Allow encoding arbitrary channel args on a per-address basis.

11 files changed, 241 insertions, 434 deletions

diff --git a/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.cc b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.cc
index a46579c7f7..a9a5965ed1 100644
--- a/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.cc
@@ -84,6 +84,7 @@
 #include "src/core/ext/filters/client_channel/lb_policy_registry.h"
 #include "src/core/ext/filters/client_channel/parse_address.h"
 #include "src/core/ext/filters/client_channel/resolver/fake/fake_resolver.h"
+#include "src/core/ext/filters/client_channel/server_address.h"
 #include "src/core/ext/filters/client_channel/subchannel_index.h"
 #include "src/core/lib/backoff/backoff.h"
 #include "src/core/lib/channel/channel_args.h"
@@ -113,6 +114,8 @@
 #define GRPC_GRPCLB_RECONNECT_JITTER 0.2
 #define GRPC_GRPCLB_DEFAULT_FALLBACK_TIMEOUT_MS 10000
 
+#define GRPC_ARG_GRPCLB_ADDRESS_LB_TOKEN "grpc.grpclb_address_lb_token"
+
 namespace grpc_core {
 
 TraceFlag grpc_lb_glb_trace(false, "glb");
@@ -121,7 +124,7 @@ namespace {
 
 class GrpcLb : public LoadBalancingPolicy {
  public:
-  GrpcLb(const grpc_lb_addresses* addresses, const Args& args);
+  explicit GrpcLb(const Args& args);
 
   void UpdateLocked(const grpc_channel_args& args,
                     grpc_json* lb_config) override;
@@ -161,9 +164,6 @@ class GrpcLb : public LoadBalancingPolicy {
     // Our on_complete closure and the original one.
     grpc_closure on_complete;
     grpc_closure* original_on_complete;
-    // The LB token associated with the pick.  This is set via user_data in
-    // the pick.
-    grpc_mdelem lb_token;
     // Stats for client-side load reporting.
     RefCountedPtr<GrpcLbClientStats> client_stats;
     // Next pending pick.
@@ -329,7 +329,7 @@ class GrpcLb : public LoadBalancingPolicy {
   // 0 means not using fallback.
   int lb_fallback_timeout_ms_ = 0;
   // The backend addresses from the resolver.
-  grpc_lb_addresses* fallback_backend_addresses_ = nullptr;
+  UniquePtr<ServerAddressList> fallback_backend_addresses_;
   // Fallback timer.
   bool fallback_timer_callback_pending_ = false;
   grpc_timer lb_fallback_timer_;
@@ -349,7 +349,7 @@ class GrpcLb : public LoadBalancingPolicy {
 // serverlist parsing code
 //
 
-// vtable for LB tokens in grpc_lb_addresses
+// vtable for LB token channel arg.
 void* lb_token_copy(void* token) {
   return token == nullptr
              ? nullptr
@@ -361,38 +361,11 @@ void lb_token_destroy(void* token) {
   }
 }
 int lb_token_cmp(void* token1, void* token2) {
-  if (token1 > token2) return 1;
-  if (token1 < token2) return -1;
-  return 0;
+  return GPR_ICMP(token1, token2);
 }
-const grpc_lb_user_data_vtable lb_token_vtable = {
+const grpc_arg_pointer_vtable lb_token_arg_vtable = {
     lb_token_copy, lb_token_destroy, lb_token_cmp};
 
-// Returns the backend addresses extracted from the given addresses.
-grpc_lb_addresses* ExtractBackendAddresses(const grpc_lb_addresses* addresses) {
-  // First pass: count the number of backend addresses.
-  size_t num_backends = 0;
-  for (size_t i = 0; i < addresses->num_addresses; ++i) {
-    if (!addresses->addresses[i].is_balancer) {
-      ++num_backends;
-    }
-  }
-  // Second pass: actually populate the addresses and (empty) LB tokens.
-  grpc_lb_addresses* backend_addresses =
-      grpc_lb_addresses_create(num_backends, &lb_token_vtable);
-  size_t num_copied = 0;
-  for (size_t i = 0; i < addresses->num_addresses; ++i) {
-    if (addresses->addresses[i].is_balancer) continue;
-    const grpc_resolved_address* addr = &addresses->addresses[i].address;
-    grpc_lb_addresses_set_address(backend_addresses, num_copied, &addr->addr,
-                                  addr->len, false /* is_balancer */,
-                                  nullptr /* balancer_name */,
-                                  (void*)GRPC_MDELEM_LB_TOKEN_EMPTY.payload);
-    ++num_copied;
-  }
-  return backend_addresses;
-}
-
 bool IsServerValid(const grpc_grpclb_server* server, size_t idx, bool log) {
   if (server->drop) return false;
   const grpc_grpclb_ip_address* ip = &server->ip_address;
@@ -440,30 +413,16 @@ void ParseServer(const grpc_grpclb_server* server,
 }
 
 // Returns addresses extracted from \a serverlist.
-grpc_lb_addresses* ProcessServerlist(const grpc_grpclb_serverlist* serverlist) {
-  size_t num_valid = 0;
-  /* first pass: count how many are valid in order to allocate the necessary
-   * memory in a single block */
+ServerAddressList ProcessServerlist(const grpc_grpclb_serverlist* serverlist) {
+  ServerAddressList addresses;
   for (size_t i = 0; i < serverlist->num_servers; ++i) {
-    if (IsServerValid(serverlist->servers[i], i, true)) ++num_valid;
-  }
-  grpc_lb_addresses* lb_addresses =
-      grpc_lb_addresses_create(num_valid, &lb_token_vtable);
-  /* second pass: actually populate the addresses and LB tokens (aka user data
-   * to the outside world) to be read by the RR policy during its creation.
-   * Given that the validity tests are very cheap, they are performed again
-   * instead of marking the valid ones during the first pass, as this would
-   * incurr in an allocation due to the arbitrary number of server */
-  size_t addr_idx = 0;
-  for (size_t sl_idx = 0; sl_idx < serverlist->num_servers; ++sl_idx) {
-    const grpc_grpclb_server* server = serverlist->servers[sl_idx];
-    if (!IsServerValid(serverlist->servers[sl_idx], sl_idx, false)) continue;
-    GPR_ASSERT(addr_idx < num_valid);
-    /* address processing */
+    const grpc_grpclb_server* server = serverlist->servers[i];
+    if (!IsServerValid(serverlist->servers[i], i, false)) continue;
+    // Address processing.
     grpc_resolved_address addr;
     ParseServer(server, &addr);
-    /* lb token processing */
-    void* user_data;
+    // LB token processing.
+    void* lb_token;
     if (server->has_load_balance_token) {
       const size_t lb_token_max_length =
           GPR_ARRAY_SIZE(server->load_balance_token);
@@ -471,7 +430,7 @@ grpc_lb_addresses* ProcessServerlist(const grpc_grpclb_serverlist* serverlist) {
           strnlen(server->load_balance_token, lb_token_max_length);
       grpc_slice lb_token_mdstr = grpc_slice_from_copied_buffer(
           server->load_balance_token, lb_token_length);
-      user_data =
+      lb_token =
           (void*)grpc_mdelem_from_slices(GRPC_MDSTR_LB_TOKEN, lb_token_mdstr)
               .payload;
     } else {
@@ -481,15 +440,16 @@ grpc_lb_addresses* ProcessServerlist(const grpc_grpclb_serverlist* serverlist) {
               "be used instead",
               uri);
       gpr_free(uri);
-      user_data = (void*)GRPC_MDELEM_LB_TOKEN_EMPTY.payload;
+      lb_token = (void*)GRPC_MDELEM_LB_TOKEN_EMPTY.payload;
     }
-    grpc_lb_addresses_set_address(lb_addresses, addr_idx, &addr.addr, addr.len,
-                                  false /* is_balancer */,
-                                  nullptr /* balancer_name */, user_data);
-    ++addr_idx;
-  }
-  GPR_ASSERT(addr_idx == num_valid);
-  return lb_addresses;
+    // Add address.
+    grpc_arg arg = grpc_channel_arg_pointer_create(
+        const_cast<char*>(GRPC_ARG_GRPCLB_ADDRESS_LB_TOKEN), lb_token,
+        &lb_token_arg_vtable);
+    grpc_channel_args* args = grpc_channel_args_copy_and_add(nullptr, &arg, 1);
+    addresses.emplace_back(addr, args);
+  }
+  return addresses;
 }
 
 //
@@ -829,8 +789,7 @@ void GrpcLb::BalancerCallState::OnBalancerMessageReceivedLocked(
         grpc_grpclb_destroy_serverlist(grpclb_policy->serverlist_);
       } else {
         // Dispose of the fallback.
-        grpc_lb_addresses_destroy(grpclb_policy->fallback_backend_addresses_);
-        grpclb_policy->fallback_backend_addresses_ = nullptr;
+        grpclb_policy->fallback_backend_addresses_.reset();
         if (grpclb_policy->fallback_timer_callback_pending_) {
           grpc_timer_cancel(&grpclb_policy->lb_fallback_timer_);
         }
@@ -910,31 +869,25 @@ void GrpcLb::BalancerCallState::OnBalancerStatusReceivedLocked(
 // helper code for creating balancer channel
 //
 
