Merge github.com:grpc/grpc into epexinf

15 files changed, 260 insertions, 93 deletions

diff --git a/src/core/ext/transport/chttp2/transport/chttp2_transport.cc b/src/core/ext/transport/chttp2/transport/chttp2_transport.cc
index 0ef06ae6e0..9462d1085e 100644
--- a/src/core/ext/transport/chttp2/transport/chttp2_transport.cc
+++ b/src/core/ext/transport/chttp2/transport/chttp2_transport.cc
@@ -152,10 +152,14 @@ static void close_transport_locked(grpc_exec_ctx *exec_ctx,
 static void end_all_the_calls(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                               grpc_error *error);
 
+static void schedule_bdp_ping_locked(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_transport *t);
 static void start_bdp_ping_locked(grpc_exec_ctx *exec_ctx, void *tp,
                                   grpc_error *error);
 static void finish_bdp_ping_locked(grpc_exec_ctx *exec_ctx, void *tp,
                                    grpc_error *error);
+static void next_bdp_ping_timer_expired_locked(grpc_exec_ctx *exec_ctx,
+                                               void *tp, grpc_error *error);
 
 static void cancel_pings(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                          grpc_error *error);
@@ -220,6 +224,7 @@ static void destruct_transport(grpc_exec_ctx *exec_ctx,
 
   t->flow_control.bdp_estimator.Destroy();
 
+  GRPC_ERROR_UNREF(t->closed_with_error);
   gpr_free(t->ping_acks);
   gpr_free(t->peer_string);
   gpr_free(t);
@@ -305,6 +310,9 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                     grpc_combiner_scheduler(t->combiner));
   GRPC_CLOSURE_INIT(&t->finish_bdp_ping_locked, finish_bdp_ping_locked, t,
                     grpc_combiner_scheduler(t->combiner));
+  GRPC_CLOSURE_INIT(&t->next_bdp_ping_timer_expired_locked,
+                    next_bdp_ping_timer_expired_locked, t,
+                    grpc_combiner_scheduler(t->combiner));
   GRPC_CLOSURE_INIT(&t->init_keepalive_ping_locked, init_keepalive_ping_locked,
                     t, grpc_combiner_scheduler(t->combiner));
   GRPC_CLOSURE_INIT(&t->start_keepalive_ping_locked,
@@ -564,6 +572,11 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
     t->keepalive_state = GRPC_CHTTP2_KEEPALIVE_STATE_DISABLED;
   }
 
+  if (t->flow_control.enable_bdp_probe) {
+    GRPC_CHTTP2_REF_TRANSPORT(t, "bdp_ping");
+    schedule_bdp_ping_locked(exec_ctx, t);
+  }
+
   grpc_chttp2_act_on_flowctl_action(
       exec_ctx,
       grpc_chttp2_flowctl_get_action(exec_ctx, &t->flow_control, NULL), t,
@@ -597,7 +610,9 @@ static void destroy_transport(grpc_exec_ctx *exec_ctx, grpc_transport *gt) {
 static void close_transport_locked(grpc_exec_ctx *exec_ctx,
                                    grpc_chttp2_transport *t,
                                    grpc_error *error) {
-  if (!t->closed) {
+  end_all_the_calls(exec_ctx, t, GRPC_ERROR_REF(error));
+  cancel_pings(exec_ctx, t, GRPC_ERROR_REF(error));
+  if (t->closed_with_error == GRPC_ERROR_NONE) {
     if (!grpc_error_has_clear_grpc_status(error)) {
       error = grpc_error_set_int(error, GRPC_ERROR_INT_GRPC_STATUS,
                                  GRPC_STATUS_UNAVAILABLE);
@@ -612,13 +627,16 @@ static void close_transport_locked(grpc_exec_ctx *exec_ctx,
           grpc_error_add_child(t->close_transport_on_writes_finished, error);
       return;
     }
-    t->closed = 1;
+    GPR_ASSERT(error != GRPC_ERROR_NONE);
+    t->closed_with_error = GRPC_ERROR_REF(error);
     connectivity_state_set(exec_ctx, t, GRPC_CHANNEL_SHUTDOWN,
                            GRPC_ERROR_REF(error), "close_transport");
-    grpc_endpoint_shutdown(exec_ctx, t->ep, GRPC_ERROR_REF(error));
     if (t->ping_state.is_delayed_ping_timer_set) {
       grpc_timer_cancel(exec_ctx, &t->ping_state.delayed_ping_timer);
     }
+    if (t->have_next_bdp_ping_timer) {
+      grpc_timer_cancel(exec_ctx, &t->next_bdp_ping_timer);
+    }
     switch (t->keepalive_state) {
       case GRPC_CHTTP2_KEEPALIVE_STATE_WAITING:
         grpc_timer_cancel(exec_ctx, &t->keepalive_ping_timer);
@@ -638,8 +656,8 @@ static void close_transport_locked(grpc_exec_ctx *exec_ctx,
     while (grpc_chttp2_list_pop_writable_stream(t, &s)) {
       GRPC_CHTTP2_STREAM_UNREF(exec_ctx, s, "chttp2_writing:close");
     }
-    end_all_the_calls(exec_ctx, t, GRPC_ERROR_REF(error));
-    cancel_pings(exec_ctx, t, GRPC_ERROR_REF(error));
+    GPR_ASSERT(t->write_state == GRPC_CHTTP2_WRITE_STATE_IDLE);
+    grpc_endpoint_shutdown(exec_ctx, t->ep, GRPC_ERROR_REF(error));
   }
   GRPC_ERROR_UNREF(error);
 }
@@ -942,7 +960,8 @@ void grpc_chttp2_initiate_write(grpc_exec_ctx *exec_ctx,
 void grpc_chttp2_mark_stream_writable(grpc_exec_ctx *exec_ctx,
                                       grpc_chttp2_transport *t,
                                       grpc_chttp2_stream *s) {
-  if (!t->closed && grpc_chttp2_list_add_writable_stream(t, s)) {
+  if (t->closed_with_error == GRPC_ERROR_NONE &&
+      grpc_chttp2_list_add_writable_stream(t, s)) {
     GRPC_CHTTP2_STREAM_REF(s, "chttp2_writing:become");
   }
 }
@@ -995,7 +1014,7 @@ static void write_action_begin_locked(grpc_exec_ctx *exec_ctx, void *gt,
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
   GPR_ASSERT(t->write_state != GRPC_CHTTP2_WRITE_STATE_IDLE);
   grpc_chttp2_begin_write_result r;
-  if (t->closed) {
+  if (t->closed_with_error != GRPC_ERROR_NONE) {
     r.writing = false;
   } else {
     r = grpc_chttp2_begin_write(exec_ctx, t);
@@ -1458,7 +1477,7 @@ static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx, void *stream_op,
       }
       if (!s->write_closed) {
         if (t->is_client) {
-          if (!t->closed) {
+          if (t->closed_with_error == GRPC_ERROR_NONE) {
             GPR_ASSERT(s->id == 0);
             grpc_chttp2_list_add_waiting_for_concurrency(t, s);
             maybe_start_some_streams(exec_ctx, t);
@@ -1466,7 +1485,8 @@ static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx, void *stream_op,
             grpc_chttp2_cancel_stream(
                 exec_ctx, t, s,
                 grpc_error_set_int(
-                    GRPC_ERROR_CREATE_FROM_STATIC_STRING("Transport closed"),
+                    GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING(
+                        "Transport closed", &t->closed_with_error, 1),
                     GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_UNAVAILABLE));
           }
         } else {
@@ -1688,6 +1708,7 @@ static void cancel_pings(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
   /* callback remaining pings: they're not allowed to call into the transpot,
      and maybe they hold resources that need to be freed */
   grpc_chttp2_ping_queue *pq = &t->ping_queue;
+  GPR_ASSERT(error != GRPC_ERROR_NONE);
   for (size_t j = 0; j < GRPC_CHTTP2_PCL_COUNT; j++) {
     grpc_closure_list_fail_all(&pq->lists[j], GRPC_ERROR_REF(error));
     GRPC_CLOSURE_LIST_SCHED(exec_ctx, &pq->lists[j]);
@@ -1697,6 +1718,12 @@ static void cancel_pings(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
 
