NAT64: Hairpinning (VPP-699)

Change-Id: I83a6c277fa211ac2c2ca2d603650c992886af0a7
Signed-off-by: Matus Fabian <matfabia@cisco.com>

7 files changed, 477 insertions, 52 deletions

diff --git a/src/plugins/snat/nat64.c b/src/plugins/snat/nat64.c
index ef745473793..1e8b75967d8 100644
--- a/src/plugins/snat/nat64.c
+++ b/src/plugins/snat/nat64.c
@@ -95,7 +95,10 @@ nat64_add_del_pool_addr (ip4_address_t * addr, u32 vrf_id, u8 is_add)
 
       vec_add2 (nm->addr_pool, a, 1);
       a->addr = *addr;
-      a->fib_index = ip4_fib_index_from_table_id (vrf_id);
+      a->fib_index = 0;
+      if (vrf_id != ~0)
+	a->fib_index =
+	  fib_table_find_or_create_and_lock (FIB_PROTOCOL_IP6, vrf_id);
 #define _(N, i, n, s) \
       clib_bitmap_alloc (a->busy_##n##_port_bitmap, 65535);
       foreach_snat_protocol
@@ -218,7 +221,7 @@ nat64_alloc_out_addr_and_port (u32 fib_index, snat_protocol_t proto,
   nat64_main_t *nm = &nat64_main;
   snat_main_t *sm = &snat_main;
   int i;
-  snat_address_t *a;
+  snat_address_t *a, *ga = 0;
   u32 portnum;
 
   for (i = 0; i < vec_len (nm->addr_pool); i++)
@@ -230,22 +233,27 @@ nat64_alloc_out_addr_and_port (u32 fib_index, snat_protocol_t proto,
         case SNAT_PROTOCOL_##N: \
           if (a->busy_##n##_ports < (65535-1024)) \
             { \
-              while (1) \
+              if (a->fib_index == fib_index) \
                 { \
-                  portnum = random_u32 (&sm->random_seed); \
-                  portnum &= 0xFFFF; \
-                  if (portnum < 1024) \
-                    continue; \
-                  if (clib_bitmap_get_no_check (a->busy_##n##_port_bitmap, \
-                                                portnum)) \
-                    continue; \
-                  clib_bitmap_set_no_check (a->busy_##n##_port_bitmap, \
-                                            portnum, 1); \
-                  a->busy_##n##_ports++; \
-                  *port = portnum; \
-                  addr->as_u32 = a->addr.as_u32; \
-                  return 0; \
-                } \
+                  while (1) \
+                    { \
+                      portnum = random_u32 (&sm->random_seed); \
+                      portnum &= 0xFFFF; \
+                      if (portnum < 1024) \
+                        continue; \
+                      if (clib_bitmap_get_no_check (a->busy_##n##_port_bitmap, \
+                                                    portnum)) \
+                        continue; \
+                      clib_bitmap_set_no_check (a->busy_##n##_port_bitmap, \
+                                                portnum, 1); \
+                      a->busy_##n##_ports++; \
+                      *port = portnum; \
+                      addr->as_u32 = a->addr.as_u32; \
+                      return 0; \
+                    } \
+                 } \
+               else if (a->fib_index == 0) \
+                 ga = a; \
             } \
           break;
 	  foreach_snat_protocol
@@ -254,8 +262,39 @@ nat64_alloc_out_addr_and_port (u32 fib_index, snat_protocol_t proto,
 	  clib_warning ("unknown protocol");
 	  return 1;
 	}
+    }
 
+  if (ga)
+    {
+      switch (proto)
+	{
+#define _(N, j, n, s) \
+        case SNAT_PROTOCOL_##N: \
+          while (1) \
+            { \
+              portnum = random_u32 (&sm->random_seed); \
+              portnum &= 0xFFFF; \
+              if (portnum < 1024) \
+                continue; \
+              if (clib_bitmap_get_no_check (a->busy_##n##_port_bitmap, \
+                                            portnum)) \
+                continue; \
+              clib_bitmap_set_no_check (a->busy_##n##_port_bitmap, \
+                                        portnum, 1); \
+              a->busy_##n##_ports++; \
+              *port = portnum; \
+              addr->as_u32 = a->addr.as_u32; \
+              return 0; \
+            }
+	  break;
+	  foreach_snat_protocol
+#undef _
+	default:
+	  clib_warning ("unknown protocol");
+	  return 1;
+	}
     }
+
   /* Totally out of translations to use... */
   //TODO: IPFix
   return 1;
diff --git a/src/plugins/snat/nat64_cli.c b/src/plugins/snat/nat64_cli.c
index 106d9aee41e..e2e3533849f 100644
--- a/src/plugins/snat/nat64_cli.c
+++ b/src/plugins/snat/nat64_cli.c
@@ -107,7 +107,7 @@ nat64_cli_pool_walk (snat_address_t * ap, void *ctx)
   if (ap->fib_index != ~0)
     {
       fib_table_t *fib;
-      fib = fib_table_get (ap->fib_index, FIB_PROTOCOL_IP4);
+      fib = fib_table_get (ap->fib_index, FIB_PROTOCOL_IP6);
       if (!fib)
 	return -1;
       vlib_cli_output (vm, " %U tenant VRF: %u", format_ip4_address,
diff --git a/src/plugins/snat/nat64_in2out.c b/src/plugins/snat/nat64_in2out.c
index eba6932681f..fd32bfc5be7 100644
--- a/src/plugins/snat/nat64_in2out.c
+++ b/src/plugins/snat/nat64_in2out.c
@@ -21,6 +21,15 @@
 #include <vnet/ip/ip6_to_ip4.h>
 #include <vnet/fib/fib_table.h>
 
