Add L3DSR feature in LB plugin

L3DSR is used to overcome Layer 2 limitations
of Direct Server Return Load Balancing.
It maps VIP to DSCP bits, and reuse TOS bits to transfer it
to server, and then server will get VIP from DSCP-to-VIP mapping.
Please refer to https://www.nanog.org/meetings/nanog51/presentations/Monday/NANOG51.Talk45.nanog51-Schaumann.pdf

Change-Id: I403ffeadfb04ed0265086eb2dc41f2e17f8f34cb
Signed-off-by: Hongjun Ni <hongjun.ni@intel.com>

8 files changed, 246 insertions, 88 deletions

diff --git a/src/plugins/lb/api.c b/src/plugins/lb/api.c
index 7eb49ff6c26..28af6daa421 100644
--- a/src/plugins/lb/api.c
+++ b/src/plugins/lb/api.c
@@ -116,14 +116,23 @@ vl_api_lb_add_del_vip_t_handler
       rv = lb_vip_del(vip_index);
   } else {
     u32 vip_index;
-    lb_vip_type_t type;
+    lb_vip_type_t type = 0;
+
     if (ip46_prefix_is_ip4(&prefix, mp->prefix_length)) {
-      type = mp->is_gre4?LB_VIP_TYPE_IP4_GRE4:LB_VIP_TYPE_IP4_GRE6;
+        if (mp->encap == LB_ENCAP_TYPE_GRE4)
+  	type = LB_VIP_TYPE_IP4_GRE4;
+        else if (mp->encap == LB_ENCAP_TYPE_GRE6)
+  	type = LB_VIP_TYPE_IP4_GRE6;
+        else if (mp->encap == LB_ENCAP_TYPE_L3DSR)
+  	type = LB_VIP_TYPE_IP4_L3DSR;
     } else {
-      type = mp->is_gre4?LB_VIP_TYPE_IP6_GRE4:LB_VIP_TYPE_IP6_GRE6;
+        if (mp->encap == LB_ENCAP_TYPE_GRE4)
+  	type = LB_VIP_TYPE_IP6_GRE4;
+        else if (mp->encap == LB_ENCAP_TYPE_GRE6)
+  	type = LB_VIP_TYPE_IP6_GRE6;
     }
 
-    rv = lb_vip_add(&prefix, mp->prefix_length, type,
+    rv = lb_vip_add(&prefix, mp->prefix_length, type, mp->dscp,
                     mp->new_flows_table_length, &vip_index);
   }
  REPLY_MACRO (VL_API_LB_CONF_REPLY);
@@ -136,7 +145,9 @@ static void *vl_api_lb_add_del_vip_t_print
   s = format (0, "SCRIPT: lb_add_del_vip ");
   s = format (s, "%U ", format_ip46_prefix,
               (ip46_address_t *)mp->ip_prefix, mp->prefix_length, IP46_TYPE_ANY);
-  s = format (s, "%s ", mp->is_gre4?"gre4":"gre6");
+
+  s = format (s, "%s ", (mp->encap==LB_ENCAP_TYPE_GRE4)?
+              "gre4":(mp->encap==LB_ENCAP_TYPE_GRE6)?"gre6":"l3dsr");
   s = format (s, "%u ", mp->new_flows_table_length);
   s = format (s, "%s ", mp->is_del?"del":"add");
   FINISH;
diff --git a/src/plugins/lb/cli.c b/src/plugins/lb/cli.c
index a5a87fccc5f..b29605af984 100644
--- a/src/plugins/lb/cli.c
+++ b/src/plugins/lb/cli.c
@@ -26,8 +26,9 @@ lb_vip_command_fn (vlib_main_t * vm,
   u32 new_len = 1024;
   u8 del = 0;
   int ret;
-  u32 gre4 = 0;
-  lb_vip_type_t type;
+  u32 encap = 0;
+  u32 dscp = ~0;
+  lb_vip_type_t type = 0;
   clib_error_t *error = 0;
 
   if (!unformat_user (input, unformat_line_input, line_input))
@@ -46,9 +47,13 @@ lb_vip_command_fn (vlib_main_t * vm,
     else if (unformat(line_input, "del"))
       del = 1;
     else if (unformat(line_input, "encap gre4"))
-      gre4 = 1;
+      encap = LB_ENCAP_TYPE_GRE4;
     else if (unformat(line_input, "encap gre6"))
-      gre4 = 0;
+      encap = LB_ENCAP_TYPE_GRE6;
+    else if (unformat(line_input, "encap l3dsr"))
+      encap = LB_ENCAP_TYPE_L3DSR;
+    else if (unformat(line_input, "dscp %d", &dscp))
+      ;
     else {
       error = clib_error_return (0, "parse error: '%U'",
                                 format_unformat_error, line_input);
@@ -56,18 +61,39 @@ lb_vip_command_fn (vlib_main_t * vm,
     }
   }
 
