c++/domain-socket-bridge/domain-socket-bridge.cpp
author František Kučera <franta-hg@frantovo.cz>
Sun, 11 Jun 2017 14:08:19 +0200
changeset 53 516358e07f9d
parent 43 b54d76467040
permissions -rw-r--r--
lpt-signal-generator: komentář
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#include <string.h>
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#include <errno.h>
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#include <stdio.h>
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#include <signal.h>
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#include <stdlib.h>
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#include <string>
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#include <regex>
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#include <event2/bufferevent.h>
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#include <event2/buffer.h>
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#include <event2/listener.h>
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#include <event2/util.h>
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#include <event2/event.h>
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#include <sys/socket.h>
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#include <sys/un.h>
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#include <unistd.h>
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using namespace std;
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static const string HELLO_MESSAGE("Hello, World!\n");
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static const string SOCKET_PATH("./roura");
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static const string COMMAND_EXIT("exit\n");
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static void listener_cb(evutil_socket_t, short, void *);
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static void conn_read_cb(struct bufferevent *, void *);
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static void conn_write_cb(struct bufferevent *, void *);
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static void conn_event_cb(struct bufferevent *, short, void *);
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static void signal_cb(evutil_socket_t, short, void *);
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static void print_socket_info(int, int);
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int main(int argc, char **argv) {
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	printf("%4s %8s\n", "*", "STARTED");
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	struct event_base *base;
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	evutil_socket_t listener;
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	struct event *listener_event;
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	struct event *signal_event;
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	struct sockaddr_un sun;
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	setvbuf(stdout, NULL, _IONBF, 0);
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	base = event_base_new();
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	if (!base) {
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		printf("%4s %8s %s\n", "*", "ERROR", "unable to initialize libevent");
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		return 1;
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	}
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	memset(&sun, 0, sizeof (sun));
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	sun.sun_family = AF_UNIX;
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	strcpy(sun.sun_path, SOCKET_PATH.c_str());
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	listener = socket(AF_UNIX, SOCK_STREAM, 0);
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	evutil_make_socket_nonblocking(listener);
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	if (bind(listener, (struct sockaddr*) &sun, sizeof (sun)) < 0) {
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		printf("%4s %8s %s: %s\n", "*", "ERROR", "unable to create domain socket:", SOCKET_PATH.c_str());
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		return 1;
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	}
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	if (listen(listener, 16) < 0) {
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		printf("%4s %8s %s\n", "*", "ERROR", "unable to listen");
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		return 1;
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	}
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	// identifikátor serverového soketu (v současnosti číslo FD)
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	printf("%4s %8s listening at: sun_path = %s → socketId = %d\n", "*", "SOCKET", sun.sun_path, listener);
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	listener_event = event_new(base, listener, EV_READ | EV_PERSIST, listener_cb, (void*) base);
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	if (!listener_event) {
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		printf("%4s %8s %s\n", "*", "ERROR", "unable to do event_new()");
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		return 1;
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	}
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	event_add(listener_event, NULL);
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	signal_event = evsignal_new(base, SIGINT, signal_cb, (void *) base);
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	if (!signal_event || event_add(signal_event, NULL) < 0) {
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		printf("%4s %8s %s\n", "*", "ERROR", "unable to create/add a signal event");
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		return 1;
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	}
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	event_base_dispatch(base);
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	event_free(listener_event);
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	event_free(signal_event);
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	event_base_free(base);
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	// smažeme soket na disku / soubor -- jinak by program příště spadl na bind()
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	// TODO: co když soket někdo přesune a místo něj dá jiný soubor?
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	unlink(SOCKET_PATH.c_str());
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	printf("%4s %8s\n", "*", "FINISHED");
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	return 0;
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}
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static void listener_cb(evutil_socket_t listener, short event, void *user_data) {
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	struct event_base *base = (event_base *) user_data;
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	struct bufferevent *bev;
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	struct sockaddr_storage ss;
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	socklen_t slen = sizeof (ss);
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	int fd = accept(listener, (struct sockaddr*) &ss, &slen);
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	// identifikátor navázaného spojení (v současnosti číslo FD)
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	int * connectionId = (int*) malloc(sizeof (fd));
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	*connectionId = fd;
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	if (fd < 0) {
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		printf("%4d %8s %s\n", *connectionId, "ERROR", "unable to accept()");
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		return;
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	} else if (fd > FD_SETSIZE) {
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		// FD_SETSIZE = 1024 -- Proč? Co když bude spojení víc?
