Start fixing http error --> grpc status conversion

14 files changed, 320 insertions, 193 deletions

diff --git a/src/core/ext/transport/chttp2/transport/chttp2_transport.c b/src/core/ext/transport/chttp2/transport/chttp2_transport.c
index 858cb41ec8..3711e0cba1 100644
--- a/src/core/ext/transport/chttp2/transport/chttp2_transport.c
+++ b/src/core/ext/transport/chttp2/transport/chttp2_transport.c
@@ -44,9 +44,7 @@
 #include <grpc/support/string_util.h>
 #include <grpc/support/useful.h>
 
-#include "src/core/ext/transport/chttp2/transport/http2_errors.h"
 #include "src/core/ext/transport/chttp2/transport/internal.h"
-#include "src/core/ext/transport/chttp2/transport/status_conversion.h"
 #include "src/core/ext/transport/chttp2/transport/varint.h"
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/http/parser.h"
@@ -55,7 +53,10 @@
 #include "src/core/lib/slice/slice_internal.h"
 #include "src/core/lib/slice/slice_string_helpers.h"
 #include "src/core/lib/support/string.h"
+#include "src/core/lib/transport/error_utils.h"
+#include "src/core/lib/transport/http2_errors.h"
 #include "src/core/lib/transport/static_metadata.h"
+#include "src/core/lib/transport/status_conversion.h"
 #include "src/core/lib/transport/timeout_encoding.h"
 #include "src/core/lib/transport/transport_impl.h"
 
@@ -1458,7 +1459,7 @@ void grpc_chttp2_cancel_stream(grpc_exec_ctx *exec_ctx,
                                grpc_chttp2_transport *t, grpc_chttp2_stream *s,
                                grpc_error *due_to_error) {
   if (!t->is_client && !s->sent_trailing_metadata &&
-      grpc_error_get_int(due_to_error, GRPC_ERROR_INT_GRPC_STATUS, NULL)) {
+      grpc_error_has_clear_grpc_status(due_to_error)) {
     close_from_api(exec_ctx, t, s, due_to_error);
     return;
   }
@@ -1634,112 +1635,97 @@ static void close_from_api(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
   uint8_t *p;
   uint32_t len = 0;
   grpc_status_code grpc_status;
-  grpc_chttp2_error_code http_error;
-  status_codes_from_error(error, s->deadline, &http_error, &grpc_status);
+  const char *msg;
+  grpc_error_get_status(error, &grpc_status, &msg);
 
   GPR_ASSERT(grpc_status >= 0 && (int)grpc_status < 100);
 