-grpc_lb_addresses* ExtractBalancerAddresses(
-    const grpc_lb_addresses* addresses) {
-  size_t num_grpclb_addrs = 0;
-  for (size_t i = 0; i < addresses->num_addresses; ++i) {
-    if (addresses->addresses[i].is_balancer) ++num_grpclb_addrs;
-  }
-  // There must be at least one balancer address, or else the
-  // client_channel would not have chosen this LB policy.
-  GPR_ASSERT(num_grpclb_addrs > 0);
-  grpc_lb_addresses* lb_addresses =
-      grpc_lb_addresses_create(num_grpclb_addrs, nullptr);
-  size_t lb_addresses_idx = 0;
-  for (size_t i = 0; i < addresses->num_addresses; ++i) {
-    if (!addresses->addresses[i].is_balancer) continue;
-    if (GPR_UNLIKELY(addresses->addresses[i].user_data != nullptr)) {
-      gpr_log(GPR_ERROR,
-              "This LB policy doesn't support user data. It will be ignored");
+ServerAddressList ExtractBalancerAddresses(const ServerAddressList& addresses) {
+  ServerAddressList balancer_addresses;
+  for (size_t i = 0; i < addresses.size(); ++i) {
+    if (addresses[i].IsBalancer()) {
+      // Strip out the is_balancer channel arg, since we don't want to
+      // recursively use the grpclb policy in the channel used to talk to
+      // the balancers.  Note that we do NOT strip out the balancer_name
+      // channel arg, since we need that to set the authority correctly
+      // to talk to the balancers.
+      static const char* args_to_remove[] = {
+          GRPC_ARG_ADDRESS_IS_BALANCER,
+      };
+      balancer_addresses.emplace_back(
+          addresses[i].address(),
+          grpc_channel_args_copy_and_remove(addresses[i].args(), args_to_remove,
+                                            GPR_ARRAY_SIZE(args_to_remove)));
     }
-    grpc_lb_addresses_set_address(
-        lb_addresses, lb_addresses_idx++, addresses->addresses[i].address.addr,
-        addresses->addresses[i].address.len, false /* is balancer */,
-        addresses->addresses[i].balancer_name, nullptr /* user data */);
   }
-  GPR_ASSERT(num_grpclb_addrs == lb_addresses_idx);
-  return lb_addresses;
+  return balancer_addresses;
 }
 
 /* Returns the channel args for the LB channel, used to create a bidirectional
@@ -946,10 +899,10 @@ grpc_lb_addresses* ExtractBalancerAddresses(
  *   above the grpclb policy.
  *   - \a args: other args inherited from the grpclb policy. */
 grpc_channel_args* BuildBalancerChannelArgs(
-    const grpc_lb_addresses* addresses,
+    const ServerAddressList& addresses,
     FakeResolverResponseGenerator* response_generator,
     const grpc_channel_args* args) {
-  grpc_lb_addresses* lb_addresses = ExtractBalancerAddresses(addresses);
+  ServerAddressList balancer_addresses = ExtractBalancerAddresses(addresses);
   // Channel args to remove.
   static const char* args_to_remove[] = {
       // LB policy name, since we want to use the default (pick_first) in
@@ -967,7 +920,7 @@ grpc_channel_args* BuildBalancerChannelArgs(
       // is_balancer=true.  We need the LB channel to return addresses with
       // is_balancer=false so that it does not wind up recursively using the
       // grpclb LB policy, as per the special case logic in client_channel.c.
-      GRPC_ARG_LB_ADDRESSES,
+      GRPC_ARG_SERVER_ADDRESS_LIST,
       // The fake resolver response generator, because we are replacing it
       // with the one from the grpclb policy, used to propagate updates to
       // the LB channel.
@@ -983,10 +936,10 @@ grpc_channel_args* BuildBalancerChannelArgs(
   };
   // Channel args to add.
   const grpc_arg args_to_add[] = {
-      // New LB addresses.
+      // New address list.
       // Note that we pass these in both when creating the LB channel
       // and via the fake resolver.  The latter is what actually gets used.
-      grpc_lb_addresses_create_channel_arg(lb_addresses),
+      CreateServerAddressListChannelArg(&balancer_addresses),
       // The fake resolver response generator, which we use to inject
       // address updates into the LB channel.
       grpc_core::FakeResolverResponseGenerator::MakeChannelArg(
@@ -1004,18 +957,14 @@ grpc_channel_args* BuildBalancerChannelArgs(
       args, args_to_remove, GPR_ARRAY_SIZE(args_to_remove), args_to_add,
       GPR_ARRAY_SIZE(args_to_add));
   // Make any necessary modifications for security.
-  new_args = grpc_lb_policy_grpclb_modify_lb_channel_args(new_args);
-  // Clean up.
-  grpc_lb_addresses_destroy(lb_addresses);
-  return new_args;
+  return grpc_lb_policy_grpclb_modify_lb_channel_args(new_args);
 }
 
 //
 // ctor and dtor
 //
 
-GrpcLb::GrpcLb(const grpc_lb_addresses* addresses,
-               const LoadBalancingPolicy::Args& args)
+GrpcLb::GrpcLb(const LoadBalancingPolicy::Args& args)
     : LoadBalancingPolicy(args),
       response_generator_(MakeRefCounted<FakeResolverResponseGenerator>()),
       lb_call_backoff_(
@@ -1072,9 +1021,6 @@ GrpcLb::~GrpcLb() {
   if (serverlist_ != nullptr) {
     grpc_grpclb_destroy_serverlist(serverlist_);
   }
-  if (fallback_backend_addresses_ != nullptr) {
-    grpc_lb_addresses_destroy(fallback_backend_addresses_);
-  }
   grpc_subchannel_index_unref();
 }
 
@@ -1122,7 +1068,6 @@ void GrpcLb::HandOffPendingPicksLocked(LoadBalancingPolicy* new_policy) {
   while ((pp = pending_picks_) != nullptr) {
     pending_picks_ = pp->next;
     pp->pick->on_complete = pp->original_on_complete;
-    pp->pick->user_data = nullptr;
     grpc_error* error = GRPC_ERROR_NONE;
     if (new_policy->PickLocked(pp->pick, &error)) {
       // Synchronous return; schedule closure.
@@ -1276,9 +1221,27 @@ void GrpcLb::NotifyOnStateChangeLocked(grpc_connectivity_state* current,
                                                  notify);
 }
 
+// Returns the backend addresses extracted from the given addresses.
+UniquePtr<ServerAddressList> ExtractBackendAddresses(
+    const ServerAddressList& addresses) {
+  void* lb_token = (void*)GRPC_MDELEM_LB_TOKEN_EMPTY.payload;
+  grpc_arg arg = grpc_channel_arg_pointer_create(
+      const_cast<char*>(GRPC_ARG_GRPCLB_ADDRESS_LB_TOKEN), lb_token,
+      &lb_token_arg_vtable);
+  auto backend_addresses = MakeUnique<ServerAddressList>();
+  for (size_t i = 0; i < addresses.size(); ++i) {
+    if (!addresses[i].IsBalancer()) {
+      backend_addresses->emplace_back(
+          addresses[i].address(),
+          grpc_channel_args_copy_and_add(addresses[i].args(), &arg, 1));
+    }
+  }
+  return backend_addresses;
+}
+
 void GrpcLb::ProcessChannelArgsLocked(const grpc_channel_args& args) {
-  const grpc_arg* arg = grpc_channel_args_find(&args, GRPC_ARG_LB_ADDRESSES);
-  if (GPR_UNLIKELY(arg == nullptr || arg->type != GRPC_ARG_POINTER)) {
+  const ServerAddressList* addresses = FindServerAddressListChannelArg(&args);
+  if (addresses == nullptr) {
     // Ignore this update.
     gpr_log(
         GPR_ERROR,
@@ -1286,13 +1249,8 @@ void GrpcLb::ProcessChannelArgsLocked(const grpc_channel_args& args) {
         this);
     return;
   }
-  const grpc_lb_addresses* addresses =
-      static_cast<const grpc_lb_addresses*>(arg->value.pointer.p);
   // Update fallback address list.
-  if (fallback_backend_addresses_ != nullptr) {
-    grpc_lb_addresses_destroy(fallback_backend_addresses_);
-  }
-  fallback_backend_addresses_ = ExtractBackendAddresses(addresses);
+  fallback_backend_addresses_ = ExtractBackendAddresses(*addresses);
   // Make sure that GRPC_ARG_LB_POLICY_NAME is set in channel args,
   // since we use this to trigger the client_load_reporting filter.
   static const char* args_to_remove[] = {GRPC_ARG_LB_POLICY_NAME};
@@ -1303,7 +1261,7 @@ void GrpcLb::ProcessChannelArgsLocked(const grpc_channel_args& args) {
       &args, args_to_remove, GPR_ARRAY_SIZE(args_to_remove), &new_arg, 1);
   // Construct args for balancer channel.
   grpc_channel_args* lb_channel_args =
-      BuildBalancerChannelArgs(addresses, response_generator_.get(), &args);
+      BuildBalancerChannelArgs(*addresses, response_generator_.get(), &args);
   // Create balancer channel if needed.
   if (lb_channel_ == nullptr) {
     char* uri_str;
@@ -1509,12 +1467,17 @@ void DestroyClientStats(void* arg) {
 }
 
