Android: ANR in Address::Resolve

[grorp]

Minetest version

5.8.1

Operating system

Android

Summary

I saw this on the Play Console and I'm opening an issue for it since it looks fixable:

Input dispatching timed out

Stacktrace for "MinetestNativeThread":

#00  pc 0x00000000000d77e4  /apex/com.android.runtime/lib64/bionic/libc.so (read+4)
#01  pc 0x00000000000e3ecc  /apex/com.android.runtime/lib64/bionic/libc.so (__sread+52)
#02  pc 0x00000000000e3dbc  /apex/com.android.runtime/lib64/bionic/libc.so (__srefill+268)
#03  pc 0x00000000000e82e0  /apex/com.android.runtime/lib64/bionic/libc.so (fread_unlocked+200)
#04  pc 0x00000000000e81d0  /apex/com.android.runtime/lib64/bionic/libc.so (fread+72)
#05  pc 0x00000000000a45c8  /apex/com.android.runtime/lib64/bionic/libc.so (android_getaddrinfo_proxy+336)
#06  pc 0x00000000000a4290  /apex/com.android.runtime/lib64/bionic/libc.so (android_getaddrinfofornetcontext+1536)
#07  pc 0x00000000000a3c68  /apex/com.android.runtime/lib64/bionic/libc.so (android_getaddrinfofornet+56)
#08  pc 0x00000000006b84a8  /data/app/~~s6S-KxZcxQcWcOCZ8pZDWA==/net.minetest.minetest-KKtd8D2AOieFwzuuxLGpGg==/split_config.arm64_v8a.apk!libminetest.so (Address::Resolve(char const*)+172)
#09  pc 0x000000000055b250  /data/app/~~s6S-KxZcxQcWcOCZ8pZDWA==/net.minetest.minetest-KKtd8D2AOieFwzuuxLGpGg==/split_config.arm64_v8a.apk!libminetest.so (Game::connectToServer(GameStartData const&, bool*, bool*)+200)
#10  pc 0x0000000000553c84  /data/app/~~s6S-KxZcxQcWcOCZ8pZDWA==/net.minetest.minetest-KKtd8D2AOieFwzuuxLGpGg==/split_config.arm64_v8a.apk!libminetest.so (Game::createClient(GameStartData const&)+184)
#11  pc 0x0000000000553994  /data/app/~~s6S-KxZcxQcWcOCZ8pZDWA==/net.minetest.minetest-KKtd8D2AOieFwzuuxLGpGg==/split_config.arm64_v8a.apk!libminetest.so (Game::startup(bool*, InputHandler*, RenderingEngine*, GameStartData const&, std::__ndk1::basic_string<char, std::__ndk1::char_traits<char>, std::__ndk1::allocator<char> >&, bool*, ChatBackend*)+480)
#12  pc 0x00000000005662d0  /data/app/~~s6S-KxZcxQcWcOCZ8pZDWA==/net.minetest.minetest-KKtd8D2AOieFwzuuxLGpGg==/split_config.arm64_v8a.apk!libminetest.so (the_game(bool*, InputHandler*, RenderingEngine*, GameStartData const&, std::__ndk1::basic_string<char, std::__ndk1::char_traits<char>, std::__ndk1::allocator<char> >&, ChatBackend&, bool*)+104)
#13  pc 0x000000000051b2b8  /data/app/~~s6S-KxZcxQcWcOCZ8pZDWA==/net.minetest.minetest-KKtd8D2AOieFwzuuxLGpGg==/split_config.arm64_v8a.apk!libminetest.so (ClientLauncher::run(GameStartData&, Settings const&)+4016)
#14  pc 0x00000000007f6c54  /data/app/~~s6S-KxZcxQcWcOCZ8pZDWA==/net.minetest.minetest-KKtd8D2AOieFwzuuxLGpGg==/split_config.arm64_v8a.apk!libminetest.so (main+8228)
#15  pc 0x000000000083e37c  /data/app/~~s6S-KxZcxQcWcOCZ8pZDWA==/net.minetest.minetest-KKtd8D2AOieFwzuuxLGpGg==/split_config.arm64_v8a.apk!libminetest.so (android_main+112)
#16  pc 0x00000000004f4cfc  /data/app/~~s6S-KxZcxQcWcOCZ8pZDWA==/net.minetest.minetest-KKtd8D2AOieFwzuuxLGpGg==/split_config.arm64_v8a.apk!libminetest.so
#17  pc 0x00000000000ecc00  /apex/com.android.runtime/lib64/bionic/libc.so (__pthread_start(void*)+64)
#18  pc 0x000000000008c360  /apex/com.android.runtime/lib64/bionic/libc.so (__start_thread+64)

Relevant code:

minetest/src/client/game.cpp

Lines 1574 to 1588 in 6303334

	bool Game::connectToServer(const GameStartData &start_data,
	bool *connect_ok, bool *connection_aborted)
	{
	*connect_ok = false; // Let's not be overly optimistic
	*connection_aborted = false;
	bool local_server_mode = false;
	const auto &address_name = start_data.address;
	showOverlayMessage(N_("Resolving address..."), 0, 15);
	Address connect_address(0, 0, 0, 0, start_data.socket_port);
	Address fallback_address;
	try {
	connect_address.Resolve(address_name.c_str(), &fallback_address);

Steps to reproduce

Idea: Have a bad internet connection so that resolving the address takes a long time.

[savilli]

It's easy to reproduce even on a PC. You need to try to connect to an address whose DNS server times out requests. A slow unstable mobile network would cause it too.

The fix is not so easy, unfortunately. We should avoid using getaddrinfo on the main thread, therefore we probably need to move it to a dedicated thread and communicate with it somehow.