-  if (s->id != 0 && !t->is_client) {
-    /* Hand roll a header block.
-       This is unnecessarily ugly - at some point we should find a more
-       elegant
-       solution.
-       It's complicated by the fact that our send machinery would be dead by
-       the
-       time we got around to sending this, so instead we ignore HPACK
-       compression
-       and just write the uncompressed bytes onto the wire. */
-    status_hdr = grpc_slice_malloc(15 + (grpc_status >= 10));
-    p = GRPC_SLICE_START_PTR(status_hdr);
-    *p++ = 0x40; /* literal header */
-    *p++ = 11;   /* len(grpc-status) */
+  /* Hand roll a header block.
+     This is unnecessarily ugly - at some point we should find a more
+     elegant solution.
+     It's complicated by the fact that our send machinery would be dead by
+     the time we got around to sending this, so instead we ignore HPACK
+     compression and just write the uncompressed bytes onto the wire. */
+  status_hdr = grpc_slice_malloc(15 + (grpc_status >= 10));
+  p = GRPC_SLICE_START_PTR(status_hdr);
+  *p++ = 0x40; /* literal header */
+  *p++ = 11;   /* len(grpc-status) */
+  *p++ = 'g';
+  *p++ = 'r';
+  *p++ = 'p';
+  *p++ = 'c';
+  *p++ = '-';
+  *p++ = 's';
+  *p++ = 't';
+  *p++ = 'a';
+  *p++ = 't';
+  *p++ = 'u';
+  *p++ = 's';
+  if (grpc_status < 10) {
+    *p++ = 1;
+    *p++ = (uint8_t)('0' + grpc_status);
+  } else {
+    *p++ = 2;
+    *p++ = (uint8_t)('0' + (grpc_status / 10));
+    *p++ = (uint8_t)('0' + (grpc_status % 10));
+  }
+  GPR_ASSERT(p == GRPC_SLICE_END_PTR(status_hdr));
+  len += (uint32_t)GRPC_SLICE_LENGTH(status_hdr);
+
+  if (msg != NULL) {
+    size_t msg_len = strlen(msg);
+    GPR_ASSERT(msg_len <= UINT32_MAX);
+    uint32_t msg_len_len = GRPC_CHTTP2_VARINT_LENGTH((uint32_t)msg_len, 0);
+    message_pfx = grpc_slice_malloc(14 + msg_len_len);
+    p = GRPC_SLICE_START_PTR(message_pfx);
+    *p++ = 0x40;
+    *p++ = 12; /* len(grpc-message) */
     *p++ = 'g';
     *p++ = 'r';
     *p++ = 'p';
     *p++ = 'c';
     *p++ = '-';
+    *p++ = 'm';
+    *p++ = 'e';
     *p++ = 's';
-    *p++ = 't';
-    *p++ = 'a';
-    *p++ = 't';
-    *p++ = 'u';
     *p++ = 's';
-    if (grpc_status < 10) {
-      *p++ = 1;
-      *p++ = (uint8_t)('0' + grpc_status);
-    } else {
-      *p++ = 2;
-      *p++ = (uint8_t)('0' + (grpc_status / 10));
-      *p++ = (uint8_t)('0' + (grpc_status % 10));
-    }
-    GPR_ASSERT(p == GRPC_SLICE_END_PTR(status_hdr));
-    len += (uint32_t)GRPC_SLICE_LENGTH(status_hdr);
-
-    const char *optional_message =
-        grpc_error_get_str(error, GRPC_ERROR_STR_GRPC_MESSAGE);
-
-    if (optional_message != NULL) {
-      size_t msg_len = strlen(optional_message);
-      GPR_ASSERT(msg_len <= UINT32_MAX);
-      uint32_t msg_len_len = GRPC_CHTTP2_VARINT_LENGTH((uint32_t)msg_len, 0);
-      message_pfx = grpc_slice_malloc(14 + msg_len_len);
-      p = GRPC_SLICE_START_PTR(message_pfx);
-      *p++ = 0x40;
-      *p++ = 12; /* len(grpc-message) */
-      *p++ = 'g';
-      *p++ = 'r';
-      *p++ = 'p';
-      *p++ = 'c';
-      *p++ = '-';
-      *p++ = 'm';
