#include <arpa/inet.h>

#include <errno.h>

#include <getopt.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <netdb.h>

#include <sys/fcntl.h>

#include <sys/socket.h>

#include <sys/un.h>

#include <unistd.h>

#include "sd-daemon.h"

#include "sd-event.h"

#include "log.h"

#include "socket-util.h"

#include "util.h"

#include "event-util.h"

#define BUFFER_SIZE 16384

#define _cleanup_freeaddrinfo_ _cleanup_(freeaddrinfop)

unsigned int total_clients = 0;

DEFINE_TRIVIAL_CLEANUP_FUNC(struct addrinfo *, freeaddrinfo);

struct proxy {

int listen_fd;

bool ignore_env;

bool remote_is_inet;

const char *remote_host;

const char *remote_service;

};

struct connection {

int fd;

uint32_t events;

sd_event_source *w;

struct connection *c_destination;

size_t buffer_filled_len;

size_t buffer_sent_len;

char buffer[BUFFER_SIZE];

};

static void free_connection(struct connection *c) {

log_debug("Freeing fd=%d (conn %p).", c->fd, c);

sd_event_source_unref(c->w);

close_nointr_nofail(c->fd);

free(c);

}

static int add_event_to_connection(struct connection *c, uint32_t events) {

int r;

log_debug("Have revents=%d. Adding revents=%d.", c->events, events);

c->events |= events;

r = sd_event_source_set_io_events(c->w, c->events);

if (r < 0) {

log_error("Error %d setting revents: %s", r, strerror(-r));

return r;

}

r = sd_event_source_set_enabled(c->w, SD_EVENT_ON);

if (r < 0) {

log_error("Error %d enabling source: %s", r, strerror(-r));

return r;

}

return 0;

}

static int remove_event_from_connection(struct connection *c, uint32_t events) {

int r;

log_debug("Have revents=%d. Removing revents=%d.", c->events, events);

c->events &= ~events;

r = sd_event_source_set_io_events(c->w, c->events);

if (r < 0) {

log_error("Error %d setting revents: %s", r, strerror(-r));

return r;

}

if (c->events == 0) {

r = sd_event_source_set_enabled(c->w, SD_EVENT_OFF);

if (r < 0) {

log_error("Error %d disabling source: %s", r, strerror(-r));

return r;

}

}

return 0;

}

static int send_buffer(struct connection *sender) {

struct connection *receiver = sender->c_destination;

ssize_t len;

int r = 0;

/* We cannot assume that even a partial send() indicates that

while (sender->buffer_filled_len > sender->buffer_sent_len) {

len = send(receiver->fd, sender->buffer + sender->buffer_sent_len, sender->buffer_filled_len - sender->buffer_sent_len, 0);

log_debug("send(%d, ...)=%ld", receiver->fd, len);

if (len < 0) {

if (errno != EWOULDBLOCK && errno != EAGAIN) {

log_error("Error %d in send to fd=%d: %m", errno, receiver->fd);

return -errno;

}

else {

/* send() is in a blocking state. */

break;

}

}

/* len < 0 can't occur here. len == 0 is possible but

assert(len > 0);

sender->buffer_sent_len += len;

}

log_debug("send(%d, ...) completed with %lu bytes still buffered.", receiver->fd, sender->buffer_filled_len - sender->buffer_sent_len);

/* Detect a would-block state or partial send. */

if (sender->buffer_filled_len > sender->buffer_sent_len) {

/* If the buffer is full, disable events coming for recv. */

if (sender->buffer_filled_len == BUFFER_SIZE) {

r = remove_event_from_connection(sender, EPOLLIN);

if (r < 0) {

log_error("Error %d disabling EPOLLIN for fd=%d: %s", r, sender->fd, strerror(-r));

return r;

}

}

/* Watch for when the recipient can be sent data again. */

r = add_event_to_connection(receiver, EPOLLOUT);

if (r < 0) {

log_error("Error %d enabling EPOLLOUT for fd=%d: %s", r, receiver->fd, strerror(-r));

return r;

}

log_debug("Done with recv for fd=%d. Waiting on send for fd=%d.", sender->fd, receiver->fd);

return r;

}

/* If we sent everything without blocking, the buffer is now empty. */

sender->buffer_filled_len = 0;

sender->buffer_sent_len = 0;

