9b
Signed-off-by: Ole Troan <ot@cisco.com>

3 files changed, 42 insertions, 123 deletions

diff --git a/src/plugins/nat/nat.api b/src/plugins/nat/nat.api
index bd880a6498d..8cf26d4900d 100644
--- a/src/plugins/nat/nat.api
+++ b/src/plugins/nat/nat.api
@@ -13,7 +13,7 @@
  * limitations under the License.
  */
 
-option version = "5.1.0";
+option version = "5.2.0";
 import "vnet/ip/ip_types.api";
 import "vnet/interface_types.api";
 
@@ -171,7 +171,7 @@ define nat_worker_details {
   u32 context;
   u32 worker_index;
   u32 lcore_id;
-  string name;
+  string name[64];
 };
 
 /** \brief Enable/disable NAT IPFIX logging
@@ -678,7 +678,7 @@ autoreply define nat44_add_del_static_mapping {
   u16 external_port;
   vl_api_interface_index_t external_sw_if_index;
   u32 vrf_id;
-  string tag;
+  string tag[64];
 };
 
 /** \brief Dump NAT44 static mappings
@@ -717,7 +717,7 @@ define nat44_static_mapping_details {
   u16 external_port;
   vl_api_interface_index_t external_sw_if_index;
   u32 vrf_id;
-  string tag;
+  string tag[64];
 };
 
 /** \brief Add/delete NAT44 identity mapping
@@ -743,7 +743,7 @@ autoreply define nat44_add_del_identity_mapping {
   u16 port;
   vl_api_interface_index_t sw_if_index;
   u32 vrf_id;
-  string tag;
+  string tag[64];
 };
 
 /** \brief Dump NAT44 identity mappings
@@ -773,7 +773,7 @@ define nat44_identity_mapping_details {
   u16 port;
   vl_api_interface_index_t sw_if_index;
   u32 vrf_id;
-  string tag;
+  string tag[64];
 };
 
 /** \brief Add/delete NAT44 pool address from specific interfce
@@ -927,9 +927,9 @@ autoreply manual_endian define nat44_add_del_lb_static_mapping {
   u16 external_port;
   u8 protocol;
   u32 affinity;
+  string tag[64];
   u32 local_num;
   vl_api_nat44_lb_addr_port_t locals[local_num];
-  string tag;
 };
 
 /** \brief Add/delete NAT44 load-balancing static mapping rule backend
@@ -983,9 +983,9 @@ manual_endian define nat44_lb_static_mapping_details {
   u8 protocol;
   vl_api_nat_config_flags_t flags;
   u32 affinity;
+  string tag[64];
   u32 local_num;
   vl_api_nat44_lb_addr_port_t locals[local_num];
-  string tag;
 };
 
 /** \brief Delete NAT44 session
diff --git a/src/plugins/nat/nat_api.c b/src/plugins/nat/nat_api.c
index ff46ae9421a..b83ea0b49f8 100644
--- a/src/plugins/nat/nat_api.c
+++ b/src/plugins/nat/nat_api.c
@@ -200,20 +200,14 @@ send_nat_worker_details (u32 worker_index, vl_api_registration_t * reg,
   snat_main_t *sm = &snat_main;
   vlib_worker_thread_t *w =
     vlib_worker_threads + worker_index + sm->first_worker_index;
-  u32 len = vec_len (w->name);
 
-  if (len)
-    --len;
-
-  rmp = vl_msg_api_alloc (sizeof (*rmp) + len);
-  clib_memset (rmp, 0, sizeof (*rmp) + len);
+  rmp = vl_msg_api_alloc (sizeof (*rmp));
+  clib_memset (rmp, 0, sizeof (*rmp));
   rmp->_vl_msg_id = ntohs (VL_API_NAT_WORKER_DETAILS + sm->msg_id_base);
   rmp->context = context;
   rmp->worker_index = htonl (worker_index);
   rmp->lcore_id = htonl (w->cpu_id);
-
-  if (len)
-    vl_api_to_api_string (len, (char *) w->name, &rmp->name);
+  strncpy ((char *) rmp->name, (char *) w->name, ARRAY_LEN (rmp->name) - 1);
 
   vl_api_send_msg (reg, (u8 *) rmp);
 }
@@ -1208,7 +1202,6 @@ static void
   int rv = 0;
   snat_protocol_t proto;
   u8 *tag = 0;
-  u32 len = 0;
 
   if (sm->deterministic)
     {
@@ -1216,14 +1209,6 @@ static void
       goto send_reply;
     }
 