-      *p++ = 'e';
-      *p++ = 's';
-      *p++ = 's';
-      *p++ = 'a';
-      *p++ = 'g';
-      *p++ = 'e';
-      GRPC_CHTTP2_WRITE_VARINT((uint32_t)msg_len, 0, 0, p,
-                               (uint32_t)msg_len_len);
-      p += msg_len_len;
-      GPR_ASSERT(p == GRPC_SLICE_END_PTR(message_pfx));
-      len += (uint32_t)GRPC_SLICE_LENGTH(message_pfx);
-      len += (uint32_t)msg_len;
-    }
-
-    hdr = grpc_slice_malloc(9);
-    p = GRPC_SLICE_START_PTR(hdr);
-    *p++ = (uint8_t)(len >> 16);
-    *p++ = (uint8_t)(len >> 8);
-    *p++ = (uint8_t)(len);
-    *p++ = GRPC_CHTTP2_FRAME_HEADER;
-    *p++ = GRPC_CHTTP2_DATA_FLAG_END_STREAM | GRPC_CHTTP2_DATA_FLAG_END_HEADERS;
-    *p++ = (uint8_t)(s->id >> 24);
-    *p++ = (uint8_t)(s->id >> 16);
-    *p++ = (uint8_t)(s->id >> 8);
-    *p++ = (uint8_t)(s->id);
-    GPR_ASSERT(p == GRPC_SLICE_END_PTR(hdr));
-
-    grpc_slice_buffer_add(&t->qbuf, hdr);
-    grpc_slice_buffer_add(&t->qbuf, status_hdr);
-    if (optional_message) {
-      grpc_slice_buffer_add(&t->qbuf, message_pfx);
-      grpc_slice_buffer_add(&t->qbuf,
-                            grpc_slice_from_copied_string(optional_message));
-    }
-    grpc_slice_buffer_add(
-        &t->qbuf, grpc_chttp2_rst_stream_create(s->id, GRPC_CHTTP2_NO_ERROR,
-                                                &s->stats.outgoing));
-  }
-
-  const char *msg = grpc_error_get_str(error, GRPC_ERROR_STR_GRPC_MESSAGE);
-  bool free_msg = false;
-  if (msg == NULL) {
-    free_msg = true;
-    msg = grpc_error_string(error);
-  }
-  grpc_slice msg_slice = grpc_slice_from_copied_string(msg);
-  grpc_chttp2_fake_status(exec_ctx, t, s, grpc_status, &msg_slice);
-  if (free_msg) grpc_error_free_string(msg);
+    *p++ = 'a';
+    *p++ = 'g';
+    *p++ = 'e';
+    GRPC_CHTTP2_WRITE_VARINT((uint32_t)msg_len, 0, 0, p, (uint32_t)msg_len_len);
+    p += msg_len_len;
+    GPR_ASSERT(p == GRPC_SLICE_END_PTR(message_pfx));
+    len += (uint32_t)GRPC_SLICE_LENGTH(message_pfx);
+    len += (uint32_t)msg_len;
+  }
+
+  hdr = grpc_slice_malloc(9);
+  p = GRPC_SLICE_START_PTR(hdr);
+  *p++ = (uint8_t)(len >> 16);
+  *p++ = (uint8_t)(len >> 8);
+  *p++ = (uint8_t)(len);
+  *p++ = GRPC_CHTTP2_FRAME_HEADER;
+  *p++ = GRPC_CHTTP2_DATA_FLAG_END_STREAM | GRPC_CHTTP2_DATA_FLAG_END_HEADERS;
+  *p++ = (uint8_t)(s->id >> 24);
+  *p++ = (uint8_t)(s->id >> 16);
+  *p++ = (uint8_t)(s->id >> 8);
+  *p++ = (uint8_t)(s->id);
+  GPR_ASSERT(p == GRPC_SLICE_END_PTR(hdr));
+
+  grpc_slice_buffer_add(&t->qbuf, hdr);
+  grpc_slice_buffer_add(&t->qbuf, status_hdr);
+  if (msg != NULL) {
+    grpc_slice_buffer_add(&t->qbuf, message_pfx);
+    grpc_slice_buffer_add(&t->qbuf, grpc_slice_from_copied_string(msg));
+  }
+  grpc_slice_buffer_add(
+      &t->qbuf, grpc_chttp2_rst_stream_create(s->id, GRPC_CHTTP2_NO_ERROR,
+                                              &s->stats.outgoing));
+
+  grpc_slice msg_slice =
+      msg == NULL ? grpc_empty_slice() : grpc_slice_from_copied_string(msg);
+  grpc_chttp2_fake_status(exec_ctx, t, s, grpc_status,
+                          msg == NULL ? NULL : &msg_slice);
 
