Use dlopen() and dlsym() for resolver functions
This is a workaround to allow us to use libnetd_resolv.so from
the resolver APEX before b/120661824 is fixed.
Test: builds, boots
Test: system/netd/tests/runtests.sh
Test: atest FrameworksNetTests android.net.cts.ConnectivityManagerTest
Change-Id: I752ae248bb59545b0a4fbc1a7b8c9bcd697a31d4
diff --git a/server/ResolvStub.cpp b/server/ResolvStub.cpp
new file mode 100644
index 0000000..5054abf
--- /dev/null
+++ b/server/ResolvStub.cpp
@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <string>
+
+#include <dlfcn.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define LOG_TAG "Netd"
+#include <log/log.h>
+
+#include <netd_resolv/resolv_stub.h>
+
+struct ResolvStub RESOLV_STUB;
+
+inline constexpr char APEX_LIB64_DIR[] = "/apex/com.android.resolv/lib64";
+inline constexpr char APEX_LIB_DIR[] = "/apex/com.android.resolv/lib";
+inline constexpr char LIBNAME[] = "libnetd_resolv.so";
+
+template <typename FunctionType>
+static void resolvStubInitFunction(void* handle, const char* symbol, FunctionType** stubPtr) {
+ void* f = dlsym(handle, symbol);
+ if (f == nullptr) {
+ ALOGE("Can't find symbol %s in %s", symbol, LIBNAME);
+ abort();
+ }
+ *stubPtr = reinterpret_cast<FunctionType*>(f);
+}
+
+int resolv_stub_init() {
+ void* netdResolvHandle;
+
+ for (const auto& dir : {APEX_LIB64_DIR, APEX_LIB_DIR}) {
+ std::string path = std::string(dir) + "/" + LIBNAME;
+ netdResolvHandle = dlopen(path.c_str(), RTLD_NOW);
+ if (netdResolvHandle != nullptr) {
+ break;
+ }
+ ALOGW("dlopen(%s) failed: %s", path.c_str(), strerror(errno));
+ }
+
+ if (netdResolvHandle == nullptr) {
+ ALOGE("Fatal: couldn't open libnetd_resolv");
+ abort();
+ }
+
+#define STR(x) #x
+#define RESOLV_STUB_LOAD_SYMBOL(x) resolvStubInitFunction(netdResolvHandle, STR(x), &RESOLV_STUB.x)
+ RESOLV_STUB_LOAD_SYMBOL(android_getaddrinfofornetcontext);
+ RESOLV_STUB_LOAD_SYMBOL(android_gethostbyaddrfornetcontext);
+ RESOLV_STUB_LOAD_SYMBOL(android_gethostbynamefornetcontext);
+ RESOLV_STUB_LOAD_SYMBOL(android_net_res_stats_aggregate);
+ RESOLV_STUB_LOAD_SYMBOL(android_net_res_stats_get_info_for_net);
+ RESOLV_STUB_LOAD_SYMBOL(android_net_res_stats_get_usable_servers);
+ RESOLV_STUB_LOAD_SYMBOL(resolv_delete_cache_for_net);
+ RESOLV_STUB_LOAD_SYMBOL(resolv_delete_private_dns_for_net);
+ RESOLV_STUB_LOAD_SYMBOL(resolv_get_private_dns_status_for_net);
+ RESOLV_STUB_LOAD_SYMBOL(resolv_has_nameservers);
+ RESOLV_STUB_LOAD_SYMBOL(resolv_register_private_dns_callback);
+ RESOLV_STUB_LOAD_SYMBOL(resolv_res_nsend);
+ RESOLV_STUB_LOAD_SYMBOL(resolv_set_nameservers_for_net);
+ RESOLV_STUB_LOAD_SYMBOL(resolv_set_private_dns_for_net);
+#undef RESOLV_STUB_LOAD_SYMBOL
+#undef STR
+
+ return 0;
+}