/* Enable the sender's receive watcher, in case the buffer was

r = add_event_to_connection(sender, EPOLLIN);

if (r < 0) {

log_error("Error %d enabling EPOLLIN for fd=%d: %s", r, sender->fd, strerror(-r));

return r;

}

/* Disable the other side's send watcher, as we have no data to send now. */

r = remove_event_from_connection(receiver, EPOLLOUT);

if (r < 0) {

log_error("Error %d disabling EPOLLOUT for fd=%d: %s", r, receiver->fd, strerror(-r));

return r;

}

return 0;

}

static int transfer_data_cb(sd_event_source *s, int fd, uint32_t revents, void *userdata) {

struct connection *c = (struct connection *) userdata;

int r = 0;

ssize_t len;

assert(revents & (EPOLLIN | EPOLLOUT));

assert(fd == c->fd);

assert(s == c->w);

log_debug("Got event revents=%d from fd=%d (conn %p).", revents, fd, c);

if (revents & EPOLLIN) {

log_debug("About to recv up to %lu bytes from fd=%d (%lu/BUFFER_SIZE).", BUFFER_SIZE - c->buffer_filled_len, fd, c->buffer_filled_len);

/* Receive until the buffer's full, there's no more data,

while (c->buffer_filled_len < BUFFER_SIZE) {

len = recv(fd, c->buffer + c->buffer_filled_len, BUFFER_SIZE - c->buffer_filled_len, 0);

log_debug("recv(%d, ...)=%ld", fd, len);

if (len < 0) {

if (errno != EWOULDBLOCK && errno != EAGAIN) {

log_error("Error %d in recv from fd=%d: %m", errno, fd);

return -errno;

}

else {

/* recv() is in a blocking state. */

break;

}

}

else if (len == 0) {

log_debug("Clean disconnection from fd=%d", fd);

total_clients--;

free_connection(c->c_destination);

free_connection(c);

return 0;

}

assert(len > 0);

log_debug("Recording that the buffer got %ld more bytes full.", len);

c->buffer_filled_len += len;

log_debug("Buffer now has %ld bytes full.", c->buffer_filled_len);

}

/* Try sending the data immediately. */

return send_buffer(c);

}

else {

return send_buffer(c->c_destination);

}

return r;

}

static int connected_to_server_cb(sd_event_source *s, int fd, uint32_t revents, void *userdata) {

struct sd_event *e = NULL;

struct connection *c_server_to_client = (struct connection *) userdata;

struct connection *c_client_to_server = c_server_to_client->c_destination;

int r;

assert(revents & EPOLLOUT);

e = sd_event_get(s);

/* Cancel the initial write watcher for the server. */

sd_event_source_unref(s);

log_debug("Connected to server. Initializing watchers for receiving data.");

/* A recv watcher for the server. */

r = sd_event_add_io(e, c_server_to_client->fd, EPOLLIN, transfer_data_cb, c_server_to_client, &c_server_to_client->w);

if (r < 0) {

log_error("Error %d creating recv watcher for fd=%d: %s", r, c_server_to_client->fd, strerror(-r));

goto fail;

}

c_server_to_client->events = EPOLLIN;

/* A recv watcher for the client. */

r = sd_event_add_io(e, c_client_to_server->fd, EPOLLIN, transfer_data_cb, c_client_to_server, &c_client_to_server->w);

if (r < 0) {

log_error("Error %d creating recv watcher for fd=%d: %s", r, c_client_to_server->fd, strerror(-r));

goto fail;

}

c_client_to_server->events = EPOLLIN;

goto finish;

fail:

free_connection(c_client_to_server);

free_connection(c_server_to_client);

finish:

return r;

}

static int get_server_connection_fd(const struct proxy *proxy) {

int server_fd;

int r = -EBADF;

int len;

if (proxy->remote_is_inet) {

int s;

_cleanup_freeaddrinfo_ struct addrinfo *result = NULL;

struct addrinfo hints = {.ai_family = AF_UNSPEC,

.ai_socktype = SOCK_STREAM,

.ai_flags = AI_PASSIVE};

log_debug("Looking up address info for %s:%s", proxy->remote_host, proxy->remote_service);

s = getaddrinfo(proxy->remote_host, proxy->remote_service, &hints, &result);

if (s != 0) {

log_error("getaddrinfo error (%d): %s", s, gai_strerror(s));

return r;