   grpc_chttp2_mark_stream_closed(exec_ctx, t, s, 1, 1, error);
   grpc_chttp2_initiate_write(exec_ctx, t, false, "close_from_api");
diff --git a/src/core/ext/transport/chttp2/transport/frame_settings.c b/src/core/ext/transport/chttp2/transport/frame_settings.c
index 98facae87f..bfed41fadb 100644
--- a/src/core/ext/transport/chttp2/transport/frame_settings.c
+++ b/src/core/ext/transport/chttp2/transport/frame_settings.c
@@ -43,8 +43,8 @@
 
 #include "src/core/ext/transport/chttp2/transport/chttp2_transport.h"
 #include "src/core/ext/transport/chttp2/transport/frame.h"
-#include "src/core/ext/transport/chttp2/transport/http2_errors.h"
 #include "src/core/lib/debug/trace.h"
+#include "src/core/lib/transport/http2_errors.h"
 
 #define MAX_MAX_HEADER_LIST_SIZE (1024 * 1024 * 1024)
 
diff --git a/src/core/ext/transport/chttp2/transport/hpack_parser.c b/src/core/ext/transport/chttp2/transport/hpack_parser.c
index 2a14167f67..6d6d0de742 100644
--- a/src/core/ext/transport/chttp2/transport/hpack_parser.c
+++ b/src/core/ext/transport/chttp2/transport/hpack_parser.c
@@ -50,10 +50,10 @@
 #include <grpc/support/useful.h>
 
 #include "src/core/ext/transport/chttp2/transport/bin_encoder.h"
-#include "src/core/ext/transport/chttp2/transport/http2_errors.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/slice/slice_internal.h"
 #include "src/core/lib/support/string.h"
+#include "src/core/lib/transport/http2_errors.h"
 
 /* TODO(ctiller): remove before submission */
 #include "src/core/lib/slice/slice_string_helpers.h"
diff --git a/src/core/lib/iomgr/error.c b/src/core/lib/iomgr/error.c
index 227c94020f..3cf644f421 100644
--- a/src/core/lib/iomgr/error.c
+++ b/src/core/lib/iomgr/error.c
@@ -33,13 +33,10 @@
 
 #include "src/core/lib/iomgr/error.h"
 
-#include <inttypes.h>
-#include <stdbool.h>
 #include <string.h>
 
 #include <grpc/status.h>
 #include <grpc/support/alloc.h>
-#include <grpc/support/avl.h>
 #include <grpc/support/log.h>
 #include <grpc/support/string_util.h>
 #include <grpc/support/useful.h>
@@ -48,6 +45,7 @@
 #include <grpc/support/log_windows.h>
 #endif
 
+#include "src/core/lib/iomgr/error_internal.h"
 #include "src/core/lib/profiling/timers.h"
 
 static void destroy_integer(void *key) {}
@@ -164,16 +162,7 @@ static const char *error_time_name(grpc_error_times key) {
   GPR_UNREACHABLE_CODE(return "unknown");
 }
 
-struct grpc_error {
-  gpr_refcount refs;
-  gpr_avl ints;
-  gpr_avl strs;
-  gpr_avl times;
-  gpr_avl errs;
-  uintptr_t next_err;
-};
-
-static bool is_special(grpc_error *err) {
+bool grpc_error_is_special(grpc_error *err) {
   return err == GRPC_ERROR_NONE || err == GRPC_ERROR_OOM ||
          err == GRPC_ERROR_CANCELLED;
 }
@@ -189,14 +178,14 @@ grpc_error *grpc_error_ref(grpc_error *err, const char *file, int line,
 }
 #else
 grpc_error *grpc_error_ref(grpc_error *err) {
-  if (is_special(err)) return err;
+  if (grpc_error_is_special(err)) return err;
   gpr_ref(&err->refs);
   return err;
 }
 #endif
 
 static void error_destroy(grpc_error *err) {
-  GPR_ASSERT(!is_special(err));
+  GPR_ASSERT(!grpc_error_is_special(err));
   gpr_avl_unref(err->ints);
   gpr_avl_unref(err->strs);
   gpr_avl_unref(err->errs);
@@ -216,7 +205,7 @@ void grpc_error_unref(grpc_error *err, const char *file, int line,
 }
 #else
 void grpc_error_unref(grpc_error *err) {
-  if (is_special(err)) return;
+  if (grpc_error_is_special(err)) return;
   if (gpr_unref(&err->refs)) {
     error_destroy(err);
   }
@@ -259,7 +248,7 @@ grpc_error *grpc_error_create(const char *file, int line, const char *desc,
 static grpc_error *copy_error_and_unref(grpc_error *in) {
   GPR_TIMER_BEGIN("copy_error_and_unref", 0);
   grpc_error *out;
-  if (is_special(in)) {
+  if (grpc_error_is_special(in)) {
     if (in == GRPC_ERROR_NONE)
       out = grpc_error_set_int(GRPC_ERROR_CREATE("no error"),
                                GRPC_ERROR_INT_GRPC_STATUS, GRPC_STATUS_OK);
@@ -297,14 +286,29 @@ grpc_error *grpc_error_set_int(grpc_error *src, grpc_error_ints which,
   return new;
 }
 