 void GrpcLb::PendingPickSetMetadataAndContext(PendingPick* pp) {
-  /* if connected_subchannel is nullptr, no pick has been made by the RR
-   * policy (e.g., all addresses failed to connect). There won't be any
-   * user_data/token available */
+  // If connected_subchannel is nullptr, no pick has been made by the RR
+  // policy (e.g., all addresses failed to connect). There won't be any
+  // LB token available.
   if (pp->pick->connected_subchannel != nullptr) {
-    if (GPR_LIKELY(!GRPC_MDISNULL(pp->lb_token))) {
-      AddLbTokenToInitialMetadata(GRPC_MDELEM_REF(pp->lb_token),
+    const grpc_arg* arg =
+        grpc_channel_args_find(pp->pick->connected_subchannel->args(),
+                               GRPC_ARG_GRPCLB_ADDRESS_LB_TOKEN);
+    if (arg != nullptr) {
+      grpc_mdelem lb_token = {
+          reinterpret_cast<uintptr_t>(arg->value.pointer.p)};
+      AddLbTokenToInitialMetadata(GRPC_MDELEM_REF(lb_token),
                                   &pp->pick->lb_token_mdelem_storage,
                                   pp->pick->initial_metadata);
     } else {
@@ -1598,12 +1561,10 @@ bool GrpcLb::PickFromRoundRobinPolicyLocked(bool force_async, PendingPick* pp,
       return true;
     }
   }
-  // Set client_stats and user_data.
+  // Set client_stats.
   if (lb_calld_ != nullptr && lb_calld_->client_stats() != nullptr) {
     pp->client_stats = lb_calld_->client_stats()->Ref();
   }
-  GPR_ASSERT(pp->pick->user_data == nullptr);
-  pp->pick->user_data = (void**)&pp->lb_token;
   // Pick via the RR policy.
   bool pick_done = rr_policy_->PickLocked(pp->pick, error);
   if (pick_done) {
@@ -1668,10 +1629,11 @@ void GrpcLb::CreateRoundRobinPolicyLocked(const Args& args) {
 }
 
 grpc_channel_args* GrpcLb::CreateRoundRobinPolicyArgsLocked() {
-  grpc_lb_addresses* addresses;
+  ServerAddressList tmp_addresses;
+  ServerAddressList* addresses = &tmp_addresses;
   bool is_backend_from_grpclb_load_balancer = false;
   if (serverlist_ != nullptr) {
-    addresses = ProcessServerlist(serverlist_);
+    tmp_addresses = ProcessServerlist(serverlist_);
     is_backend_from_grpclb_load_balancer = true;
   } else {
     // If CreateOrUpdateRoundRobinPolicyLocked() is invoked when we haven't
@@ -1680,14 +1642,14 @@ grpc_channel_args* GrpcLb::CreateRoundRobinPolicyArgsLocked() {
     // empty, in which case the new round_robin policy will keep the requested
     // picks pending.
     GPR_ASSERT(fallback_backend_addresses_ != nullptr);
-    addresses = grpc_lb_addresses_copy(fallback_backend_addresses_);
+    addresses = fallback_backend_addresses_.get();
   }
   GPR_ASSERT(addresses != nullptr);
-  // Replace the LB addresses in the channel args that we pass down to
+  // Replace the server address list in the channel args that we pass down to
   // the subchannel.
-  static const char* keys_to_remove[] = {GRPC_ARG_LB_ADDRESSES};
+  static const char* keys_to_remove[] = {GRPC_ARG_SERVER_ADDRESS_LIST};
   grpc_arg args_to_add[3] = {
-      grpc_lb_addresses_create_channel_arg(addresses),
+      CreateServerAddressListChannelArg(addresses),
       // A channel arg indicating if the target is a backend inferred from a
       // grpclb load balancer.
       grpc_channel_arg_integer_create(
@@ -1704,7 +1666,6 @@ grpc_channel_args* GrpcLb::CreateRoundRobinPolicyArgsLocked() {
   grpc_channel_args* args = grpc_channel_args_copy_and_add_and_remove(
       args_, keys_to_remove, GPR_ARRAY_SIZE(keys_to_remove), args_to_add,
       num_args_to_add);
-  grpc_lb_addresses_destroy(addresses);
   return args;
 }
 
@@ -1837,19 +1798,18 @@ class GrpcLbFactory : public LoadBalancingPolicyFactory {
   OrphanablePtr<LoadBalancingPolicy> CreateLoadBalancingPolicy(
       const LoadBalancingPolicy::Args& args) const override {
     /* Count the number of gRPC-LB addresses. There must be at least one. */
-    const grpc_arg* arg =
-        grpc_channel_args_find(args.args, GRPC_ARG_LB_ADDRESSES);
-    if (arg == nullptr || arg->type != GRPC_ARG_POINTER) {
-      return nullptr;
-    }
-    grpc_lb_addresses* addresses =
-        static_cast<grpc_lb_addresses*>(arg->value.pointer.p);
-    size_t num_grpclb_addrs = 0;
-    for (size_t i = 0; i < addresses->num_addresses; ++i) {
-      if (addresses->addresses[i].is_balancer) ++num_grpclb_addrs;
+    const ServerAddressList* addresses =
+        FindServerAddressListChannelArg(args.args);
+    if (addresses == nullptr) return nullptr;
+    bool found_balancer = false;
+    for (size_t i = 0; i < addresses->size(); ++i) {
+      if ((*addresses)[i].IsBalancer()) {
+        found_balancer = true;
+        break;
+      }
     }
-    if (num_grpclb_addrs == 0) return nullptr;
-    return OrphanablePtr<LoadBalancingPolicy>(New<GrpcLb>(addresses, args));
+    if (!found_balancer) return nullptr;
+    return OrphanablePtr<LoadBalancingPolicy>(New<GrpcLb>(args));
   }
 
   const char* name() const override { return "grpclb"; }
diff --git a/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel.h b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel.h
index 825065a9c3..3b2dc370eb 100644
--- a/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel.h
+++ b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel.h
@@ -21,7 +21,7 @@
 
 #include <grpc/support/port_platform.h>
 
-#include "src/core/ext/filters/client_channel/lb_policy_factory.h"
+#include <grpc/impl/codegen/grpc_types.h>
 
 /// Makes any necessary modifications to \a args for use in the grpclb
 /// balancer channel.
diff --git a/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel_secure.cc b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel_secure.cc
index 441efd5e23..6e8fbdcab7 100644
--- a/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel_secure.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_channel_secure.cc
@@ -26,6 +26,7 @@
 #include <grpc/support/string_util.h>
 
 #include "src/core/ext/filters/client_channel/client_channel.h"
+#include "src/core/ext/filters/client_channel/server_address.h"
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/iomgr/sockaddr_utils.h"
@@ -42,22 +43,23 @@ int BalancerNameCmp(const grpc_core::UniquePtr<char>& a,
 }
 
 RefCountedPtr<TargetAuthorityTable> CreateTargetAuthorityTable(
-    grpc_lb_addresses* addresses) {
+    const ServerAddressList& addresses) {
   TargetAuthorityTable::Entry* target_authority_entries =
-      static_cast<TargetAuthorityTable::Entry*>(gpr_zalloc(
-          sizeof(*target_authority_entries) * addresses->num_addresses));
-  for (size_t i = 0; i < addresses->num_addresses; ++i) {
+      static_cast<TargetAuthorityTable::Entry*>(
+          gpr_zalloc(sizeof(*target_authority_entries) * addresses.size()));
+  for (size_t i = 0; i < addresses.size(); ++i) {
     char* addr_str;
-    GPR_ASSERT(grpc_sockaddr_to_string(
-                   &addr_str, &addresses->addresses[i].address, true) > 0);
+    GPR_ASSERT(
+        grpc_sockaddr_to_string(&addr_str, &addresses[i].address(), true) > 0);
     target_authority_entries[i].key = grpc_slice_from_copied_string(addr_str);
-    target_authority_entries[i].value.reset(
-        gpr_strdup(addresses->addresses[i].balancer_name));
     gpr_free(addr_str);
+    char* balancer_name = grpc_channel_arg_get_string(grpc_channel_args_find(
+        addresses[i].args(), GRPC_ARG_ADDRESS_BALANCER_NAME));
+    target_authority_entries[i].value.reset(gpr_strdup(balancer_name));
   }
   RefCountedPtr<TargetAuthorityTable> target_authority_table =
-      TargetAuthorityTable::Create(addresses->num_addresses,
-                                   target_authority_entries, BalancerNameCmp);
+      TargetAuthorityTable::Create(addresses.size(), target_authority_entries,
+                                   BalancerNameCmp);
   gpr_free(target_authority_entries);
   return target_authority_table;
 }
@@ -72,13 +74,12 @@ grpc_channel_args* grpc_lb_policy_grpclb_modify_lb_channel_args(
   grpc_arg args_to_add[2];
   size_t num_args_to_add = 0;
   // Add arg for targets info table.
-  const grpc_arg* arg = grpc_channel_args_find(args, GRPC_ARG_LB_ADDRESSES);
-  GPR_ASSERT(arg != nullptr);
-  GPR_ASSERT(arg->type == GRPC_ARG_POINTER);
-  grpc_lb_addresses* addresses =
-      static_cast<grpc_lb_addresses*>(arg->value.pointer.p);
+  grpc_core::ServerAddressList* addresses =
+      grpc_core::FindServerAddressListChannelArg(args);
+  GPR_ASSERT(addresses != nullptr);
   grpc_core::RefCountedPtr<grpc_core::TargetAuthorityTable>
-      target_authority_table = grpc_core::CreateTargetAuthorityTable(addresses);
+      target_authority_table =
+          grpc_core::CreateTargetAuthorityTable(*addresses);
   args_to_add[num_args_to_add++] =
       grpc_core::CreateTargetAuthorityTableChannelArg(
           target_authority_table.get());
diff --git a/src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.h b/src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.h
index 9ca7b28d8e..71d371c880 100644
--- a/src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.h
+++ b/src/core/ext/filters/client_channel/lb_policy/grpclb/load_balancer_api.h
@@ -25,7 +25,7 @@
 