-  len = vl_api_string_len (&mp->tag);
-
-  if (len > 64)
-    {
-      rv = VNET_API_ERROR_INVALID_VALUE;
-      goto send_reply;
-    }
-
   memcpy (&local_addr.as_u8, mp->local_ip_address, 4);
   memcpy (&external_addr.as_u8, mp->external_ip_address, 4);
 
@@ -1241,10 +1226,8 @@ static void
     twice_nat = TWICE_NAT;
   else if (mp->flags & NAT_API_IS_SELF_TWICE_NAT)
     twice_nat = TWICE_NAT_SELF;
-
-  tag = vec_new (u8, len);
-
-  memcpy (tag, mp->tag.buf, len);
+  mp->tag[sizeof (mp->tag) - 1] = 0;
+  tag = format (0, "%s", mp->tag);
   vec_terminate_c_string (tag);
 
   rv = snat_add_static_mapping (local_addr, external_addr, local_port,
@@ -1296,19 +1279,8 @@ send_nat44_static_mapping_details (snat_static_mapping_t * m,
   snat_main_t *sm = &snat_main;
   u32 len = sizeof (*rmp);
 
-  if (m->tag)
-    {
-      len += vec_len (m->tag);
-      rmp = vl_msg_api_alloc (len);
-      clib_memset (rmp, 0, len);
-      vl_api_to_api_string (vec_len (m->tag), (char *) m->tag, &rmp->tag);
-    }
-  else
-    {
-      rmp = vl_msg_api_alloc (len);
-      clib_memset (rmp, 0, len);
-    }
-
+  rmp = vl_msg_api_alloc (len);
+  clib_memset (rmp, 0, len);
   rmp->_vl_msg_id =
     ntohs (VL_API_NAT44_STATIC_MAPPING_DETAILS + sm->msg_id_base);
 
@@ -1337,6 +1309,9 @@ send_nat44_static_mapping_details (snat_static_mapping_t * m,
       rmp->local_port = htons (m->local_port);
     }
 
+  if (m->tag)
+    strncpy ((char *) rmp->tag, (char *) m->tag, vec_len (m->tag));
+
   vl_api_send_msg (reg, (u8 *) rmp);
 }
 
@@ -1347,21 +1322,9 @@ send_nat44_static_map_resolve_details (snat_static_map_resolve_t * m,
 {
   vl_api_nat44_static_mapping_details_t *rmp;
   snat_main_t *sm = &snat_main;
-  u32 len = sizeof (*rmp);
-
-  if (m->tag)
-    {
-      len += vec_len (m->tag);
-      rmp = vl_msg_api_alloc (len);
-      clib_memset (rmp, 0, len);
-      vl_api_to_api_string (vec_len (m->tag), (char *) m->tag, &rmp->tag);
-    }
-  else
-    {
-      rmp = vl_msg_api_alloc (len);
-      clib_memset (rmp, 0, len);
-    }
 