+/* *INDENT-OFF* */
+static u8 well_known_prefix[] = {
+  0x00, 0x64, 0xff, 0x9b,
+  0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00
+};
+/* *INDENT-ON* */
+
 typedef struct
 {
   u32 sw_if_index;
@@ -65,7 +74,8 @@ static char *nat64_in2out_error_strings[] = {
 
 typedef enum
 {
-  NAT64_IN2OUT_NEXT_LOOKUP,
+  NAT64_IN2OUT_NEXT_IP4_LOOKUP,
+  NAT64_IN2OUT_NEXT_IP6_LOOKUP,
   NAT64_IN2OUT_NEXT_DROP,
   NAT64_IN2OUT_N_NEXT,
 } nat64_in2out_next_t;
@@ -76,6 +86,31 @@ typedef struct nat64_in2out_set_ctx_t_
   vlib_main_t *vm;
 } nat64_in2out_set_ctx_t;
 
+/**
+ * @brief Check whether is a hairpinning.
+ *
+ * If the destination IP address of the packet is an IPv4 address assigned to
+ * the NAT64 itself, then the packet is a hairpin packet.
+ *
+ * param dst_addr Destination address of the packet.
+ *
+ * @returns 1 if hairpinning, otherwise 0.
+ */
+static_always_inline int
+is_hairpinning (ip6_address_t * dst_addr)
+{
+  nat64_main_t *nm = &nat64_main;
+  int i;
+
+  for (i = 0; i < vec_len (nm->addr_pool); i++)
+    {
+      if (nm->addr_pool[i].addr.as_u32 == dst_addr->as_u32[3])
+	return 1;
+    }
+
+  return 0;
+}
+
 static int
 nat64_in2out_tcp_udp_set_cb (ip6_header_t * ip6, ip4_header_t * ip4,
 			     void *arg)
@@ -145,6 +180,18 @@ nat64_in2out_tcp_udp_set_cb (ip6_header_t * ip6, ip4_header_t * ip4,
 
   ip4->dst_address.as_u32 = daddr.ip4.as_u32;
 
+  if (proto == SNAT_PROTOCOL_TCP)
+    {
+      u16 *checksum;
+      ip_csum_t csum;
+      tcp_header_t *tcp = ip6_next_header (ip6);
+
+      checksum = &tcp->checksum;
+      csum = ip_csum_sub_even (*checksum, sport);
+      csum = ip_csum_add_even (csum, udp->src_port);
+      *checksum = ip_csum_fold (csum);
+    }
+
   return 0;
 }
 
@@ -279,6 +326,10 @@ nat64_in2out_inner_icmp_set_cb (ip6_header_t * ip6, ip4_header_t * ip4,
   else
     {
       udp_header_t *udp = ip6_next_header (ip6);
+      tcp_header_t *tcp = ip6_next_header (ip6);
+      u16 *checksum;
+      ip_csum_t csum;
+
       u16 sport = udp->src_port;
       u16 dport = udp->dst_port;
 
@@ -295,11 +346,267 @@ nat64_in2out_inner_icmp_set_cb (ip6_header_t * ip6, ip4_header_t * ip4,
       ip4->dst_address.as_u32 = bibe->out_addr.as_u32;
       udp->dst_port = bibe->out_port;
       ip4->src_address.as_u32 = saddr.ip4.as_u32;
+
+      if (proto == SNAT_PROTOCOL_TCP)
+	checksum = &tcp->checksum;
+      else
+	checksum = &udp->checksum;
+      csum = ip_csum_sub_even (*checksum, dport);
+      csum = ip_csum_add_even (csum, udp->dst_port);
+      *checksum = ip_csum_fold (csum);
     }
 