+typedef struct {
+  grpc_error *error;
+  grpc_status_code code;
+  const char *msg;
+} special_error_status_map;
+static special_error_status_map error_status_map[] = {
+    {GRPC_ERROR_NONE, GRPC_STATUS_OK, NULL},
+    {GRPC_ERROR_CANCELLED, GRPC_STATUS_CANCELLED, "Cancelled"},
+    {GRPC_ERROR_OOM, GRPC_STATUS_RESOURCE_EXHAUSTED, "Out of memory"},
+};
+
 bool grpc_error_get_int(grpc_error *err, grpc_error_ints which, intptr_t *p) {
   GPR_TIMER_BEGIN("grpc_error_get_int", 0);
   void *pp;
-  if (is_special(err)) {
-    if (err == GRPC_ERROR_CANCELLED && which == GRPC_ERROR_INT_GRPC_STATUS) {
-      *p = GRPC_STATUS_CANCELLED;
-      GPR_TIMER_END("grpc_error_get_int", 0);
-      return true;
+  if (grpc_error_is_special(err)) {
+    if (which == GRPC_ERROR_INT_GRPC_STATUS) {
+      for (size_t i = 0; i < GPR_ARRAY_SIZE(error_status_map); i++) {
+        if (error_status_map[i].error == err) {
+          if (p != NULL) *p = error_status_map[i].code;
+          GPR_TIMER_END("grpc_error_get_int", 0);
+          return true;
+        }
+      }
     }
     GPR_TIMER_END("grpc_error_get_int", 0);
     return false;
@@ -329,67 +333,17 @@ grpc_error *grpc_error_set_str(grpc_error *src, grpc_error_strs which,
 }
 
 const char *grpc_error_get_str(grpc_error *err, grpc_error_strs which) {
-  if (is_special(err)) return NULL;
-  return gpr_avl_get(err->strs, (void *)(uintptr_t)which);
-}
-
-typedef struct {
-  grpc_error *error;
-  grpc_status_code code;
-  const char *msg;
-} special_error_status_map;
-static special_error_status_map error_status_map[] = {
-    {GRPC_ERROR_NONE, GRPC_STATUS_OK, ""},
-    {GRPC_ERROR_CANCELLED, GRPC_STATUS_CANCELLED, "RPC cancelled"},
-    {GRPC_ERROR_OOM, GRPC_STATUS_RESOURCE_EXHAUSTED, "Out of memory"},
-};
-
-static grpc_error *recursively_find_error_with_status(grpc_error *error,
-                                                      intptr_t *status) {
-  // If the error itself has a status code, return it.
-  if (grpc_error_get_int(error, GRPC_ERROR_INT_GRPC_STATUS, status)) {
-    return error;
-  }
-  if (is_special(error)) return NULL;
-  // Otherwise, search through its children.
-  intptr_t key = 0;
-  while (true) {
-    grpc_error *child_error = gpr_avl_get(error->errs, (void *)key++);
-    if (child_error == NULL) break;
-    grpc_error *result =
-        recursively_find_error_with_status(child_error, status);
-    if (result != NULL) return result;
-  }
-  return NULL;
-}
-
-void grpc_error_get_status(grpc_error *error, grpc_status_code *code,
-                           const char **msg) {
-  // Handle special errors via the static map.
-  for (size_t i = 0; i < GPR_ARRAY_SIZE(error_status_map); ++i) {
-    if (error == error_status_map[i].error) {
-      *code = error_status_map[i].code;
-      *msg = error_status_map[i].msg;
-      return;
+  if (grpc_error_is_special(err)) {
+    if (which == GRPC_ERROR_STR_GRPC_MESSAGE) {
+      for (size_t i = 0; i < GPR_ARRAY_SIZE(error_status_map); i++) {
+        if (error_status_map[i].error == err) {
+          return error_status_map[i].msg;
+        }
+      }
     }
+    return NULL;
   }
-  // Populate code.
-  // Start with the parent error and recurse through the tree of children
-  // until we find the first one that has a status code.
-  intptr_t status = GRPC_STATUS_UNKNOWN;  // Default in case we don't find one.
-  grpc_error *found_error = recursively_find_error_with_status(error, &status);
-  *code = (grpc_status_code)status;
-  // Now populate msg.
-  // If we found an error with a status code above, use that; otherwise,
-  // fall back to using the parent error.
-  if (found_error == NULL) found_error = error;
-  // If the error has a status message, use it.  Otherwise, fall back to
-  // the error description.
-  *msg = grpc_error_get_str(found_error, GRPC_ERROR_STR_GRPC_MESSAGE);
-  if (*msg == NULL && status != GRPC_STATUS_OK) {
-    *msg = grpc_error_get_str(found_error, GRPC_ERROR_STR_DESCRIPTION);
-    if (*msg == NULL) *msg = "unknown error";  // Just in case.
-  }
+  return gpr_avl_get(err->strs, (void *)(uintptr_t)which);
 }
 