 static void send_ping_locked(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                              grpc_closure *on_initiate, grpc_closure *on_ack) {
+  if (t->closed_with_error != GRPC_ERROR_NONE) {
+    GRPC_CLOSURE_SCHED(exec_ctx, on_initiate,
+                       GRPC_ERROR_REF(t->closed_with_error));
+    GRPC_CLOSURE_SCHED(exec_ctx, on_ack, GRPC_ERROR_REF(t->closed_with_error));
+    return;
+  }
   grpc_chttp2_ping_queue *pq = &t->ping_queue;
   grpc_closure_list_append(&pq->lists[GRPC_CHTTP2_PCL_INITIATE], on_initiate,
                            GRPC_ERROR_NONE);
@@ -1755,7 +1782,9 @@ void grpc_chttp2_add_ping_strike(grpc_exec_ctx *exec_ctx,
                     GRPC_ERROR_INT_HTTP2_ERROR, GRPC_HTTP2_ENHANCE_YOUR_CALM));
     /*The transport will be closed after the write is done */
     close_transport_locked(
-        exec_ctx, t, GRPC_ERROR_CREATE_FROM_STATIC_STRING("Too many pings"));
+        exec_ctx, t, grpc_error_set_int(
+                         GRPC_ERROR_CREATE_FROM_STATIC_STRING("Too many pings"),
+                         GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_UNAVAILABLE));
   }
 }
 
@@ -2434,12 +2463,6 @@ void grpc_chttp2_act_on_flowctl_action(grpc_exec_ctx *exec_ctx,
                                  GRPC_CHTTP2_INITIATE_WRITE_SEND_SETTINGS);
     }
   }
-  if (action.need_ping) {
-    GRPC_CHTTP2_REF_TRANSPORT(t, "bdp_ping");
-    t->flow_control.bdp_estimator->SchedulePing();
-    send_ping_locked(exec_ctx, t, &t->start_bdp_ping_locked,
-                     &t->finish_bdp_ping_locked);
-  }
 }
 
 static grpc_error *try_http_parsing(grpc_exec_ctx *exec_ctx,
@@ -2489,7 +2512,7 @@ static void read_action_locked(grpc_exec_ctx *exec_ctx, void *tp,
   }
   GPR_SWAP(grpc_error *, err, error);
   GRPC_ERROR_UNREF(err);
-  if (!t->closed) {
+  if (t->closed_with_error == GRPC_ERROR_NONE) {
     GPR_TIMER_BEGIN("reading_action.parse", 0);
     size_t i = 0;
     grpc_error *errors[3] = {GRPC_ERROR_REF(error), GRPC_ERROR_NONE,
@@ -2529,13 +2552,14 @@ static void read_action_locked(grpc_exec_ctx *exec_ctx, void *tp,
 
   GPR_TIMER_BEGIN("post_reading_action_locked", 0);
   bool keep_reading = false;
-  if (error == GRPC_ERROR_NONE && t->closed) {
-    error = GRPC_ERROR_CREATE_FROM_STATIC_STRING("Transport closed");
+  if (error == GRPC_ERROR_NONE && t->closed_with_error != GRPC_ERROR_NONE) {
+    error = GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING(
+        "Transport closed", &t->closed_with_error, 1);
   }
   if (error != GRPC_ERROR_NONE) {
     close_transport_locked(exec_ctx, t, GRPC_ERROR_REF(error));
     t->endpoint_reading = 0;
-  } else if (!t->closed) {
+  } else if (t->closed_with_error == GRPC_ERROR_NONE) {
     keep_reading = true;
     GRPC_CHTTP2_REF_TRANSPORT(t, "keep_reading");
   }
@@ -2560,11 +2584,21 @@ static void read_action_locked(grpc_exec_ctx *exec_ctx, void *tp,
   GPR_TIMER_END("reading_action_locked", 0);
 }
 
