Single thread fake name resolution for fuzzing

src/core/ext/resolver/dns/native/dns_resolver.c

@@ -86,7 +86,8 @@ typedef struct {
 
 static void dns_destroy(grpc_exec_ctx *exec_ctx, grpc_resolver *r);
 
-static void dns_start_resolving_locked(dns_resolver *r);
+static void dns_start_resolving_locked(grpc_exec_ctx *exec_ctx,
+                                       dns_resolver *r);
 static void dns_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,
                                          dns_resolver *r);
 
@@ -119,7 +120,7 @@ static void dns_channel_saw_error(grpc_exec_ctx *exec_ctx,
   gpr_mu_lock(&r->mu);
   if (!r->resolving) {
     gpr_backoff_reset(&r->backoff_state);
-    dns_start_resolving_locked(r);
+    dns_start_resolving_locked(exec_ctx, r);
   }
   gpr_mu_unlock(&r->mu);
 }
@@ -134,7 +135,7 @@ static void dns_next(grpc_exec_ctx *exec_ctx, grpc_resolver *resolver,
   r->target_config = target_config;
   if (r->resolved_version == 0 && !r->resolving) {
     gpr_backoff_reset(&r->backoff_state);
-    dns_start_resolving_locked(r);
+    dns_start_resolving_locked(exec_ctx, r);
   } else {
     dns_maybe_finish_next_locked(exec_ctx, r);
   }
@@ -149,7 +150,7 @@ static void dns_on_retry_timer(grpc_exec_ctx *exec_ctx, void *arg,
   r->have_retry_timer = false;
   if (success) {
     if (!r->resolving) {
-      dns_start_resolving_locked(r);
+      dns_start_resolving_locked(exec_ctx, r);
     }
   }
   gpr_mu_unlock(&r->mu);
@@ -201,11 +202,12 @@ static void dns_on_resolved(grpc_exec_ctx *exec_ctx, void *arg,
   GRPC_RESOLVER_UNREF(exec_ctx, &r->base, "dns-resolving");
 }
 
-static void dns_start_resolving_locked(dns_resolver *r) {
+static void dns_start_resolving_locked(grpc_exec_ctx *exec_ctx,
+                                       dns_resolver *r) {
   GRPC_RESOLVER_REF(&r->base, "dns-resolving");
   GPR_ASSERT(!r->resolving);
   r->resolving = 1;
-  grpc_resolve_address(r->name, r->default_port, dns_on_resolved, r);
+  grpc_resolve_address(exec_ctx, r->name, r->default_port, dns_on_resolved, r);
 }
 
 static void dns_maybe_finish_next_locked(grpc_exec_ctx *exec_ctx,

src/core/ext/resolver/zookeeper/zookeeper_resolver.c

@@ -299,7 +299,7 @@ static void zookeeper_get_children_node_completion(int rc, const char *value,
   address = zookeeper_parse_address(value, (size_t)value_len);
   if (address != NULL) {
     /** Further resolves address by DNS */
-    grpc_resolve_address(address, NULL, zookeeper_dns_resolved, r);
+    grpc_resolve_address(&exec_ctx, address, NULL, zookeeper_dns_resolved, r);
     gpr_free(address);
   } else {
     gpr_log(GPR_ERROR, "Error in resolving a child node of %s", r->name);
@@ -375,7 +375,7 @@ static void zookeeper_get_node_completion(int rc, const char *value,
     r->resolved_addrs->naddrs = 0;
     r->resolved_total = 1;
     /** Further resolves address by DNS */
-    grpc_resolve_address(address, NULL, zookeeper_dns_resolved, r);
+    grpc_resolve_address(&exec_ctx, address, NULL, zookeeper_dns_resolved, r);
     gpr_free(address);
     return;
   }

src/core/lib/http/httpcli.c

@@ -246,7 +246,7 @@ static void internal_request_begin(
 
   grpc_pollset_set_add_pollset(exec_ctx, req->context->pollset_set,
                                req->pollset);
-  grpc_resolve_address(request->host, req->handshaker->default_port,
+  grpc_resolve_address(exec_ctx, request->host, req->handshaker->default_port,
                        on_resolved, req);
 }
 

src/core/lib/iomgr/resolve_address.h

@@ -59,8 +59,9 @@ typedef void (*grpc_resolve_cb)(grpc_exec_ctx *exec_ctx, void *arg,
 /* Asynchronously resolve addr. Use default_port if a port isn't designated
    in addr, otherwise use the port in addr. */
 /* TODO(ctiller): add a timeout here */
-void grpc_resolve_address(const char *addr, const char *default_port,
-                          grpc_resolve_cb cb, void *arg);
+extern void (*grpc_resolve_address)(grpc_exec_ctx *exec_ctx, const char *addr,
+                                    const char *default_port,
+                                    grpc_resolve_cb cb, void *arg);
 /* Destroy resolved addresses */
 void grpc_resolved_addresses_destroy(grpc_resolved_addresses *addresses);
 

src/core/lib/iomgr/resolve_address_posix.c

@@ -164,8 +164,9 @@ void grpc_resolved_addresses_destroy(grpc_resolved_addresses *addrs) {
   gpr_free(addrs);
 }
 