 #include "src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb_client_stats.h"
 #include "src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.h"
-#include "src/core/ext/filters/client_channel/lb_policy_factory.h"
+#include "src/core/lib/iomgr/exec_ctx.h"
 
 #define GRPC_GRPCLB_SERVICE_NAME_MAX_LENGTH 128
 
diff --git a/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc b/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc
index d1a05f1255..74c17612a2 100644
--- a/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc
@@ -24,6 +24,7 @@
 
 #include "src/core/ext/filters/client_channel/lb_policy/subchannel_list.h"
 #include "src/core/ext/filters/client_channel/lb_policy_registry.h"
+#include "src/core/ext/filters/client_channel/server_address.h"
 #include "src/core/ext/filters/client_channel/subchannel.h"
 #include "src/core/ext/filters/client_channel/subchannel_index.h"
 #include "src/core/lib/channel/channel_args.h"
@@ -75,11 +76,9 @@ class PickFirst : public LoadBalancingPolicy {
     PickFirstSubchannelData(
         SubchannelList<PickFirstSubchannelList, PickFirstSubchannelData>*
             subchannel_list,
-        const grpc_lb_user_data_vtable* user_data_vtable,
-        const grpc_lb_address& address, grpc_subchannel* subchannel,
+        const ServerAddress& address, grpc_subchannel* subchannel,
         grpc_combiner* combiner)
-        : SubchannelData(subchannel_list, user_data_vtable, address, subchannel,
-                         combiner) {}
+        : SubchannelData(subchannel_list, address, subchannel, combiner) {}
 
     void ProcessConnectivityChangeLocked(
         grpc_connectivity_state connectivity_state, grpc_error* error) override;
@@ -95,7 +94,7 @@ class PickFirst : public LoadBalancingPolicy {
                               PickFirstSubchannelData> {
    public:
     PickFirstSubchannelList(PickFirst* policy, TraceFlag* tracer,
-                            const grpc_lb_addresses* addresses,
+                            const ServerAddressList& addresses,
                             grpc_combiner* combiner,
                             grpc_client_channel_factory* client_channel_factory,
                             const grpc_channel_args& args)
@@ -337,8 +336,8 @@ void PickFirst::UpdateChildRefsLocked() {
 void PickFirst::UpdateLocked(const grpc_channel_args& args,
                              grpc_json* lb_config) {
   AutoChildRefsUpdater guard(this);
-  const grpc_arg* arg = grpc_channel_args_find(&args, GRPC_ARG_LB_ADDRESSES);
-  if (arg == nullptr || arg->type != GRPC_ARG_POINTER) {
+  const ServerAddressList* addresses = FindServerAddressListChannelArg(&args);
+  if (addresses == nullptr) {
     if (subchannel_list_ == nullptr) {
       // If we don't have a current subchannel list, go into TRANSIENT FAILURE.
       grpc_connectivity_state_set(
@@ -354,19 +353,17 @@ void PickFirst::UpdateLocked(const grpc_channel_args& args,
     }
     return;
   }
-  const grpc_lb_addresses* addresses =
-      static_cast<const grpc_lb_addresses*>(arg->value.pointer.p);
   if (grpc_lb_pick_first_trace.enabled()) {
     gpr_log(GPR_INFO,
             "Pick First %p received update with %" PRIuPTR " addresses", this,
-            addresses->num_addresses);
+            addresses->size());
   }
   grpc_arg new_arg = grpc_channel_arg_integer_create(
       const_cast<char*>(GRPC_ARG_INHIBIT_HEALTH_CHECKING), 1);
   grpc_channel_args* new_args =
       grpc_channel_args_copy_and_add(&args, &new_arg, 1);
   auto subchannel_list = MakeOrphanable<PickFirstSubchannelList>(
-      this, &grpc_lb_pick_first_trace, addresses, combiner(),
+      this, &grpc_lb_pick_first_trace, *addresses, combiner(),
       client_channel_factory(), *new_args);
   grpc_channel_args_destroy(new_args);
   if (subchannel_list->num_subchannels() == 0) {
diff --git a/src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc b/src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc
index 2a16975131..63089afbd7 100644
--- a/src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.cc
@@ -82,8 +82,6 @@ class RoundRobin : public LoadBalancingPolicy {
 
   // Data for a particular subchannel in a subchannel list.
   // This subclass adds the following functionality:
-  // - Tracks user_data associated with each address, which will be
-  //   returned along with picks that select the subchannel.
   // - Tracks the previous connectivity state of the subchannel, so that
   //   we know how many subchannels are in each state.
   class RoundRobinSubchannelData
@@ -93,26 +91,9 @@ class RoundRobin : public LoadBalancingPolicy {
     RoundRobinSubchannelData(
         SubchannelList<RoundRobinSubchannelList, RoundRobinSubchannelData>*
             subchannel_list,
-        const grpc_lb_user_data_vtable* user_data_vtable,
-        const grpc_lb_address& address, grpc_subchannel* subchannel,
+        const ServerAddress& address, grpc_subchannel* subchannel,
         grpc_combiner* combiner)
-        : SubchannelData(subchannel_list, user_data_vtable, address, subchannel,
-                         combiner),
-          user_data_vtable_(user_data_vtable),
-          user_data_(user_data_vtable_ != nullptr
-                         ? user_data_vtable_->copy(address.user_data)
-                         : nullptr) {}
-
-    void UnrefSubchannelLocked(const char* reason) override {
-      SubchannelData::UnrefSubchannelLocked(reason);
-      if (user_data_ != nullptr) {
-        GPR_ASSERT(user_data_vtable_ != nullptr);
-        user_data_vtable_->destroy(user_data_);
-        user_data_ = nullptr;
-      }
-    }
-
-    void* user_data() const { return user_data_; }
+        : SubchannelData(subchannel_list, address, subchannel, combiner) {}
 
     grpc_connectivity_state connectivity_state() const {
       return last_connectivity_state_;
@@ -125,8 +106,6 @@ class RoundRobin : public LoadBalancingPolicy {
     void ProcessConnectivityChangeLocked(
         grpc_connectivity_state connectivity_state, grpc_error* error) override;
 
-    const grpc_lb_user_data_vtable* user_data_vtable_;
-    void* user_data_ = nullptr;
     grpc_connectivity_state last_connectivity_state_ = GRPC_CHANNEL_IDLE;
   };
 
@@ -137,7 +116,7 @@ class RoundRobin : public LoadBalancingPolicy {
    public:
     RoundRobinSubchannelList(
         RoundRobin* policy, TraceFlag* tracer,
-        const grpc_lb_addresses* addresses, grpc_combiner* combiner,
+        const ServerAddressList& addresses, grpc_combiner* combiner,
         grpc_client_channel_factory* client_channel_factory,
         const grpc_channel_args& args)
         : SubchannelList(policy, tracer, addresses, combiner,
@@ -354,9 +333,6 @@ bool RoundRobin::DoPickLocked(PickState* pick) {
         subchannel_list_->subchannel(next_ready_index);
     GPR_ASSERT(sd->connected_subchannel() != nullptr);
     pick->connected_subchannel = sd->connected_subchannel()->Ref();
-    if (pick->user_data != nullptr) {
-      *pick->user_data = sd->user_data();
-    }
     if (grpc_lb_round_robin_trace.enabled()) {
       gpr_log(GPR_INFO,
               "[RR %p] Picked target <-- Subchannel %p (connected %p) (sl %p, "
@@ -667,9 +643,9 @@ void RoundRobin::NotifyOnStateChangeLocked(grpc_connectivity_state* current,
 
 void RoundRobin::UpdateLocked(const grpc_channel_args& args,
                               grpc_json* lb_config) {
-  const grpc_arg* arg = grpc_channel_args_find(&args, GRPC_ARG_LB_ADDRESSES);
   AutoChildRefsUpdater guard(this);
-  if (GPR_UNLIKELY(arg == nullptr || arg->type != GRPC_ARG_POINTER)) {
+  const ServerAddressList* addresses = FindServerAddressListChannelArg(&args);
+  if (addresses == nullptr) {
     gpr_log(GPR_ERROR, "[RR %p] update provided no addresses; ignoring", this);
     // If we don't have a current subchannel list, go into TRANSIENT_FAILURE.
     // Otherwise, keep using the current subchannel list (ignore this update).
@@ -681,11 +657,9 @@ void RoundRobin::UpdateLocked(const grpc_channel_args& args,
     }
     return;
   }
-  grpc_lb_addresses* addresses =
-      static_cast<grpc_lb_addresses*>(arg->value.pointer.p);
   if (grpc_lb_round_robin_trace.enabled()) {
     gpr_log(GPR_INFO, "[RR %p] received update with %" PRIuPTR " addresses",
-            this, addresses->num_addresses);
+            this, addresses->size());
   }
   // Replace latest_pending_subchannel_list_.
   if (latest_pending_subchannel_list_ != nullptr) {
@@ -696,7 +670,7 @@ void RoundRobin::UpdateLocked(const grpc_channel_args& args,
     }
   }
   latest_pending_subchannel_list_ = MakeOrphanable<RoundRobinSubchannelList>(
-      this, &grpc_lb_round_robin_trace, addresses, combiner(),
+      this, &grpc_lb_round_robin_trace, *addresses, combiner(),
       client_channel_factory(), args);
   // If we haven't started picking yet or the new list is empty,
   // immediately promote the new list to the current list.
diff --git a/src/core/ext/filters/client_channel/lb_policy/subchannel_list.h b/src/core/ext/filters/client_channel/lb_policy/subchannel_list.h
index f31401502c..6f31a643c1 100644
--- a/src/core/ext/filters/client_channel/lb_policy/subchannel_list.h
+++ b/src/core/ext/filters/client_channel/lb_policy/subchannel_list.h
@@ -26,6 +26,7 @@
 #include <grpc/support/alloc.h>
 