   return 0;
 }
 
+static int
+nat64_in2out_tcp_udp_hairpinning (vlib_main_t * vm, vlib_buffer_t * b,
+				  ip6_header_t * ip6)
+{
+  nat64_main_t *nm = &nat64_main;
+  nat64_db_bib_entry_t *bibe;
+  nat64_db_st_entry_t *ste;
+  ip46_address_t saddr, daddr;
+  u32 sw_if_index, fib_index;
+  udp_header_t *udp = ip6_next_header (ip6);
+  tcp_header_t *tcp = ip6_next_header (ip6);
+  snat_protocol_t proto = ip_proto_to_snat_proto (ip6->protocol);
+  u16 sport = udp->src_port;
+  u16 dport = udp->dst_port;
+  u16 *checksum;
+  ip_csum_t csum;
+
+  sw_if_index = vnet_buffer (b)->sw_if_index[VLIB_RX];
+  fib_index =
+    fib_table_get_index_for_sw_if_index (FIB_PROTOCOL_IP6, sw_if_index);
+
+  saddr.as_u64[0] = ip6->src_address.as_u64[0];
+  saddr.as_u64[1] = ip6->src_address.as_u64[1];
+  daddr.as_u64[0] = ip6->dst_address.as_u64[0];
+  daddr.as_u64[1] = ip6->dst_address.as_u64[1];
+
+  if (proto == SNAT_PROTOCOL_UDP)
+    checksum = &udp->checksum;
+  else
+    checksum = &tcp->checksum;
+
+  csum = ip_csum_sub_even (*checksum, ip6->src_address.as_u64[0]);
+  csum = ip_csum_sub_even (csum, ip6->src_address.as_u64[1]);
+  csum = ip_csum_sub_even (csum, ip6->dst_address.as_u64[0]);
+  csum = ip_csum_sub_even (csum, ip6->dst_address.as_u64[1]);
+  csum = ip_csum_sub_even (csum, sport);
+  csum = ip_csum_sub_even (csum, dport);
+
+  ste =
+    nat64_db_st_entry_find (&nm->db, &saddr, &daddr, sport, dport, proto,
+			    fib_index, 1);
+
+  if (ste)
+    {
+      bibe = nat64_db_bib_entry_by_index (&nm->db, proto, ste->bibe_index);
+      if (!bibe)
+	return -1;
+    }
+  else
+    {
+      bibe =
+	nat64_db_bib_entry_find (&nm->db, &saddr, sport, proto, fib_index, 1);
+
+      if (!bibe)
+	{
+	  u16 out_port;
+	  ip4_address_t out_addr;
+	  if (nat64_alloc_out_addr_and_port
+	      (fib_index, proto, &out_addr, &out_port))
+	    return -1;
+
+	  bibe =
+	    nat64_db_bib_entry_create (&nm->db, &ip6->src_address, &out_addr,
+				       sport, clib_host_to_net_u16 (out_port),
+				       fib_index, proto, 0);
+	  if (!bibe)
+	    return -1;
+	}
+
+      ste =
+	nat64_db_st_entry_create (&nm->db, bibe, &ip6->dst_address,
+				  &daddr.ip4, dport);
+      if (!ste)
+	return -1;
+    }
+
+  nat64_session_reset_timeout (ste, vm);
+
+  sport = udp->src_port = bibe->out_port;
+  memcpy (&ip6->src_address, well_known_prefix, sizeof (ip6_address_t));
+  saddr.ip6.as_u32[3] = ip6->src_address.as_u32[3] = bibe->out_addr.as_u32;
+
+  saddr.ip6.as_u32[0] = 0;
+  saddr.ip6.as_u32[1] = 0;
+  saddr.ip6.as_u32[2] = 0;
+  daddr.ip6.as_u32[0] = 0;
+  daddr.ip6.as_u32[1] = 0;
+  daddr.ip6.as_u32[2] = 0;
+
+  ste =
+    nat64_db_st_entry_find (&nm->db, &daddr, &saddr, dport, sport, proto, 0,
+			    0);
+
+  if (ste)
+    {
+      bibe = nat64_db_bib_entry_by_index (&nm->db, proto, ste->bibe_index);
+      if (!bibe)
+	return -1;
+    }
+  else
+    {
+      bibe = nat64_db_bib_entry_find (&nm->db, &daddr, dport, proto, 0, 0);
+
+      if (!bibe)
+	return -1;
+
+      ste =
+	nat64_db_st_entry_create (&nm->db, bibe, &ip6->src_address,
+				  &saddr.ip4, sport);
+    }
+
+  ip6->dst_address.as_u64[0] = bibe->in_addr.as_u64[0];
+  ip6->dst_address.as_u64[1] = bibe->in_addr.as_u64[1];
+  udp->dst_port = bibe->in_port;
+
+  csum = ip_csum_add_even (csum, ip6->src_address.as_u64[0]);
+  csum = ip_csum_add_even (csum, ip6->src_address.as_u64[1]);
+  csum = ip_csum_add_even (csum, ip6->dst_address.as_u64[0]);
+  csum = ip_csum_add_even (csum, ip6->dst_address.as_u64[1]);
+  csum = ip_csum_add_even (csum, udp->src_port);
+  csum = ip_csum_add_even (csum, udp->dst_port);
+  *checksum = ip_csum_fold (csum);
+
+  return 0;
+}
+
+static int
+nat64_in2out_icmp_hairpinning (vlib_main_t * vm, vlib_buffer_t * b,
+			       ip6_header_t * ip6)
+{
+  nat64_main_t *nm = &nat64_main;
+  nat64_db_bib_entry_t *bibe;
+  nat64_db_st_entry_t *ste;
+  icmp46_header_t *icmp = ip6_next_header (ip6);
+  ip6_header_t *inner_ip6;
+  ip46_address_t saddr, daddr;