+// t is reffed prior to calling the first time, and once the callback chain
+// that kicks off finishes, it's unreffed
+static void schedule_bdp_ping_locked(grpc_exec_ctx *exec_ctx,
+                                     grpc_chttp2_transport *t) {
+  t->flow_control.bdp_estimator->SchedulePing();
+  send_ping_locked(exec_ctx, t, &t->start_bdp_ping_locked,
+                   &t->finish_bdp_ping_locked);
+}
+
 static void start_bdp_ping_locked(grpc_exec_ctx *exec_ctx, void *tp,
                                   grpc_error *error) {
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)tp;
   if (GRPC_TRACER_ON(grpc_http_trace)) {
-    gpr_log(GPR_DEBUG, "%s: Start BDP ping", t->peer_string);
+    gpr_log(GPR_DEBUG, "%s: Start BDP ping err=%s", t->peer_string,
+            grpc_error_string(error));
   }
   /* Reset the keepalive ping timer */
   if (t->keepalive_state == GRPC_CHTTP2_KEEPALIVE_STATE_WAITING) {
@@ -2577,11 +2611,30 @@ static void finish_bdp_ping_locked(grpc_exec_ctx *exec_ctx, void *tp,
                                    grpc_error *error) {
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)tp;
   if (GRPC_TRACER_ON(grpc_http_trace)) {
-    gpr_log(GPR_DEBUG, "%s: Complete BDP ping", t->peer_string);
+    gpr_log(GPR_DEBUG, "%s: Complete BDP ping err=%s", t->peer_string,
+            grpc_error_string(error));
   }
-  t->flow_control.bdp_estimator->CompletePing(exec_ctx);
+  if (error != GRPC_ERROR_NONE) {
+    GRPC_CHTTP2_UNREF_TRANSPORT(exec_ctx, t, "bdp_ping");
+    return;
+  }
+  grpc_millis next_ping = t->flow_control.bdp_estimator->CompletePing(exec_ctx);
+  GPR_ASSERT(!t->have_next_bdp_ping_timer);
+  t->have_next_bdp_ping_timer = true;
+  grpc_timer_init(exec_ctx, &t->next_bdp_ping_timer, next_ping,
+                  &t->next_bdp_ping_timer_expired_locked);
+}
 
-  GRPC_CHTTP2_UNREF_TRANSPORT(exec_ctx, t, "bdp_ping");
+static void next_bdp_ping_timer_expired_locked(grpc_exec_ctx *exec_ctx,
+                                               void *tp, grpc_error *error) {
+  grpc_chttp2_transport *t = (grpc_chttp2_transport *)tp;
+  GPR_ASSERT(t->have_next_bdp_ping_timer);
+  t->have_next_bdp_ping_timer = false;
+  if (error != GRPC_ERROR_NONE) {
+    GRPC_CHTTP2_UNREF_TRANSPORT(exec_ctx, t, "bdp_ping");
+    return;
+  }
+  schedule_bdp_ping_locked(exec_ctx, t);
 }
 
 void grpc_chttp2_config_default_keepalive_args(grpc_channel_args *args,
@@ -2646,7 +2699,7 @@ static void init_keepalive_ping_locked(grpc_exec_ctx *exec_ctx, void *arg,
                                        grpc_error *error) {
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)arg;
   GPR_ASSERT(t->keepalive_state == GRPC_CHTTP2_KEEPALIVE_STATE_WAITING);
-  if (t->destroying || t->closed) {
+  if (t->destroying || t->closed_with_error != GRPC_ERROR_NONE) {
     t->keepalive_state = GRPC_CHTTP2_KEEPALIVE_STATE_DYING;
   } else if (error == GRPC_ERROR_NONE) {
     if (t->keepalive_permit_without_calls ||
@@ -2704,8 +2757,11 @@ static void keepalive_watchdog_fired_locked(grpc_exec_ctx *exec_ctx, void *arg,
   if (t->keepalive_state == GRPC_CHTTP2_KEEPALIVE_STATE_PINGING) {
     if (error == GRPC_ERROR_NONE) {
       t->keepalive_state = GRPC_CHTTP2_KEEPALIVE_STATE_DYING;
-      close_transport_locked(exec_ctx, t, GRPC_ERROR_CREATE_FROM_STATIC_STRING(
-                                              "keepalive watchdog timeout"));
+      close_transport_locked(
+          exec_ctx, t,
+          grpc_error_set_int(GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+                                 "keepalive watchdog timeout"),
+                             GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_INTERNAL));
     }
   } else {
     /* The watchdog timer should have been cancelled by
diff --git a/src/core/ext/transport/chttp2/transport/flow_control.cc b/src/core/ext/transport/chttp2/transport/flow_control.cc
index 60c43d840a..d0e80c4bd5 100644
--- a/src/core/ext/transport/chttp2/transport/flow_control.cc
+++ b/src/core/ext/transport/chttp2/transport/flow_control.cc
@@ -459,8 +459,6 @@ grpc_chttp2_flowctl_action grpc_chttp2_flowctl_get_action(
     }
   }
   if (tfc->enable_bdp_probe) {
-    action.need_ping = tfc->bdp_estimator->NeedPing(exec_ctx);
-
     // get bdp estimate and update initial_window accordingly.
     int64_t estimate = -1;
     if (tfc->bdp_estimator->EstimateBdp(&estimate)) {
diff --git a/src/core/ext/transport/chttp2/transport/internal.h b/src/core/ext/transport/chttp2/transport/internal.h
index f7a57a6543..703f3ba348 100644
--- a/src/core/ext/transport/chttp2/transport/internal.h
+++ b/src/core/ext/transport/chttp2/transport/internal.h
@@ -298,7 +298,7 @@ struct grpc_chttp2_transport {
   /** is the transport destroying itself? */
   uint8_t destroying;
   /** has the upper layer closed the transport? */
-  uint8_t closed;
+  grpc_error *closed_with_error;
 
   /** is there a read request to the endpoint outstanding? */
   uint8_t endpoint_reading;
@@ -340,7 +340,7 @@ struct grpc_chttp2_transport {
   /** hpack encoding */
   grpc_chttp2_hpack_compressor hpack_compressor;
   /** is this a client? */
-  uint8_t is_client;
+  bool is_client;
 
   /** data to write next write */
   grpc_slice_buffer qbuf;
@@ -350,14 +350,14 @@ struct grpc_chttp2_transport {
   uint32_t write_buffer_size;
 
   /** have we seen a goaway */
-  uint8_t seen_goaway;
+  bool seen_goaway;
   /** have we sent a goaway */
   grpc_chttp2_sent_goaway_state sent_goaway_state;
 
   /** are the local settings dirty and need to be sent? */
-  uint8_t dirtied_local_settings;
+  bool dirtied_local_settings;
   /** have local settings been sent? */
-  uint8_t sent_local_settings;
+  bool sent_local_settings;
   /** bitmask of setting indexes to send out */
   uint32_t force_send_settings;
   /** settings values */
@@ -422,6 +422,7 @@ struct grpc_chttp2_transport {
   grpc_chttp2_write_cb *write_cb_pool;
 
   /* bdp estimator */
+  grpc_closure next_bdp_ping_timer_expired_locked;
   grpc_closure start_bdp_ping_locked;
   grpc_closure finish_bdp_ping_locked;
 
@@ -442,6 +443,10 @@ struct grpc_chttp2_transport {
   /** destructive cleanup closure */
   grpc_closure destructive_reclaimer_locked;
 