+  if ((encap != LB_ENCAP_TYPE_L3DSR) && (dscp != ~0) )
+    {
+      error = clib_error_return (0, "lb_vip_add error: "
+	        "should not configure dscp for none L3DSR.");
+      goto done;
+    }
+
+  if ((encap == LB_ENCAP_TYPE_L3DSR) && (dscp >= 64 ) )
+    {
+      error = clib_error_return (0, "lb_vip_add error: "
+	        "dscp for L3DSR should be less than 64.");
+      goto done;
+    }
 
   if (ip46_prefix_is_ip4(&prefix, plen)) {
-    type = (gre4)?LB_VIP_TYPE_IP4_GRE4:LB_VIP_TYPE_IP4_GRE6;
+      if (encap == LB_ENCAP_TYPE_GRE4)
+	type = LB_VIP_TYPE_IP4_GRE4;
+      else if (encap == LB_ENCAP_TYPE_GRE6)
+	type = LB_VIP_TYPE_IP4_GRE6;
+      else if (encap == LB_ENCAP_TYPE_L3DSR)
+	type = LB_VIP_TYPE_IP4_L3DSR;
   } else {
-    type = (gre4)?LB_VIP_TYPE_IP6_GRE4:LB_VIP_TYPE_IP6_GRE6;
+      if (encap == LB_ENCAP_TYPE_GRE4)
+	type = LB_VIP_TYPE_IP6_GRE4;
+      else if (encap == LB_ENCAP_TYPE_GRE6)
+	type = LB_VIP_TYPE_IP6_GRE6;
   }
 
   lb_garbage_collection();
 
   u32 index;
   if (!del) {
-    if ((ret = lb_vip_add(&prefix, plen, type, new_len, &index))) {
+    if ((ret = lb_vip_add(&prefix, plen, type, (u8)(dscp & 0x3F), new_len, &index))) {
       error = clib_error_return (0, "lb_vip_add error %d", ret);
       goto done;
     } else {
@@ -92,7 +118,7 @@ done:
 VLIB_CLI_COMMAND (lb_vip_command, static) =
 {
   .path = "lb vip",
-  .short_help = "lb vip <prefix> [encap (gre6|gre4)] [new_len <n>] [del]",
+  .short_help = "lb vip <prefix> [encap (gre6|gre4|l3dsr)] [dscp <n>] [new_len <n>] [del]",
   .function = lb_vip_command_fn,
 };
 
diff --git a/src/plugins/lb/lb.api b/src/plugins/lb/lb.api
index f5036edf79d..101cee88ded 100644
--- a/src/plugins/lb/lb.api
+++ b/src/plugins/lb/lb.api
@@ -23,9 +23,10 @@ autoreply define lb_conf
 /** \brief Add a virtual address (or prefix)
     @param client_index - opaque cookie to identify the sender
     @param context - sender context, to match reply w/ request
-    @param ip_prefix - IP address (IPv4 in lower order 32 bits). 
-    @param prefix_length - IP prefix length (96 + 'IPv4 prefix length' for IPv4).  
-    @param is_gre4 - Encap is ip4 GRE (ip6 GRE otherwise).
+    @param ip_prefix - IP address (IPv4 in lower order 32 bits).
+    @param prefix_length - IP prefix length (96 + 'IPv4 prefix length' for IPv4).
+    @param encap - Encap is ip4 GRE(0) or ip6 GRE(1) or L3DSR(2).
+    @param dscp - DSCP bit corresponding to VIP(applicable in L3DSR mode only).
     @param new_flows_table_length - Size of the new connections flow table used
            for this VIP (must be power of 2).
     @param is_del - The VIP should be removed.
@@ -35,7 +36,8 @@ autoreply define lb_add_del_vip {
   u32 context;
   u8 ip_prefix[16];
   u8 prefix_length;
-  u8 is_gre4;
+  u8 encap;
+  u8 dscp;
   u32 new_flows_table_length;
   u8 is_del;
 };
@@ -43,8 +45,8 @@ autoreply define lb_add_del_vip {
 /** \brief Add an application server for a given VIP
     @param client_index - opaque cookie to identify the sender
     @param context - sender context, to match reply w/ request
-    @param vip_ip_prefix - VIP IP address (IPv4 in lower order 32 bits). 
-    @param vip_ip_prefix - VIP IP prefix length (96 + 'IPv4 prefix length' for IPv4). 
+    @param vip_ip_prefix - VIP IP address (IPv4 in lower order 32 bits).
+    @param vip_ip_prefix - VIP IP prefix length (96 + 'IPv4 prefix length' for IPv4).
     @param as_address - The application server address (IPv4 in lower order 32 bits).
     @param is_del - The AS should be removed.
 */
diff --git a/src/plugins/lb/lb.c b/src/plugins/lb/lb.c
index fee88056eb4..06953a45aaa 100644
--- a/src/plugins/lb/lb.c
+++ b/src/plugins/lb/lb.c
@@ -48,6 +48,12 @@ const static char* const * const lb_dpo_gre6_nodes[DPO_PROTO_NUM] =
 	[DPO_PROTO_IP6]  = lb_dpo_gre6_ip6,
     };
 
