1 files changed, 70 insertions, 0 deletions
diff --git a/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc b/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc
index ee827e284e..7e34784691 100644
--- a/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc
+++ b/src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper_windows.cc
@@ -21,9 +21,79 @@
 #include "src/core/lib/iomgr/port.h"
 #if GRPC_ARES == 1 && defined(GPR_WINDOWS)
 
+#include <grpc/support/string_util.h>
+
+#include "src/core/ext/filters/client_channel/lb_policy_factory.h"
+#include "src/core/ext/filters/client_channel/parse_address.h"
 #include "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h"
+#include "src/core/lib/gpr/host_port.h"
+#include "src/core/lib/gpr/string.h"
 #include "src/core/lib/iomgr/socket_windows.h"
 
 bool grpc_ares_query_ipv6() { return grpc_ipv6_loopback_available(); }
 
+static bool inner_maybe_resolve_localhost_manually_locked(
+    const char* name, const char* default_port, grpc_lb_addresses** addrs,
+    char** host, char** port) {
+  gpr_split_host_port(name, host, port);
+  if (*host == nullptr) {
+    gpr_log(GPR_ERROR,
+            "Failed to parse %s into host:port during Windows localhost "
+            "resolution check.",
+            name);
+    return false;
+  }
+  if (*port == nullptr) {
+    if (default_port == nullptr) {
+      gpr_log(GPR_ERROR,
+              "No port or default port for %s during Windows localhost "
+              "resolution check.",
+              name);
+      return false;
+    }
+    *port = gpr_strdup(default_port);
+  }
+  if (gpr_stricmp(*host, "localhost") == 0) {
+    GPR_ASSERT(*addrs == nullptr);
+    *addrs = grpc_lb_addresses_create(2, nullptr);
+    uint16_t numeric_port = grpc_strhtons(*port);
+    // Append the ipv6 loopback address.
+    struct sockaddr_in6 ipv6_loopback_addr;
+    memset(&ipv6_loopback_addr, 0, sizeof(ipv6_loopback_addr));
+    ((char*)&ipv6_loopback_addr.sin6_addr)[15] = 1;
+    ipv6_loopback_addr.sin6_family = AF_INET6;
+    ipv6_loopback_addr.sin6_port = numeric_port;
+    grpc_lb_addresses_set_address(
+        *addrs, 0, &ipv6_loopback_addr, sizeof(ipv6_loopback_addr),
+        false /* is_balancer */, nullptr /* balancer_name */,
+        nullptr /* user_data */);
+    // Append the ipv4 loopback address.
+    struct sockaddr_in ipv4_loopback_addr;
+    memset(&ipv4_loopback_addr, 0, sizeof(ipv4_loopback_addr));
+    ((char*)&ipv4_loopback_addr.sin_addr)[0] = 0x7f;
+    ((char*)&ipv4_loopback_addr.sin_addr)[3] = 0x01;
+    ipv4_loopback_addr.sin_family = AF_INET;
+    ipv4_loopback_addr.sin_port = numeric_port;
+    grpc_lb_addresses_set_address(
+        *addrs, 1, &ipv4_loopback_addr, sizeof(ipv4_loopback_addr),
+        false /* is_balancer */, nullptr /* balancer_name */,
+        nullptr /* user_data */);
+    // Let the address sorter figure out which one should be tried first.
+    grpc_cares_wrapper_address_sorting_sort(*addrs);
+    return true;
+  }
+  return false;
+}
+
+bool grpc_ares_maybe_resolve_localhost_manually_locked(
+    const char* name, const char* default_port, grpc_lb_addresses** addrs) {
+  char* host = nullptr;
+  char* port = nullptr;
+  bool out = inner_maybe_resolve_localhost_manually_locked(name, default_port,
+                                                           addrs, &host, &port);
+  gpr_free(host);
+  gpr_free(port);
+  return out;
+}
+
 #endif /* GRPC_ARES == 1 && defined(GPR_WINDOWS) */