+  /* next bdp ping timer */
+  bool have_next_bdp_ping_timer;
+  grpc_timer next_bdp_ping_timer;
+
   /* keep-alive ping support */
   /** Closure to initialize a keepalive ping */
   grpc_closure init_keepalive_ping_locked;
@@ -749,7 +754,6 @@ typedef struct {
   grpc_chttp2_flowctl_urgency send_setting_update;
   uint32_t initial_window_size;
   uint32_t max_frame_size;
-  bool need_ping;
 } grpc_chttp2_flowctl_action;
 
 // Reads the flow control data and returns and actionable struct that will tell
diff --git a/src/core/ext/transport/chttp2/transport/writing.cc b/src/core/ext/transport/chttp2/transport/writing.cc
index 25c1a5ef05..c6fecf2ee9 100644
--- a/src/core/ext/transport/chttp2/transport/writing.cc
+++ b/src/core/ext/transport/chttp2/transport/writing.cc
@@ -245,7 +245,8 @@ class WriteContext {
   void UpdateStreamsNoLongerStalled() {
     grpc_chttp2_stream *s;
     while (grpc_chttp2_list_pop_stalled_by_transport(t_, &s)) {
-      if (!t_->closed && grpc_chttp2_list_add_writable_stream(t_, s)) {
+      if (t_->closed_with_error == GRPC_ERROR_NONE &&
+          grpc_chttp2_list_add_writable_stream(t_, s)) {
         if (!stream_ref_if_not_destroyed(&s->refcount->refs)) {
           grpc_chttp2_list_remove_writable_stream(t_, s);
         }
diff --git a/src/core/lib/http/httpcli_security_connector.cc b/src/core/lib/http/httpcli_security_connector.cc
index ef6c4a509b..d832dacb69 100644
--- a/src/core/lib/http/httpcli_security_connector.cc
+++ b/src/core/lib/http/httpcli_security_connector.cc
@@ -91,8 +91,17 @@ static void httpcli_ssl_check_peer(grpc_exec_ctx *exec_ctx,
   tsi_peer_destruct(&peer);
 }
 
+static int httpcli_ssl_cmp(grpc_security_connector *sc1,
+                           grpc_security_connector *sc2) {
+  grpc_httpcli_ssl_channel_security_connector *c1 =
+      (grpc_httpcli_ssl_channel_security_connector *)sc1;
+  grpc_httpcli_ssl_channel_security_connector *c2 =
+      (grpc_httpcli_ssl_channel_security_connector *)sc2;
+  return strcmp(c1->secure_peer_name, c2->secure_peer_name);
+}
+
 static grpc_security_connector_vtable httpcli_ssl_vtable = {
-    httpcli_ssl_destroy, httpcli_ssl_check_peer};
+    httpcli_ssl_destroy, httpcli_ssl_check_peer, httpcli_ssl_cmp};
 
 static grpc_security_status httpcli_ssl_channel_security_connector_create(
     grpc_exec_ctx *exec_ctx, const char *pem_root_certs,
@@ -123,6 +132,10 @@ static grpc_security_status httpcli_ssl_channel_security_connector_create(
     *sc = NULL;
     return GRPC_SECURITY_ERROR;
   }
+  // We don't actually need a channel credentials object in this case,
+  // but we set it to a non-NULL address so that we don't trigger
+  // assertions in grpc_channel_security_connector_cmp().
+  c->base.channel_creds = (grpc_channel_credentials *)1;
   c->base.add_handshakers = httpcli_ssl_add_handshakers;
   *sc = &c->base;
   return GRPC_SECURITY_OK;
diff --git a/src/core/lib/security/credentials/fake/fake_credentials.cc b/src/core/lib/security/credentials/fake/fake_credentials.cc
index 795ca0660a..cf10bf24c8 100644
--- a/src/core/lib/security/credentials/fake/fake_credentials.cc
+++ b/src/core/lib/security/credentials/fake/fake_credentials.cc
@@ -38,7 +38,8 @@ static grpc_security_status fake_transport_security_create_security_connector(
     grpc_call_credentials *call_creds, const char *target,
     const grpc_channel_args *args, grpc_channel_security_connector **sc,
     grpc_channel_args **new_args) {
-  *sc = grpc_fake_channel_security_connector_create(call_creds, target, args);
+  *sc =
+      grpc_fake_channel_security_connector_create(c, call_creds, target, args);
   return GRPC_SECURITY_OK;
 }
 
@@ -46,7 +47,7 @@ static grpc_security_status
 fake_transport_security_server_create_security_connector(
     grpc_exec_ctx *exec_ctx, grpc_server_credentials *c,
     grpc_server_security_connector **sc) {
-  *sc = grpc_fake_server_security_connector_create();
+  *sc = grpc_fake_server_security_connector_create(c);
   return GRPC_SECURITY_OK;
 }
 
diff --git a/src/core/lib/security/credentials/oauth2/oauth2_credentials.cc b/src/core/lib/security/credentials/oauth2/oauth2_credentials.cc
index f52a424e36..7867105f56 100644
--- a/src/core/lib/security/credentials/oauth2/oauth2_credentials.cc
+++ b/src/core/lib/security/credentials/oauth2/oauth2_credentials.cc
@@ -262,7 +262,7 @@ static bool oauth2_token_fetcher_get_request_metadata(
   grpc_mdelem cached_access_token_md = GRPC_MDNULL;
   gpr_mu_lock(&c->mu);
   if (!GRPC_MDISNULL(c->access_token_md) &&
-      (c->token_expiration + grpc_exec_ctx_now(exec_ctx) > refresh_threshold)) {
+      (c->token_expiration - grpc_exec_ctx_now(exec_ctx) > refresh_threshold)) {
     cached_access_token_md = GRPC_MDELEM_REF(c->access_token_md);
   }
   if (!GRPC_MDISNULL(cached_access_token_md)) {
diff --git a/src/core/lib/security/credentials/ssl/ssl_credentials.cc b/src/core/lib/security/credentials/ssl/ssl_credentials.cc
index 9df69a2a3d..290336adc0 100644
--- a/src/core/lib/security/credentials/ssl/ssl_credentials.cc
+++ b/src/core/lib/security/credentials/ssl/ssl_credentials.cc
@@ -62,7 +62,8 @@ static grpc_security_status ssl_create_security_connector(
     }
   }
   status = grpc_ssl_channel_security_connector_create(
-      exec_ctx, call_creds, &c->config, target, overridden_target_name, sc);
+      exec_ctx, creds, call_creds, &c->config, target, overridden_target_name,
+      sc);
   if (status != GRPC_SECURITY_OK) {
     return status;
   }
@@ -128,7 +129,8 @@ static grpc_security_status ssl_server_create_security_connector(
     grpc_exec_ctx *exec_ctx, grpc_server_credentials *creds,
     grpc_server_security_connector **sc) {
   grpc_ssl_server_credentials *c = (grpc_ssl_server_credentials *)creds;
-  return grpc_ssl_server_security_connector_create(exec_ctx, &c->config, sc);
+  return grpc_ssl_server_security_connector_create(exec_ctx, creds, &c->config,
+                                                   sc);
 }
 
 static grpc_server_credentials_vtable ssl_server_vtable = {
diff --git a/src/core/lib/security/transport/security_connector.cc b/src/core/lib/security/transport/security_connector.cc
index 51844fb91f..80d9a7b77f 100644
--- a/src/core/lib/security/transport/security_connector.cc
+++ b/src/core/lib/security/transport/security_connector.cc
@@ -136,6 +136,39 @@ void grpc_security_connector_check_peer(grpc_exec_ctx *exec_ctx,
   }
 }
 
