1 files changed, 16 insertions, 2 deletions
diff --git a/src/core/lib/channel/channel_args.c b/src/core/lib/channel/channel_args.c
index 247b134938..2df07c8ae6 100644
--- a/src/core/lib/channel/channel_args.c
+++ b/src/core/lib/channel/channel_args.c
@@ -129,9 +129,23 @@ grpc_channel_args *grpc_channel_args_copy(const grpc_channel_args *src) {
   return grpc_channel_args_copy_and_add(src, NULL, 0);
 }
 
-grpc_channel_args *grpc_channel_args_merge(const grpc_channel_args *a,
+grpc_channel_args *grpc_channel_args_union(const grpc_channel_args *a,
                                            const grpc_channel_args *b) {
-  return grpc_channel_args_copy_and_add(a, b->args, b->num_args);
+  const size_t max_out = (a->num_args + b->num_args);
+  grpc_arg *uniques = gpr_malloc(sizeof(*uniques) * max_out);
+  for (size_t i = 0; i < a->num_args; ++i) uniques[i] = a->args[i];
+
+  size_t uniques_idx = a->num_args;
+  for (size_t i = 0; i < b->num_args; ++i) {
+    const char *b_key = b->args[i].key;
+    if (grpc_channel_args_find(a, b_key) == NULL) {  // not found
+      uniques[uniques_idx++] = b->args[i];
+    }
+  }
+  grpc_channel_args *result =
+      grpc_channel_args_copy_and_add(NULL, uniques, uniques_idx);
+  gpr_free(uniques);
+  return result;
 }
 
 static int cmp_arg(const grpc_arg *a, const grpc_arg *b) {