-void grpc_resolve_address(const char *name, const char *default_port,
-                          grpc_resolve_cb cb, void *arg) {
+static void resolve_address_impl(grpc_exec_ctx *exec_ctx, const char *name,
+                                 const char *default_port, grpc_resolve_cb cb,
+                                 void *arg) {
   request *r = gpr_malloc(sizeof(request));
   grpc_closure_init(&r->request_closure, do_request_thread, r);
   r->name = gpr_strdup(name);
@@ -175,4 +176,8 @@ void grpc_resolve_address(const char *name, const char *default_port,
   grpc_executor_enqueue(&r->request_closure, 1);
 }
 
+void (*grpc_resolve_address)(grpc_exec_ctx *exec_ctx, const char *name,
+                             const char *default_port, grpc_resolve_cb cb,
+                             void *arg) = resolve_address_impl;
+
 #endif

src/core/lib/iomgr/resolve_address_windows.c

@@ -155,8 +155,9 @@ void grpc_resolved_addresses_destroy(grpc_resolved_addresses *addrs) {
   gpr_free(addrs);
 }
 
-void grpc_resolve_address(const char *name, const char *default_port,
-                          grpc_resolve_cb cb, void *arg) {
+static void resolve_address_impl(grpc_exec_ctx *exec_ctx, const char *name,
+                                 const char *default_port, grpc_resolve_cb cb,
+                                 void *arg) {
   request *r = gpr_malloc(sizeof(request));
   grpc_closure_init(&r->request_closure, do_request_thread, r);
   r->name = gpr_strdup(name);
@@ -166,4 +167,8 @@ void grpc_resolve_address(const char *name, const char *default_port,
   grpc_executor_enqueue(&r->request_closure, 1);
 }
 
+void (*grpc_resolved_address)(grpc_exec_ctx *exec_ctx, const char *name,
+                              const char *default_port, grpc_resolve_cb cb,
+                              void *arg) = resolve_address_impl;
+
 #endif

test/core/end2end/fuzzers/api_fuzzer.c

@@ -41,6 +41,7 @@
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/iomgr/resolve_address.h"
 #include "src/core/lib/iomgr/tcp_client.h"
+#include "src/core/lib/iomgr/timer.h"
 #include "src/core/lib/transport/metadata.h"
 #include "test/core/util/mock_endpoint.h"
 
@@ -153,23 +154,44 @@ static void wait_until(gpr_timespec when) {
 ////////////////////////////////////////////////////////////////////////////////
 // dns resolution
 
-static grpc_resolved_addresses *my_resolve_address(const char *name,
-                                                   const char *default_port) {
-  if (0 == strcmp(name, "server")) {
+typedef struct addr_req {
+  grpc_timer timer;
+  char *addr;
+  grpc_resolve_cb cb;
+  void *arg;
+} addr_req;
+
+static void finish_resolve(grpc_exec_ctx *exec_ctx, void *arg, bool success) {
+  GPR_ASSERT(success);
+  addr_req *r = arg;
+
+  if (0 == strcmp(r->addr, "server")) {
     wait_until(gpr_time_add(gpr_now(GPR_CLOCK_REALTIME),
                             gpr_time_from_seconds(1, GPR_TIMESPAN)));
     grpc_resolved_addresses *addrs = gpr_malloc(sizeof(*addrs));
     addrs->naddrs = 1;
     addrs->addrs = gpr_malloc(sizeof(*addrs->addrs));
     addrs->addrs[0].len = 0;
-    return addrs;
-  } else if (0 == strcmp(name, "wait")) {
-    wait_until(gpr_time_add(gpr_now(GPR_CLOCK_REALTIME),
-                            gpr_time_from_seconds(1, GPR_TIMESPAN)));
-    return NULL;
+    r->cb(exec_ctx, r->arg, addrs);
   } else {
-    return NULL;
+    r->cb(exec_ctx, r->arg, NULL);
   }
+
+  gpr_free(r->addr);
+  gpr_free(r);
+}
+
+void my_resolve_address(grpc_exec_ctx *exec_ctx, const char *addr,
+                        const char *default_port, grpc_resolve_cb cb,
+                        void *arg) {
+  addr_req *r = gpr_malloc(sizeof(*r));
+  r->addr = gpr_strdup(addr);
+  r->cb = cb;
+  r->arg = arg;
+  grpc_timer_init(exec_ctx, &r->timer,
+                  gpr_time_add(gpr_now(GPR_CLOCK_MONOTONIC),
+                               gpr_time_from_seconds(1, GPR_TIMESPAN)),
+                  finish_resolve, r, gpr_now(GPR_CLOCK_MONOTONIC));
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -202,7 +224,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
   grpc_test_only_set_metadata_hash_seed(0);
   if (squelch) gpr_set_log_function(dont_log);
   input_stream inp = {data, data + size};
-  grpc_blocking_resolve_address = my_resolve_address;
+  grpc_resolve_address = my_resolve_address;
   grpc_tcp_client_connect_impl = my_tcp_client_connect;
   gpr_mu_init(&g_mu);
   gpr_cv_init(&g_cv);