using URI query to communicate payload

When using GET verb, the request payload is now communicated as a base64
encoded string in the query parameter. Deleted the code that wrote/read
a custom header field (payload-bin), since caches don't consider this
field when looking for a cache hit.

src/core/lib/channel/http_client_filter.c

@@ -36,6 +36,7 @@
 #include <grpc/support/string_util.h>
 #include <string.h>
 #include "src/core/lib/profiling/timers.h"
+#include "src/core/lib/security/util/b64.h"
 #include "src/core/lib/slice/percent_encoding.h"
 #include "src/core/lib/slice/slice_internal.h"
 #include "src/core/lib/slice/slice_string_helpers.h"
@@ -56,7 +57,6 @@ typedef struct call_data {
   grpc_linked_mdelem te_trailers;
   grpc_linked_mdelem content_type;
   grpc_linked_mdelem user_agent;
-  grpc_linked_mdelem payload_bin;
 
   grpc_metadata_batch *recv_initial_metadata;
   grpc_metadata_batch *recv_trailing_metadata;
@@ -292,16 +292,37 @@ static grpc_error *hc_mutate_op(grpc_exec_ctx *exec_ctx,
       continue_send_message(exec_ctx, elem);
 
       if (calld->send_message_blocked == false) {
-        /* when all the send_message data is available, then create a MDELEM and
-        append to headers */
-        grpc_mdelem payload_bin = grpc_mdelem_from_slices(
-            exec_ctx, GRPC_MDSTR_GRPC_PAYLOAD_BIN,
-            grpc_slice_from_copied_buffer((const char *)calld->payload_bytes,
-                                          op->send_message->length));
-        error =
-            grpc_metadata_batch_add_tail(exec_ctx, op->send_initial_metadata,
-                                         &calld->payload_bin, payload_bin);
+        /* when all the send_message data is available, then modify the path
+         * MDELEM by appending base64 encoded query to the path */
+        static const int k_url_safe = 1;
+        static const int k_multi_line = 0;
+        static char *k_query_separator = "?";
+        char *strs_to_concatenate[3];
+        strs_to_concatenate[0] = grpc_dump_slice(
+            GRPC_MDVALUE(op->send_initial_metadata->idx.named.path->md),
+            GPR_DUMP_ASCII);
+        strs_to_concatenate[1] = k_query_separator;
+        strs_to_concatenate[2] = grpc_base64_encode(
+            (const void *)calld->payload_bytes, op->send_message->length,
+            k_url_safe, k_multi_line);
+        size_t concatenated_len;
+        char *path_with_query = gpr_strjoin((const char **)strs_to_concatenate,
+                                            3, &concatenated_len);
+        gpr_log(GPR_DEBUG, "Path with query: %s\n", path_with_query);
+        gpr_free(strs_to_concatenate[0]);
+        gpr_free(strs_to_concatenate[2]);
+
+        /* substitute previous path with the new path */
+        grpc_mdelem mdelem_path_and_query = grpc_mdelem_from_slices(
+            exec_ctx, GRPC_MDSTR_PATH,
+            grpc_slice_from_copied_buffer((const char *)path_with_query,
+                                          concatenated_len));
+        gpr_free(path_with_query);
+        grpc_metadata_batch *b = op->send_initial_metadata;
+        error = grpc_metadata_batch_substitute(exec_ctx, b, b->idx.named.path,
+                                               mdelem_path_and_query);
         if (error != GRPC_ERROR_NONE) return error;
+
         calld->on_complete = op->on_complete;
         op->on_complete = &calld->hc_on_complete;
         op->send_message = NULL;

src/core/lib/channel/http_server_filter.c

@@ -37,6 +37,7 @@
 #include <grpc/support/log.h>
 #include <string.h>
 #include "src/core/lib/profiling/timers.h"
+#include "src/core/lib/security/util/b64.h"
 #include "src/core/lib/slice/percent_encoding.h"
 #include "src/core/lib/slice/slice_internal.h"
 #include "src/core/lib/slice/slice_string_helpers.h"
@@ -51,8 +52,8 @@ typedef struct call_data {
   grpc_linked_mdelem status;
   grpc_linked_mdelem content_type;
 
-  /* did this request come with payload-bin */
-  bool seen_payload_bin;
+  /* did this request come with path query containing request payload */
+  bool seen_path_with_query;
   /* flag to ensure payload_bin is delivered only once */
   bool payload_bin_delivered;
 