}

if (result == NULL) {

log_error("getaddrinfo: no result");

return r;

}

/* @TODO: Try connecting to all results instead of just the first. */

server_fd = socket(result->ai_family, result->ai_socktype | SOCK_NONBLOCK, result->ai_protocol);

if (server_fd < 0) {

log_error("Error %d creating socket: %m", errno);

return r;

}

r = connect(server_fd, result->ai_addr, result->ai_addrlen);

/* Ignore EINPROGRESS errors because they're expected for a nonblocking socket. */

if (r < 0 && errno != EINPROGRESS) {

log_error("Error %d while connecting to socket %s:%s: %m", errno, proxy->remote_host, proxy->remote_service);

return r;

}

}

else {

struct sockaddr_un remote;

server_fd = socket(AF_UNIX, SOCK_STREAM | SOCK_NONBLOCK, 0);

if (server_fd < 0) {

log_error("Error %d creating socket: %m", errno);

return -EBADFD;

}

remote.sun_family = AF_UNIX;

strncpy(remote.sun_path, proxy->remote_host, sizeof(remote.sun_path));

len = strlen(remote.sun_path) + sizeof(remote.sun_family);

r = connect(server_fd, (struct sockaddr *) &remote, len);

if (r < 0 && errno != EINPROGRESS) {

log_error("Error %d while connecting to Unix domain socket %s: %m", errno, proxy->remote_host);

return -EBADFD;

}

}

log_debug("Server connection is fd=%d", server_fd);

return server_fd;

}

static int accept_cb(sd_event_source *s, int fd, uint32_t revents, void *userdata) {

struct proxy *proxy = (struct proxy *) userdata;

struct connection *c_server_to_client;

struct connection *c_client_to_server;

int r = 0;

union sockaddr_union sa;

socklen_t salen = sizeof(sa);

assert(revents & EPOLLIN);

c_server_to_client = new0(struct connection, 1);

if (c_server_to_client == NULL) {

log_oom();

goto fail;

}

c_client_to_server = new0(struct connection, 1);

if (c_client_to_server == NULL) {

log_oom();

goto fail;

}

c_server_to_client->fd = get_server_connection_fd(proxy);

if (c_server_to_client->fd < 0) {

log_error("Error initiating server connection.");

goto fail;

}

c_client_to_server->fd = accept4(fd, (struct sockaddr *) &sa, &salen, SOCK_NONBLOCK|SOCK_CLOEXEC);

if (c_client_to_server->fd < 0) {

log_error("Error accepting client connection.");

goto fail;

}

if (sa.sa.sa_family == AF_INET || sa.sa.sa_family == AF_INET6) {

char sa_str[INET6_ADDRSTRLEN];

const char *success;

success = inet_ntop(sa.sa.sa_family, &sa.in6.sin6_addr, sa_str, INET6_ADDRSTRLEN);

if (success == NULL)

log_warning("Error %d calling inet_ntop: %m", errno);

else

log_debug("Accepted client connection from %s as fd=%d", sa_str, c_client_to_server->fd);

}

else {

log_debug("Accepted client connection (non-IP) as fd=%d", c_client_to_server->fd);

}

total_clients++;

log_debug("Client fd=%d (conn %p) successfully connected. Total clients: %u", c_client_to_server->fd, c_client_to_server, total_clients);

log_debug("Server fd=%d (conn %p) successfully initialized.", c_server_to_client->fd, c_server_to_client);

/* Initialize watcher for send to server; this shows connectivity. */

r = sd_event_add_io(sd_event_get(s), c_server_to_client->fd, EPOLLOUT, connected_to_server_cb, c_server_to_client, &c_server_to_client->w);

if (r < 0) {

log_error("Error %d creating connectivity watcher for fd=%d: %s", r, c_server_to_client->fd, strerror(-r));

goto fail;

}

/* Allow lookups of the opposite connection. */

c_server_to_client->c_destination = c_client_to_server;

c_client_to_server->c_destination = c_server_to_client;

goto finish;

fail:

log_warning("Accepting a client connection or connecting to the server failed.");

free_connection(c_client_to_server);

free_connection(c_server_to_client);

finish:

