Merge pull request #8192 from dgquintas/resolver_prefix

Rewrote handling of default resolver prefix

src/core/ext/client_config/client_config_plugin.c

@@ -43,10 +43,6 @@
 #include "src/core/ext/client_config/subchannel_index.h"
 #include "src/core/lib/surface/channel_init.h"
 
-#ifndef GRPC_DEFAULT_NAME_PREFIX
-#define GRPC_DEFAULT_NAME_PREFIX "dns:///"
-#endif
-
 static bool append_filter(grpc_channel_stack_builder *builder, void *arg) {
   return grpc_channel_stack_builder_append_filter(
       builder, (const grpc_channel_filter *)arg, NULL, NULL);
@@ -79,7 +75,7 @@ static bool set_default_host_if_unset(grpc_channel_stack_builder *builder,
 
 void grpc_client_config_init(void) {
   grpc_lb_policy_registry_init();
-  grpc_resolver_registry_init(GRPC_DEFAULT_NAME_PREFIX);
+  grpc_resolver_registry_init();
   grpc_subchannel_index_init();
   grpc_channel_init_register_stage(GRPC_CLIENT_CHANNEL, INT_MIN,
                                    set_default_host_if_unset, NULL);

src/core/ext/client_config/resolver_registry.c

@@ -40,22 +40,20 @@
 #include <grpc/support/string_util.h>
 
 #define MAX_RESOLVERS 10
+#define DEFAULT_RESOLVER_PREFIX_MAX_LENGTH 32
 
 static grpc_resolver_factory *g_all_of_the_resolvers[MAX_RESOLVERS];
 static int g_number_of_resolvers = 0;
 
-static char *g_default_resolver_prefix;
+static char g_default_resolver_prefix[DEFAULT_RESOLVER_PREFIX_MAX_LENGTH] =
+    "dns:///";
 
-void grpc_resolver_registry_init(const char *default_resolver_prefix) {
-  g_default_resolver_prefix = gpr_strdup(default_resolver_prefix);
-}
+void grpc_resolver_registry_init() {}
 
 void grpc_resolver_registry_shutdown(void) {
-  int i;
-  for (i = 0; i < g_number_of_resolvers; i++) {
+  for (int i = 0; i < g_number_of_resolvers; i++) {
     grpc_resolver_factory_unref(g_all_of_the_resolvers[i]);
   }
-  gpr_free(g_default_resolver_prefix);
   // FIXME(ctiller): this should live in grpc_resolver_registry_init,
   // however that would have the client_config plugin call this AFTER we start
   // registering resolvers from third party plugins, and so they'd never show
@@ -65,6 +63,17 @@ void grpc_resolver_registry_shutdown(void) {
   g_number_of_resolvers = 0;
 }
 
+void grpc_resolver_registry_set_default_prefix(
+    const char *default_resolver_prefix) {
+  const size_t len = strlen(default_resolver_prefix);
+  GPR_ASSERT(len < DEFAULT_RESOLVER_PREFIX_MAX_LENGTH &&
+             "default resolver prefix too long");
+  GPR_ASSERT(len > 0 && "default resolver prefix can't be empty");
+  // By the previous assert, default_resolver_prefix is safe to be copied with a
+  // plain strcpy.
+  strcpy(g_default_resolver_prefix, default_resolver_prefix);
+}
+
 void grpc_register_resolver_type(grpc_resolver_factory *factory) {
   int i;
   for (i = 0; i < g_number_of_resolvers; i++) {
@@ -108,22 +117,16 @@ static grpc_resolver_factory *resolve_factory(const char *target,
   *uri = grpc_uri_parse(target, 1);
   factory = lookup_factory_by_uri(*uri);
   if (factory == NULL) {
-    if (g_default_resolver_prefix != NULL) {
-      grpc_uri_destroy(*uri);
-      gpr_asprintf(&tmp, "%s%s", g_default_resolver_prefix, target);
-      *uri = grpc_uri_parse(tmp, 1);
-      factory = lookup_factory_by_uri(*uri);
-      if (factory == NULL) {
-        grpc_uri_destroy(grpc_uri_parse(target, 0));
-        grpc_uri_destroy(grpc_uri_parse(tmp, 0));
-        gpr_log(GPR_ERROR, "don't know how to resolve '%s' or '%s'", target,
-                tmp);
-      }
-      gpr_free(tmp);
-    } else {
+    grpc_uri_destroy(*uri);
+    gpr_asprintf(&tmp, "%s%s", g_default_resolver_prefix, target);
+    *uri = grpc_uri_parse(tmp, 1);
+    factory = lookup_factory_by_uri(*uri);
+    if (factory == NULL) {
       grpc_uri_destroy(grpc_uri_parse(target, 0));
-      gpr_log(GPR_ERROR, "don't know how to resolve '%s'", target);
+      grpc_uri_destroy(grpc_uri_parse(tmp, 0));
+      gpr_log(GPR_ERROR, "don't know how to resolve '%s' or '%s'", target, tmp);
     }
+    gpr_free(tmp);
   }
   return factory;
 }

src/core/ext/client_config/resolver_registry.h

@@ -36,9 +36,12 @@
 
 #include "src/core/ext/client_config/resolver_factory.h"
 
-void grpc_resolver_registry_init(const char *default_prefix);
+void grpc_resolver_registry_init();
 void grpc_resolver_registry_shutdown(void);
 
+/** Set the default URI prefix to \a default_prefix. */
+void grpc_resolver_registry_set_default_prefix(const char *default_prefix);
+
 /** Register a resolver type.
     URI's of \a scheme will be resolved with the given resolver.
     If \a priority is greater than zero, then the resolver will be eligible

test/core/surface/channel_create_test.c

@@ -40,7 +40,7 @@ void test_unknown_scheme_target(void) {
   grpc_channel *chan;
   /* avoid default prefix */
   grpc_resolver_registry_shutdown();
-  grpc_resolver_registry_init("");
+  grpc_resolver_registry_init();
 
   chan = grpc_insecure_channel_create("blah://blah", NULL, NULL);
   GPR_ASSERT(chan != NULL);

test/core/surface/secure_channel_create_test.c

@@ -46,7 +46,7 @@ void test_unknown_scheme_target(void) {
   grpc_channel *chan;
   grpc_channel_credentials *creds;
   grpc_resolver_registry_shutdown();
-  grpc_resolver_registry_init("");
+  grpc_resolver_registry_init();
 
   creds = grpc_fake_transport_security_credentials_create();
   chan = grpc_secure_channel_create(creds, "blah://blah", NULL, NULL);