+const static char * const lb_dpo_l3dsr_ip4[] = { "lb4-l3dsr" , NULL };
+const static char* const * const lb_dpo_l3dsr_nodes[DPO_PROTO_NUM] =
+    {
+	[DPO_PROTO_IP4]  = lb_dpo_l3dsr_ip4,
+    };
+
 u32 lb_hash_time_now(vlib_main_t * vm)
 {
   return (u32) (vlib_time_now(vm) + 10000);
@@ -81,6 +87,7 @@ static char *lb_vip_type_strings[] = {
     [LB_VIP_TYPE_IP6_GRE4] = "ip6-gre4",
     [LB_VIP_TYPE_IP4_GRE6] = "ip4-gre6",
     [LB_VIP_TYPE_IP4_GRE4] = "ip4-gre4",
+    [LB_VIP_TYPE_IP4_L3DSR] = "ip4-l3dsr",
 };
 
 u8 *format_lb_vip_type (u8 * s, va_list * args)
@@ -140,6 +147,13 @@ u8 *format_lb_vip_detailed (u8 * s, va_list * args)
                   format_white_space, indent,
                   vip->new_flow_table_mask + 1);
 
+  if (vip->type == LB_VIP_TYPE_IP4_L3DSR)
+    {
+      s = format(s, "%U  dscp:%u\n",
+                    format_white_space, indent,
+		    vip->dscp);
+    }
+
   //Print counters
   s = format(s, "%U  counters:\n",
              format_white_space, indent);
@@ -434,7 +448,7 @@ int lb_vip_add_ass(u32 vip_index, ip46_address_t *addresses, u32 n)
     return VNET_API_ERROR_NO_SUCH_ENTRY;
   }
 
-  ip46_type_t type = lb_vip_is_gre4(vip)?IP46_TYPE_IP4:IP46_TYPE_IP6;
+  ip46_type_t type = lb_encap_is_ip4(vip)?IP46_TYPE_IP4:IP46_TYPE_IP6;
   u32 *to_be_added = 0;
   u32 *to_be_updated = 0;
   u32 i;
@@ -497,7 +511,7 @@ next:
      * so we are informed when its forwarding changes
      */
     fib_prefix_t nh = {};
-    if (lb_vip_is_gre4(vip)) {
+    if (lb_encap_is_ip4(vip)) {
 	nh.fp_addr.ip4 = as->address.ip4;
 	nh.fp_len = 32;
 	nh.fp_proto = FIB_PROTOCOL_IP4;
@@ -595,6 +609,8 @@ int lb_vip_del_ass(u32 vip_index, ip46_address_t *addresses, u32 n)
 static void lb_vip_add_adjacency(lb_main_t *lbm, lb_vip_t *vip)
 {
   dpo_proto_t proto = 0;
+  dpo_type_t dpo_type = 0;
+
   dpo_id_t dpo = DPO_INVALID;
   fib_prefix_t pfx = {};
   if (lb_vip_is_ip4(vip)) {
@@ -608,8 +624,15 @@ static void lb_vip_add_adjacency(lb_main_t *lbm, lb_vip_t *vip)
       pfx.fp_proto = FIB_PROTOCOL_IP6;
       proto = DPO_PROTO_IP6;
   }
-  dpo_set(&dpo, lb_vip_is_gre4(vip)?lbm->dpo_gre4_type:lbm->dpo_gre6_type,
-      proto, vip - lbm->vips);
+
+  if(lb_vip_is_gre4(vip))
+    dpo_type = lbm->dpo_gre4_type;
+  else if (lb_vip_is_gre6(vip))
+    dpo_type = lbm->dpo_gre6_type;
+  else if (lb_vip_is_l3dsr(vip))
+    dpo_type = lbm->dpo_l3dsr_type;
+
+  dpo_set(&dpo, dpo_type, proto, vip - lbm->vips);
   fib_table_entry_special_dpo_add(0,
 				  &pfx,
 				  FIB_SOURCE_PLUGIN_HI,
@@ -636,10 +659,12 @@ static void lb_vip_del_adjacency(lb_main_t *lbm, lb_vip_t *vip)
   fib_table_entry_special_remove(0, &pfx, FIB_SOURCE_PLUGIN_HI);
 }
 