 grpc_error *grpc_error_add_child(grpc_error *src, grpc_error *child) {
diff --git a/src/core/lib/iomgr/error.h b/src/core/lib/iomgr/error.h
index a2ba84deed..75ca9c4bf9 100644
--- a/src/core/lib/iomgr/error.h
+++ b/src/core/lib/iomgr/error.h
@@ -193,12 +193,6 @@ grpc_error *grpc_error_set_str(grpc_error *src, grpc_error_strs which,
 /// Caller does NOT own return value.
 const char *grpc_error_get_str(grpc_error *error, grpc_error_strs which);
 
-/// A utility function to get the status code and message to be returned
-/// to the application.  If not set in the top-level message, looks
-/// through child errors until it finds the first one with these attributes.
-void grpc_error_get_status(grpc_error *error, grpc_status_code *code,
-                           const char **msg);
-
 /// Add a child error: an error that is believed to have contributed to this
 /// error occurring. Allows root causing high level errors from lower level
 /// errors that contributed to them.
diff --git a/src/core/lib/iomgr/error_internal.h b/src/core/lib/iomgr/error_internal.h
new file mode 100644
index 0000000000..5afe9edc7f
--- /dev/null
+++ b/src/core/lib/iomgr/error_internal.h
@@ -0,0 +1,53 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_ERROR_INTERNAL_H
+#define GRPC_ERROR_INTERNAL_H
+
+#include <inttypes.h>
+#include <stdbool.h>
+
+#include <grpc/support/avl.h>
+
+struct grpc_error {
+  gpr_refcount refs;
+  gpr_avl ints;
+  gpr_avl strs;
+  gpr_avl times;
+  gpr_avl errs;
+  uintptr_t next_err;
+};
+
+bool grpc_error_is_special(grpc_error *err);
+
+#endif
diff --git a/src/core/lib/security/transport/server_auth_filter.c b/src/core/lib/security/transport/server_auth_filter.c
index 6b04ad2385..36e81d6501 100644
--- a/src/core/lib/security/transport/server_auth_filter.c
+++ b/src/core/lib/security/transport/server_auth_filter.c
@@ -130,7 +130,6 @@ static void on_md_processing_done(
     grpc_metadata_array_destroy(&calld->md);
     grpc_closure_sched(&exec_ctx, calld->on_done_recv, GRPC_ERROR_NONE);
   } else {
-    grpc_slice message;
     for (size_t i = 0; i < calld->md.count; i++) {
       grpc_slice_unref_internal(&exec_ctx, calld->md.metadata[i].key);
       grpc_slice_unref_internal(&exec_ctx, calld->md.metadata[i].value);
@@ -139,7 +138,6 @@ static void on_md_processing_done(
     error_details = error_details != NULL
                         ? error_details
                         : "Authentication metadata processing failed.";
-    message = grpc_slice_from_copied_string(error_details);
     calld->transport_op->send_initial_metadata = NULL;
     if (calld->transport_op->send_message != NULL) {
       grpc_byte_stream_destroy(&exec_ctx, calld->transport_op->send_message);
diff --git a/src/core/lib/surface/call.c b/src/core/lib/surface/call.c
index 57603ca386..4abf981997 100644
--- a/src/core/lib/surface/call.c
+++ b/src/core/lib/surface/call.c
@@ -56,6 +56,7 @@
 #include "src/core/lib/surface/call.h"
 #include "src/core/lib/surface/channel.h"
 #include "src/core/lib/surface/completion_queue.h"
+#include "src/core/lib/transport/error_utils.h"
 #include "src/core/lib/transport/metadata.h"
 #include "src/core/lib/transport/static_metadata.h"
 #include "src/core/lib/transport/transport.h"
diff --git a/src/core/lib/transport/error_utils.c b/src/core/lib/transport/error_utils.c
new file mode 100644
index 0000000000..6403cf80d8
--- /dev/null
+++ b/src/core/lib/transport/error_utils.c
@@ -0,0 +1,90 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/lib/transport/error_utils.h"
+#include "src/core/lib/iomgr/error_internal.h"
+
+static grpc_error *recursively_find_error_with_status(grpc_error *error,
