[CLATJ#1] libclat: move makeChecksumNeutral() from netd to apex
Introduce the library libclat to implement clat functions for jni.
It is helpful for unit test.
makeChecksumNeutral() and its test are moved from ClatdController
without behavior change.
Bug: 212345928
Test: build and boot
atest libclat_test
Change-Id: I1c0981d98141fc1cc07b2d3a0f3cbddf38683ff3
diff --git a/service/native/libs/libclat/Android.bp b/service/native/libs/libclat/Android.bp
new file mode 100644
index 0000000..a45ffa6
--- /dev/null
+++ b/service/native/libs/libclat/Android.bp
@@ -0,0 +1,42 @@
+// Copyright (C) 2022 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.
+
+package {
+ default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+cc_library_static {
+ name: "libclat",
+ defaults: ["netd_defaults"],
+ srcs: ["clatutils.cpp"],
+ stl: "libc++_static",
+ static_libs: ["libip_checksum"],
+ export_include_dirs: ["include"],
+ min_sdk_version: "30",
+ apex_available: ["com.android.tethering"],
+}
+
+cc_test {
+ name: "libclat_test",
+ defaults: ["netd_defaults"],
+ test_suites: ["device-tests"],
+ srcs: [
+ "clatutils_test.cpp",
+ ],
+ static_libs: [
+ "libbase",
+ "libclat",
+ "libip_checksum",
+ ],
+}
\ No newline at end of file
diff --git a/service/native/libs/libclat/clatutils.cpp b/service/native/libs/libclat/clatutils.cpp
new file mode 100644
index 0000000..2a53ba8
--- /dev/null
+++ b/service/native/libs/libclat/clatutils.cpp
@@ -0,0 +1,51 @@
+// Copyright (C) 2022 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 "libclat/clatutils.h"
+
+#include <stdlib.h>
+
+extern "C" {
+#include "checksum.h"
+}
+
+namespace android {
+namespace net {
+namespace clat {
+
+// Alters the bits in the IPv6 address to make them checksum neutral with v4 and nat64Prefix.
+void makeChecksumNeutral(in6_addr* v6, const in_addr v4, const in6_addr& nat64Prefix) {
+ // Fill last 8 bytes of IPv6 address with random bits.
+ arc4random_buf(&v6->s6_addr[8], 8);
+
+ // Make the IID checksum-neutral. That is, make it so that:
+ // checksum(Local IPv4 | Remote IPv4) = checksum(Local IPv6 | Remote IPv6)
+ // in other words (because remote IPv6 = NAT64 prefix | Remote IPv4):
+ // checksum(Local IPv4) = checksum(Local IPv6 | NAT64 prefix)
+ // Do this by adjusting the two bytes in the middle of the IID.
+
+ uint16_t middlebytes = (v6->s6_addr[11] << 8) + v6->s6_addr[12];
+
+ uint32_t c1 = ip_checksum_add(0, &v4, sizeof(v4));
+ uint32_t c2 = ip_checksum_add(0, &nat64Prefix, sizeof(nat64Prefix)) +
+ ip_checksum_add(0, v6, sizeof(*v6));
+
+ uint16_t delta = ip_checksum_adjust(middlebytes, c1, c2);
+ v6->s6_addr[11] = delta >> 8;
+ v6->s6_addr[12] = delta & 0xff;
+}
+
+} // namespace clat
+} // namespace net
+} // namespace android
diff --git a/service/native/libs/libclat/clatutils_test.cpp b/service/native/libs/libclat/clatutils_test.cpp
new file mode 100644
index 0000000..1900abf
--- /dev/null
+++ b/service/native/libs/libclat/clatutils_test.cpp
@@ -0,0 +1,93 @@
+// Copyright (C) 2022 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 "libclat/clatutils.h"
+
+#include <android-base/stringprintf.h>
+#include <arpa/inet.h>
+#include <gtest/gtest.h>
+
+extern "C" {
+#include "checksum.h"
+}
+
+// Default translation parameters.