+  rmp = vl_msg_api_alloc (sizeof (*rmp));
+  clib_memset (rmp, 0, sizeof (*rmp));
   rmp->_vl_msg_id =
     ntohs (VL_API_NAT44_STATIC_MAPPING_DETAILS + sm->msg_id_base);
   clib_memcpy (rmp->local_ip_address, &(m->l_addr), 4);
@@ -1382,6 +1345,8 @@ send_nat44_static_map_resolve_details (snat_static_map_resolve_t * m,
       rmp->external_port = htons (m->e_port);
       rmp->local_port = htons (m->l_port);
     }
+  if (m->tag)
+    strncpy ((char *) rmp->tag, (char *) m->tag, vec_len (m->tag));
 
   vl_api_send_msg (reg, (u8 *) rmp);
 }
@@ -1442,7 +1407,6 @@ static void
   int rv = 0;
   snat_protocol_t proto = ~0;
   u8 *tag = 0;
-  u32 len = 0;
 
   if (sm->deterministic)
     {
@@ -1461,11 +1425,8 @@ static void
     addr.as_u32 = 0;
   else
     memcpy (&addr.as_u8, mp->ip_address, 4);
-
-  len = vl_api_string_len (&mp->tag);
-
-  tag = vec_new (u8, len);
-  memcpy (tag, mp->tag.buf, len);
+  mp->tag[sizeof (mp->tag) - 1] = 0;
+  tag = format (0, "%s", mp->tag);
   vec_terminate_c_string (tag);
 
   rv =
@@ -1507,21 +1468,9 @@ send_nat44_identity_mapping_details (snat_static_mapping_t * m, int index,
   vl_api_nat44_identity_mapping_details_t *rmp;
   snat_main_t *sm = &snat_main;
   nat44_lb_addr_port_t *local = pool_elt_at_index (m->locals, index);
-  u32 len = sizeof (*rmp);
-
-  if (m->tag)
-    {
-      len += vec_len (m->tag);
-      rmp = vl_msg_api_alloc (len);
-      clib_memset (rmp, 0, len);
-      vl_api_to_api_string (vec_len (m->tag), (char *) m->tag, &rmp->tag);
-    }
-  else
-    {
-      rmp = vl_msg_api_alloc (len);
-      clib_memset (rmp, 0, len);
-    }
 
+  rmp = vl_msg_api_alloc (sizeof (*rmp));
+  clib_memset (rmp, 0, sizeof (*rmp));
   rmp->_vl_msg_id =
     ntohs (VL_API_NAT44_IDENTITY_MAPPING_DETAILS + sm->msg_id_base);
 
@@ -1534,6 +1483,8 @@ send_nat44_identity_mapping_details (snat_static_mapping_t * m, int index,
   rmp->vrf_id = htonl (local->vrf_id);
   rmp->protocol = snat_proto_to_ip_proto (m->proto);
   rmp->context = context;
+  if (m->tag)
+    strncpy ((char *) rmp->tag, (char *) m->tag, vec_len (m->tag));
 
   vl_api_send_msg (reg, (u8 *) rmp);
 }
@@ -1545,21 +1496,9 @@ send_nat44_identity_map_resolve_details (snat_static_map_resolve_t * m,
 {
   vl_api_nat44_identity_mapping_details_t *rmp;
   snat_main_t *sm = &snat_main;
-  u32 len = sizeof (*rmp);
-
-  if (m->tag)
-    {
-      len += vec_len (m->tag);
-      rmp = vl_msg_api_alloc (len);
-      clib_memset (rmp, 0, len);
-      vl_api_to_api_string (vec_len (m->tag), (char *) m->tag, &rmp->tag);
-    }
-  else
-    {
-      rmp = vl_msg_api_alloc (len);
-      clib_memset (rmp, 0, len);
-    }
 
+  rmp = vl_msg_api_alloc (sizeof (*rmp));
+  clib_memset (rmp, 0, sizeof (*rmp));
   rmp->_vl_msg_id =
     ntohs (VL_API_NAT44_IDENTITY_MAPPING_DETAILS + sm->msg_id_base);
 