/* Preserve the main loop even if a single proxy setup fails. */

return 1;

}

static int run_main_loop(struct proxy *proxy) {

_cleanup_event_source_unref_ sd_event_source *w_accept = NULL;

_cleanup_event_unref_ sd_event *e = NULL;

int r = EXIT_SUCCESS;

r = sd_event_new(&e);

if (r < 0) {

log_error("Failed to allocate event loop: %s", strerror(-r));

return r;

}

r = fd_nonblock(proxy->listen_fd, true);

if (r < 0) {

log_error("Failed to make listen file descriptor non-blocking: %s", strerror(-r));

return r;

}

log_debug("Initializing main listener fd=%d", proxy->listen_fd);

r = sd_event_add_io(e, proxy->listen_fd, EPOLLIN, accept_cb, proxy, &w_accept);

if (r < 0) {

log_error("Failed to add event IO source: %s", strerror(-r));

return r;

}

log_debug("Initialized main listener. Entering loop.");

return sd_event_loop(e);

}

static int help(void) {

printf("%s hostname-or-ip port-or-service\n"

"%s unix-domain-socket-path\n\n"

"Inherit a socket. Bidirectionally proxy.\n\n"

" -h --help Show this help\n"

" --version Print version and exit\n"

" --ignore-env Ignore expected systemd environment\n",

program_invocation_short_name,

program_invocation_short_name);

return 0;

}

static void version(void) {

puts(PACKAGE_STRING " socket-proxyd");

}

static int parse_argv(int argc, char *argv[], struct proxy *p) {

enum {

ARG_VERSION = 0x100,

ARG_IGNORE_ENV

};

static const struct option options[] = {

{ "help", no_argument, NULL, 'h' },

{ "version", no_argument, NULL, ARG_VERSION },

{ "ignore-env", no_argument, NULL, ARG_IGNORE_ENV},

{ NULL, 0, NULL, 0 }

};

int c;

assert(argc >= 0);

assert(argv);

while ((c = getopt_long(argc, argv, "h", options, NULL)) >= 0) {

switch (c) {

case 'h':

help();

return 0;

case '?':

return -EINVAL;

case ARG_VERSION:

version();

return 0;

case ARG_IGNORE_ENV:

p->ignore_env = true;

continue;

default:

log_error("Unknown option code %c", c);

return -EINVAL;

}

}

if (optind + 1 != argc && optind + 2 != argc) {

log_error("Incorrect number of positional arguments.");

help();

return -EINVAL;

}

p->remote_host = argv[optind];

assert(p->remote_host);

p->remote_is_inet = p->remote_host[0] != '/';

if (optind == argc - 2) {

if (!p->remote_is_inet) {

log_error("A port or service is not allowed for Unix socket destinations.");

help();

return -EINVAL;

}

p->remote_service = argv[optind + 1];

assert(p->remote_service);

} else if (p->remote_is_inet) {

log_error("A port or service is required for IP destinations.");

help();

return -EINVAL;

}

return 1;

}

int main(int argc, char *argv[]) {

struct proxy p = {};

int r;

log_parse_environment();

log_open();

r = parse_argv(argc, argv, &p);

if (r <= 0)

goto finish;

p.listen_fd = SD_LISTEN_FDS_START;

if (!p.ignore_env) {

int n;

n = sd_listen_fds(1);

if (n == 0) {

log_error("Found zero inheritable sockets. Are you sure this is running as a socket-activated service?");

r = EXIT_FAILURE;

goto finish;

} else if (n < 0) {

log_error("Error %d while finding inheritable sockets: %s", n, strerror(-n));

r = EXIT_FAILURE;

goto finish;

} else if (n > 1) {

log_error("Can't listen on more than one socket.");

r = EXIT_FAILURE;

goto finish;

}

}

/* @TODO: Check if this proxy can work with datagram sockets. */

r = sd_is_socket(p.listen_fd, 0, SOCK_STREAM, 1);

if (r < 0) {

log_error("Error %d while checking inherited socket: %s", r, strerror(-r));

goto finish;

}

log_info("Starting the socket activation proxy with listener fd=%d.", p.listen_fd);

r = run_main_loop(&p);

finish:

return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;

}