+int grpc_security_connector_cmp(grpc_security_connector *sc,
+                                grpc_security_connector *other) {
+  if (sc == NULL || other == NULL) return GPR_ICMP(sc, other);
+  int c = GPR_ICMP(sc->vtable, other->vtable);
+  if (c != 0) return c;
+  return sc->vtable->cmp(sc, other);
+}
+
+int grpc_channel_security_connector_cmp(grpc_channel_security_connector *sc1,
+                                        grpc_channel_security_connector *sc2) {
+  GPR_ASSERT(sc1->channel_creds != NULL);
+  GPR_ASSERT(sc2->channel_creds != NULL);
+  int c = GPR_ICMP(sc1->channel_creds, sc2->channel_creds);
+  if (c != 0) return c;
+  c = GPR_ICMP(sc1->request_metadata_creds, sc2->request_metadata_creds);
+  if (c != 0) return c;
+  c = GPR_ICMP((void *)sc1->check_call_host, (void *)sc2->check_call_host);
+  if (c != 0) return c;
+  c = GPR_ICMP((void *)sc1->cancel_check_call_host,
+               (void *)sc2->cancel_check_call_host);
+  if (c != 0) return c;
+  return GPR_ICMP((void *)sc1->add_handshakers, (void *)sc2->add_handshakers);
+}
+
+int grpc_server_security_connector_cmp(grpc_server_security_connector *sc1,
+                                       grpc_server_security_connector *sc2) {
+  GPR_ASSERT(sc1->server_creds != NULL);
+  GPR_ASSERT(sc2->server_creds != NULL);
+  int c = GPR_ICMP(sc1->server_creds, sc2->server_creds);
+  if (c != 0) return c;
+  return GPR_ICMP((void *)sc1->add_handshakers, (void *)sc2->add_handshakers);
+}
+
 bool grpc_channel_security_connector_check_call_host(
     grpc_exec_ctx *exec_ctx, grpc_channel_security_connector *sc,
     const char *host, grpc_auth_context *auth_context,
@@ -199,25 +232,27 @@ void grpc_security_connector_unref(grpc_exec_ctx *exec_ctx,
   if (gpr_unref(&sc->refcount)) sc->vtable->destroy(exec_ctx, sc);
 }
 
-static void connector_pointer_arg_destroy(grpc_exec_ctx *exec_ctx, void *p) {
+static void connector_arg_destroy(grpc_exec_ctx *exec_ctx, void *p) {
   GRPC_SECURITY_CONNECTOR_UNREF(exec_ctx, (grpc_security_connector *)p,
-                                "connector_pointer_arg_destroy");
+                                "connector_arg_destroy");
 }
 
-static void *connector_pointer_arg_copy(void *p) {
+static void *connector_arg_copy(void *p) {
   return GRPC_SECURITY_CONNECTOR_REF((grpc_security_connector *)p,
-                                     "connector_pointer_arg_copy");
+                                     "connector_arg_copy");
 }
 
-static int connector_pointer_cmp(void *a, void *b) { return GPR_ICMP(a, b); }
+static int connector_cmp(void *a, void *b) {
+  return grpc_security_connector_cmp((grpc_security_connector *)a,
+                                     (grpc_security_connector *)b);
+}
 
-static const grpc_arg_pointer_vtable connector_pointer_vtable = {
-    connector_pointer_arg_copy, connector_pointer_arg_destroy,
-    connector_pointer_cmp};
+static const grpc_arg_pointer_vtable connector_arg_vtable = {
+    connector_arg_copy, connector_arg_destroy, connector_cmp};
 
 grpc_arg grpc_security_connector_to_arg(grpc_security_connector *sc) {
   return grpc_channel_arg_pointer_create((char *)GRPC_ARG_SECURITY_CONNECTOR,
-                                         sc, &connector_pointer_vtable);
+                                         sc, &connector_arg_vtable);
 }
 
 grpc_security_connector *grpc_security_connector_from_arg(const grpc_arg *arg) {
@@ -382,6 +417,32 @@ static void fake_server_check_peer(grpc_exec_ctx *exec_ctx,
   fake_check_peer(exec_ctx, sc, peer, auth_context, on_peer_checked);
 }
 
+static int fake_channel_cmp(grpc_security_connector *sc1,
+                            grpc_security_connector *sc2) {
+  grpc_fake_channel_security_connector *c1 =
+      (grpc_fake_channel_security_connector *)sc1;
+  grpc_fake_channel_security_connector *c2 =
+      (grpc_fake_channel_security_connector *)sc2;
+  int c = grpc_channel_security_connector_cmp(&c1->base, &c2->base);
+  if (c != 0) return c;
+  c = strcmp(c1->target, c2->target);
+  if (c != 0) return c;
+  if (c1->expected_targets == NULL || c2->expected_targets == NULL) {
+    c = GPR_ICMP(c1->expected_targets, c2->expected_targets);
+  } else {
+    c = strcmp(c1->expected_targets, c2->expected_targets);
+  }
+  if (c != 0) return c;
+  return GPR_ICMP(c1->is_lb_channel, c2->is_lb_channel);
+}
+
+static int fake_server_cmp(grpc_security_connector *sc1,
+                           grpc_security_connector *sc2) {
+  return grpc_server_security_connector_cmp(
+      (grpc_server_security_connector *)sc1,
+      (grpc_server_security_connector *)sc2);
+}
+
 static bool fake_channel_check_call_host(grpc_exec_ctx *exec_ctx,
                                          grpc_channel_security_connector *sc,
                                          const char *host,
@@ -418,12 +479,13 @@ static void fake_server_add_handshakers(grpc_exec_ctx *exec_ctx,
 }
 