-int lb_vip_add(ip46_address_t *prefix, u8 plen, lb_vip_type_t type, u32 new_length, u32 *vip_index)
+int lb_vip_add(ip46_address_t *prefix, u8 plen, lb_vip_type_t type, u8 dscp,
+	       u32 new_length, u32 *vip_index)
 {
   lb_main_t *lbm = &lb_main;
   lb_vip_t *vip;
+
   lb_get_writer_lock();
   ip46_prefix_normalize(prefix, plen);
 
@@ -655,9 +680,19 @@ int lb_vip_add(ip46_address_t *prefix, u8 plen, lb_vip_type_t type, u32 new_leng
 
   if (ip46_prefix_is_ip4(prefix, plen) &&
       (type != LB_VIP_TYPE_IP4_GRE4) &&
-      (type != LB_VIP_TYPE_IP4_GRE6))
+      (type != LB_VIP_TYPE_IP4_GRE6) &&
+      (type != LB_VIP_TYPE_IP4_L3DSR))
+    return VNET_API_ERROR_INVALID_ADDRESS_FAMILY;
+
+  if ((!ip46_prefix_is_ip4(prefix, plen)) &&
+      (type != LB_VIP_TYPE_IP6_GRE4) &&
+      (type != LB_VIP_TYPE_IP6_GRE6))
     return VNET_API_ERROR_INVALID_ADDRESS_FAMILY;
 
+  if ((type == LB_VIP_TYPE_IP4_L3DSR) && (dscp >= 64 ) )
+    {
+      return VNET_API_ERROR_VALUE_EXIST;
+    }
 
   //Allocate
   pool_get(lbm->vips, vip);
@@ -667,6 +702,7 @@ int lb_vip_add(ip46_address_t *prefix, u8 plen, lb_vip_type_t type, u32 new_leng
   vip->plen = plen;
   vip->last_garbage_collection = (u32) vlib_time_now(vlib_get_main());
   vip->type = type;
+  vip->dscp = dscp;
   vip->flags = LB_VIP_FLAGS_USED;
   vip->as_indexes = 0;
 
@@ -775,7 +811,16 @@ lb_as_stack (lb_as_t *as)
 {
   lb_main_t *lbm = &lb_main;
   lb_vip_t *vip = &lbm->vips[as->vip_index];
-  dpo_stack(lb_vip_is_gre4(vip)?lbm->dpo_gre4_type:lbm->dpo_gre6_type,
+  dpo_type_t dpo_type = 0;
+
+  if(lb_vip_is_gre4(vip))
+    dpo_type = lbm->dpo_gre4_type;
+  else if (lb_vip_is_gre6(vip))
+    dpo_type = lbm->dpo_gre6_type;
+  else if (lb_vip_is_l3dsr(vip))
+    dpo_type = lbm->dpo_l3dsr_type;
+
+  dpo_stack(dpo_type,
 	    lb_vip_is_ip4(vip)?DPO_PROTO_IP4:DPO_PROTO_IP6,
 	    &as->dpo,
 	    fib_entry_contribute_ip_forwarding(
@@ -819,6 +864,7 @@ lb_init (vlib_main_t * vm)
   lbm->ip6_src_address.as_u64[1] = 0xffffffffffffffffL;
   lbm->dpo_gre4_type = dpo_register_new_type(&lb_vft, lb_dpo_gre4_nodes);
   lbm->dpo_gre6_type = dpo_register_new_type(&lb_vft, lb_dpo_gre6_nodes);
+  lbm->dpo_l3dsr_type = dpo_register_new_type(&lb_vft, lb_dpo_l3dsr_nodes);
   lbm->fib_node_type = fib_node_register_new_type(&lb_fib_node_vft);
 