 #include "src/core/ext/filters/client_channel/lb_policy_registry.h"
+#include "src/core/ext/filters/client_channel/server_address.h"
 #include "src/core/ext/filters/client_channel/subchannel.h"
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/debug/trace.h"
@@ -141,8 +142,7 @@ class SubchannelData {
  protected:
   SubchannelData(
       SubchannelList<SubchannelListType, SubchannelDataType>* subchannel_list,
-      const grpc_lb_user_data_vtable* user_data_vtable,
-      const grpc_lb_address& address, grpc_subchannel* subchannel,
+      const ServerAddress& address, grpc_subchannel* subchannel,
       grpc_combiner* combiner);
 
   virtual ~SubchannelData();
@@ -156,9 +156,8 @@ class SubchannelData {
       grpc_connectivity_state connectivity_state,
       grpc_error* error) GRPC_ABSTRACT;
 
-  // Unrefs the subchannel.  May be overridden by subclasses that need
-  // to perform extra cleanup when unreffing the subchannel.
-  virtual void UnrefSubchannelLocked(const char* reason);
+  // Unrefs the subchannel.
+  void UnrefSubchannelLocked(const char* reason);
 
  private:
   // Updates connected_subchannel_ based on pending_connectivity_state_unsafe_.
@@ -232,7 +231,7 @@ class SubchannelList : public InternallyRefCounted<SubchannelListType> {
 
  protected:
   SubchannelList(LoadBalancingPolicy* policy, TraceFlag* tracer,
-                 const grpc_lb_addresses* addresses, grpc_combiner* combiner,
+                 const ServerAddressList& addresses, grpc_combiner* combiner,
                  grpc_client_channel_factory* client_channel_factory,
                  const grpc_channel_args& args);
 
@@ -277,8 +276,7 @@ class SubchannelList : public InternallyRefCounted<SubchannelListType> {
 template <typename SubchannelListType, typename SubchannelDataType>
 SubchannelData<SubchannelListType, SubchannelDataType>::SubchannelData(
     SubchannelList<SubchannelListType, SubchannelDataType>* subchannel_list,
-    const grpc_lb_user_data_vtable* user_data_vtable,
-    const grpc_lb_address& address, grpc_subchannel* subchannel,
+    const ServerAddress& address, grpc_subchannel* subchannel,
     grpc_combiner* combiner)
     : subchannel_list_(subchannel_list),
       subchannel_(subchannel),
@@ -488,7 +486,7 @@ void SubchannelData<SubchannelListType, SubchannelDataType>::ShutdownLocked() {
 template <typename SubchannelListType, typename SubchannelDataType>
 SubchannelList<SubchannelListType, SubchannelDataType>::SubchannelList(
     LoadBalancingPolicy* policy, TraceFlag* tracer,
-    const grpc_lb_addresses* addresses, grpc_combiner* combiner,
+    const ServerAddressList& addresses, grpc_combiner* combiner,
     grpc_client_channel_factory* client_channel_factory,
     const grpc_channel_args& args)
     : InternallyRefCounted<SubchannelListType>(tracer),
@@ -498,9 +496,9 @@ SubchannelList<SubchannelListType, SubchannelDataType>::SubchannelList(
   if (tracer_->enabled()) {
     gpr_log(GPR_INFO,
             "[%s %p] Creating subchannel list %p for %" PRIuPTR " subchannels",
-            tracer_->name(), policy, this, addresses->num_addresses);
+            tracer_->name(), policy, this, addresses.size());
   }
-  subchannels_.reserve(addresses->num_addresses);
+  subchannels_.reserve(addresses.size());
   // We need to remove the LB addresses in order to be able to compare the
   // subchannel keys of subchannels from a different batch of addresses.
   // We also remove the inhibit-health-checking arg, since we are
@@ -508,19 +506,27 @@ SubchannelList<SubchannelListType, SubchannelDataType>::SubchannelList(
   inhibit_health_checking_ = grpc_channel_arg_get_bool(
       grpc_channel_args_find(&args, GRPC_ARG_INHIBIT_HEALTH_CHECKING), false);
   static const char* keys_to_remove[] = {GRPC_ARG_SUBCHANNEL_ADDRESS,
-                                         GRPC_ARG_LB_ADDRESSES,
+                                         GRPC_ARG_SERVER_ADDRESS_LIST,
                                          GRPC_ARG_INHIBIT_HEALTH_CHECKING};
   // Create a subchannel for each address.
   grpc_subchannel_args sc_args;
-  for (size_t i = 0; i < addresses->num_addresses; i++) {
-    // If there were any balancer, we would have chosen grpclb policy instead.
-    GPR_ASSERT(!addresses->addresses[i].is_balancer);
+  for (size_t i = 0; i < addresses.size(); i++) {
+    // If there were any balancer addresses, we would have chosen grpclb
+    // policy, which does not use a SubchannelList.
+    GPR_ASSERT(!addresses[i].IsBalancer());
     memset(&sc_args, 0, sizeof(grpc_subchannel_args));
-    grpc_arg addr_arg =
-        grpc_create_subchannel_address_arg(&addresses->addresses[i].address);
+    InlinedVector<grpc_arg, 4> args_to_add;
+    args_to_add.emplace_back(
+        grpc_create_subchannel_address_arg(&addresses[i].address()));
+    if (addresses[i].args() != nullptr) {
+      for (size_t j = 0; j < addresses[i].args()->num_args; ++j) {
+        args_to_add.emplace_back(addresses[i].args()->args[j]);
+      }
+    }
     grpc_channel_args* new_args = grpc_channel_args_copy_and_add_and_remove(
-        &args, keys_to_remove, GPR_ARRAY_SIZE(keys_to_remove), &addr_arg, 1);
-    gpr_free(addr_arg.value.string);
+        &args, keys_to_remove, GPR_ARRAY_SIZE(keys_to_remove),
+        args_to_add.data(), args_to_add.size());
+    gpr_free(args_to_add[0].value.string);
     sc_args.args = new_args;
     grpc_subchannel* subchannel = grpc_client_channel_factory_create_subchannel(
         client_channel_factory, &sc_args);
@@ -528,8 +534,7 @@ SubchannelList<SubchannelListType, SubchannelDataType>::SubchannelList(
     if (subchannel == nullptr) {
       // Subchannel could not be created.
       if (tracer_->enabled()) {
-        char* address_uri =
-            grpc_sockaddr_to_uri(&addresses->addresses[i].address);
+        char* address_uri = grpc_sockaddr_to_uri(&addresses[i].address());
         gpr_log(GPR_INFO,
                 "[%s %p] could not create subchannel for address uri %s, "
                 "ignoring",
@@ -539,8 +544,7 @@ SubchannelList<SubchannelListType, SubchannelDataType>::SubchannelList(
       continue;
     }
     if (tracer_->enabled()) {
-      char* address_uri =
-          grpc_sockaddr_to_uri(&addresses->addresses[i].address);
+      char* address_uri = grpc_sockaddr_to_uri(&addresses[i].address());
       gpr_log(GPR_INFO,
               "[%s %p] subchannel list %p index %" PRIuPTR
               ": Created subchannel %p for address uri %s",
@@ -548,8 +552,7 @@ SubchannelList<SubchannelListType, SubchannelDataType>::SubchannelList(
               address_uri);
       gpr_free(address_uri);
     }
-    subchannels_.emplace_back(this, addresses->user_data_vtable,
-                              addresses->addresses[i], subchannel, combiner);
+    subchannels_.emplace_back(this, addresses[i], subchannel, combiner);
   }
 }
 
diff --git a/src/core/ext/filters/client_channel/lb_policy/xds/xds.cc b/src/core/ext/filters/client_channel/lb_policy/xds/xds.cc
index faedc0a919..3c25de2386 100644
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds.cc
@@ -79,6 +79,7 @@
 #include "src/core/ext/filters/client_channel/lb_policy_registry.h"
 #include "src/core/ext/filters/client_channel/parse_address.h"
 #include "src/core/ext/filters/client_channel/resolver/fake/fake_resolver.h"
+#include "src/core/ext/filters/client_channel/server_address.h"
 #include "src/core/ext/filters/client_channel/subchannel_index.h"
 #include "src/core/lib/backoff/backoff.h"
 #include "src/core/lib/channel/channel_args.h"
@@ -116,7 +117,7 @@ namespace {
 
 class XdsLb : public LoadBalancingPolicy {
  public:
-  XdsLb(const grpc_lb_addresses* addresses, const Args& args);
+  explicit XdsLb(const Args& args);
 
   void UpdateLocked(const grpc_channel_args& args,
                     grpc_json* lb_config) override;
@@ -156,9 +157,6 @@ class XdsLb : public LoadBalancingPolicy {
     // Our on_complete closure and the original one.
     grpc_closure on_complete;
     grpc_closure* original_on_complete;
-    // The LB token associated with the pick.  This is set via user_data in
-    // the pick.
-    grpc_mdelem lb_token;
     // Stats for client-side load reporting.
     RefCountedPtr<XdsLbClientStats> client_stats;
     // Next pending pick.
@@ -256,7 +254,7 @@ class XdsLb : public LoadBalancingPolicy {
                                                          grpc_error* error);
 