+                                                      intptr_t *status) {
+  // If the error itself has a status code, return it.
+  if (grpc_error_get_int(error, GRPC_ERROR_INT_GRPC_STATUS, status)) {
+    return error;
+  }
+  if (grpc_error_is_special(error)) return NULL;
+  // Otherwise, search through its children.
+  intptr_t key = 0;
+  while (true) {
+    grpc_error *child_error = gpr_avl_get(error->errs, (void *)key++);
+    if (child_error == NULL) break;
+    grpc_error *result =
+        recursively_find_error_with_status(child_error, status);
+    if (result != NULL) return result;
+  }
+  return NULL;
+}
+
+void grpc_error_get_status(grpc_error *error, grpc_status_code *code,
+                           const char **msg) {
+  // Populate code.
+  // Start with the parent error and recurse through the tree of children
+  // until we find the first one that has a status code.
+  intptr_t status = GRPC_STATUS_UNKNOWN;  // Default in case we don't find one.
+  grpc_error *found_error = recursively_find_error_with_status(error, &status);
+  *code = (grpc_status_code)status;
+  // Now populate msg.
+  // If we found an error with a status code above, use that; otherwise,
+  // fall back to using the parent error.
+  if (found_error == NULL) found_error = error;
+  // If the error has a status message, use it.  Otherwise, fall back to
+  // the error description.
+  *msg = grpc_error_get_str(found_error, GRPC_ERROR_STR_GRPC_MESSAGE);
+  if (*msg == NULL && status != GRPC_STATUS_OK) {
+    *msg = grpc_error_get_str(found_error, GRPC_ERROR_STR_DESCRIPTION);
+    if (*msg == NULL) *msg = "unknown error";  // Just in case.
+  }
+}
+
+bool grpc_error_has_clear_grpc_status(grpc_error *error) {
+  if (grpc_error_get_int(error, GRPC_ERROR_INT_GRPC_STATUS, NULL)) {
+    return true;
+  }
+  intptr_t key = 0;
+  while (true) {
+    grpc_error *child_error = gpr_avl_get(error->errs, (void *)key++);
+    if (child_error == NULL) break;
+    if (grpc_error_has_clear_grpc_status(child_error)) {
+      return true;
+    }
+  }
+  return false;
+}
diff --git a/src/core/lib/transport/error_utils.h b/src/core/lib/transport/error_utils.h
new file mode 100644
index 0000000000..541dba852f
--- /dev/null
+++ b/src/core/lib/transport/error_utils.h
@@ -0,0 +1,50 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_ERROR_UTILS_H
+#define GRPC_ERROR_UTILS_H
+
+#include "src/core/lib/iomgr/error.h"
+
+/// A utility function to get the status code and message to be returned
+/// to the application.  If not set in the top-level message, looks
+/// through child errors until it finds the first one with these attributes.
+void grpc_error_get_status(grpc_error *error, grpc_status_code *code,
+                           const char **msg);
+/// A utility function to check whether there is a clear status code that
+/// doesn't need to be guessed in \a error. This means that \a error or some
+/// child has GRPC_ERROR_INT_GRPC_STATUS set, or that it is GRPC_ERROR_NONE or
+/// GRPC_ERROR_CANCELLED
+bool grpc_error_has_clear_grpc_status(grpc_error *error);
+
+#endif
diff --git a/src/core/ext/transport/chttp2/transport/http2_errors.h b/src/core/lib/transport/http2_errors.h
index deab2b7e3e..deab2b7e3e 100644
--- a/src/core/ext/transport/chttp2/transport/http2_errors.h
+++ b/src/core/lib/transport/http2_errors.h
diff --git a/src/core/ext/transport/chttp2/transport/status_conversion.c b/src/core/lib/transport/status_conversion.c
index 5dce2f2d0c..eb1d53c8d1 100644
--- a/src/core/ext/transport/chttp2/transport/status_conversion.c
+++ b/src/core/lib/transport/status_conversion.c
@@ -31,7 +31,7 @@
  *
  */
 
