nat: fix EI hairpinning thread safety

Avoid doing inter-thread reads without locks by doing a handoff before
destination address rewrite. Destination address is read from a session
which is possibly owned by a different thread. By splitting the work in
two parts with a handoff in the middle, we can do both in a thread safe
way.

Type: improvement
Signed-off-by: Klement Sekera <ksekera@cisco.com>
Change-Id: I1c50d188393a610f5564fa230c75771a8065f273

1 files changed, 242 insertions, 24 deletions

diff --git a/src/plugins/nat/nat44-ei/nat44_ei_in2out.c b/src/plugins/nat/nat44-ei/nat44_ei_in2out.c
index ad0007bb8df..54ed1a92e8b 100644
--- a/src/plugins/nat/nat44-ei/nat44_ei_in2out.c
+++ b/src/plugins/nat/nat44-ei/nat44_ei_in2out.c
@@ -35,6 +35,7 @@
 #include <vppinfra/error.h>
 #include <vppinfra/elog.h>
 #include <nat/lib/nat_inlines.h>
+#include <nat/nat44_hairpinning.h>
 
 typedef struct
 {
@@ -108,9 +109,17 @@ typedef enum
   SNAT_IN2OUT_NEXT_DROP,
   SNAT_IN2OUT_NEXT_ICMP_ERROR,
   SNAT_IN2OUT_NEXT_SLOW_PATH,
+  SNAT_IN2OUT_NEXT_HAIRPINNING_HANDOFF,
   SNAT_IN2OUT_N_NEXT,
 } snat_in2out_next_t;
 
+typedef enum
+{
+  NAT44_IN2OUT_HAIRPINNING_FINISH_NEXT_DROP,
+  NAT44_IN2OUT_HAIRPINNING_FINISH_NEXT_LOOKUP,
+  NAT44_IN2OUT_HAIRPINNING_FINISH_N_NEXT,
+} nat44_in2out_hairpinnig_finish_next_t;
+
 static inline int
 snat_not_translate (snat_main_t * sm, vlib_node_runtime_t * node,
 		    u32 sw_if_index0, ip4_header_t * ip0, u32 proto0,
@@ -167,13 +176,11 @@ nat_not_translate_output_feature (snat_main_t * sm, ip4_header_t * ip0,
   if (!clib_bihash_search_8_8 (&sm->in2out, &kv0, &value0))
     {
       /* hairpinning */
-    /* *INDENT-OFF* */
-    pool_foreach (i, sm->output_feature_interfaces)
-     {
-      if ((nat_interface_is_inside(i)) && (sw_if_index == i->sw_if_index))
-        return 0;
-    }
-    /* *INDENT-ON* */
+      pool_foreach (i, sm->output_feature_interfaces)
+	{
+	  if ((nat_interface_is_inside (i)) && (sw_if_index == i->sw_if_index))
+	    return 0;
+	}
       return 1;
     }
 
@@ -328,7 +335,6 @@ slow_path (snat_main_t * sm, vlib_buffer_t * b0,
       s->out2in.fib_index = sm->outside_fibs[0].fib_index;
       break;
     default:
-      /* *INDENT-OFF* */
       vec_foreach (outside_fib, sm->outside_fibs)
         {
           fei = fib_table_lookup (outside_fib->fib_index, &pfx);
@@ -341,7 +347,6 @@ slow_path (snat_main_t * sm, vlib_buffer_t * b0,
                 }
             }
         }
-      /* *INDENT-ON* */
       break;
     }
   s->ext_host_addr.as_u32 = ip0->dst_address.as_u32;
@@ -660,6 +665,7 @@ icmp_in2out (snat_main_t *sm, vlib_buffer_t *b0, ip4_header_t *ip0,
   ip_csum_t sum0;
   u16 checksum0;
   u32 next0_tmp;
+  u32 required_thread_index = thread_index;
 
   echo0 = (icmp_echo_header_t *) (icmp0 + 1);
 