+  u32 sw_if_index, fib_index;
+  snat_protocol_t proto;
+  udp_header_t *udp;
+  tcp_header_t *tcp;
+  u16 *checksum, sport, dport;
+  ip_csum_t csum;
+
+  if (icmp->type == ICMP6_echo_request || icmp->type == ICMP6_echo_reply)
+    return -1;
+
+  inner_ip6 = (ip6_header_t *) u8_ptr_add (icmp, 8);
+
+  proto = ip_proto_to_snat_proto (inner_ip6->protocol);
+
+  if (proto == SNAT_PROTOCOL_ICMP)
+    return -1;
+
+  sw_if_index = vnet_buffer (b)->sw_if_index[VLIB_RX];
+  fib_index =
+    fib_table_get_index_for_sw_if_index (FIB_PROTOCOL_IP6, sw_if_index);
+
+  saddr.as_u64[0] = inner_ip6->src_address.as_u64[0];
+  saddr.as_u64[1] = inner_ip6->src_address.as_u64[1];
+  daddr.as_u64[0] = inner_ip6->dst_address.as_u64[0];
+  daddr.as_u64[1] = inner_ip6->dst_address.as_u64[1];
+
+  udp = ip6_next_header (inner_ip6);
+  tcp = ip6_next_header (inner_ip6);
+
+  sport = udp->src_port;
+  dport = udp->dst_port;
+
+  if (proto == SNAT_PROTOCOL_UDP)
+    checksum = &udp->checksum;
+  else
+    checksum = &tcp->checksum;
+
+  csum = ip_csum_sub_even (*checksum, inner_ip6->src_address.as_u64[0]);
+  csum = ip_csum_sub_even (csum, inner_ip6->src_address.as_u64[1]);
+  csum = ip_csum_sub_even (csum, inner_ip6->dst_address.as_u64[0]);
+  csum = ip_csum_sub_even (csum, inner_ip6->dst_address.as_u64[1]);
+  csum = ip_csum_sub_even (csum, sport);
+  csum = ip_csum_sub_even (csum, dport);
+
+  ste =
+    nat64_db_st_entry_find (&nm->db, &daddr, &saddr, dport, sport, proto,
+			    fib_index, 1);
+  if (!ste)
+    return -1;
+
+  clib_warning ("");
+  bibe = nat64_db_bib_entry_by_index (&nm->db, proto, ste->bibe_index);
+  if (!bibe)
+    return -1;
+
+  dport = udp->dst_port = bibe->out_port;
+  memcpy (&inner_ip6->dst_address, well_known_prefix, sizeof (ip6_address_t));
+  daddr.ip6.as_u32[3] = inner_ip6->dst_address.as_u32[3] =
+    bibe->out_addr.as_u32;
+
+  saddr.ip6.as_u32[0] = 0;
+  saddr.ip6.as_u32[1] = 0;
+  saddr.ip6.as_u32[2] = 0;
+  daddr.ip6.as_u32[0] = 0;
+  daddr.ip6.as_u32[1] = 0;
+  daddr.ip6.as_u32[2] = 0;
+
+  ste =
+    nat64_db_st_entry_find (&nm->db, &saddr, &daddr, sport, dport, proto, 0,
+			    0);
+  if (!ste)
+    return -1;
+
+  bibe = nat64_db_bib_entry_by_index (&nm->db, proto, ste->bibe_index);
+  if (!bibe)
+    return -1;
+
+  inner_ip6->src_address.as_u64[0] = bibe->in_addr.as_u64[0];
+  inner_ip6->src_address.as_u64[1] = bibe->in_addr.as_u64[1];
+  udp->src_port = bibe->in_port;
+
+  csum = ip_csum_add_even (csum, inner_ip6->src_address.as_u64[0]);
+  csum = ip_csum_add_even (csum, inner_ip6->src_address.as_u64[1]);
+  csum = ip_csum_add_even (csum, inner_ip6->dst_address.as_u64[0]);
+  csum = ip_csum_add_even (csum, inner_ip6->dst_address.as_u64[1]);
+  csum = ip_csum_add_even (csum, udp->src_port);
+  csum = ip_csum_add_even (csum, udp->dst_port);
+  *checksum = ip_csum_fold (csum);
+
+  if (!vec_len (nm->addr_pool))
+    return -1;
+
+  memcpy (&ip6->src_address, well_known_prefix, sizeof (ip6_address_t));
+  ip6->src_address.as_u32[3] = nm->addr_pool[0].addr.as_u32;
+  ip6->dst_address.as_u64[0] = inner_ip6->src_address.as_u64[0];
+  ip6->dst_address.as_u64[1] = inner_ip6->src_address.as_u64[1];
+
+  icmp->checksum = 0;
+  csum = ip_csum_with_carry (0, ip6->payload_length);
+  csum = ip_csum_with_carry (csum, clib_host_to_net_u16 (ip6->protocol));
+  csum = ip_csum_with_carry (csum, ip6->src_address.as_u64[0]);
+  csum = ip_csum_with_carry (csum, ip6->src_address.as_u64[1]);
+  csum = ip_csum_with_carry (csum, ip6->dst_address.as_u64[0]);
+  csum = ip_csum_with_carry (csum, ip6->dst_address.as_u64[1]);
+  csum =
+    ip_incremental_checksum (csum, icmp,
+			     clib_net_to_host_u16 (ip6->payload_length));
+  icmp->checksum = ~ip_csum_fold (csum);
+
+  return 0;
+}
+
 static uword
 nat64_in2out_node_fn (vlib_main_t * vm, vlib_node_runtime_t * node,
 		      vlib_frame_t * frame)
@@ -343,7 +650,7 @@ nat64_in2out_node_fn (vlib_main_t * vm, vlib_node_runtime_t * node,
 	  ctx0.b = b0;
 	  ctx0.vm = vm;
 