 static grpc_security_connector_vtable fake_channel_vtable = {
-    fake_channel_destroy, fake_channel_check_peer};
+    fake_channel_destroy, fake_channel_check_peer, fake_channel_cmp};
 
 static grpc_security_connector_vtable fake_server_vtable = {
-    fake_server_destroy, fake_server_check_peer};
+    fake_server_destroy, fake_server_check_peer, fake_server_cmp};
 
 grpc_channel_security_connector *grpc_fake_channel_security_connector_create(
+    grpc_channel_credentials *channel_creds,
     grpc_call_credentials *request_metadata_creds, const char *target,
     const grpc_channel_args *args) {
   grpc_fake_channel_security_connector *c =
@@ -431,6 +493,7 @@ grpc_channel_security_connector *grpc_fake_channel_security_connector_create(
   gpr_ref_init(&c->base.base.refcount, 1);
   c->base.base.url_scheme = GRPC_FAKE_SECURITY_URL_SCHEME;
   c->base.base.vtable = &fake_channel_vtable;
+  c->base.channel_creds = channel_creds;
   c->base.request_metadata_creds =
       grpc_call_credentials_ref(request_metadata_creds);
   c->base.check_call_host = fake_channel_check_call_host;
@@ -444,13 +507,14 @@ grpc_channel_security_connector *grpc_fake_channel_security_connector_create(
 }
 
 grpc_server_security_connector *grpc_fake_server_security_connector_create(
-    void) {
+    grpc_server_credentials *server_creds) {
   grpc_server_security_connector *c =
       (grpc_server_security_connector *)gpr_zalloc(
           sizeof(grpc_server_security_connector));
   gpr_ref_init(&c->base.refcount, 1);
   c->base.vtable = &fake_server_vtable;
   c->base.url_scheme = GRPC_FAKE_SECURITY_URL_SCHEME;
+  c->server_creds = server_creds;
   c->add_handshakers = fake_server_add_handshakers;
   return c;
 }
@@ -473,6 +537,7 @@ static void ssl_channel_destroy(grpc_exec_ctx *exec_ctx,
                                 grpc_security_connector *sc) {
   grpc_ssl_channel_security_connector *c =
       (grpc_ssl_channel_security_connector *)sc;
+  grpc_channel_credentials_unref(exec_ctx, c->base.channel_creds);
   grpc_call_credentials_unref(exec_ctx, c->base.request_metadata_creds);
   tsi_ssl_client_handshaker_factory_unref(c->client_handshaker_factory);
   c->client_handshaker_factory = NULL;
@@ -485,6 +550,7 @@ static void ssl_server_destroy(grpc_exec_ctx *exec_ctx,
                                grpc_security_connector *sc) {
   grpc_ssl_server_security_connector *c =
       (grpc_ssl_server_security_connector *)sc;
+  grpc_server_credentials_unref(exec_ctx, c->base.server_creds);
   tsi_ssl_server_handshaker_factory_unref(c->server_handshaker_factory);
   c->server_handshaker_factory = NULL;
   gpr_free(sc);
@@ -641,6 +707,29 @@ static void ssl_server_check_peer(grpc_exec_ctx *exec_ctx,
   GRPC_CLOSURE_SCHED(exec_ctx, on_peer_checked, error);
 }
 
+static int ssl_channel_cmp(grpc_security_connector *sc1,
+                           grpc_security_connector *sc2) {
+  grpc_ssl_channel_security_connector *c1 =
+      (grpc_ssl_channel_security_connector *)sc1;
+  grpc_ssl_channel_security_connector *c2 =
+      (grpc_ssl_channel_security_connector *)sc2;
+  int c = grpc_channel_security_connector_cmp(&c1->base, &c2->base);
+  if (c != 0) return c;
+  c = strcmp(c1->target_name, c2->target_name);
+  if (c != 0) return c;
+  return (c1->overridden_target_name == NULL ||
+          c2->overridden_target_name == NULL)
+             ? GPR_ICMP(c1->overridden_target_name, c2->overridden_target_name)
+             : strcmp(c1->overridden_target_name, c2->overridden_target_name);
+}
+
+static int ssl_server_cmp(grpc_security_connector *sc1,
+                          grpc_security_connector *sc2) {
+  return grpc_server_security_connector_cmp(
+      (grpc_server_security_connector *)sc1,
+      (grpc_server_security_connector *)sc2);
+}
+
 static void add_shallow_auth_property_to_peer(tsi_peer *peer,
                                               const grpc_auth_property *prop,
                                               const char *tsi_prop_name) {
@@ -717,10 +806,10 @@ static void ssl_channel_cancel_check_call_host(
 }
 
 static grpc_security_connector_vtable ssl_channel_vtable = {
-    ssl_channel_destroy, ssl_channel_check_peer};
+    ssl_channel_destroy, ssl_channel_check_peer, ssl_channel_cmp};
 
 static grpc_security_connector_vtable ssl_server_vtable = {
-    ssl_server_destroy, ssl_server_check_peer};
+    ssl_server_destroy, ssl_server_check_peer, ssl_server_cmp};
 
 /* returns a NULL terminated slice. */
 static grpc_slice compute_default_pem_root_certs_once(void) {
@@ -804,7 +893,8 @@ const char *grpc_get_default_ssl_roots(void) {
 }
 
 grpc_security_status grpc_ssl_channel_security_connector_create(
-    grpc_exec_ctx *exec_ctx, grpc_call_credentials *request_metadata_creds,
+    grpc_exec_ctx *exec_ctx, grpc_channel_credentials *channel_creds,
+    grpc_call_credentials *request_metadata_creds,
     const grpc_ssl_config *config, const char *target_name,
     const char *overridden_target_name, grpc_channel_security_connector **sc) {
   size_t num_alpn_protocols = grpc_chttp2_num_alpn_versions();
@@ -840,6 +930,7 @@ grpc_security_status grpc_ssl_channel_security_connector_create(
   gpr_ref_init(&c->base.base.refcount, 1);
   c->base.base.vtable = &ssl_channel_vtable;
   c->base.base.url_scheme = GRPC_SSL_URL_SCHEME;
+  c->base.channel_creds = grpc_channel_credentials_ref(channel_creds);
   c->base.request_metadata_creds =
       grpc_call_credentials_ref(request_metadata_creds);
   c->base.check_call_host = ssl_channel_check_call_host;
@@ -874,8 +965,8 @@ error:
 }
 
