Add asynchronous DNS query API and basic tests.
Adds support for asynchronous "raw" DNS API for clients.
API allows apps to use multinetworking capability correctly
and also allows other query types than A/AAAA.
Test: built, flashed, booted/ runtest.sh
Change-Id: I98931cd561821cd396f8421e9419a289b371468a
diff --git a/client/NetdClient.cpp b/client/NetdClient.cpp
index 4497877..de9b0f5 100644
--- a/client/NetdClient.cpp
+++ b/client/NetdClient.cpp
@@ -19,12 +19,15 @@
#include <arpa/inet.h>
#include <errno.h>
#include <math.h>
+#include <resolv.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <atomic>
+#include <string>
+#include <vector>
#include "Fwmark.h"
#include "FwmarkClient.h"
@@ -32,8 +35,15 @@
#include "Stopwatch.h"
#include "netid_client.h"
+#include "android-base/unique_fd.h"
+
+using android::base::unique_fd;
+
namespace {
+// Keep this in sync with CMD_BUF_SIZE in FrameworkListener.cpp.
+constexpr size_t MAX_CMD_SIZE = 1024;
+
std::atomic_uint netIdForProcess(NETID_UNSET);
std::atomic_uint netIdForResolv(NETID_UNSET);
@@ -206,6 +216,59 @@
return s;
}
+auto divCeil(size_t dividend, size_t divisor) {
+ return ((dividend + divisor - 1) / divisor);
+}
+
+// FrameworkListener only does only read() call, and fails if the read doesn't contain \0
+// Do single write here
+int sendData(int fd, const void* buf, size_t size) {
+ if (fd < 0) {
+ return -EBADF;
+ }
+
+ ssize_t rc = TEMP_FAILURE_RETRY(write(fd, (char*) buf, size));
+ if (rc > 0) {
+ return rc;
+ } else if (rc == 0) {
+ return -EIO;
+ } else {
+ return -errno;
+ }
+}
+
+int readData(int fd, void* buf, size_t size) {
+ if (fd < 0) {
+ return -EBADF;
+ }
+
+ size_t current = 0;
+ for (;;) {
+ ssize_t rc = TEMP_FAILURE_RETRY(read(fd, (char*) buf + current, size - current));
+ if (rc > 0) {
+ current += rc;
+ if (current == size) {
+ break;
+ }
+ } else if (rc == 0) {
+ return -EIO;
+ } else {
+ return -errno;
+ }
+ }
+ return 0;
+}
+
+bool readBE32(int fd, int32_t* result) {
+ int32_t tmp;
+ int n = TEMP_FAILURE_RETRY(read(fd, &tmp, sizeof(tmp)));
+ if (n < 0) {
+ return false;
+ }
+ *result = ntohl(tmp);
+ return true;
+}
+
} // namespace
#define CHECK_SOCKET_IS_MARKABLE(sock) \
@@ -321,3 +384,80 @@
FwmarkCommand command = {FwmarkCommand::DELETE_TAGDATA, 0, uid, tag};
return FwmarkClient().send(&command, -1, nullptr);
}
+
+extern "C" int resNetworkQuery(unsigned netId, const char* dname, int ns_class, int ns_type) {
+ u_char buf[MAX_CMD_SIZE] = {};
+ int len = res_mkquery(QUERY, dname, ns_class, ns_type, NULL, 0, NULL, buf, sizeof(buf));
+
+ return resNetworkSend(netId, buf, len);
+}
+
+extern "C" int resNetworkSend(unsigned netId, const uint8_t* msg, int msglen) {
+ // Encode
+ // Base 64 encodes every 3 bytes into 4 characters, but then adds padding to the next
+ // multiple of 4 and a \0
+ const size_t encodedLen = divCeil(msglen, 3) * 4 + 1;
+ auto encodedQuery = std::string(encodedLen - 1, 0);
+ int enLen = b64_ntop(msg, msglen, encodedQuery.data(), encodedLen);
+
+ if (enLen < 0) {
+ // Unexpected behavior, encode failed
+ // b64_ntop only fails when size is too long.
+ return -EMSGSIZE;
+ }
+ // Send
+ netId = getNetworkForResolv(netId);
+ const std::string cmd = "resnsend " + encodedQuery + " " + std::to_string(netId) + '\0';
+ if (cmd.size() > MAX_CMD_SIZE) {
+ // Cmd size must less than buffer size of FrameworkListener
+ return -EMSGSIZE;
+ }
+ int fd = dns_open_proxy();
+ if (fd == -1) {
+ return -errno;
+ }
+ ssize_t rc = sendData(fd, cmd.c_str(), cmd.size());
+ if (rc < 0) {
+ close(fd);
+ return rc;
+ }
+ shutdown(fd, SHUT_WR);
+ return fd;
+}
+
+extern "C" int resNetworkResult(int fd, int* rcode, uint8_t* answer, int anslen) {
+ int32_t result = 0;
+ unique_fd ufd(fd);
+ // Read -errno/rcode
+ if (!readBE32(fd, &result)) {
+ // Unexpected behavior, read -errno/rcode fail
+ return -errno;
+ }
+ if (result < 0) {
+ // result < 0, it's -errno
+ return result;
+ }
+ // result >= 0, it's rcode
+ *rcode = result;
+
+ // Read answer
+ int32_t size = 0;
+ if (!readBE32(fd, &size)) {
+ // Unexpected behavior, read ans len fail
+ return -EREMOTEIO;
+ }
+ if (anslen < size) {
+ // Answer buffer is too small
+ return -EMSGSIZE;
+ }
+ int rc = readData(fd, answer, size);
+ if (rc < 0) {
+ // Reading the answer failed.
+ return rc;
+ }
+ return size;
+}
+
+extern "C" void resNetworkCancel(int fd) {
+ close(fd);
+}
\ No newline at end of file