Do not block on accept() if server died
The server may die before connecting to the client. In that case, the client was blocked indefinitely (until Ctrl+C) on accept(). To avoid the problem, close the server socket once the server process is dead.
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d421741a83
commit
a346bb80f4
2 changed files with 34 additions and 12 deletions
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@ -318,14 +318,12 @@ connect_to_server(uint16_t port, uint32_t attempts, uint32_t delay) {
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}
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static void
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close_socket(socket_t *socket) {
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assert(*socket != INVALID_SOCKET);
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net_shutdown(*socket, SHUT_RDWR);
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if (!net_close(*socket)) {
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close_socket(socket_t socket) {
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assert(socket != INVALID_SOCKET);
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net_shutdown(socket, SHUT_RDWR);
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if (!net_close(socket)) {
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LOGW("Could not close socket");
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return;
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}
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*socket = INVALID_SOCKET;
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}
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void
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@ -337,6 +335,14 @@ static int
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run_wait_server(void *data) {
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struct server *server = data;
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cmd_simple_wait(server->process, NULL); // ignore exit code
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// no need for synchronization, server_socket is initialized before this
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// thread was created
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if (server->server_socket != INVALID_SOCKET
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&& SDL_AtomicCAS(&server->server_socket_closed, 0, 1)) {
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// On Linux, accept() is unblocked by shutdown(), but on Windows, it is
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// unblocked by closesocket(). Therefore, call both (close_socket()).
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close_socket(server->server_socket);
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}
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LOGD("Server terminated");
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return 0;
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}
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@ -367,6 +373,12 @@ server_start(struct server *server, const char *serial,
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goto error2;
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}
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// If the server process dies before connecting to the server socket, then
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// the client will be stuck forever on accept(). To avoid the problem, we
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// must be able to wake up the accept() call when the server dies. To keep
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// things simple and multiplatform, just spawn a new thread waiting for the
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// server process and calling shutdown()/close() on the server socket if
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// necessary to wake up any accept() blocking call.
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server->wait_server_thread =
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SDL_CreateThread(run_wait_server, "wait-server", server);
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if (!server->wait_server_thread) {
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@ -383,7 +395,9 @@ server_start(struct server *server, const char *serial,
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error2:
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if (!server->tunnel_forward) {
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close_socket(&server->server_socket);
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// the wait server thread is not started, SDL_AtomicSet() is sufficient
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SDL_AtomicSet(&server->server_socket_closed, 1);
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close_socket(server->server_socket);
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}
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disable_tunnel(server);
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error1:
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@ -406,7 +420,11 @@ server_connect_to(struct server *server) {
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}
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// we don't need the server socket anymore
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close_socket(&server->server_socket);
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if (SDL_AtomicCAS(&server->server_socket_closed, 0, 1)) {
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// close it from here
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close_socket(server->server_socket);
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// otherwise, it is closed by run_wait_server()
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}
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} else {
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uint32_t attempts = 100;
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uint32_t delay = 100; // ms
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@ -433,14 +451,15 @@ server_connect_to(struct server *server) {
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void
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server_stop(struct server *server) {
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if (server->server_socket != INVALID_SOCKET) {
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close_socket(&server->server_socket);
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if (server->server_socket != INVALID_SOCKET
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&& SDL_AtomicCAS(&server->server_socket_closed, 0, 1)) {
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close_socket(server->server_socket);
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}
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if (server->video_socket != INVALID_SOCKET) {
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close_socket(&server->video_socket);
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close_socket(server->video_socket);
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}
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if (server->control_socket != INVALID_SOCKET) {
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close_socket(&server->control_socket);
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close_socket(server->control_socket);
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}
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assert(server->process != PROCESS_NONE);
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@ -3,6 +3,7 @@
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#include <stdbool.h>
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#include <stdint.h>
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#include <SDL2/SDL_atomic.h>
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#include <SDL2/SDL_thread.h>
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#include "config.h"
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@ -14,6 +15,7 @@ struct server {
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char *serial;
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process_t process;
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SDL_Thread *wait_server_thread;
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SDL_atomic_t server_socket_closed;
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socket_t server_socket; // only used if !tunnel_forward
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socket_t video_socket;
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socket_t control_socket;
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@ -27,6 +29,7 @@ struct server {
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.serial = NULL, \
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.process = PROCESS_NONE, \
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.wait_server_thread = NULL, \
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.server_socket_closed = {0}, \
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.server_socket = INVALID_SOCKET, \
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.video_socket = INVALID_SOCKET, \
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.control_socket = INVALID_SOCKET, \
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