cnat: Destination based NAT

Type: feature

Signed-off-by: Neale Ranns <nranns@cisco.com>
Change-Id: I64a99a4fbc674212944247793fd5c1fb701408cb

1 files changed, 237 insertions, 0 deletions

diff --git a/src/plugins/cnat/cnat_node_snat.c b/src/plugins/cnat/cnat_node_snat.c
new file mode 100644
index 00000000000..cc1421be084
--- /dev/null
+++ b/src/plugins/cnat/cnat_node_snat.c
@@ -0,0 +1,237 @@
+/*
+ * Copyright (c) 2020 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <vlibmemory/api.h>
+#include <cnat/cnat_node.h>
+#include <cnat/cnat_snat.h>
+
+typedef enum cnat_snat_next_
+{
+  CNAT_SNAT_NEXT_DROP,
+  CNAT_SNAT_N_NEXT,
+} cnat_snat_next_t;
+
+typedef struct cnat_snat_trace_
+{
+  u32 found;
+  cnat_session_t session;
+} cnat_snat_trace_t;
+
+vlib_node_registration_t cnat_snat_ip4_node;
+vlib_node_registration_t cnat_snat_ip6_node;
+
+static u8 *
+format_cnat_snat_trace (u8 * s, va_list * args)
+{
+  CLIB_UNUSED (vlib_main_t * vm) = va_arg (*args, vlib_main_t *);
+  CLIB_UNUSED (vlib_node_t * node) = va_arg (*args, vlib_node_t *);
+  cnat_snat_trace_t *t = va_arg (*args, cnat_snat_trace_t *);
+
+  if (t->found)
+    s = format (s, "found: %U", format_cnat_session, &t->session, 1);
+  else
+    s = format (s, "not found");
+  return s;
+}
+
+/* CNat sub for source NAT as a feature arc on ip[46]-unicast
+   This node's sub shouldn't apply to the same flows as
+   cnat_vip_inline */
+always_inline uword
+cnat_snat_inline (vlib_main_t * vm,
+		  vlib_node_runtime_t * node,
+		  vlib_buffer_t * b,
+		  cnat_node_ctx_t * ctx, int rv, cnat_session_t * session)
+{
+  cnat_main_t *cm = &cnat_main;
+  ip4_header_t *ip4;
+  ip_protocol_t iproto;
+  ip6_header_t *ip6;
+  udp_header_t *udp0;
+  u32 arc_next0;
+  u16 next0;
+  u16 sport;
+
+  if (AF_IP4 == ctx->af)
+    {
+      ip4 = vlib_buffer_get_current (b);
+      iproto = ip4->protocol;
+      udp0 = (udp_header_t *) (ip4 + 1);
+    }
+  else
+    {
+      ip6 = vlib_buffer_get_current (b);
+      iproto = ip6->protocol;
+      udp0 = (udp_header_t *) (ip6 + 1);
+    }
+
+  /* By default don't follow previous next0 */
+  vnet_feature_next (&arc_next0, b);
+  next0 = arc_next0;
+
+  if (iproto != IP_PROTOCOL_UDP && iproto != IP_PROTOCOL_TCP)
+    {
+      /* Dont translate */
+      goto trace;
+    }
+
+  if (!rv)
+    {
+      /* session table hit */
+      cnat_timestamp_update (session->value.cs_ts_index, ctx->now);
+    }
+  else
+    {
+      ip46_address_t ip46_dst_address;
+      if (AF_IP4 == ctx->af)
+	ip46_address_set_ip4 (&ip46_dst_address, &ip4->dst_address);
+      else
+	ip46_address_set_ip6 (&ip46_dst_address, &ip6->dst_address);
+      rv = cnat_search_snat_prefix (&ip46_dst_address, ctx->af);
+      if (!rv)
+	{
+	  /* Prefix table hit, we shouldn't source NAT */
+	  goto trace;
+	}
+      /* New flow, create the sessions if necessary. session will be a snat
+         session, and rsession will be a dnat session
+         Note: packet going through this path are going to the outside,
+         so they will never hit the NAT again (they are not going towards
+         a VIP) */
+      if (AF_IP4 == ctx->af)
+	{
+	  ip46_address_set_ip4 (&session->value.cs_ip[VLIB_RX],
+				&cm->snat_ip4);
