Make res_init() work again.
Change 75830fb836621ebbcf68155e466983eb231f9ca1 to fix _nres
initialization to be thread safe accidentally introduced a behavior
change whereby res_init() became a no-op. It also failed to remove all
direct accesses to _nres.
Move the file over to C++ so we can let RAII ensure we're always holding
a lock while using the global state, make all callers access the global
state via this class, and restore the previous behavior of res_init().
Test: atest DnsResolverTest
Bug: 166235340
Change-Id: Ib390a7eac063bc0ff5eeba755e8c74ef1383004e
diff --git a/libc/dns/resolv/res_data.cpp b/libc/dns/resolv/res_data.cpp
new file mode 100644
index 0000000..22d9f7b
--- /dev/null
+++ b/libc/dns/resolv/res_data.cpp
@@ -0,0 +1,157 @@
+/* $NetBSD: res_data.c,v 1.8 2004/06/09 18:07:03 christos Exp $ */
+
+/*
+ * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
+ * Copyright (c) 1995-1999 by Internet Software Consortium.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
+ * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "resolv_private.h"
+
+#include <pthread.h>
+
+extern "C" int res_ourserver_p(const res_state, const struct sockaddr*);
+extern "C" int __res_vinit(res_state, int);
+
+class GlobalStateAccessor {
+ public:
+ GlobalStateAccessor() {
+ pthread_mutex_lock(&mutex);
+ if (!initialized) {
+ init();
+ initialized = true;
+ }
+ }
+
+ ~GlobalStateAccessor() {
+ pthread_mutex_unlock(&mutex);
+ }
+
+ __res_state* get() {
+ return &state;
+ }
+
+ int init();
+
+ private:
+ static __res_state state;
+ static bool initialized;
+ static pthread_mutex_t mutex;
+};
+__res_state GlobalStateAccessor::state;
+bool GlobalStateAccessor::initialized = false;
+pthread_mutex_t GlobalStateAccessor::mutex = PTHREAD_MUTEX_INITIALIZER;
+
+int GlobalStateAccessor::init() {
+ // These three fields used to be statically initialized. This made
+ // it hard to use this code in a shared library. It is necessary,
+ // now that we're doing dynamic initialization here, that we preserve
+ // the old semantics: if an application modifies one of these three
+ // fields of _res before res_init() is called, res_init() will not
+ // alter them. Of course, if an application is setting them to
+ // _zero_ before calling res_init(), hoping to override what used
+ // to be the static default, we can't detect it and unexpected results
+ // will follow. Zero for any of these fields would make no sense,
+ // so one can safely assume that the applications were already getting
+ // unexpected results.
+ // g_nres.options is tricky since some apps were known to diddle the bits
+ // before res_init() was first called. We can't replicate that semantic
+ // with dynamic initialization (they may have turned bits off that are
+ // set in RES_DEFAULT). Our solution is to declare such applications
+ // "broken". They could fool us by setting RES_INIT but none do (yet).
+ if (!state.retrans) state.retrans = RES_TIMEOUT;
+ if (!state.retry) state.retry = 4;
+ if (!(state.options & RES_INIT)) state.options = RES_DEFAULT;
+
+ // This one used to initialize implicitly to zero, so unless the app
+ // has set it to something in particular, we can randomize it now.
+ if (!state.id) state.id = res_randomid();
+
+ return __res_vinit(&state, 1);
+}
+
+int res_init(void) {
+ GlobalStateAccessor gsa;
+ return gsa.init();
+}
+
+void p_query(const u_char* msg) {
+ fp_query(msg, stdout);
+}
+
+void fp_query(const u_char* msg, FILE* file) {
+ fp_nquery(msg, PACKETSZ, file);
+}
+
+void fp_nquery(const u_char* msg, int len, FILE* file) {
+ GlobalStateAccessor gsa;
+ res_pquery(gsa.get(), msg, len, file);
+}
+
+int
+res_mkquery(int op, const char* dname, int klass, int type, const u_char* data,
+ int datalen, const u_char* newrr_in, u_char* buf, int buflen) {
+ GlobalStateAccessor gsa;
+ return res_nmkquery(gsa.get(), op, dname, klass, type, data, datalen, newrr_in, buf, buflen);
+}
+
+int res_query(const char* name, int klass, int type, u_char* answer, int anslen) {
+ GlobalStateAccessor gsa;
+ return res_nquery(gsa.get(), name, klass, type, answer, anslen);
+}
+
+void res_send_setqhook(res_send_qhook hook) {
+ GlobalStateAccessor gsa;
+ gsa.get()->qhook = hook;
+}
+
+void res_send_setrhook(res_send_rhook hook) {
+ GlobalStateAccessor gsa;
+ gsa.get()->rhook = hook;
+}
+
+int res_isourserver(const struct sockaddr_in* inp) {
+ GlobalStateAccessor gsa;
+ return res_ourserver_p(gsa.get(), reinterpret_cast<const sockaddr*>(inp));
+}
+
+int res_send(const u_char* buf, int buflen, u_char* ans, int anssiz) {
+ GlobalStateAccessor gsa;
+ return res_nsend(gsa.get(), buf, buflen, ans, anssiz);
+}
+
+void res_close(void) {
+ GlobalStateAccessor gsa;
+ res_nclose(gsa.get());
+}
+
+int res_search(const char* name, int klass, int type, u_char* answer, int anslen) {
+ GlobalStateAccessor gsa;
+ return res_nsearch(gsa.get(), name, klass, type, answer, anslen);
+}
+
+int res_querydomain(const char* name, const char* domain, int klass, int type, u_char* answer,
+ int anslen) {
+ GlobalStateAccessor gsa;
+ return res_nquerydomain(gsa.get(), name, domain, klass, type, answer, anslen);
+}
+
+int res_opt(int a, u_char* b, int c, int d) {
+ GlobalStateAccessor gsa;
+ return res_nopt(gsa.get(), a, b, c, d);
+}
+
+const char* hostalias(const char* name) {
+ return NULL;
+}