-	  next0 = NAT64_IN2OUT_NEXT_LOOKUP;
+	  next0 = NAT64_IN2OUT_NEXT_IP4_LOOKUP;
 
 	  if (PREDICT_FALSE
 	      (ip6_parse
@@ -366,6 +673,18 @@ nat64_in2out_node_fn (vlib_main_t * vm, vlib_node_runtime_t * node,
 
 	  if (proto0 == SNAT_PROTOCOL_ICMP)
 	    {
+	      if (is_hairpinning (&ip60->dst_address))
+		{
+		  next0 = NAT64_IN2OUT_NEXT_IP6_LOOKUP;
+		  if (nat64_in2out_icmp_hairpinning (vm, b0, ip60))
+		    {
+		      next0 = NAT64_IN2OUT_NEXT_DROP;
+		      b0->error =
+			node->errors[NAT64_IN2OUT_ERROR_NO_TRANSLATION];
+		    }
+		  goto trace0;
+		}
+
 	      if (icmp6_to_icmp
 		  (b0, nat64_in2out_icmp_set_cb, &ctx0,
 		   nat64_in2out_inner_icmp_set_cb, &ctx0))
@@ -377,6 +696,18 @@ nat64_in2out_node_fn (vlib_main_t * vm, vlib_node_runtime_t * node,
 	    }
 	  else
 	    {
+	      if (is_hairpinning (&ip60->dst_address))
+		{
+		  next0 = NAT64_IN2OUT_NEXT_IP6_LOOKUP;
+		  if (nat64_in2out_tcp_udp_hairpinning (vm, b0, ip60))
+		    {
+		      next0 = NAT64_IN2OUT_NEXT_DROP;
+		      b0->error =
+			node->errors[NAT64_IN2OUT_ERROR_NO_TRANSLATION];
+		    }
+		  goto trace0;
+		}
+
 	      if (ip6_to_ip4_tcp_udp
 		  (b0, nat64_in2out_tcp_udp_set_cb, &ctx0, 0))
 		{
@@ -422,7 +753,8 @@ VLIB_REGISTER_NODE (nat64_in2out_node) = {
   /* edit / add dispositions here */
   .next_nodes = {
     [NAT64_IN2OUT_NEXT_DROP] = "error-drop",
-    [NAT64_IN2OUT_NEXT_LOOKUP] = "ip4-lookup",
+    [NAT64_IN2OUT_NEXT_IP4_LOOKUP] = "ip4-lookup",
+    [NAT64_IN2OUT_NEXT_IP6_LOOKUP] = "ip6-lookup",
   },
 };
 /* *INDENT-ON* */
diff --git a/src/plugins/snat/nat64_out2in.c b/src/plugins/snat/nat64_out2in.c
index c11bbb5a7b1..0a5fbe5b357 100644
--- a/src/plugins/snat/nat64_out2in.c
+++ b/src/plugins/snat/nat64_out2in.c
@@ -27,8 +27,9 @@ static u8 well_known_prefix[] = {
   0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00
- };
+};
 /* *INDENT-ON* */
+
 typedef struct
 {
   u32 sw_if_index;
@@ -95,10 +96,13 @@ nat64_out2in_tcp_udp_set_cb (ip4_header_t * ip4, ip6_header_t * ip6,
   ip46_address_t saddr, daddr;
   ip6_address_t ip6_saddr;
   udp_header_t *udp = ip4_next_header (ip4);
+  tcp_header_t *tcp = ip4_next_header (ip4);
   snat_protocol_t proto = ip_proto_to_snat_proto (ip4->protocol);
   u16 dport = udp->dst_port;
   u16 sport = udp->src_port;
   u32 sw_if_index, fib_index;
+  u16 *checksum;
+  ip_csum_t csum;
 
   sw_if_index = vnet_buffer (ctx->b)->sw_if_index[VLIB_RX];
   fib_index = ip4_fib_table_get_index_for_sw_if_index (sw_if_index);
@@ -142,6 +146,16 @@ nat64_out2in_tcp_udp_set_cb (ip4_header_t * ip4, ip6_header_t * ip6,
   ip6->dst_address.as_u64[1] = bibe->in_addr.as_u64[1];
   udp->dst_port = bibe->in_port;
 