@@ -61,7 +62,7 @@ typedef struct call_data {
   bool *recv_cacheable_request;
   /** Closure to call when finished with the hs_on_recv hook */
   grpc_closure *on_done_recv;
-  /** Closure to call when we retrieve read message from the payload-bin header
+  /** Closure to call when we retrieve read message from the path URI
    */
   grpc_closure *recv_message_ready;
   grpc_closure *on_complete;
@@ -196,6 +197,35 @@ static grpc_error *server_filter_incoming_metadata(grpc_exec_ctx *exec_ctx,
     add_error(error_name, &error,
               grpc_error_set_str(GRPC_ERROR_CREATE("Missing header"),
                                  GRPC_ERROR_STR_KEY, ":path"));
+  } else if (*calld->recv_cacheable_request == true) {
+    /* We have a cacheable request made with GET verb. The path contains the
+     * query parameter which is base64 encoded request payload. */
+    char *path =
+        grpc_dump_slice(GRPC_MDVALUE(b->idx.named.path->md), GPR_DUMP_ASCII);
+    static const char *QUERY_SEPARATOR = "?";
+    char **query_parts;
+    size_t num_query_parts;
+    gpr_string_split(path, QUERY_SEPARATOR, &query_parts, &num_query_parts);
+    GPR_ASSERT(num_query_parts == 2);
+    /* substitute path metadata with just the path (not query) */
+    grpc_mdelem mdelem_path_without_query = grpc_mdelem_from_slices(
+        exec_ctx, GRPC_MDSTR_PATH,
+        grpc_slice_from_copied_buffer((const char *)query_parts[0],
+                                      strlen(query_parts[0])));
+    grpc_metadata_batch_substitute(exec_ctx, b, b->idx.named.path,
+                                   mdelem_path_without_query);
+    gpr_free(query_parts[0]);
+
+    /* decode query into payload and add it to the slice buffer to be returned
+     * */
+    static const int k_url_safe = 1;
+    grpc_slice_buffer_add(
+        &calld->read_slice_buffer,
+        grpc_base64_decode(exec_ctx, (const char *)query_parts[1], k_url_safe));
+    grpc_slice_buffer_stream_init(&calld->read_stream,
+                                  &calld->read_slice_buffer, 0);
+    gpr_free(query_parts[1]);
+    calld->seen_path_with_query = true;
   }
 
   if (b->idx.named.host != NULL && b->idx.named.authority == NULL) {
@@ -217,16 +247,6 @@ static grpc_error *server_filter_incoming_metadata(grpc_exec_ctx *exec_ctx,
                                  GRPC_ERROR_STR_KEY, ":authority"));
   }
 
-  if (b->idx.named.grpc_payload_bin != NULL) {
-    calld->seen_payload_bin = true;
-    grpc_slice_buffer_add(&calld->read_slice_buffer,
-                          grpc_slice_ref_internal(
-                              GRPC_MDVALUE(b->idx.named.grpc_payload_bin->md)));
-    grpc_slice_buffer_stream_init(&calld->read_stream,
-                                  &calld->read_slice_buffer, 0);
-    grpc_metadata_batch_remove(exec_ctx, b, b->idx.named.grpc_payload_bin);
-  }
-
   return error;
 }
 
@@ -247,8 +267,8 @@ static void hs_on_complete(grpc_exec_ctx *exec_ctx, void *user_data,
                            grpc_error *err) {
   grpc_call_element *elem = user_data;
   call_data *calld = elem->call_data;
-  /* Call recv_message_ready if we got the payload via the header field */
-  if (calld->seen_payload_bin && calld->recv_message_ready != NULL) {
+  /* Call recv_message_ready if we got the payload via the path field */
+  if (calld->seen_path_with_query && calld->recv_message_ready != NULL) {
     *calld->pp_recv_message = calld->payload_bin_delivered
                                   ? NULL
                                   : (grpc_byte_stream *)&calld->read_stream;
@@ -263,7 +283,7 @@ static void hs_recv_message_ready(grpc_exec_ctx *exec_ctx, void *user_data,
                                   grpc_error *err) {
   grpc_call_element *elem = user_data;
   call_data *calld = elem->call_data;
-  if (calld->seen_payload_bin) {
+  if (calld->seen_path_with_query) {
     /* do nothing. This is probably a GET request, and payload will be returned
     in hs_on_complete callback. */
   } else {