-#include "src/core/ext/transport/chttp2/transport/status_conversion.h"
+#include "src/core/lib/transport/status_conversion.h"
 
 int grpc_chttp2_grpc_status_to_http2_error(grpc_status_code status) {
   switch (status) {
diff --git a/src/core/ext/transport/chttp2/transport/status_conversion.h b/src/core/lib/transport/status_conversion.h
index 953bc9f1e1..592411529d 100644
--- a/src/core/ext/transport/chttp2/transport/status_conversion.h
+++ b/src/core/lib/transport/status_conversion.h
@@ -35,7 +35,7 @@
 #define GRPC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_STATUS_CONVERSION_H
 
 #include <grpc/grpc.h>
-#include "src/core/ext/transport/chttp2/transport/http2_errors.h"
+#include "src/core/lib/transport/http2_errors.h"
 
 /* Conversion of grpc status codes to http2 error codes (for RST_STREAM) */
 grpc_chttp2_error_code grpc_chttp2_grpc_status_to_http2_error(
diff --git a/src/python/grpcio/grpc_core_dependencies.py b/src/python/grpcio/grpc_core_dependencies.py
index 8397224a02..dfb64f8744 100644
--- a/src/python/grpcio/grpc_core_dependencies.py
+++ b/src/python/grpcio/grpc_core_dependencies.py
@@ -180,11 +180,13 @@ CORE_SOURCE_FILES = [
   'src/core/lib/surface/version.c',
   'src/core/lib/transport/byte_stream.c',
   'src/core/lib/transport/connectivity_state.c',
+  'src/core/lib/transport/error_utils.c',
   'src/core/lib/transport/metadata.c',
   'src/core/lib/transport/metadata_batch.c',
   'src/core/lib/transport/pid_controller.c',
   'src/core/lib/transport/service_config.c',
   'src/core/lib/transport/static_metadata.c',
+  'src/core/lib/transport/status_conversion.c',
   'src/core/lib/transport/timeout_encoding.c',
   'src/core/lib/transport/transport.c',
   'src/core/lib/transport/transport_op_string.c',
@@ -205,7 +207,6 @@ CORE_SOURCE_FILES = [
   'src/core/ext/transport/chttp2/transport/huffsyms.c',
   'src/core/ext/transport/chttp2/transport/incoming_metadata.c',
   'src/core/ext/transport/chttp2/transport/parsing.c',
-  'src/core/ext/transport/chttp2/transport/status_conversion.c',
   'src/core/ext/transport/chttp2/transport/stream_lists.c',
   'src/core/ext/transport/chttp2/transport/stream_map.c',
   'src/core/ext/transport/chttp2/transport/varint.c',