+  if (proto == SNAT_PROTOCOL_UDP)
+    checksum = &udp->checksum;
+  else
+    checksum = &tcp->checksum;
+  csum = ip_csum_sub_even (*checksum, dport);
+  csum = ip_csum_add_even (csum, udp->dst_port);
+  *checksum = ip_csum_fold (csum);
+
+  vnet_buffer (ctx->b)->sw_if_index[VLIB_TX] = bibe->fib_index;
+
   return 0;
 }
 
@@ -205,6 +219,7 @@ nat64_out2in_icmp_set_cb (ip4_header_t * ip4, ip6_header_t * ip6, void *arg)
       ip6->dst_address.as_u64[1] = bibe->in_addr.as_u64[1];
       ((u16 *) (icmp))[2] = bibe->in_port;
 
+      vnet_buffer (ctx->b)->sw_if_index[VLIB_TX] = bibe->fib_index;
     }
   else
     {
@@ -269,12 +284,17 @@ nat64_out2in_inner_icmp_set_cb (ip4_header_t * ip4, ip6_header_t * ip6,
       ip6->src_address.as_u64[0] = bibe->in_addr.as_u64[0];
       ip6->src_address.as_u64[1] = bibe->in_addr.as_u64[1];
       ((u16 *) (icmp))[2] = bibe->in_port;
+
+      vnet_buffer (ctx->b)->sw_if_index[VLIB_TX] = bibe->fib_index;
     }
   else
     {
       udp_header_t *udp = ip4_next_header (ip4);
+      tcp_header_t *tcp = ip4_next_header (ip4);
       u16 dport = udp->dst_port;
       u16 sport = udp->src_port;
+      u16 *checksum;
+      ip_csum_t csum;
 
       ste =
 	nat64_db_st_entry_find (&nm->db, &saddr, &daddr, sport, dport, proto,
@@ -291,6 +311,19 @@ nat64_out2in_inner_icmp_set_cb (ip4_header_t * ip4, ip6_header_t * ip6,
       ip6->src_address.as_u64[0] = bibe->in_addr.as_u64[0];
       ip6->src_address.as_u64[1] = bibe->in_addr.as_u64[1];
       udp->src_port = bibe->in_port;
+
+      if (proto == SNAT_PROTOCOL_UDP)
+	checksum = &udp->checksum;
+      else
+	checksum = &tcp->checksum;
+      if (*checksum)
+	{
+	  csum = ip_csum_sub_even (*checksum, sport);
+	  csum = ip_csum_add_even (csum, udp->src_port);
+	  *checksum = ip_csum_fold (csum);
+	}
+
+      vnet_buffer (ctx->b)->sw_if_index[VLIB_TX] = bibe->fib_index;
     }
 
   return 0;
diff --git a/src/plugins/snat/snat_api.c b/src/plugins/snat/snat_api.c
index 2a7f115fc44..383df39958b 100644
--- a/src/plugins/snat/snat_api.c
+++ b/src/plugins/snat/snat_api.c
@@ -1245,7 +1245,7 @@ static void *vl_api_nat64_add_del_pool_addr_range_t_print
 {
   u8 *s;
 
-  s = format (0, "SCRIPT: nat64_add_del_pool_addr_range");
+  s = format (0, "SCRIPT: nat64_add_del_pool_addr_range ");
   s = format (s, "%U - %U vrf_id %u %s\n",
 	      format_ip4_address, mp->start_addr,
 	      format_ip4_address, mp->end_addr,
@@ -1273,7 +1273,7 @@ nat64_api_pool_walk (snat_address_t * a, void *arg)
   clib_memcpy (rmp->address, &(a->addr), 4);
   if (a->fib_index != ~0)
     {
-      fib_table_t *fib = fib_table_get (a->fib_index, FIB_PROTOCOL_IP4);
+      fib_table_t *fib = fib_table_get (a->fib_index, FIB_PROTOCOL_IP6);
       if (!fib)
 	return -1;
       rmp->vrf_id = ntohl (fib->ft_table_id);
diff --git a/src/vnet/ip/ip4_to_ip6.h b/src/vnet/ip/ip4_to_ip6.h
index dad35230b12..cdd370723f2 100644
--- a/src/vnet/ip/ip4_to_ip6.h
+++ b/src/vnet/ip/ip4_to_ip6.h
@@ -321,17 +321,9 @@ icmp_to_icmp6 (vlib_buffer_t * p, ip4_to_ip6_set_fn_t fn, void *ctx,
 	  //We have an ICMP inside an ICMP
 	  //It needs to be translated, but not for error ICMP messages
 	  icmp46_header_t *inner_icmp = (icmp46_header_t *) (inner_ip4 + 1);
-	  csum = inner_icmp->checksum;
 	  //Only types ICMP4_echo_request and ICMP4_echo_reply are handled by icmp_to_icmp6_header
-	  csum = ip_csum_sub_even (csum, *((u16 *) inner_icmp));
 	  inner_icmp->type = (inner_icmp->type == ICMP4_echo_request) ?
 	    ICMP6_echo_request : ICMP6_echo_reply;
-	  csum = ip_csum_add_even (csum, *((u16 *) inner_icmp));
-	  csum =
-	    ip_csum_add_even (csum, clib_host_to_net_u16 (IP_PROTOCOL_ICMP6));
-	  csum =
-	    ip_csum_add_even (csum, inner_ip4->length - sizeof (*inner_ip4));
-	  inner_icmp->checksum = ip_csum_fold (csum);
 	  inner_L4_checksum = &inner_icmp->checksum;
 	  inner_ip4->protocol = IP_PROTOCOL_ICMP6;
 	}
@@ -341,8 +333,6 @@ icmp_to_icmp6 (vlib_buffer_t * p, ip4_to_ip6_set_fn_t fn, void *ctx,
 	  os_panic ();
 	}
 