 grpc_security_status grpc_ssl_server_security_connector_create(
-    grpc_exec_ctx *exec_ctx, const grpc_ssl_server_config *config,
-    grpc_server_security_connector **sc) {
+    grpc_exec_ctx *exec_ctx, grpc_server_credentials *server_creds,
+    const grpc_ssl_server_config *config, grpc_server_security_connector **sc) {
   size_t num_alpn_protocols = grpc_chttp2_num_alpn_versions();
   const char **alpn_protocol_strings =
       (const char **)gpr_malloc(sizeof(const char *) * num_alpn_protocols);
@@ -897,6 +988,7 @@ grpc_security_status grpc_ssl_server_security_connector_create(
   gpr_ref_init(&c->base.base.refcount, 1);
   c->base.base.url_scheme = GRPC_SSL_URL_SCHEME;
   c->base.base.vtable = &ssl_server_vtable;
+  c->base.server_creds = grpc_server_credentials_ref(server_creds);
   result = tsi_create_ssl_server_handshaker_factory_ex(
       config->pem_key_cert_pairs, config->num_key_cert_pairs,
       config->pem_root_certs, get_tsi_client_certificate_request_type(
diff --git a/src/core/lib/security/transport/security_connector.h b/src/core/lib/security/transport/security_connector.h
index 4d87cd0c80..216bb35e81 100644
--- a/src/core/lib/security/transport/security_connector.h
+++ b/src/core/lib/security/transport/security_connector.h
@@ -60,13 +60,9 @@ typedef struct {
   void (*check_peer)(grpc_exec_ctx *exec_ctx, grpc_security_connector *sc,
                      tsi_peer peer, grpc_auth_context **auth_context,
                      grpc_closure *on_peer_checked);
+  int (*cmp)(grpc_security_connector *sc, grpc_security_connector *other);
 } grpc_security_connector_vtable;
 
-typedef struct grpc_security_connector_handshake_list {
-  void *handshake;
-  struct grpc_security_connector_handshake_list *next;
-} grpc_security_connector_handshake_list;
-
 struct grpc_security_connector {
   const grpc_security_connector_vtable *vtable;
   gpr_refcount refcount;
@@ -104,6 +100,10 @@ void grpc_security_connector_check_peer(grpc_exec_ctx *exec_ctx,
                                         grpc_auth_context **auth_context,
                                         grpc_closure *on_peer_checked);
 
+/* Compares two security connectors. */
+int grpc_security_connector_cmp(grpc_security_connector *sc,
+                                grpc_security_connector *other);
+
 /* Util to encapsulate the connector in a channel arg. */
 grpc_arg grpc_security_connector_to_arg(grpc_security_connector *sc);
 
@@ -116,13 +116,14 @@ grpc_security_connector *grpc_security_connector_find_in_args(
 
 /* --- channel_security_connector object. ---
 
-    A channel security connector object represents away to configure the
+    A channel security connector object represents a way to configure the
     underlying transport security mechanism on the client side.  */
 
 typedef struct grpc_channel_security_connector grpc_channel_security_connector;
 
 struct grpc_channel_security_connector {
   grpc_security_connector base;
+  grpc_channel_credentials *channel_creds;
   grpc_call_credentials *request_metadata_creds;
   bool (*check_call_host)(grpc_exec_ctx *exec_ctx,
                           grpc_channel_security_connector *sc, const char *host,
@@ -138,6 +139,10 @@ struct grpc_channel_security_connector {
                           grpc_handshake_manager *handshake_mgr);
 };
 
+/// A helper function for use in grpc_security_connector_cmp() implementations.
+int grpc_channel_security_connector_cmp(grpc_channel_security_connector *sc1,
+                                        grpc_channel_security_connector *sc2);
+
 /// Checks that the host that will be set for a call is acceptable.
 /// Returns true if completed synchronously, in which case \a error will
 /// be set to indicate the result.  Otherwise, \a on_call_host_checked
@@ -161,18 +166,23 @@ void grpc_channel_security_connector_add_handshakers(
 
 /* --- server_security_connector object. ---
 
-    A server security connector object represents away to configure the
+    A server security connector object represents a way to configure the
     underlying transport security mechanism on the server side.  */
 
 typedef struct grpc_server_security_connector grpc_server_security_connector;
 
 struct grpc_server_security_connector {
   grpc_security_connector base;
+  grpc_server_credentials *server_creds;
   void (*add_handshakers)(grpc_exec_ctx *exec_ctx,
                           grpc_server_security_connector *sc,
                           grpc_handshake_manager *handshake_mgr);
 };
 
+/// A helper function for use in grpc_security_connector_cmp() implementations.
+int grpc_server_security_connector_cmp(grpc_server_security_connector *sc1,
+                                       grpc_server_security_connector *sc2);
+
 void grpc_server_security_connector_add_handshakers(
     grpc_exec_ctx *exec_ctx, grpc_server_security_connector *sc,
     grpc_handshake_manager *handshake_mgr);
@@ -182,13 +192,14 @@ void grpc_server_security_connector_add_handshakers(
 /* For TESTING ONLY!
    Creates a fake connector that emulates real channel security.  */
 grpc_channel_security_connector *grpc_fake_channel_security_connector_create(
+    grpc_channel_credentials *channel_creds,
     grpc_call_credentials *request_metadata_creds, const char *target,
     const grpc_channel_args *args);
 
 /* For TESTING ONLY!
    Creates a fake connector that emulates real server security.  */
 grpc_server_security_connector *grpc_fake_server_security_connector_create(
-    void);
+    grpc_server_credentials *server_creds);
 
 /* Config for ssl clients. */
 
@@ -211,7 +222,8 @@ typedef struct {
   specific error code otherwise.
 */
 grpc_security_status grpc_ssl_channel_security_connector_create(
-    grpc_exec_ctx *exec_ctx, grpc_call_credentials *request_metadata_creds,
+    grpc_exec_ctx *exec_ctx, grpc_channel_credentials *channel_creds,
+    grpc_call_credentials *request_metadata_creds,
     const grpc_ssl_config *config, const char *target_name,
     const char *overridden_target_name, grpc_channel_security_connector **sc);
 
@@ -236,8 +248,8 @@ typedef struct {
   specific error code otherwise.
 */
 grpc_security_status grpc_ssl_server_security_connector_create(
-    grpc_exec_ctx *exec_ctx, const grpc_ssl_server_config *config,
-    grpc_server_security_connector **sc);
+    grpc_exec_ctx *exec_ctx, grpc_server_credentials *server_creds,
+    const grpc_ssl_server_config *config, grpc_server_security_connector **sc);
 