   // Pending pick methods.
-  static void PendingPickSetMetadataAndContext(PendingPick* pp);
+  static void PendingPickCleanup(PendingPick* pp);
   PendingPick* PendingPickCreate(PickState* pick);
   void AddPendingPick(PendingPick* pp);
   static void OnPendingPickComplete(void* arg, grpc_error* error);
@@ -319,7 +317,7 @@ class XdsLb : public LoadBalancingPolicy {
   // 0 means not using fallback.
   int lb_fallback_timeout_ms_ = 0;
   // The backend addresses from the resolver.
-  grpc_lb_addresses* fallback_backend_addresses_ = nullptr;
+  UniquePtr<ServerAddressList> fallback_backend_addresses_;
   // Fallback timer.
   bool fallback_timer_callback_pending_ = false;
   grpc_timer lb_fallback_timer_;
@@ -339,47 +337,15 @@ class XdsLb : public LoadBalancingPolicy {
 // serverlist parsing code
 //
 
-// vtable for LB tokens in grpc_lb_addresses
-void* lb_token_copy(void* token) {
-  return token == nullptr
-             ? nullptr
-             : (void*)GRPC_MDELEM_REF(grpc_mdelem{(uintptr_t)token}).payload;
-}
-void lb_token_destroy(void* token) {
-  if (token != nullptr) {
-    GRPC_MDELEM_UNREF(grpc_mdelem{(uintptr_t)token});
-  }
-}
-int lb_token_cmp(void* token1, void* token2) {
-  if (token1 > token2) return 1;
-  if (token1 < token2) return -1;
-  return 0;
-}
-const grpc_lb_user_data_vtable lb_token_vtable = {
-    lb_token_copy, lb_token_destroy, lb_token_cmp};
-
 // Returns the backend addresses extracted from the given addresses.
-grpc_lb_addresses* ExtractBackendAddresses(const grpc_lb_addresses* addresses) {
-  // First pass: count the number of backend addresses.
-  size_t num_backends = 0;
-  for (size_t i = 0; i < addresses->num_addresses; ++i) {
-    if (!addresses->addresses[i].is_balancer) {
-      ++num_backends;
+UniquePtr<ServerAddressList> ExtractBackendAddresses(
+    const ServerAddressList& addresses) {
+  auto backend_addresses = MakeUnique<ServerAddressList>();
+  for (size_t i = 0; i < addresses.size(); ++i) {
+    if (!addresses[i].IsBalancer()) {
+      backend_addresses->emplace_back(addresses[i]);
     }
   }
-  // Second pass: actually populate the addresses and (empty) LB tokens.
-  grpc_lb_addresses* backend_addresses =
-      grpc_lb_addresses_create(num_backends, &lb_token_vtable);
-  size_t num_copied = 0;
-  for (size_t i = 0; i < addresses->num_addresses; ++i) {
-    if (addresses->addresses[i].is_balancer) continue;
-    const grpc_resolved_address* addr = &addresses->addresses[i].address;
-    grpc_lb_addresses_set_address(backend_addresses, num_copied, &addr->addr,
-                                  addr->len, false /* is_balancer */,
-                                  nullptr /* balancer_name */,
-                                  (void*)GRPC_MDELEM_LB_TOKEN_EMPTY.payload);
-    ++num_copied;
-  }
   return backend_addresses;
 }
 
@@ -429,56 +395,17 @@ void ParseServer(const xds_grpclb_server* server, grpc_resolved_address* addr) {
 }
 
 // Returns addresses extracted from \a serverlist.
-grpc_lb_addresses* ProcessServerlist(const xds_grpclb_serverlist* serverlist) {
-  size_t num_valid = 0;
-  /* first pass: count how many are valid in order to allocate the necessary
-   * memory in a single block */
+UniquePtr<ServerAddressList> ProcessServerlist(
+    const xds_grpclb_serverlist* serverlist) {
+  auto addresses = MakeUnique<ServerAddressList>();
   for (size_t i = 0; i < serverlist->num_servers; ++i) {
-    if (IsServerValid(serverlist->servers[i], i, true)) ++num_valid;
-  }
-  grpc_lb_addresses* lb_addresses =
-      grpc_lb_addresses_create(num_valid, &lb_token_vtable);
-  /* second pass: actually populate the addresses and LB tokens (aka user data
-   * to the outside world) to be read by the child policy during its creation.
-   * Given that the validity tests are very cheap, they are performed again
-   * instead of marking the valid ones during the first pass, as this would
-   * incurr in an allocation due to the arbitrary number of server */
-  size_t addr_idx = 0;
-  for (size_t sl_idx = 0; sl_idx < serverlist->num_servers; ++sl_idx) {
-    const xds_grpclb_server* server = serverlist->servers[sl_idx];
-    if (!IsServerValid(serverlist->servers[sl_idx], sl_idx, false)) continue;
-    GPR_ASSERT(addr_idx < num_valid);
-    /* address processing */
+    const xds_grpclb_server* server = serverlist->servers[i];
+    if (!IsServerValid(serverlist->servers[i], i, false)) continue;
     grpc_resolved_address addr;
     ParseServer(server, &addr);
-    /* lb token processing */
-    void* user_data;
-    if (server->has_load_balance_token) {
-      const size_t lb_token_max_length =
-          GPR_ARRAY_SIZE(server->load_balance_token);
-      const size_t lb_token_length =
-          strnlen(server->load_balance_token, lb_token_max_length);
-      grpc_slice lb_token_mdstr = grpc_slice_from_copied_buffer(
-          server->load_balance_token, lb_token_length);
-      user_data =
-          (void*)grpc_mdelem_from_slices(GRPC_MDSTR_LB_TOKEN, lb_token_mdstr)
-              .payload;
-    } else {
-      char* uri = grpc_sockaddr_to_uri(&addr);
-      gpr_log(GPR_INFO,
-              "Missing LB token for backend address '%s'. The empty token will "
-              "be used instead",
-              uri);
-      gpr_free(uri);
-      user_data = (void*)GRPC_MDELEM_LB_TOKEN_EMPTY.payload;
-    }
-    grpc_lb_addresses_set_address(lb_addresses, addr_idx, &addr.addr, addr.len,
-                                  false /* is_balancer */,
-                                  nullptr /* balancer_name */, user_data);
-    ++addr_idx;
+    addresses->emplace_back(addr, nullptr);
   }
-  GPR_ASSERT(addr_idx == num_valid);
-  return lb_addresses;
+  return addresses;
 }
 
 //
@@ -789,8 +716,7 @@ void XdsLb::BalancerCallState::OnBalancerMessageReceivedLocked(
           xds_grpclb_destroy_serverlist(xdslb_policy->serverlist_);
         } else {
           /* or dispose of the fallback */
-          grpc_lb_addresses_destroy(xdslb_policy->fallback_backend_addresses_);
-          xdslb_policy->fallback_backend_addresses_ = nullptr;
+          xdslb_policy->fallback_backend_addresses_.reset();
           if (xdslb_policy->fallback_timer_callback_pending_) {
             grpc_timer_cancel(&xdslb_policy->lb_fallback_timer_);
           }
@@ -876,31 +802,15 @@ void XdsLb::BalancerCallState::OnBalancerStatusReceivedLocked(
 // helper code for creating balancer channel
 //
 
-grpc_lb_addresses* ExtractBalancerAddresses(
-    const grpc_lb_addresses* addresses) {
-  size_t num_grpclb_addrs = 0;
-  for (size_t i = 0; i < addresses->num_addresses; ++i) {
-    if (addresses->addresses[i].is_balancer) ++num_grpclb_addrs;
-  }
-  // There must be at least one balancer address, or else the
-  // client_channel would not have chosen this LB policy.
-  GPR_ASSERT(num_grpclb_addrs > 0);
-  grpc_lb_addresses* lb_addresses =
-      grpc_lb_addresses_create(num_grpclb_addrs, nullptr);
-  size_t lb_addresses_idx = 0;
-  for (size_t i = 0; i < addresses->num_addresses; ++i) {
-    if (!addresses->addresses[i].is_balancer) continue;
-    if (GPR_UNLIKELY(addresses->addresses[i].user_data != nullptr)) {
-      gpr_log(GPR_ERROR,
-              "This LB policy doesn't support user data. It will be ignored");
+UniquePtr<ServerAddressList> ExtractBalancerAddresses(
+    const ServerAddressList& addresses) {
+  auto balancer_addresses = MakeUnique<ServerAddressList>();
+  for (size_t i = 0; i < addresses.size(); ++i) {
+    if (addresses[i].IsBalancer()) {
+      balancer_addresses->emplace_back(addresses[i]);
     }
-    grpc_lb_addresses_set_address(
-        lb_addresses, lb_addresses_idx++, addresses->addresses[i].address.addr,
-        addresses->addresses[i].address.len, false /* is balancer */,
-        addresses->addresses[i].balancer_name, nullptr /* user data */);
   }
-  GPR_ASSERT(num_grpclb_addrs == lb_addresses_idx);
-  return lb_addresses;
+  return balancer_addresses;
 }
 