-      csum = *inner_L4_checksum;	//Initial checksum of the inner L4 header
-
       inner_ip6->ip_version_traffic_class_and_flow_label =
 	clib_host_to_net_u32 ((6 << 28) + (inner_ip4->tos << 20));
       inner_ip6->payload_length =
@@ -367,14 +357,42 @@ icmp_to_icmp6 (vlib_buffer_t * p, ip4_to_ip6_set_fn_t fn, void *ctx,
 				  sizeof (*inner_frag));
 	}
 
-      /* UDP checksum is optional */
-      if (csum)
+      csum = *inner_L4_checksum;
+      if (inner_ip6->protocol == IP_PROTOCOL_ICMP6)
 	{
-	  csum = ip_csum_add_even (csum, inner_ip6->src_address.as_u64[0]);
-	  csum = ip_csum_add_even (csum, inner_ip6->src_address.as_u64[1]);
-	  csum = ip_csum_add_even (csum, inner_ip6->dst_address.as_u64[0]);
-	  csum = ip_csum_add_even (csum, inner_ip6->dst_address.as_u64[1]);
-	  *inner_L4_checksum = ip_csum_fold (csum);
+	  //Recompute ICMP checksum
+	  icmp46_header_t *inner_icmp = (icmp46_header_t *) (inner_ip4 + 1);
+
+	  inner_icmp->checksum = 0;
+	  csum = ip_csum_with_carry (0, inner_ip6->payload_length);
+	  csum =
+	    ip_csum_with_carry (csum,
+				clib_host_to_net_u16 (inner_ip6->protocol));
+	  csum = ip_csum_with_carry (csum, inner_ip6->src_address.as_u64[0]);
+	  csum = ip_csum_with_carry (csum, inner_ip6->src_address.as_u64[1]);
+	  csum = ip_csum_with_carry (csum, inner_ip6->dst_address.as_u64[0]);
+	  csum = ip_csum_with_carry (csum, inner_ip6->dst_address.as_u64[1]);
+	  csum =
+	    ip_incremental_checksum (csum, inner_icmp,
+				     clib_net_to_host_u16
+				     (inner_ip6->payload_length));
+	  inner_icmp->checksum = ~ip_csum_fold (csum);
+	}
+      else
+	{
+	  /* UDP checksum is optional */
+	  if (csum)
+	    {
+	      csum =
+		ip_csum_add_even (csum, inner_ip6->src_address.as_u64[0]);
+	      csum =
+		ip_csum_add_even (csum, inner_ip6->src_address.as_u64[1]);
+	      csum =
+		ip_csum_add_even (csum, inner_ip6->dst_address.as_u64[0]);
+	      csum =
+		ip_csum_add_even (csum, inner_ip6->dst_address.as_u64[1]);
+	      *inner_L4_checksum = ip_csum_fold (csum);
+	    }
 	}
     }
   else
@@ -518,6 +536,7 @@ ip4_to_ip6_tcp_udp (vlib_buffer_t * p, ip4_to_ip6_set_fn_t fn, void *ctx)
 
   csum = ip_csum_sub_even (*checksum, ip4->src_address.as_u32);
   csum = ip_csum_sub_even (csum, ip4->dst_address.as_u32);
+  *checksum = ip_csum_fold (csum);
 
   // Deal with fragmented packets
   if (PREDICT_FALSE (ip4->flags_and_fragment_offset &
@@ -558,7 +577,7 @@ ip4_to_ip6_tcp_udp (vlib_buffer_t * p, ip4_to_ip6_set_fn_t fn, void *ctx)
   if ((rv = fn (ip4, ip6, ctx)) != 0)
     return rv;
 