   //Init AS reference counters
diff --git a/src/plugins/lb/lb.h b/src/plugins/lb/lb.h
index fa0b5d48b07..8db0394075c 100644
--- a/src/plugins/lb/lb.h
+++ b/src/plugins/lb/lb.h
@@ -37,6 +37,7 @@
 #include <vnet/ip/ip.h>
 #include <vnet/dpo/dpo.h>
 #include <vnet/fib/fib_table.h>
+#include <vppinfra/hash.h>
 
 #include <lb/lbhash.h>
 
@@ -128,18 +129,27 @@ typedef enum {
   LB_N_VIP_COUNTERS
 } lb_vip_counter_t;
 
+typedef enum {
+  LB_ENCAP_TYPE_GRE4,
+  LB_ENCAP_TYPE_GRE6,
+  LB_ENCAP_TYPE_L3DSR,
+  LB_ENCAP_N_TYPES,
+} lb_encap_type_t;
+
 /**
  * The load balancer supports IPv4 and IPv6 traffic
- * and GRE4 and GRE6 encap.
+ * and GRE4, GRE6 and L3DSR encap.
  */
 typedef enum {
   LB_VIP_TYPE_IP6_GRE6,
   LB_VIP_TYPE_IP6_GRE4,
   LB_VIP_TYPE_IP4_GRE6,
   LB_VIP_TYPE_IP4_GRE4,
+  LB_VIP_TYPE_IP4_L3DSR,
   LB_VIP_N_TYPES,
 } lb_vip_type_t;
 
+
 format_function_t format_lb_vip_type;
 unformat_function_t unformat_lb_vip_type;
 
@@ -196,6 +206,11 @@ typedef struct {
   lb_vip_type_t type;
 
   /**
+   * DSCP bits for L3DSR
+   */
+  u8 dscp;
+
+  /**
    * Flags related to this VIP.
    * LB_VIP_FLAGS_USED means the VIP is active.
    * When it is not set, the VIP in the process of being removed.
@@ -212,8 +227,20 @@ typedef struct {
   u32 *as_indexes;
 } lb_vip_t;
 
-#define lb_vip_is_ip4(vip) ((vip)->type == LB_VIP_TYPE_IP4_GRE6 || (vip)->type == LB_VIP_TYPE_IP4_GRE4)
-#define lb_vip_is_gre4(vip) ((vip)->type == LB_VIP_TYPE_IP6_GRE4 || (vip)->type == LB_VIP_TYPE_IP4_GRE4)
+#define lb_vip_is_ip4(vip) ((vip)->type == LB_VIP_TYPE_IP4_GRE6 \
+                            || (vip)->type == LB_VIP_TYPE_IP4_GRE4 \
+			    || (vip)->type == LB_VIP_TYPE_IP4_L3DSR )
+
+#define lb_vip_is_gre4(vip) ((vip)->type == LB_VIP_TYPE_IP6_GRE4 \
+                             || (vip)->type == LB_VIP_TYPE_IP4_GRE4)
+#define lb_vip_is_gre6(vip) ((vip)->type == LB_VIP_TYPE_IP6_GRE6 \
+                             || (vip)->type == LB_VIP_TYPE_IP4_GRE6)
+#define lb_vip_is_l3dsr(vip) ((vip)->type == LB_VIP_TYPE_IP4_L3DSR)
+
+#define lb_encap_is_ip4(vip) ((vip)->type == LB_VIP_TYPE_IP6_GRE4 \
+                             || (vip)->type == LB_VIP_TYPE_IP4_GRE4 \
+			     || (vip)->type == LB_VIP_TYPE_IP4_L3DSR)
+
 format_function_t format_lb_vip;
 format_function_t format_lb_vip_detailed;
 
@@ -286,6 +313,7 @@ typedef struct {
    */
   dpo_type_t dpo_gre4_type;
   dpo_type_t dpo_gre6_type;
+  dpo_type_t dpo_l3dsr_type;
 
   /**
    * Node type for registering to fib changes.
@@ -313,8 +341,8 @@ extern vlib_node_registration_t lb4_node;
 int lb_conf(ip4_address_t *ip4_address, ip6_address_t *ip6_address,
             u32 sticky_buckets, u32 flow_timeout);
 
-int lb_vip_add(ip46_address_t *prefix, u8 plen, lb_vip_type_t type,
-               u32 new_length, u32 *vip_index);
+int lb_vip_add(ip46_address_t *prefix, u8 plen, lb_vip_type_t type, u8 dscp,
+	       u32 new_length, u32 *vip_index);
 int lb_vip_del(u32 vip_index);
 
 int lb_vip_find_index(ip46_address_t *prefix, u8 plen, u32 *vip_index);
diff --git a/src/plugins/lb/lb_plugin_doc.md b/src/plugins/lb/lb_plugin_doc.md
index c7885ffb837..7672b1e88d7 100644
--- a/src/plugins/lb/lb_plugin_doc.md
+++ b/src/plugins/lb/lb_plugin_doc.md
@@ -8,19 +8,26 @@ Wich also means feedback is really welcome regarding features, apis, etc...
 