+static const char kIPv4LocalAddr[] = "192.0.0.4";
+
+namespace android {
+namespace net {
+namespace clat {
+
+using base::StringPrintf;
+
+class ClatUtils : public ::testing::Test {};
+
+TEST_F(ClatUtils, MakeChecksumNeutral) {
+ // We can't test generateIPv6Address here since it requires manipulating routing, which we can't
+ // do without talking to the real netd on the system.
+ uint32_t rand = arc4random_uniform(0xffffffff);
+ uint16_t rand1 = rand & 0xffff;
+ uint16_t rand2 = (rand >> 16) & 0xffff;
+ std::string v6PrefixStr = StringPrintf("2001:db8:%x:%x", rand1, rand2);
+ std::string v6InterfaceAddrStr = StringPrintf("%s::%x:%x", v6PrefixStr.c_str(), rand2, rand1);
+ std::string nat64PrefixStr = StringPrintf("2001:db8:%x:%x::", rand2, rand1);
+
+ in_addr v4 = {inet_addr(kIPv4LocalAddr)};
+ in6_addr v6InterfaceAddr;
+ ASSERT_TRUE(inet_pton(AF_INET6, v6InterfaceAddrStr.c_str(), &v6InterfaceAddr));
+ in6_addr nat64Prefix;
+ ASSERT_TRUE(inet_pton(AF_INET6, nat64PrefixStr.c_str(), &nat64Prefix));
+
+ // Generate a boatload of random IIDs.
+ int onebits = 0;
+ uint64_t prev_iid = 0;
+ for (int i = 0; i < 100000; i++) {
+ in6_addr v6 = v6InterfaceAddr;
+ makeChecksumNeutral(&v6, v4, nat64Prefix);
+
+ // Check the generated IP address is in the same prefix as the interface IPv6 address.
+ EXPECT_EQ(0, memcmp(&v6, &v6InterfaceAddr, 8));
+
+ // Check that consecutive IIDs are not the same.
+ uint64_t iid = *(uint64_t*)(&v6.s6_addr[8]);
+ ASSERT_TRUE(iid != prev_iid)
+ << "Two consecutive random IIDs are the same: " << std::showbase << std::hex << iid
+ << "\n";
+ prev_iid = iid;
+
+ // Check that the IID is checksum-neutral with the NAT64 prefix and the
+ // local prefix.
+ uint16_t c1 = ip_checksum_finish(ip_checksum_add(0, &v4, sizeof(v4)));
+ uint16_t c2 = ip_checksum_finish(ip_checksum_add(0, &nat64Prefix, sizeof(nat64Prefix)) +
+ ip_checksum_add(0, &v6, sizeof(v6)));
+
+ if (c1 != c2) {
+ char v6Str[INET6_ADDRSTRLEN];
+ inet_ntop(AF_INET6, &v6, v6Str, sizeof(v6Str));
+ FAIL() << "Bad IID: " << v6Str << " not checksum-neutral with " << kIPv4LocalAddr
+ << " and " << nat64PrefixStr.c_str() << std::showbase << std::hex
+ << "\n IPv4 checksum: " << c1 << "\n IPv6 checksum: " << c2 << "\n";
+ }
+
+ // Check that IIDs are roughly random and use all the bits by counting the
+ // total number of bits set to 1 in a random sample of 100000 generated IIDs.
+ onebits += __builtin_popcountll(*(uint64_t*)&iid);
+ }
+ EXPECT_LE(3190000, onebits);
+ EXPECT_GE(3210000, onebits);
+}
+
+} // namespace clat
+} // namespace net
+} // namespace android
diff --git a/service/native/libs/libclat/include/libclat/clatutils.h b/service/native/libs/libclat/include/libclat/clatutils.h
new file mode 100644
index 0000000..05c99df
--- /dev/null
+++ b/service/native/libs/libclat/include/libclat/clatutils.h
@@ -0,0 +1,26 @@
+// Copyright (C) 2022 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.
+
+#pragma once
+#include <netinet/in.h>
+#include <netinet/in6.h>
+
+namespace android {
+namespace net {
+namespace clat {
+
+void makeChecksumNeutral(in6_addr* v6, const in_addr v4, const in6_addr& nat64Prefix);
+} // namespace clat
+} // namespace net
+} // namespace android