-  csum = ip_csum_add_even (csum, ip6->src_address.as_u64[0]);
+  csum = ip_csum_add_even (*checksum, ip6->src_address.as_u64[0]);
   csum = ip_csum_add_even (csum, ip6->src_address.as_u64[1]);
   csum = ip_csum_add_even (csum, ip6->dst_address.as_u64[0]);
   csum = ip_csum_add_even (csum, ip6->dst_address.as_u64[1]);
diff --git a/src/vnet/ip/ip6_to_ip4.h b/src/vnet/ip/ip6_to_ip4.h
index 92f73ba165d..7a0d534959c 100644
--- a/src/vnet/ip/ip6_to_ip4.h
+++ b/src/vnet/ip/ip6_to_ip4.h
@@ -314,13 +314,9 @@ icmp6_to_icmp (vlib_buffer_t * p, ip6_to_ip4_set_fn_t fn, void *ctx,
       else if (inner_protocol == IP_PROTOCOL_ICMP6)
 	{
 	  icmp46_header_t *inner_icmp = (icmp46_header_t *) inner_l4;
-	  csum = inner_icmp->checksum;
-	  csum = ip_csum_sub_even (csum, *((u16 *) inner_icmp));
 	  //It cannot be of a different type as ip6_icmp_to_icmp6_in_place succeeded
 	  inner_icmp->type = (inner_icmp->type == ICMP6_echo_request) ?
 	    ICMP4_echo_request : ICMP4_echo_reply;
-	  csum = ip_csum_add_even (csum, *((u16 *) inner_icmp));
-	  inner_icmp->checksum = ip_csum_fold (csum);
 	  inner_protocol = IP_PROTOCOL_ICMP;	//Will be copied to ip6 later
 	  inner_L4_checksum = &inner_icmp->checksum;
 	}
@@ -334,6 +330,7 @@ icmp6_to_icmp (vlib_buffer_t * p, ip6_to_ip4_set_fn_t fn, void *ctx,
       csum = ip_csum_sub_even (csum, inner_ip6->src_address.as_u64[1]);
       csum = ip_csum_sub_even (csum, inner_ip6->dst_address.as_u64[0]);
       csum = ip_csum_sub_even (csum, inner_ip6->dst_address.as_u64[1]);
+      *inner_L4_checksum = ip_csum_fold (csum);
 
       if ((rv = inner_fn (inner_ip6, inner_ip4, inner_ctx)) != 0)
 	return rv;
@@ -353,19 +350,23 @@ icmp6_to_icmp (vlib_buffer_t * p, ip6_to_ip4_set_fn_t fn, void *ctx,
 
       if (inner_ip4->protocol == IP_PROTOCOL_ICMP)
 	{
-	  //Remove remainings of the pseudo-header in the csum
-	  csum =
-	    ip_csum_sub_even (csum, clib_host_to_net_u16 (IP_PROTOCOL_ICMP6));
+	  //Recompute ICMP checksum
+	  icmp46_header_t *inner_icmp = (icmp46_header_t *) inner_l4;
+	  inner_icmp->checksum = 0;
 	  csum =
-	    ip_csum_sub_even (csum, inner_ip4->length - sizeof (*inner_ip4));
+	    ip_incremental_checksum (0, inner_icmp,
+				     clib_net_to_host_u16 (inner_ip4->length)
+				     - sizeof (*inner_ip4));
+	  inner_icmp->checksum = ~ip_csum_fold (csum);
 	}
       else
 	{
 	  //Update to new pseudo-header
+	  csum = *inner_L4_checksum;
 	  csum = ip_csum_add_even (csum, inner_ip4->src_address.as_u32);
 	  csum = ip_csum_add_even (csum, inner_ip4->dst_address.as_u32);
+	  *inner_L4_checksum = ip_csum_fold (csum);
 	}
-      *inner_L4_checksum = ip_csum_fold (csum);
 
       //Move up icmp header
       ip4 = (ip4_header_t *) u8_ptr_add (inner_l4, -2 * sizeof (*ip4) - 8);
@@ -512,6 +513,7 @@ ip6_to_ip4_tcp_udp (vlib_buffer_t * p, ip6_to_ip4_set_fn_t fn, void *ctx,
   csum = ip_csum_sub_even (csum, ip6->src_address.as_u64[1]);
   csum = ip_csum_sub_even (csum, ip6->dst_address.as_u64[0]);
   csum = ip_csum_sub_even (csum, ip6->dst_address.as_u64[1]);
+  *checksum = ip_csum_fold (csum);
 
 no_csum:
   ip4 = (ip4_header_t *) u8_ptr_add (ip6, l4_offset - sizeof (*ip4));
@@ -552,7 +554,7 @@ no_csum:
     }
   else
     {
-      csum = ip_csum_add_even (csum, ip4->dst_address.as_u32);
+      csum = ip_csum_add_even (*checksum, ip4->dst_address.as_u32);
       csum = ip_csum_add_even (csum, ip4->src_address.as_u32);
       *checksum = ip_csum_fold (csum);
     }