Merge libnetddns into libnetd_resolv

libnetddns is the library for DNS-over-TLS and is statically
linked to netd. Deprecate it and move them to libnetd_resolv
as a more general DNS library for netd.

This change comprises:

[1] Clean up netd/server/dns/*. Move all DnsTls* files to
    netd/resolv/ to parts of libnetd_resolv library.

[2] Export DnsTls* classes being visible for netd. It will only
    be temporary for a while.

[3] Remove the libssl dependency in netd. The relevant stuff is
    moved to libnetd_resolv.

Note that DnsTls* classes are still required for DnsProxyListener
and ResolverController to manipulate private DNS servers even after
this change.

Bug: 113628807
Test: as follows
    - built, flashed, booted
    - system/netd/tests/runtests.sh
    - DNS-over-TLS in live network passed

Change-Id: Ieac5889b4ebe737f876b3dcbe1a8da2b2b1b629d
diff --git a/resolv/DnsTlsServer.cpp b/resolv/DnsTlsServer.cpp
new file mode 100644
index 0000000..b1ee481
--- /dev/null
+++ b/resolv/DnsTlsServer.cpp
@@ -0,0 +1,133 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "netd_resolv/DnsTlsServer.h"
+
+#include <algorithm>
+
+namespace {
+
+// Returns a tuple of references to the elements of a.
+auto make_tie(const sockaddr_in& a) {
+    return std::tie(a.sin_port, a.sin_addr.s_addr);
+}
+
+// Returns a tuple of references to the elements of a.
+auto make_tie(const sockaddr_in6& a) {
+    // Skip flowinfo, which is not relevant.
+    return std::tie(
+        a.sin6_port,
+        a.sin6_addr,
+        a.sin6_scope_id
+    );
+}
+
+} // namespace
+
+// These binary operators make sockaddr_storage comparable.  They need to be
+// in the global namespace so that the std::tuple < and == operators can see them.
+static bool operator <(const in6_addr& x, const in6_addr& y) {
+    return std::lexicographical_compare(
+            std::begin(x.s6_addr), std::end(x.s6_addr),
+            std::begin(y.s6_addr), std::end(y.s6_addr));
+}
+
+static bool operator ==(const in6_addr& x, const in6_addr& y) {
+    return std::equal(
+            std::begin(x.s6_addr), std::end(x.s6_addr),
+            std::begin(y.s6_addr), std::end(y.s6_addr));
+}
+
+static bool operator <(const sockaddr_storage& x, const sockaddr_storage& y) {
+    if (x.ss_family != y.ss_family) {
+        return x.ss_family < y.ss_family;
+    }
+    // Same address family.
+    if (x.ss_family == AF_INET) {
+        const sockaddr_in& x_sin = reinterpret_cast<const sockaddr_in&>(x);
+        const sockaddr_in& y_sin = reinterpret_cast<const sockaddr_in&>(y);
+        return make_tie(x_sin) < make_tie(y_sin);
+    } else if (x.ss_family == AF_INET6) {
+        const sockaddr_in6& x_sin6 = reinterpret_cast<const sockaddr_in6&>(x);
+        const sockaddr_in6& y_sin6 = reinterpret_cast<const sockaddr_in6&>(y);
+        return make_tie(x_sin6) < make_tie(y_sin6);
+    }
+    return false;  // Unknown address type.  This is an error.
+}
+
+static bool operator ==(const sockaddr_storage& x, const sockaddr_storage& y) {
+    if (x.ss_family != y.ss_family) {
+        return false;
+    }
+    // Same address family.
+    if (x.ss_family == AF_INET) {
+        const sockaddr_in& x_sin = reinterpret_cast<const sockaddr_in&>(x);
+        const sockaddr_in& y_sin = reinterpret_cast<const sockaddr_in&>(y);
+        return make_tie(x_sin) == make_tie(y_sin);
+    } else if (x.ss_family == AF_INET6) {
+        const sockaddr_in6& x_sin6 = reinterpret_cast<const sockaddr_in6&>(x);
+        const sockaddr_in6& y_sin6 = reinterpret_cast<const sockaddr_in6&>(y);
+        return make_tie(x_sin6) == make_tie(y_sin6);
+    }
+    return false;  // Unknown address type.  This is an error.
+}
+
+namespace android {
+namespace net {
+
+// This comparison ignores ports and fingerprints.
+bool AddressComparator::operator() (const DnsTlsServer& x, const DnsTlsServer& y) const {
+    if (x.ss.ss_family != y.ss.ss_family) {
+        return x.ss.ss_family < y.ss.ss_family;
+    }
+    // Same address family.
+    if (x.ss.ss_family == AF_INET) {
+        const sockaddr_in& x_sin = reinterpret_cast<const sockaddr_in&>(x.ss);
+        const sockaddr_in& y_sin = reinterpret_cast<const sockaddr_in&>(y.ss);
+        return x_sin.sin_addr.s_addr < y_sin.sin_addr.s_addr;
+    } else if (x.ss.ss_family == AF_INET6) {
+        const sockaddr_in6& x_sin6 = reinterpret_cast<const sockaddr_in6&>(x.ss);
+        const sockaddr_in6& y_sin6 = reinterpret_cast<const sockaddr_in6&>(y.ss);
+        return std::tie(x_sin6.sin6_addr, x_sin6.sin6_scope_id) <
+                std::tie(y_sin6.sin6_addr, y_sin6.sin6_scope_id);
+    }
+    return false;  // Unknown address type.  This is an error.
+}
+
+// Returns a tuple of references to the elements of s.
+auto make_tie(const DnsTlsServer& s) {
+    return std::tie(
+        s.ss,
+        s.name,
+        s.fingerprints,
+        s.protocol
+    );
+}
+
+bool DnsTlsServer::operator <(const DnsTlsServer& other) const {
+    return make_tie(*this) < make_tie(other);
+}
+
+bool DnsTlsServer::operator ==(const DnsTlsServer& other) const {
+    return make_tie(*this) == make_tie(other);
+}
+
+bool DnsTlsServer::wasExplicitlyConfigured() const {
+    return !name.empty() || !fingerprints.empty();
+}
+
+}  // namespace net
+}  // namespace android