 /* Util. */
 const tsi_peer_property *tsi_peer_get_property_by_name(const tsi_peer *peer,
diff --git a/src/core/lib/support/cpu_linux.cc b/src/core/lib/support/cpu_linux.cc
index 2280668442..53619caa5f 100644
--- a/src/core/lib/support/cpu_linux.cc
+++ b/src/core/lib/support/cpu_linux.cc
@@ -38,8 +38,9 @@ static int ncpus = 0;
 static void init_num_cpus() {
   /* This must be signed. sysconf returns -1 when the number cannot be
      determined */
+  int cpu = sched_getcpu();
   ncpus = (int)sysconf(_SC_NPROCESSORS_ONLN);
-  if (ncpus < 1) {
+  if (ncpus < 1 || cpu < 0) {
     gpr_log(GPR_ERROR, "Cannot determine number of CPUs: assuming 1");
     ncpus = 1;
   }
@@ -56,6 +57,9 @@ unsigned gpr_cpu_current_cpu(void) {
   // sched_getcpu() is undefined on musl
   return 0;
 #else
+  if (gpr_cpu_num_cores() == 1) {
+    return 0;
+  }
   int cpu = sched_getcpu();
   if (cpu < 0) {
     gpr_log(GPR_ERROR, "Error determining current CPU: %s\n", strerror(errno));
diff --git a/src/core/lib/transport/bdp_estimator.cc b/src/core/lib/transport/bdp_estimator.cc
index 2a1c97c84e..f1597014b1 100644
--- a/src/core/lib/transport/bdp_estimator.cc
+++ b/src/core/lib/transport/bdp_estimator.cc
@@ -33,13 +33,12 @@ BdpEstimator::BdpEstimator(const char *name)
       accumulator_(0),
       estimate_(65536),
       ping_start_time_(gpr_time_0(GPR_CLOCK_MONOTONIC)),
-      next_ping_scheduled_(0),
       inter_ping_delay_(100.0),  // start at 100ms
       stable_estimate_count_(0),
       bw_est_(0),
       name_(name) {}
 
-void BdpEstimator::CompletePing(grpc_exec_ctx *exec_ctx) {
+grpc_millis BdpEstimator::CompletePing(grpc_exec_ctx *exec_ctx) {
   gpr_timespec now = gpr_now(GPR_CLOCK_MONOTONIC);
   gpr_timespec dt_ts = gpr_time_sub(now, ping_start_time_);
   double dt = (double)dt_ts.tv_sec + 1e-9 * (double)dt_ts.tv_nsec;
@@ -79,7 +78,7 @@ void BdpEstimator::CompletePing(grpc_exec_ctx *exec_ctx) {
   }
   ping_state_ = PingState::UNSCHEDULED;
   accumulator_ = 0;
-  next_ping_scheduled_ = grpc_exec_ctx_now(exec_ctx) + inter_ping_delay_;
+  return grpc_exec_ctx_now(exec_ctx) + inter_ping_delay_;
 }
 
 }  // namespace grpc_core
diff --git a/src/core/lib/transport/bdp_estimator.h b/src/core/lib/transport/bdp_estimator.h
index 6447f2d62c..470c127f7f 100644
--- a/src/core/lib/transport/bdp_estimator.h
+++ b/src/core/lib/transport/bdp_estimator.h
@@ -52,18 +52,6 @@ class BdpEstimator {
 
   void AddIncomingBytes(int64_t num_bytes) { accumulator_ += num_bytes; }
 
-  // Returns true if the user should schedule a ping
-  bool NeedPing(grpc_exec_ctx *exec_ctx) const {
-    switch (ping_state_) {
-      case PingState::UNSCHEDULED:
-        return grpc_exec_ctx_now(exec_ctx) >= next_ping_scheduled_;
-      case PingState::SCHEDULED:
-      case PingState::STARTED:
-        return false;
-    }
-    GPR_UNREACHABLE_CODE(return false);
-  }
-
   // Schedule a ping: call in response to receiving a true from
   // grpc_bdp_estimator_add_incoming_bytes once a ping has been scheduled by a
   // transport (but not necessarily started)
@@ -91,8 +79,8 @@ class BdpEstimator {
     ping_start_time_ = gpr_now(GPR_CLOCK_MONOTONIC);
   }
 
-  // Completes a previously started ping
-  void CompletePing(grpc_exec_ctx *exec_ctx);
+  // Completes a previously started ping, returns when to schedule the next one
+  grpc_millis CompletePing(grpc_exec_ctx *exec_ctx);
 
  private:
   enum class PingState { UNSCHEDULED, SCHEDULED, STARTED };
@@ -102,8 +90,6 @@ class BdpEstimator {
   int64_t estimate_;
   // when was the current ping started?
   gpr_timespec ping_start_time_;
-  // when should the next ping start?
-  grpc_millis next_ping_scheduled_;
   int inter_ping_delay_;
   int stable_estimate_count_;
   double bw_est_;
diff --git a/src/cpp/client/create_channel.cc b/src/cpp/client/create_channel.cc
index e2893c8f3c..de67281dd4 100644
--- a/src/cpp/client/create_channel.cc
+++ b/src/cpp/client/create_channel.cc
@@ -38,8 +38,7 @@ std::shared_ptr<Channel> CreateCustomChannel(
     const grpc::string& target,
     const std::shared_ptr<ChannelCredentials>& creds,
     const ChannelArguments& args) {
-  internal::GrpcLibrary
-      init_lib;  // We need to call init in case of a bad creds.
+  GrpcLibraryCodegen init_lib;  // We need to call init in case of a bad creds.
   return creds
              ? creds->CreateChannel(target, args)
              : CreateChannelInternal("", grpc_lame_client_channel_create(
diff --git a/src/objective-c/tests/GRPCClientTests.m b/src/objective-c/tests/GRPCClientTests.m
index 4d887fe970..5672bdad4c 100644
--- a/src/objective-c/tests/GRPCClientTests.m
+++ b/src/objective-c/tests/GRPCClientTests.m
@@ -289,7 +289,7 @@ static GRPCProtoMethod *kFullDuplexCallMethod;
     XCTAssertEqualObjects(userAgent, expectedUserAgent);
 
     // Change in format of user-agent field in a direction that does not match the regex will likely
-    // cause problem for certain gRPC users. @muxi for details.
+    // cause problem for certain gRPC users. For details, refer to internal doc https://goo.gl/c2diBc
     NSRegularExpression *regex =
         [NSRegularExpression regularExpressionWithPattern:@" grpc-[a-zA-Z0-9]+(-[a-zA-Z0-9]+)?/[^ ,]+( \\([^)]*\\))?"
                                                   options:0