 /* Returns the channel args for the LB channel, used to create a bidirectional
@@ -912,10 +822,11 @@ grpc_lb_addresses* ExtractBalancerAddresses(
  *   above the grpclb policy.
  *   - \a args: other args inherited from the xds policy. */
 grpc_channel_args* BuildBalancerChannelArgs(
-    const grpc_lb_addresses* addresses,
+    const ServerAddressList& addresses,
     FakeResolverResponseGenerator* response_generator,
     const grpc_channel_args* args) {
-  grpc_lb_addresses* lb_addresses = ExtractBalancerAddresses(addresses);
+  UniquePtr<ServerAddressList> balancer_addresses =
+      ExtractBalancerAddresses(addresses);
   // Channel args to remove.
   static const char* args_to_remove[] = {
       // LB policy name, since we want to use the default (pick_first) in
@@ -933,7 +844,7 @@ grpc_channel_args* BuildBalancerChannelArgs(
       // is_balancer=true.  We need the LB channel to return addresses with
       // is_balancer=false so that it does not wind up recursively using the
       // xds LB policy, as per the special case logic in client_channel.c.
-      GRPC_ARG_LB_ADDRESSES,
+      GRPC_ARG_SERVER_ADDRESS_LIST,
       // The fake resolver response generator, because we are replacing it
       // with the one from the xds policy, used to propagate updates to
       // the LB channel.
@@ -949,10 +860,10 @@ grpc_channel_args* BuildBalancerChannelArgs(
   };
   // Channel args to add.
   const grpc_arg args_to_add[] = {
-      // New LB addresses.
+      // New server address list.
       // Note that we pass these in both when creating the LB channel
       // and via the fake resolver.  The latter is what actually gets used.
-      grpc_lb_addresses_create_channel_arg(lb_addresses),
+      CreateServerAddressListChannelArg(balancer_addresses.get()),
       // The fake resolver response generator, which we use to inject
       // address updates into the LB channel.
       grpc_core::FakeResolverResponseGenerator::MakeChannelArg(
@@ -970,10 +881,7 @@ grpc_channel_args* BuildBalancerChannelArgs(
       args, args_to_remove, GPR_ARRAY_SIZE(args_to_remove), args_to_add,
       GPR_ARRAY_SIZE(args_to_add));
   // Make any necessary modifications for security.
-  new_args = grpc_lb_policy_xds_modify_lb_channel_args(new_args);
-  // Clean up.
-  grpc_lb_addresses_destroy(lb_addresses);
-  return new_args;
+  return grpc_lb_policy_xds_modify_lb_channel_args(new_args);
 }
 
 //
@@ -981,8 +889,7 @@ grpc_channel_args* BuildBalancerChannelArgs(
 //
 
 // TODO(vishalpowar): Use lb_config in args to configure LB policy.
-XdsLb::XdsLb(const grpc_lb_addresses* addresses,
-             const LoadBalancingPolicy::Args& args)
+XdsLb::XdsLb(const LoadBalancingPolicy::Args& args)
     : LoadBalancingPolicy(args),
       response_generator_(MakeRefCounted<FakeResolverResponseGenerator>()),
       lb_call_backoff_(
@@ -1038,9 +945,6 @@ XdsLb::~XdsLb() {
   if (serverlist_ != nullptr) {
     xds_grpclb_destroy_serverlist(serverlist_);
   }
-  if (fallback_backend_addresses_ != nullptr) {
-    grpc_lb_addresses_destroy(fallback_backend_addresses_);
-  }
   grpc_subchannel_index_unref();
 }
 
@@ -1088,7 +992,6 @@ void XdsLb::HandOffPendingPicksLocked(LoadBalancingPolicy* new_policy) {
   while ((pp = pending_picks_) != nullptr) {
     pending_picks_ = pp->next;
     pp->pick->on_complete = pp->original_on_complete;
-    pp->pick->user_data = nullptr;
     grpc_error* error = GRPC_ERROR_NONE;
     if (new_policy->PickLocked(pp->pick, &error)) {
       // Synchronous return; schedule closure.
@@ -1241,21 +1144,16 @@ void XdsLb::NotifyOnStateChangeLocked(grpc_connectivity_state* current,
 }
 
 void XdsLb::ProcessChannelArgsLocked(const grpc_channel_args& args) {
-  const grpc_arg* arg = grpc_channel_args_find(&args, GRPC_ARG_LB_ADDRESSES);
-  if (GPR_UNLIKELY(arg == nullptr || arg->type != GRPC_ARG_POINTER)) {
+  const ServerAddressList* addresses = FindServerAddressListChannelArg(&args);
+  if (addresses == nullptr) {
     // Ignore this update.
     gpr_log(GPR_ERROR,
             "[xdslb %p] No valid LB addresses channel arg in update, ignoring.",
             this);
     return;
   }
-  const grpc_lb_addresses* addresses =
-      static_cast<const grpc_lb_addresses*>(arg->value.pointer.p);
   // Update fallback address list.
-  if (fallback_backend_addresses_ != nullptr) {
-    grpc_lb_addresses_destroy(fallback_backend_addresses_);
-  }
-  fallback_backend_addresses_ = ExtractBackendAddresses(addresses);
+  fallback_backend_addresses_ = ExtractBackendAddresses(*addresses);
   // Make sure that GRPC_ARG_LB_POLICY_NAME is set in channel args,
   // since we use this to trigger the client_load_reporting filter.
   static const char* args_to_remove[] = {GRPC_ARG_LB_POLICY_NAME};
@@ -1266,7 +1164,7 @@ void XdsLb::ProcessChannelArgsLocked(const grpc_channel_args& args) {
       &args, args_to_remove, GPR_ARRAY_SIZE(args_to_remove), &new_arg, 1);
   // Construct args for balancer channel.
   grpc_channel_args* lb_channel_args =
-      BuildBalancerChannelArgs(addresses, response_generator_.get(), &args);
+      BuildBalancerChannelArgs(*addresses, response_generator_.get(), &args);
   // Create balancer channel if needed.
   if (lb_channel_ == nullptr) {
     char* uri_str;
@@ -1457,37 +1355,15 @@ void XdsLb::OnBalancerChannelConnectivityChangedLocked(void* arg,
 // PendingPick
 //
 
-// Adds lb_token of selected subchannel (address) to the call's initial
-// metadata.
-grpc_error* AddLbTokenToInitialMetadata(
-    grpc_mdelem lb_token, grpc_linked_mdelem* lb_token_mdelem_storage,
-    grpc_metadata_batch* initial_metadata) {
-  GPR_ASSERT(lb_token_mdelem_storage != nullptr);
-  GPR_ASSERT(!GRPC_MDISNULL(lb_token));
-  return grpc_metadata_batch_add_tail(initial_metadata, lb_token_mdelem_storage,
-                                      lb_token);
-}
-
 // Destroy function used when embedding client stats in call context.
 void DestroyClientStats(void* arg) {
   static_cast<XdsLbClientStats*>(arg)->Unref();
 }
 
-void XdsLb::PendingPickSetMetadataAndContext(PendingPick* pp) {
-  /* if connected_subchannel is nullptr, no pick has been made by the
-   * child policy (e.g., all addresses failed to connect). There won't be any
-   * user_data/token available */
+void XdsLb::PendingPickCleanup(PendingPick* pp) {
+  // If connected_subchannel is nullptr, no pick has been made by the
+  // child policy (e.g., all addresses failed to connect).
   if (pp->pick->connected_subchannel != nullptr) {
-    if (GPR_LIKELY(!GRPC_MDISNULL(pp->lb_token))) {
-      AddLbTokenToInitialMetadata(GRPC_MDELEM_REF(pp->lb_token),
-                                  &pp->pick->lb_token_mdelem_storage,
-                                  pp->pick->initial_metadata);
-    } else {
-      gpr_log(GPR_ERROR,
-              "[xdslb %p] No LB token for connected subchannel pick %p",
-              pp->xdslb_policy, pp->pick);
-      abort();
-    }
     // Pass on client stats via context. Passes ownership of the reference.
     if (pp->client_stats != nullptr) {
       pp->pick->subchannel_call_context[GRPC_GRPCLB_CLIENT_STATS].value =
@@ -1505,7 +1381,7 @@ void XdsLb::PendingPickSetMetadataAndContext(PendingPick* pp) {
  * order to unref the child policy instance upon its invocation */
 void XdsLb::OnPendingPickComplete(void* arg, grpc_error* error) {
   PendingPick* pp = static_cast<PendingPick*>(arg);
-  PendingPickSetMetadataAndContext(pp);
+  PendingPickCleanup(pp);
   GRPC_CLOSURE_SCHED(pp->original_on_complete, GRPC_ERROR_REF(error));
   Delete(pp);
 }
@@ -1537,16 +1413,14 @@ void XdsLb::AddPendingPick(PendingPick* pp) {
 // completion callback even if the pick is available immediately.
 bool XdsLb::PickFromChildPolicyLocked(bool force_async, PendingPick* pp,
                                       grpc_error** error) {
-  // Set client_stats and user_data.
+  // Set client_stats.
   if (lb_calld_ != nullptr && lb_calld_->client_stats() != nullptr) {
     pp->client_stats = lb_calld_->client_stats()->Ref();
   }
-  GPR_ASSERT(pp->pick->user_data == nullptr);
-  pp->pick->user_data = (void**)&pp->lb_token;
   // Pick via the child policy.
   bool pick_done = child_policy_->PickLocked(pp->pick, error);
   if (pick_done) {
-    PendingPickSetMetadataAndContext(pp);
+    PendingPickCleanup(pp);
     if (force_async) {
       GRPC_CLOSURE_SCHED(pp->original_on_complete, *error);
       *error = GRPC_ERROR_NONE;
@@ -1608,20 +1482,19 @@ void XdsLb::CreateChildPolicyLocked(const Args& args) {
 }
 