@@ -784,8 +790,14 @@ icmp_in2out (snat_main_t *sm, vlib_buffer_t *b0, ip4_header_t *ip0,
 
   if (vnet_buffer (b0)->sw_if_index[VLIB_TX] == ~0)
     {
-      if (0 != snat_icmp_hairpinning (sm, b0, ip0, icmp0))
+      if (0 != snat_icmp_hairpinning (sm, b0, thread_index, ip0, icmp0,
+				      &required_thread_index))
 	vnet_buffer (b0)->sw_if_index[VLIB_TX] = fib_index;
+      if (thread_index != required_thread_index)
+	{
+	  vnet_buffer (b0)->snat.required_thread_index = required_thread_index;
+	  next0 = SNAT_IN2OUT_NEXT_HAIRPINNING_HANDOFF;
+	}
     }
 
 out:
@@ -1623,7 +1635,6 @@ VLIB_NODE_FN (snat_in2out_node) (vlib_main_t * vm,
 				     0);
 }
 
-/* *INDENT-OFF* */
 VLIB_REGISTER_NODE (snat_in2out_node) = {
   .name = "nat44-in2out",
   .vector_size = sizeof (u32),
@@ -1643,9 +1654,9 @@ VLIB_REGISTER_NODE (snat_in2out_node) = {
     [SNAT_IN2OUT_NEXT_LOOKUP] = "ip4-lookup",
     [SNAT_IN2OUT_NEXT_SLOW_PATH] = "nat44-in2out-slowpath",
     [SNAT_IN2OUT_NEXT_ICMP_ERROR] = "ip4-icmp-error",
+    [SNAT_IN2OUT_NEXT_HAIRPINNING_HANDOFF] = "nat44-in2out-hairpinning-handoff-ip4-lookup",
   },
 };
-/* *INDENT-ON* */
 
 VLIB_NODE_FN (snat_in2out_output_node) (vlib_main_t * vm,
 					vlib_node_runtime_t * node,
@@ -1655,7 +1666,6 @@ VLIB_NODE_FN (snat_in2out_output_node) (vlib_main_t * vm,
 				     1);
 }
 
-/* *INDENT-OFF* */
 VLIB_REGISTER_NODE (snat_in2out_output_node) = {
   .name = "nat44-in2out-output",
   .vector_size = sizeof (u32),
@@ -1675,9 +1685,9 @@ VLIB_REGISTER_NODE (snat_in2out_output_node) = {
     [SNAT_IN2OUT_NEXT_LOOKUP] = "interface-output",
     [SNAT_IN2OUT_NEXT_SLOW_PATH] = "nat44-in2out-output-slowpath",
     [SNAT_IN2OUT_NEXT_ICMP_ERROR] = "ip4-icmp-error",
+    [SNAT_IN2OUT_NEXT_HAIRPINNING_HANDOFF] = "nat44-in2out-hairpinning-handoff-interface-output",
   },
 };
-/* *INDENT-ON* */
 
 VLIB_NODE_FN (snat_in2out_slowpath_node) (vlib_main_t * vm,
 					  vlib_node_runtime_t * node,
@@ -1687,7 +1697,6 @@ VLIB_NODE_FN (snat_in2out_slowpath_node) (vlib_main_t * vm,
 				     0);
 }
 
-/* *INDENT-OFF* */
 VLIB_REGISTER_NODE (snat_in2out_slowpath_node) = {
   .name = "nat44-in2out-slowpath",
   .vector_size = sizeof (u32),
@@ -1707,9 +1716,9 @@ VLIB_REGISTER_NODE (snat_in2out_slowpath_node) = {
     [SNAT_IN2OUT_NEXT_LOOKUP] = "ip4-lookup",
     [SNAT_IN2OUT_NEXT_SLOW_PATH] = "nat44-in2out-slowpath",
     [SNAT_IN2OUT_NEXT_ICMP_ERROR] = "ip4-icmp-error",
+    [SNAT_IN2OUT_NEXT_HAIRPINNING_HANDOFF] = "nat44-in2out-hairpinning-handoff-ip4-lookup",
   },
 };
-/* *INDENT-ON* */
 
 VLIB_NODE_FN (snat_in2out_output_slowpath_node) (vlib_main_t * vm,
 						 vlib_node_runtime_t * node,
@@ -1719,7 +1728,6 @@ VLIB_NODE_FN (snat_in2out_output_slowpath_node) (vlib_main_t * vm,
 				     1);
 }
 
-/* *INDENT-OFF* */
 VLIB_REGISTER_NODE (snat_in2out_output_slowpath_node) = {
   .name = "nat44-in2out-output-slowpath",
   .vector_size = sizeof (u32),
@@ -1739,15 +1747,16 @@ VLIB_REGISTER_NODE (snat_in2out_output_slowpath_node) = {
     [SNAT_IN2OUT_NEXT_LOOKUP] = "interface-output",
     [SNAT_IN2OUT_NEXT_SLOW_PATH] = "nat44-in2out-output-slowpath",
     [SNAT_IN2OUT_NEXT_ICMP_ERROR] = "ip4-icmp-error",
+    [SNAT_IN2OUT_NEXT_HAIRPINNING_HANDOFF] = "nat44-in2out-hairpinning-handoff-interface-output",
   },
 };
-/* *INDENT-ON* */
 
 VLIB_NODE_FN (snat_in2out_fast_node) (vlib_main_t * vm,
 				      vlib_node_runtime_t * node,
 				      vlib_frame_t * frame)
 {
   u32 n_left_from, *from, *to_next;
+  u32 thread_index = vm->thread_index;
   snat_in2out_next_t next_index;
   snat_main_t *sm = &snat_main;
   int is_hairpinning = 0;
@@ -1780,7 +1789,7 @@ VLIB_NODE_FN (snat_in2out_fast_node) (vlib_main_t * vm,
 	  ip4_address_t sm0_addr;
 	  u16 sm0_port;
 	  u32 sm0_fib_index;
-
+	  u32 required_thread_index = thread_index;
 
 	  /* speculatively enqueue b0 to the current next frame */
 	  bi0 = from[0];
@@ -1896,8 +1905,16 @@ VLIB_NODE_FN (snat_in2out_fast_node) (vlib_main_t * vm,
 	    }
 
 	  /* Hairpinning */
-	  is_hairpinning = snat_hairpinning (vm, node, sm, b0, ip0, udp0, tcp0,
-					     proto0, 0 /* do_trace */);
+	  is_hairpinning = snat_hairpinning (
+	    vm, node, sm, thread_index, b0, ip0, udp0, tcp0, proto0,
+	    0 /* do_trace */, &required_thread_index);
+
+	  if (thread_index != required_thread_index)
+	    {
+	      vnet_buffer (b0)->snat.required_thread_index =
+		required_thread_index;
+	      next0 = SNAT_IN2OUT_NEXT_HAIRPINNING_HANDOFF;
+	    }
 
 	trace0:
 	  if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE)
@@ -1930,8 +1947,6 @@ VLIB_NODE_FN (snat_in2out_fast_node) (vlib_main_t * vm,
   return frame->n_vectors;
 }
 
-
-/* *INDENT-OFF* */
 VLIB_REGISTER_NODE (snat_in2out_fast_node) = {
   .name = "nat44-in2out-fast",
   .vector_size = sizeof (u32),
@@ -1951,9 +1966,212 @@ VLIB_REGISTER_NODE (snat_in2out_fast_node) = {
     [SNAT_IN2OUT_NEXT_LOOKUP] = "ip4-lookup",
     [SNAT_IN2OUT_NEXT_SLOW_PATH] = "nat44-in2out-slowpath",
     [SNAT_IN2OUT_NEXT_ICMP_ERROR] = "ip4-icmp-error",
+    [SNAT_IN2OUT_NEXT_HAIRPINNING_HANDOFF] = "nat44-in2out-hairpinning-handoff-ip4-lookup",
+  },
+};
+
+VLIB_NODE_FN (nat44_in2out_hairpinning_handoff_ip4_lookup_node)
+(vlib_main_t *vm, vlib_node_runtime_t *node, vlib_frame_t *frame)
+{
+  return nat44_hairpinning_handoff_fn_inline (
+    vm, node, frame,
+    snat_main.nat44_in2out_hairpinning_finish_ip4_lookup_node_fq_index);
+}
+
+VLIB_REGISTER_NODE (nat44_in2out_hairpinning_handoff_ip4_lookup_node) = {
+  .name = "nat44-in2out-hairpinning-handoff-ip4-lookup",
+  .vector_size = sizeof (u32),
+  .n_errors = ARRAY_LEN(nat44_hairpinning_handoff_error_strings),
+  .error_strings = nat44_hairpinning_handoff_error_strings,
+  .format_trace = format_nat44_hairpinning_handoff_trace,
+
+  .n_next_nodes = 1,
+
+  .next_nodes = {
+    [0] = "error-drop",
+  },
+};
+
+VLIB_NODE_FN (nat44_in2out_hairpinning_handoff_interface_output_node)
+(vlib_main_t *vm, vlib_node_runtime_t *node, vlib_frame_t *frame)
+{
+  return nat44_hairpinning_handoff_fn_inline (
+    vm, node, frame,
+    snat_main.nat44_in2out_hairpinning_finish_interface_output_node_fq_index);
+}
+
+VLIB_REGISTER_NODE (nat44_in2out_hairpinning_handoff_interface_output_node) = {
+  .name = "nat44-in2out-hairpinning-handoff-interface-output",
+  .vector_size = sizeof (u32),
+  .n_errors = ARRAY_LEN(nat44_hairpinning_handoff_error_strings),
+  .error_strings = nat44_hairpinning_handoff_error_strings,
+  .format_trace = format_nat44_hairpinning_handoff_trace,
+
+  .n_next_nodes = 1,
+
+  .next_nodes = {
+    [0] = "error-drop",
+  },
+};
+
+static_always_inline int
+nat44_in2out_hairpinning_finish_inline (vlib_main_t *vm,
+					vlib_node_runtime_t *node,
+					vlib_frame_t *frame)
+{
+  u32 n_left_from, *from, *to_next;
+  u32 thread_index = vm->thread_index;
+  snat_in2out_next_t next_index;
+  snat_main_t *sm = &snat_main;
+  int is_hairpinning = 0;
+
+  from = vlib_frame_vector_args (frame);
+  n_left_from = frame->n_vectors;
+  next_index = node->cached_next_index;
+
+  while (n_left_from > 0)
+    {
+      u32 n_left_to_next;
+
+      vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);
+
+      while (n_left_from > 0 && n_left_to_next > 0)
+	{
+	  u32 bi0;
+	  vlib_buffer_t *b0;
+	  u32 next0;
+	  u32 sw_if_index0;
+	  ip4_header_t *ip0;
+	  udp_header_t *udp0;
+	  tcp_header_t *tcp0;
+	  icmp46_header_t *icmp0;
+	  u32 proto0;
+	  u32 required_thread_index = thread_index;
+
+	  /* speculatively enqueue b0 to the current next frame */
+	  bi0 = from[0];
+	  to_next[0] = bi0;
+	  from += 1;
+	  to_next += 1;
+	  n_left_from -= 1;
+	  n_left_to_next -= 1;
+
+	  b0 = vlib_get_buffer (vm, bi0);
+	  next0 = NAT44_IN2OUT_HAIRPINNING_FINISH_NEXT_LOOKUP;
+
+	  ip0 = vlib_buffer_get_current (b0);
+	  udp0 = ip4_next_header (ip0);
+	  tcp0 = (tcp_header_t *) udp0;
+	  icmp0 = (icmp46_header_t *) udp0;
+
+	  sw_if_index0 = vnet_buffer (b0)->sw_if_index[VLIB_RX];
+	  proto0 = ip_proto_to_nat_proto (ip0->protocol);
+
+	  switch (proto0)
+	    {
+	    case NAT_PROTOCOL_TCP:
+	      // fallthrough
+	    case NAT_PROTOCOL_UDP:
+	      is_hairpinning = snat_hairpinning (
+		vm, node, sm, thread_index, b0, ip0, udp0, tcp0, proto0,
+		0 /* do_trace */, &required_thread_index);
+	      break;
+	    case NAT_PROTOCOL_ICMP:
+	      is_hairpinning =
+		(0 == snat_icmp_hairpinning (sm, b0, thread_index, ip0, icmp0,
+					     &required_thread_index));
+	      break;
+	    case NAT_PROTOCOL_OTHER:
+	      // this should never happen
+	      next0 = NAT44_IN2OUT_HAIRPINNING_FINISH_NEXT_DROP;
+	      break;
+	    }
+
+	  if (thread_index != required_thread_index)
+	    {
+	      // but we already did a handoff ...
+	      next0 = NAT44_IN2OUT_HAIRPINNING_FINISH_NEXT_DROP;
+	    }
+
+	  if (PREDICT_FALSE ((node->flags & VLIB_NODE_FLAG_TRACE) &&
+			     (b0->flags & VLIB_BUFFER_IS_TRACED)))
+	    {
+	      snat_in2out_trace_t *t =
+		vlib_add_trace (vm, node, b0, sizeof (*t));
+	      t->sw_if_index = sw_if_index0;
+	      t->next_index = next0;
+	      t->is_hairpinning = is_hairpinning;
+	    }
+
+	  if (next0 != NAT44_IN2OUT_HAIRPINNING_FINISH_NEXT_DROP)
+	    {
+	      vlib_increment_simple_counter (
+		&sm->counters.fastpath.in2out.other, sw_if_index0,
+		vm->thread_index, 1);
+	    }
+
+	  /* verify speculative enqueue, maybe switch current next frame */
+	  vlib_validate_buffer_enqueue_x1 (vm, node, next_index, to_next,
+					   n_left_to_next, bi0, next0);
+	}
+
+      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
+    }
+
+  return frame->n_vectors;
+}
+
+VLIB_NODE_FN (nat44_in2out_hairpinning_finish_ip4_lookup_node)
+(vlib_main_t *vm, vlib_node_runtime_t *node, vlib_frame_t *frame)
+{
+  return nat44_in2out_hairpinning_finish_inline (vm, node, frame);
+}
+
+VLIB_REGISTER_NODE (nat44_in2out_hairpinning_finish_ip4_lookup_node) = {
+  .name = "nat44-in2out-hairpinning-finish-ip4-lookup",
+  .vector_size = sizeof (u32),
+  .format_trace = format_snat_in2out_fast_trace,
+  .type = VLIB_NODE_TYPE_INTERNAL,
+
+  .n_errors = ARRAY_LEN(snat_in2out_error_strings),
+  .error_strings = snat_in2out_error_strings,
+
+  .runtime_data_bytes = sizeof (snat_runtime_t),
+
+  .n_next_nodes = NAT44_IN2OUT_HAIRPINNING_FINISH_N_NEXT,
+
+  /* edit / add dispositions here */
+  .next_nodes = {
+    [NAT44_IN2OUT_HAIRPINNING_FINISH_NEXT_DROP] = "error-drop",
+    [NAT44_IN2OUT_HAIRPINNING_FINISH_NEXT_LOOKUP] = "ip4-lookup",
+  },
+};
+
+VLIB_NODE_FN (nat44_in2out_hairpinning_finish_interface_output_node)
+(vlib_main_t *vm, vlib_node_runtime_t *node, vlib_frame_t *frame)
+{
+  return nat44_in2out_hairpinning_finish_inline (vm, node, frame);
+}
+
+VLIB_REGISTER_NODE (nat44_in2out_hairpinning_finish_interface_output_node) = {
+  .name = "nat44-in2out-hairpinning-finish-interface-output",
+  .vector_size = sizeof (u32),
+  .format_trace = format_snat_in2out_fast_trace,
+  .type = VLIB_NODE_TYPE_INTERNAL,
+
+  .n_errors = ARRAY_LEN(snat_in2out_error_strings),
+  .error_strings = snat_in2out_error_strings,
+
+  .runtime_data_bytes = sizeof (snat_runtime_t),
+
+  .n_next_nodes = NAT44_IN2OUT_HAIRPINNING_FINISH_N_NEXT,
+
+  /* edit / add dispositions here */
+  .next_nodes = {
+    [NAT44_IN2OUT_HAIRPINNING_FINISH_NEXT_DROP] = "error-drop",
+    [NAT44_IN2OUT_HAIRPINNING_FINISH_NEXT_LOOKUP] = "interface-output",
   },
 };
-/* *INDENT-ON* */
 
 /*
  * fd.io coding-style-patch-verification: ON