 ## Overview
 
-This plugin provides load balancing for VPP in a way that is largely inspired 
+This plugin provides load balancing for VPP in a way that is largely inspired
 from Google's MagLev: http://research.google.com/pubs/pub44824.html
 
-The load balancer is configured with a set of Virtual IPs (VIP, which can be 
+The load balancer is configured with a set of Virtual IPs (VIP, which can be
 prefixes), and for each VIP, with a set of Application Server addresses (ASs).
 
+There are four encap types to steer traffic to different ASs:
+1). IPv4+GRE ad IPv6+GRE encap types:
 Traffic received for a given VIP (or VIP prefix) is tunneled using GRE towards
-the different ASs in a way that (tries to) ensure that a given session will 
+the different ASs in a way that (tries to) ensure that a given session will
 always be tunneled to the same AS.
 
+2). IPv4+L3DSR encap types:
+L3DSR is used to overcome Layer 2 limitations of Direct Server Return Load Balancing.
+It maps VIP to DSCP bits, and reuse TOS bits to transfer DSCP bits
+to server, and then server will get VIP from DSCP-to-VIP mapping.
+
 Both VIPs or ASs can be IPv4 or IPv6, but for a given VIP, all ASs must be using
-the same encap. type (i.e. IPv4+GRE or IPv6+GRE). Meaning that for a given VIP,
-all AS addresses must be of the same family.
+the same encap. type (i.e. IPv4+GRE or IPv6+GRE or IPv4+L3DSR).
+Meaning that for a given VIP, all AS addresses must be of the same family.
 
 ## Performances
 
@@ -35,34 +42,36 @@ in next versions.
 
 The load balancer needs to be configured with some parameters:
 
-	lb conf [ip4-src-address <addr>] [ip6-src-address <addr>] 
+	lb conf [ip4-src-address <addr>] [ip6-src-address <addr>]
 	        [buckets <n>] [timeout <s>]
-	       
+
 ip4-src-address: the source address used to send encap. packets using IPv4.
 
 ip6-src-address: the source address used to send encap. packets using IPv6.
 
 buckets:         the *per-thread* established-connexions-table number of buckets.
 
-timeout:         the number of seconds a connection will remain in the 
+timeout:         the number of seconds a connection will remain in the
                  established-connexions-table while no packet for this flow
                  is received.
-                 
 
 ### Configure the VIPs
 
-    lb vip <prefix> [encap (gre6|gre4)] [new_len <n>] [del]
-    
+    lb vip <prefix> [encap (gre6|gre4|l3dsr)] [dscp <n>] [new_len <n>] [del]
+
 new_len is the size of the new-connection-table. It should be 1 or 2 orders of
 magnitude bigger than the number of ASs for the VIP in order to ensure a good
 load balancing.
+Encap l3dsr and dscp is used to map VIP to dscp bit and rewrite DSCP bit in packets.
+So the selected server could get VIP from DSCP bit in this packet and perform DSR.
 
 Examples:
-    
+
     lb vip 2002::/16 encap gre6 new_len 1024
     lb vip 2003::/16 encap gre4 new_len 2048
     lb vip 80.0.0.0/8 encap gre6 new_len 16
     lb vip 90.0.0.0/8 encap gre4 new_len 1024
+    lb vip 100.0.0.0/8 encap l3dsr dscp 2 new_len 32
 