@@ -1571,6 +1510,8 @@ send_nat44_identity_map_resolve_details (snat_static_map_resolve_t * m,
   rmp->vrf_id = htonl (m->vrf_id);
   rmp->protocol = snat_proto_to_ip_proto (m->proto);
   rmp->context = context;
+  if (m->tag)
+    strncpy ((char *) rmp->tag, (char *) m->tag, vec_len (m->tag));
 
   vl_api_send_msg (reg, (u8 *) rmp);
 }
@@ -1936,9 +1877,7 @@ static void
   nat44_lb_addr_port_t *locals = 0;
   ip4_address_t e_addr;
   snat_protocol_t proto;
-  vl_api_string_t *sp;
   u8 *tag = 0;
-  u32 len = 0;
 
   if (!sm->endpoint_dependent)
     {
@@ -1956,15 +1895,8 @@ static void
     twice_nat = TWICE_NAT;
   else if (mp->flags & NAT_API_IS_SELF_TWICE_NAT)
     twice_nat = TWICE_NAT_SELF;
-
-  sp = (void *) &mp->locals +
-    sizeof (vl_api_nat44_lb_addr_port_t) *
-    clib_net_to_host_u32 (mp->local_num);
-
-  len = vl_api_string_len (sp);
-
-  tag = vec_new (u8, len);
-  memcpy (tag, sp->buf, len);
+  mp->tag[sizeof (mp->tag) - 1] = 0;
+  tag = format (0, "%s", mp->tag);
   vec_terminate_c_string (tag);
 
   rv =
@@ -2051,28 +1983,13 @@ send_nat44_lb_static_mapping_details (snat_static_mapping_t * m,
   snat_main_t *sm = &snat_main;
   nat44_lb_addr_port_t *ap;
   vl_api_nat44_lb_addr_port_t *locals;
-  vl_api_string_t *sp;
   u32 local_num = 0;
-  u32 len = sizeof (*rmp);
-
-  if (m->tag)
-    {
-      len += pool_elts (m->locals) *
-	sizeof (nat44_lb_addr_port_t) + vec_len (m->tag);
-      rmp = vl_msg_api_alloc (len);
-      clib_memset (rmp, 0, len);
-
-      sp = (void *) &rmp->locals +
-	sizeof (vl_api_nat44_lb_addr_port_t) * pool_elts (m->locals);
-      vl_api_to_api_string (vec_len (m->tag), (char *) m->tag, sp);
-    }
-  else
-    {
-      len += pool_elts (m->locals) * sizeof (nat44_lb_addr_port_t);
-      rmp = vl_msg_api_alloc (len);
-      clib_memset (rmp, 0, len);
-    }
 
+  rmp =
+    vl_msg_api_alloc (sizeof (*rmp) +
+		      (pool_elts (m->locals) *
+		       sizeof (nat44_lb_addr_port_t)));
+  clib_memset (rmp, 0, sizeof (*rmp));
   rmp->_vl_msg_id =
     ntohs (VL_API_NAT44_LB_STATIC_MAPPING_DETAILS + sm->msg_id_base);
 
@@ -2087,6 +2004,8 @@ send_nat44_lb_static_mapping_details (snat_static_mapping_t * m,
     rmp->flags |= NAT_API_IS_SELF_TWICE_NAT;
   if (is_out2in_only_static_mapping (m))
     rmp->flags |= NAT_API_IS_OUT2IN_ONLY;
+  if (m->tag)
+    strncpy ((char *) rmp->tag, (char *) m->tag, vec_len (m->tag));
 
   locals = (vl_api_nat44_lb_addr_port_t *) rmp->locals;
   /* *INDENT-OFF* */
diff --git a/src/plugins/nat/test/test_nat.py b/src/plugins/nat/test/test_nat.py
index a64b5709c72..4d48ee494c6 100644
--- a/src/plugins/nat/test/test_nat.py
+++ b/src/plugins/nat/test/test_nat.py
@@ -1894,7 +1894,7 @@ class TestNAT44(MethodHolder):
             is_add=1)
         sm = self.vapi.nat44_static_mapping_dump()
         self.assertEqual(len(sm), 1)
-        self.assertEqual((sm[0].tag).split(b'\0', 1)[0], b'')
+        self.assertEqual(sm[0].tag, '')
         self.assertEqual(sm[0].protocol, 0)
         self.assertEqual(sm[0].local_port, 0)
         self.assertEqual(sm[0].external_port, 0)