+	  ip46_address_set_ip4 (&session->value.cs_ip[VLIB_TX],
+				&ip4->dst_address);
+	}
+      else
+	{
+	  ip46_address_set_ip6 (&session->value.cs_ip[VLIB_RX],
+				&cm->snat_ip6);
+	  ip46_address_set_ip6 (&session->value.cs_ip[VLIB_TX],
+				&ip6->dst_address);
+	}
+
+      /* Port allocation, first try to use the original port, allocate one
+         if it is already used */
+      sport = udp0->src_port;
+      rv = cnat_allocate_port (cm, &sport);
+      if (rv)
+	{
+	  vlib_node_increment_counter (vm, cnat_snat_ip4_node.index,
+				       CNAT_ERROR_EXHAUSTED_PORTS, 1);
+	  next0 = CNAT_SNAT_NEXT_DROP;
+	  goto trace;
+	}
+
+      session->value.cs_port[VLIB_RX] = sport;
+      session->value.cs_port[VLIB_TX] = udp0->dst_port;
+      session->value.cs_lbi = INDEX_INVALID;
+      session->value.flags =
+	CNAT_SESSION_FLAG_NO_CLIENT | CNAT_SESSION_FLAG_ALLOC_PORT;
+
+      cnat_session_create (session, ctx, CNAT_SESSION_FLAG_HAS_SNAT);
+    }
+
+
+  if (AF_IP4 == ctx->af)
+    cnat_translation_ip4 (session, ip4, udp0);
+  else
+    cnat_translation_ip6 (session, ip6, udp0);
+
+trace:
+  if (PREDICT_FALSE (b->flags & VLIB_BUFFER_IS_TRACED))
+    {
+      cnat_snat_trace_t *t;
+
+      t = vlib_add_trace (vm, node, b, sizeof (*t));
+
+      if (NULL != session)
+	clib_memcpy (&t->session, session, sizeof (t->session));
+    }
+  return next0;
+}
+
+VLIB_NODE_FN (cnat_snat_ip4_node) (vlib_main_t * vm,
+				   vlib_node_runtime_t * node,
+				   vlib_frame_t * frame)
+{
+  if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)))
+    return cnat_node_inline (vm, node, frame, cnat_snat_inline, AF_IP4,
+			     1 /* do_trace */ );
+  return cnat_node_inline (vm, node, frame, cnat_snat_inline, AF_IP4,
+			   0 /* do_trace */ );
+}
+
+VLIB_NODE_FN (cnat_snat_ip6_node) (vlib_main_t * vm,
+				   vlib_node_runtime_t * node,
+				   vlib_frame_t * frame)
+{
+  if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)))
+    return cnat_node_inline (vm, node, frame, cnat_snat_inline, AF_IP6,
+			     1 /* do_trace */ );
+  return cnat_node_inline (vm, node, frame, cnat_snat_inline, AF_IP6,
+			   0 /* do_trace */ );
+}
+
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (cnat_snat_ip4_node) =
+{
+  .name = "ip4-cnat-snat",
+  .vector_size = sizeof (u32),
+  .format_trace = format_cnat_snat_trace,
+  .type = VLIB_NODE_TYPE_INTERNAL,
+  .n_errors = CNAT_N_ERROR,
+  .error_strings = cnat_error_strings,
+  .n_next_nodes = CNAT_SNAT_N_NEXT,
+  .next_nodes =
+  {
+    [CNAT_SNAT_NEXT_DROP] = "ip4-drop",
+  }
+};
+
+VLIB_REGISTER_NODE (cnat_snat_ip6_node) =
+{
+  .name = "ip6-cnat-snat",
+  .vector_size = sizeof (u32),
+  .format_trace = format_cnat_snat_trace,
+  .type = VLIB_NODE_TYPE_INTERNAL,
+  .n_errors = CNAT_N_ERROR,
+  .error_strings = cnat_error_strings,
+  .n_next_nodes = CNAT_SNAT_N_NEXT,
+  .next_nodes =
+  {
+    [CNAT_SNAT_NEXT_DROP] = "ip6-drop",
+  }
+};
+/* *INDENT-ON* */
+
+
+VNET_FEATURE_INIT (cnat_snat_ip4_node, static) =
+{
+.arc_name = "ip4-unicast",.node_name = "ip4-cnat-snat",};
+
+VNET_FEATURE_INIT (cnat_snat_ip6_node, static) =
+{
+.arc_name = "ip6-unicast",.node_name = "ip6-cnat-snat",};
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */