Reflexive ACL support on ICMP

Normally session keys are generated by mirroring the packets sent.
ICMP message type should be used and inverted for the stateful ACL.

Supported ICMP messages with this patch:
 - ICMPv4: Echo/Timestamp/Information/Address Mask requests
 - ICMPv6: Echo request/Node Information Queury

The invmap & valid_new tables can be modified to make any other
ICMP messages to be reflexive ACL.

Change-Id: Ia47b08b79fe0a5b1f7a995af78de3763d275dbd9
Signed-off-by: Steve Shin <jonshin@cisco.com>

1 files changed, 113 insertions, 25 deletions

diff --git a/src/plugins/acl/fa_node.c b/src/plugins/acl/fa_node.c
index 5fa45098559..fb23a354358 100644
--- a/src/plugins/acl/fa_node.c
+++ b/src/plugins/acl/fa_node.c
@@ -24,6 +24,7 @@
 
 #include <vppinfra/bihash_template.h>
 #include <vppinfra/bihash_template.c>
+#include <vnet/ip/icmp46_packet.h>
 
 #include "fa_node.h"
 #include "hash_lookup.h"
@@ -39,6 +40,37 @@ typedef struct
   u8 action;
 } acl_fa_trace_t;
 
+/* ICMPv4 invert type for stateful ACL */
+static const u8 icmp4_invmap[] = {
+  [ICMP4_echo_reply] = ICMP4_echo_request + 1,
+  [ICMP4_timestamp_reply] = ICMP4_timestamp_request + 1,
+  [ICMP4_information_reply] = ICMP4_information_request + 1,
+  [ICMP4_address_mask_reply] = ICMP4_address_mask_request + 1
+};
+
+/* Supported ICMPv4 messages for session creation */
+static const u8 icmp4_valid_new[] = {
+  [ICMP4_echo_request] = 1,
+  [ICMP4_timestamp_request] = 1,
+  [ICMP4_information_request] = 1,
+  [ICMP4_address_mask_request] = 1
+};
+
+/* ICMPv6 invert type for stateful ACL */
+static const u8 icmp6_invmap[] = {
+  [ICMP6_echo_reply - 128]   = ICMP6_echo_request + 1,
+  [ICMP6_node_information_response - 128] = ICMP6_node_information_request + 1
+};
+
+/* Supported ICMPv6 messages for session creation */
+static const u8 icmp6_valid_new[] = {
+  [ICMP6_echo_request - 128] = 1,
+  [ICMP6_node_information_request - 128] = 1
+};
+
+/* IP4 and IP6 protocol numbers of ICMP */
+static u8 icmp_protos[] = { IP_PROTOCOL_ICMP, IP_PROTOCOL_ICMP6 };
+
 static u8 *
 format_fa_5tuple (u8 * s, va_list * args)
 {
@@ -365,9 +397,6 @@ acl_fill_5tuple (acl_main_t * am, vlib_buffer_t * b0, int is_ip6,
   u16 ports[2];
   u16 proto;
 
-  /* IP4 and IP6 protocol numbers of ICMP */
-  static u8 icmp_protos[] = { IP_PROTOCOL_ICMP, IP_PROTOCOL_ICMP6 };
-
   if (is_l2_path)
     {
       l3_offset = ethernet_buffer_header_size(b0);
@@ -529,22 +558,6 @@ acl_fill_5tuple (acl_main_t * am, vlib_buffer_t * b0, int is_ip6,
     }
 }
 
-
-/* Session keys match the packets received, and mirror the packets sent */
-static void
-acl_make_5tuple_session_key (int is_input, fa_5tuple_t * p5tuple_pkt,
-			     fa_5tuple_t * p5tuple_sess)
-{
-  int src_index = is_input ? 0 : 1;
-  int dst_index = is_input ? 1 : 0;
-  p5tuple_sess->addr[src_index] = p5tuple_pkt->addr[0];
-  p5tuple_sess->addr[dst_index] = p5tuple_pkt->addr[1];
-  p5tuple_sess->l4.as_u64 = p5tuple_pkt->l4.as_u64;
-  p5tuple_sess->l4.port[src_index] = p5tuple_pkt->l4.port[0];
-  p5tuple_sess->l4.port[dst_index] = p5tuple_pkt->l4.port[1];
-}
-
-
 static int
 acl_fa_ifc_has_sessions (acl_main_t * am, int sw_if_index0)
 {
@@ -565,6 +578,70 @@ acl_fa_ifc_has_out_acl (acl_main_t * am, int sw_if_index0)
   return it_has;
 }
 
+/* Session keys match the packets received, and mirror the packets sent */
+static u32
+acl_make_5tuple_session_key (acl_main_t * am, int is_input, int is_ip6,
+                             u32 sw_if_index, fa_5tuple_t * p5tuple_pkt,
+                             fa_5tuple_t * p5tuple_sess)
+{
+  int src_index = is_input ? 0 : 1;
+  int dst_index = is_input ? 1 : 0;
+  u32 valid_new_sess = 1;
+  p5tuple_sess->addr[src_index] = p5tuple_pkt->addr[0];
+  p5tuple_sess->addr[dst_index] = p5tuple_pkt->addr[1];
+  p5tuple_sess->l4.as_u64 = p5tuple_pkt->l4.as_u64;
+
+  if (PREDICT_TRUE(p5tuple_pkt->l4.proto != icmp_protos[is_ip6]))
+    {
+      p5tuple_sess->l4.port[src_index] = p5tuple_pkt->l4.port[0];
+      p5tuple_sess->l4.port[dst_index] = p5tuple_pkt->l4.port[1];
+    }
+  else
+    {
+      static const u8 * icmp_invmap[] = { icmp4_invmap, icmp6_invmap };
+      static const u8 * icmp_valid_new[] = { icmp4_valid_new, icmp6_valid_new };
+      static const u8 icmp_invmap_size[] = { sizeof(icmp4_invmap),
+                                             sizeof(icmp6_invmap) };
+      static const u8 icmp_valid_new_size[] = { sizeof(icmp4_valid_new),
+                                                sizeof(icmp6_valid_new) };
+      int type = is_ip6 ? p5tuple_pkt->l4.port[0]-128: p5tuple_pkt->l4.port[0];
+
+      p5tuple_sess->l4.port[0] = p5tuple_pkt->l4.port[0];
+      p5tuple_sess->l4.port[1] = p5tuple_pkt->l4.port[1];
+
+      /*
+       * Invert ICMP type for valid icmp_invmap messages:
+       *  1) input node with outbound ACL interface
+       *  2) output node with inbound ACL interface
+       *
+       */
+      if ((is_input && acl_fa_ifc_has_out_acl(am, sw_if_index)) ||
+          (!is_input && acl_fa_ifc_has_in_acl(am, sw_if_index)))
+        {
+          if (type >= 0 &&
+              type <= icmp_invmap_size[is_ip6] &&
+              icmp_invmap[is_ip6][type])
+            {
+              p5tuple_sess->l4.port[0] = icmp_invmap[is_ip6][type] - 1;
+            }
+        }
+
+      /*
+       * ONLY ICMP messages defined in icmp4_valid_new/icmp6_valid_new table
+       * are allowed to create stateful ACL.
+       * The other messages will be forwarded without creating a reflexive ACL.
+       */
+      if (type < 0 ||
+          type > icmp_valid_new_size[is_ip6] ||
+          !icmp_valid_new[is_ip6][type])
+        {
+          valid_new_sess = 0;
+        }
+    }
+
+    return valid_new_sess;
+}
+
 
 static int
 fa_session_get_timeout_type (acl_main_t * am, fa_session_t * sess)
@@ -1016,6 +1093,7 @@ acl_fa_node_fn (vlib_main_t * vm,
 	  u32 match_acl_in_index = ~0;
 	  u32 match_rule_index = ~0;
 	  u8 error0 = 0;
+	  u32 valid_new_sess;
 
 	  /* speculatively enqueue b0 to the current next frame */
 	  bi0 = from[0];
@@ -1040,7 +1118,7 @@ acl_fa_node_fn (vlib_main_t * vm,
 
 	  acl_fill_5tuple (am, b0, is_ip6, is_input, is_l2_path, &fa_5tuple);
           fa_5tuple.l4.lsb_of_sw_if_index = sw_if_index0 & 0xffff;
-	  acl_make_5tuple_session_key (is_input, &fa_5tuple, &kv_sess);
+	  valid_new_sess = acl_make_5tuple_session_key (am, is_input, is_ip6, sw_if_index0,  &fa_5tuple, &kv_sess);
 	  fa_5tuple.pkt.sw_if_index = sw_if_index0;
           fa_5tuple.pkt.is_ip6 = is_ip6;
           fa_5tuple.pkt.is_input = is_input;
@@ -1124,11 +1202,21 @@ acl_fa_node_fn (vlib_main_t * vm,
 
 		  if (acl_fa_can_add_session (am, is_input, sw_if_index0))
 		    {
-                      fa_session_t *sess = acl_fa_add_session (am, is_input, sw_if_index0, now,
-					                       &kv_sess);
-                      acl_fa_track_session (am, is_input, sw_if_index0, now,
-                                            sess, &fa_5tuple);
-		      pkts_new_session += 1;
+                      if (PREDICT_TRUE (valid_new_sess)) {
+                        fa_session_t *sess = acl_fa_add_session (am, is_input,
+                                                                 sw_if_index0,
+                                                                 now, &kv_sess);
+                        acl_fa_track_session (am, is_input, sw_if_index0, now,
+                                              sess, &fa_5tuple);
+                        pkts_new_session += 1;
+                      } else {
+                        /*
+                         *  ICMP packets with non-icmp_valid_new type will be
+                         *  forwared without being dropped.
+                         */
+                        action = 1;
+                        pkts_acl_permit += 1;
+                      }
 		    }
 		  else
 		    {