 ### Configure the ASs (for each VIP)
 
diff --git a/src/plugins/lb/lb_test.c b/src/plugins/lb/lb_test.c
index 35bda262fee..b02793944c5 100644
--- a/src/plugins/lb/lb_test.c
+++ b/src/plugins/lb/lb_test.c
@@ -157,7 +157,7 @@ static int api_lb_add_del_vip (vat_main_t * vam)
   vl_api_lb_add_del_vip_t mps, *mp;
   int ret;
   mps.is_del = 0;
-  mps.is_gre4 = 0;
+  mps.encap = LB_ENCAP_TYPE_GRE4;
 
   if (!unformat(i, "%U",
                 unformat_ip46_prefix, mps.ip_prefix, &mps.prefix_length, IP46_TYPE_ANY)) {
@@ -166,9 +166,11 @@ static int api_lb_add_del_vip (vat_main_t * vam)
   }
 
   if (unformat(i, "gre4")) {
-    mps.is_gre4 = 1;
+    mps.encap = LB_ENCAP_TYPE_GRE4;
   } else if (unformat(i, "gre6")) {
-    mps.is_gre4 = 0;
+    mps.encap = LB_ENCAP_TYPE_GRE6;
+  } else if (unformat(i, "l3dsr")) {
+    mps.encap = LB_ENCAP_TYPE_L3DSR;
   } else {
     errmsg ("no encap\n");
     return -99;
diff --git a/src/plugins/lb/node.c b/src/plugins/lb/node.c
index 4a7485eb835..22ba3104f92 100644
--- a/src/plugins/lb/node.c
+++ b/src/plugins/lb/node.c
@@ -149,7 +149,7 @@ static_always_inline uword
 lb_node_fn (vlib_main_t * vm,
          vlib_node_runtime_t * node, vlib_frame_t * frame,
          u8 is_input_v4, //Compile-time parameter stating that is input is v4 (or v6)
-         u8 is_encap_v4) //Compile-time parameter stating that is GRE encap is v4 (or v6)
+	 lb_encap_type_t encap_type) //Compile-time parameter stating that is GRE4 or GRE6 or L3DSR
 {
   lb_main_t *lbm = &lb_main;
   u32 n_left_from, *from, next_index, *to_next, n_left_to_next;
@@ -265,43 +265,54 @@ lb_node_fn (vlib_main_t * vm,
 				    1);
 
       //Now let's encap
-      {
-	gre_header_t *gre0;
-	if (is_encap_v4)
-	  {
-	    ip4_header_t *ip40;
-	    vlib_buffer_advance(p0, - sizeof(ip4_header_t) - sizeof(gre_header_t));
-	    ip40 = vlib_buffer_get_current(p0);
-	    gre0 = (gre_header_t *)(ip40 + 1);
-	    ip40->src_address = lbm->ip4_src_address;
-	    ip40->dst_address = lbm->ass[asindex0].address.ip4;
-	    ip40->ip_version_and_header_length = 0x45;
-	    ip40->ttl = 128;
-	    ip40->fragment_id = 0;
-	    ip40->flags_and_fragment_offset = 0;
-	    ip40->length = clib_host_to_net_u16(len0 + sizeof(gre_header_t) + sizeof(ip4_header_t));
-	    ip40->protocol = IP_PROTOCOL_GRE;
-	    ip40->checksum = ip4_header_checksum (ip40);
-	  }
-	else
-	  {
-	    ip6_header_t *ip60;
-	    vlib_buffer_advance(p0, - sizeof(ip6_header_t) - sizeof(gre_header_t));
-	    ip60 = vlib_buffer_get_current(p0);
-	    gre0 = (gre_header_t *)(ip60 + 1);
-	    ip60->dst_address = lbm->ass[asindex0].address.ip6;
-	    ip60->src_address = lbm->ip6_src_address;
-	    ip60->hop_limit = 128;
-	    ip60->ip_version_traffic_class_and_flow_label = clib_host_to_net_u32 (0x6<<28);
-	    ip60->payload_length = clib_host_to_net_u16(len0 + sizeof(gre_header_t));
-	    ip60->protocol = IP_PROTOCOL_GRE;
-	  }
-
-	gre0->flags_and_version = 0;
-	gre0->protocol = (is_input_v4)?
-	    clib_host_to_net_u16(0x0800):
-	    clib_host_to_net_u16(0x86DD);
-      }
+      if ( (encap_type == LB_ENCAP_TYPE_GRE4)
+	   || (encap_type == LB_ENCAP_TYPE_GRE6) )
+        {
+	  gre_header_t *gre0;
+	  if (encap_type == LB_ENCAP_TYPE_GRE4) /* encap GRE4*/
+	    {
+	      ip4_header_t *ip40;
+	      vlib_buffer_advance(p0, - sizeof(ip4_header_t) - sizeof(gre_header_t));
+	      ip40 = vlib_buffer_get_current(p0);
+	      gre0 = (gre_header_t *)(ip40 + 1);
+	      ip40->src_address = lbm->ip4_src_address;
+	      ip40->dst_address = lbm->ass[asindex0].address.ip4;
+	      ip40->ip_version_and_header_length = 0x45;
+	      ip40->ttl = 128;
+	      ip40->fragment_id = 0;
+	      ip40->flags_and_fragment_offset = 0;
+	      ip40->length = clib_host_to_net_u16(len0 + sizeof(gre_header_t) + sizeof(ip4_header_t));
+	      ip40->protocol = IP_PROTOCOL_GRE;
+	      ip40->checksum = ip4_header_checksum (ip40);
+	    }
+	  else /* encap GRE6*/
+	    {
+	      ip6_header_t *ip60;
+	      vlib_buffer_advance(p0, - sizeof(ip6_header_t) - sizeof(gre_header_t));
+	      ip60 = vlib_buffer_get_current(p0);
+	      gre0 = (gre_header_t *)(ip60 + 1);
+	      ip60->dst_address = lbm->ass[asindex0].address.ip6;
+	      ip60->src_address = lbm->ip6_src_address;
+	      ip60->hop_limit = 128;
+	      ip60->ip_version_traffic_class_and_flow_label = clib_host_to_net_u32 (0x6<<28);
+	      ip60->payload_length = clib_host_to_net_u16(len0 + sizeof(gre_header_t));
+	      ip60->protocol = IP_PROTOCOL_GRE;
+	    }
+
+	  gre0->flags_and_version = 0;
+	  gre0->protocol = (is_input_v4)?
+	      clib_host_to_net_u16(0x0800):
+	      clib_host_to_net_u16(0x86DD);
+      } else if (encap_type == LB_ENCAP_TYPE_L3DSR) /* encap L3DSR*/
+	{
+	  ip4_header_t *ip40;
+
+	  ip40 = vlib_buffer_get_current(p0);
+	  ip40->dst_address = lbm->ass[asindex0].address.ip4;
+	  /* Get and rewrite DSCP bit */
+          ip40->tos = (u8)((vip0->dscp & 0x3F)<<2);
+	  ip40->checksum = ip4_header_checksum (ip40);
+	}
 