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		printf("%4d %8s fd (%d) > FD_SETSIZE (%d)\n", *connectionId, "ERROR", fd, FD_SETSIZE);
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		close(fd);
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		return;
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	}
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	evutil_make_socket_nonblocking(fd);
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	bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
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	if (!bev) {
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		printf("%4d %8s %s\n", *connectionId, "ERROR", "constructing bufferevent");
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		event_base_loopbreak(base);
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		return;
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	}
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	bufferevent_setcb(bev, conn_read_cb, conn_write_cb, conn_event_cb, (void*) connectionId);
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	bufferevent_enable(bev, EV_READ | EV_WRITE);
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	printf("%4d %8s somebody has connected: socketId = %d → connectionId = %d\n", *connectionId, "CONN", listener, *connectionId);
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	print_socket_info(*connectionId, fd);
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	bufferevent_write(bev, HELLO_MESSAGE.c_str(), strlen(HELLO_MESSAGE.c_str()));
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}
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static void conn_read_cb(struct bufferevent *bev, void *user_data) {
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	int connectionId = *((int*) user_data);
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	/* This callback is invoked when there is data to read on bev. */
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	struct evbuffer *input = bufferevent_get_input(bev);
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	struct evbuffer *output = bufferevent_get_output(bev);
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	struct event_base *base = bufferevent_get_base(bev);
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	size_t len = evbuffer_get_length(input);
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	char *data = (char*) malloc(len + 1);
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	data[len] = 0; // as a string must be terminated by \0 
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	evbuffer_copyout(input, data, len);
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	//TODO: there might already be \0 in the byte stream, only the part before the first \0 will be formatted as a string
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	string dataFormated(data);
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	dataFormated = regex_replace(dataFormated, regex("\\n"), "\\n");
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	printf("%4d %8s '%s'\n", connectionId, "IN", dataFormated.c_str());
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	if (COMMAND_EXIT.compare(data) == 0) {
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		struct timeval delay = {2, 123};
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		printf("%4d %8s client asks us to terminate; finishing in %ld sesonds and %ld microseconds\n", connectionId, "EXIT", delay.tv_sec, delay.tv_usec);
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		event_base_loopexit(base, &delay);
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	}
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	evbuffer_add(output, "echo: ", 6);
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	/* Copy all the data from the input buffer to the output buffer. */
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	evbuffer_add_buffer(output, input);
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	free(data);
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}
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static void conn_write_cb(struct bufferevent *bev, void *user_data) {
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	int connectionId = *((int*) user_data);
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	struct evbuffer *output = bufferevent_get_output(bev);
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	if (evbuffer_get_length(output) == 0) {
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		printf("%4d %8s\n", connectionId, "FLUSH");
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		/* nebudeme ukončovat spojení
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		bufferevent_free(bev);
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		 */
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	} else {
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		// FIXME: sem to nikdy nepřijde
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		size_t len = evbuffer_get_length(output);
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		char *data = (char*) malloc(len);
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		evbuffer_copyout(output, data, len);
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		printf("%4d %8s '%s'\n", connectionId, "OUT", data);
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		free(data);
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	}
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}
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static void conn_event_cb(struct bufferevent *bev, short events, void *user_data) {
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	int connectionId = *((int*) user_data);
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	if (events & BEV_EVENT_EOF) {
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		printf("%4d %8s\n", connectionId, "CLOSE");
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	} else if (events & BEV_EVENT_ERROR) {
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		printf("%4d %8s %s\n", connectionId, "ERROR", strerror(errno));
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	} else {
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		printf("%4d %8s\n", connectionId, "OTHER");
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		// None of the other events can happen here, since we haven't enabled timeouts
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	}
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	bufferevent_free(bev);
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	free(user_data);
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}
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static void signal_cb(evutil_socket_t sig, short events, void *user_data) {
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	struct event_base *base = (event_base *) user_data;
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	struct timeval delay = {2, 123};
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	printf("\n%4s %8s got SIGINT (Ctrl+C); finishing in %ld sesonds and %ld microseconds\n", "*", "SIGNAL", delay.tv_sec, delay.tv_usec);
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	event_base_loopexit(base, &delay);
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}
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static void print_socket_info(int connectionId, int fd) {
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	struct ucred cr;
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	unsigned int cl = sizeof (cr);
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	if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &cr, &cl) == 0) {
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		printf("%4d %8s client identification: pid=%d, uid=%d, gid=%d\n", connectionId, "CONN", cr.pid, cr.uid, cr.gid);
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	}
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}