 grpc_channel_args* XdsLb::CreateChildPolicyArgsLocked() {
-  grpc_lb_addresses* addresses;
   bool is_backend_from_grpclb_load_balancer = false;
   // This should never be invoked if we do not have serverlist_, as fallback
   // mode is disabled for xDS plugin.
   GPR_ASSERT(serverlist_ != nullptr);
   GPR_ASSERT(serverlist_->num_servers > 0);
-  addresses = ProcessServerlist(serverlist_);
-  is_backend_from_grpclb_load_balancer = true;
+  UniquePtr<ServerAddressList> addresses = ProcessServerlist(serverlist_);
   GPR_ASSERT(addresses != nullptr);
-  // Replace the LB addresses in the channel args that we pass down to
+  is_backend_from_grpclb_load_balancer = true;
+  // Replace the server address list in the channel args that we pass down to
   // the subchannel.
-  static const char* keys_to_remove[] = {GRPC_ARG_LB_ADDRESSES};
+  static const char* keys_to_remove[] = {GRPC_ARG_SERVER_ADDRESS_LIST};
   const grpc_arg args_to_add[] = {
-      grpc_lb_addresses_create_channel_arg(addresses),
+      CreateServerAddressListChannelArg(addresses.get()),
       // A channel arg indicating if the target is a backend inferred from a
       // grpclb load balancer.
       grpc_channel_arg_integer_create(
@@ -1631,7 +1504,6 @@ grpc_channel_args* XdsLb::CreateChildPolicyArgsLocked() {
   grpc_channel_args* args = grpc_channel_args_copy_and_add_and_remove(
       args_, keys_to_remove, GPR_ARRAY_SIZE(keys_to_remove), args_to_add,
       GPR_ARRAY_SIZE(args_to_add));
-  grpc_lb_addresses_destroy(addresses);
   return args;
 }
 
@@ -1765,19 +1637,18 @@ class XdsFactory : public LoadBalancingPolicyFactory {
   OrphanablePtr<LoadBalancingPolicy> CreateLoadBalancingPolicy(
       const LoadBalancingPolicy::Args& args) const override {
     /* Count the number of gRPC-LB addresses. There must be at least one. */
-    const grpc_arg* arg =
-        grpc_channel_args_find(args.args, GRPC_ARG_LB_ADDRESSES);
-    if (arg == nullptr || arg->type != GRPC_ARG_POINTER) {
-      return nullptr;
-    }
-    grpc_lb_addresses* addresses =
-        static_cast<grpc_lb_addresses*>(arg->value.pointer.p);
-    size_t num_grpclb_addrs = 0;
-    for (size_t i = 0; i < addresses->num_addresses; ++i) {
-      if (addresses->addresses[i].is_balancer) ++num_grpclb_addrs;
+    const ServerAddressList* addresses =
+        FindServerAddressListChannelArg(args.args);
+    if (addresses == nullptr) return nullptr;
+    bool found_balancer_address = false;
+    for (size_t i = 0; i < addresses->size(); ++i) {
+      if ((*addresses)[i].IsBalancer()) {
+        found_balancer_address = true;
+        break;
+      }
     }
-    if (num_grpclb_addrs == 0) return nullptr;
-    return OrphanablePtr<LoadBalancingPolicy>(New<XdsLb>(addresses, args));
+    if (!found_balancer_address) return nullptr;
+    return OrphanablePtr<LoadBalancingPolicy>(New<XdsLb>(args));
   }
 
   const char* name() const override { return "xds_experimental"; }
diff --git a/src/core/ext/filters/client_channel/lb_policy/xds/xds_channel.h b/src/core/ext/filters/client_channel/lb_policy/xds/xds_channel.h
index 32c4acc8a3..f713b7f563 100644
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds_channel.h
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds_channel.h
@@ -21,7 +21,7 @@
 
 #include <grpc/support/port_platform.h>
 
-#include "src/core/ext/filters/client_channel/lb_policy_factory.h"
+#include <grpc/impl/codegen/grpc_types.h>
 
 /// Makes any necessary modifications to \a args for use in the xds
 /// balancer channel.
diff --git a/src/core/ext/filters/client_channel/lb_policy/xds/xds_channel_secure.cc b/src/core/ext/filters/client_channel/lb_policy/xds/xds_channel_secure.cc
index 5ab72efce4..9a11f8e39f 100644
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds_channel_secure.cc
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds_channel_secure.cc
@@ -25,6 +25,7 @@
 #include <string.h>
 
 #include "src/core/ext/filters/client_channel/client_channel.h"
+#include "src/core/ext/filters/client_channel/server_address.h"
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/gpr/string.h"
 #include "src/core/lib/iomgr/sockaddr_utils.h"
@@ -41,22 +42,23 @@ int BalancerNameCmp(const grpc_core::UniquePtr<char>& a,
 }
 
 RefCountedPtr<TargetAuthorityTable> CreateTargetAuthorityTable(
-    grpc_lb_addresses* addresses) {
+    const ServerAddressList& addresses) {
   TargetAuthorityTable::Entry* target_authority_entries =
-      static_cast<TargetAuthorityTable::Entry*>(gpr_zalloc(
-          sizeof(*target_authority_entries) * addresses->num_addresses));
-  for (size_t i = 0; i < addresses->num_addresses; ++i) {
+      static_cast<TargetAuthorityTable::Entry*>(
+          gpr_zalloc(sizeof(*target_authority_entries) * addresses.size()));
+  for (size_t i = 0; i < addresses.size(); ++i) {
     char* addr_str;
-    GPR_ASSERT(grpc_sockaddr_to_string(
-                   &addr_str, &addresses->addresses[i].address, true) > 0);
+    GPR_ASSERT(
+        grpc_sockaddr_to_string(&addr_str, &addresses[i].address(), true) > 0);
     target_authority_entries[i].key = grpc_slice_from_copied_string(addr_str);
-    target_authority_entries[i].value.reset(
-        gpr_strdup(addresses->addresses[i].balancer_name));
     gpr_free(addr_str);
+    char* balancer_name = grpc_channel_arg_get_string(grpc_channel_args_find(
+        addresses[i].args(), GRPC_ARG_ADDRESS_BALANCER_NAME));
+    target_authority_entries[i].value.reset(gpr_strdup(balancer_name));
   }
   RefCountedPtr<TargetAuthorityTable> target_authority_table =
-      TargetAuthorityTable::Create(addresses->num_addresses,
-                                   target_authority_entries, BalancerNameCmp);
+      TargetAuthorityTable::Create(addresses.size(), target_authority_entries,
+                                   BalancerNameCmp);
   gpr_free(target_authority_entries);
   return target_authority_table;
 }
@@ -71,13 +73,12 @@ grpc_channel_args* grpc_lb_policy_xds_modify_lb_channel_args(
   grpc_arg args_to_add[2];
   size_t num_args_to_add = 0;
   // Add arg for targets info table.
-  const grpc_arg* arg = grpc_channel_args_find(args, GRPC_ARG_LB_ADDRESSES);
-  GPR_ASSERT(arg != nullptr);
-  GPR_ASSERT(arg->type == GRPC_ARG_POINTER);
-  grpc_lb_addresses* addresses =
-      static_cast<grpc_lb_addresses*>(arg->value.pointer.p);
+  grpc_core::ServerAddressList* addresses =
+      grpc_core::FindServerAddressListChannelArg(args);
+  GPR_ASSERT(addresses != nullptr);
   grpc_core::RefCountedPtr<grpc_core::TargetAuthorityTable>
-      target_authority_table = grpc_core::CreateTargetAuthorityTable(addresses);
+      target_authority_table =
+          grpc_core::CreateTargetAuthorityTable(*addresses);
   args_to_add[num_args_to_add++] =
       grpc_core::CreateTargetAuthorityTableChannelArg(
           target_authority_table.get());
diff --git a/src/core/ext/filters/client_channel/lb_policy/xds/xds_load_balancer_api.h b/src/core/ext/filters/client_channel/lb_policy/xds/xds_load_balancer_api.h
index 9d08defa7e..6704995641 100644
--- a/src/core/ext/filters/client_channel/lb_policy/xds/xds_load_balancer_api.h
+++ b/src/core/ext/filters/client_channel/lb_policy/xds/xds_load_balancer_api.h
@@ -25,7 +25,7 @@
 
 #include "src/core/ext/filters/client_channel/lb_policy/grpclb/proto/grpc/lb/v1/load_balancer.pb.h"
 #include "src/core/ext/filters/client_channel/lb_policy/xds/xds_client_stats.h"
-#include "src/core/ext/filters/client_channel/lb_policy_factory.h"
+#include "src/core/lib/iomgr/exec_ctx.h"
 
 #define XDS_SERVICE_NAME_MAX_LENGTH 128