       if (PREDICT_FALSE (p0->flags & VLIB_BUFFER_IS_TRACED))
 	{
@@ -327,28 +338,35 @@ static uword
 lb6_gre6_node_fn (vlib_main_t * vm,
          vlib_node_runtime_t * node, vlib_frame_t * frame)
 {
-  return lb_node_fn(vm, node, frame, 0, 0);
+  return lb_node_fn(vm, node, frame, 0, LB_ENCAP_TYPE_GRE6);
 }
 
 static uword
 lb6_gre4_node_fn (vlib_main_t * vm,
          vlib_node_runtime_t * node, vlib_frame_t * frame)
 {
-  return lb_node_fn(vm, node, frame, 0, 1);
+  return lb_node_fn(vm, node, frame, 0, LB_ENCAP_TYPE_GRE4);
 }
 
 static uword
 lb4_gre6_node_fn (vlib_main_t * vm,
          vlib_node_runtime_t * node, vlib_frame_t * frame)
 {
-  return lb_node_fn(vm, node, frame, 1, 0);
+  return lb_node_fn(vm, node, frame, 1, LB_ENCAP_TYPE_GRE6);
 }
 
 static uword
 lb4_gre4_node_fn (vlib_main_t * vm,
          vlib_node_runtime_t * node, vlib_frame_t * frame)
 {
-  return lb_node_fn(vm, node, frame, 1, 1);
+  return lb_node_fn(vm, node, frame, 1, LB_ENCAP_TYPE_GRE4);
+}
+
+static uword
+lb4_l3dsr_node_fn (vlib_main_t * vm,
+         vlib_node_runtime_t * node, vlib_frame_t * frame)
+{
+  return lb_node_fn(vm, node, frame, 1, LB_ENCAP_TYPE_L3DSR);
 }
 
 VLIB_REGISTER_NODE (lb6_gre6_node) =
@@ -419,3 +437,19 @@ VLIB_REGISTER_NODE (lb4_gre4_node) =
   },
 };
 
+VLIB_REGISTER_NODE (lb4_l3dsr_node) =
+{
+  .function = lb4_l3dsr_node_fn,
+  .name = "lb4-l3dsr",
+  .vector_size = sizeof (u32),
+  .format_trace = format_lb_trace,
+
+  .n_errors = LB_N_ERROR,
+  .error_strings = lb_error_strings,
+
+  .n_next_nodes = LB_N_NEXT,
+  .next_nodes =
+  {
+      [LB_NEXT_DROP] = "error-drop"
+  },
+};