#include <errno.h>

#include <fcntl.h>

#include <getopt.h>

#include <netdb.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <sys/socket.h>

#include <sys/un.h>

#include <unistd.h>

#include "sd-daemon.h"

#include "sd-event.h"

#include "sd-resolve.h"

#include "alloc-util.h"

#include "fd-util.h"

#include "log.h"

#include "path-util.h"

#include "set.h"

#include "socket-util.h"

#include "string-util.h"

#include "util.h"

#define BUFFER_SIZE (256 * 1024)

#define CONNECTIONS_MAX 256

static const char *arg_remote_host = NULL;

typedef struct Context {

sd_event *event;

sd_resolve *resolve;

Set *listen;

Set *connections;

} Context;

typedef struct Connection {

Context *context;

int server_fd, client_fd;

int server_to_client_buffer[2]; /* a pipe */

int client_to_server_buffer[2]; /* a pipe */

size_t server_to_client_buffer_full, client_to_server_buffer_full;

size_t server_to_client_buffer_size, client_to_server_buffer_size;

sd_event_source *server_event_source, *client_event_source;

sd_resolve_query *resolve_query;

} Connection;

static void connection_free(Connection *c) {

assert(c);

if (c->context)

set_remove(c->context->connections, c);

sd_event_source_unref(c->server_event_source);

sd_event_source_unref(c->client_event_source);

safe_close(c->server_fd);

safe_close(c->client_fd);

safe_close_pair(c->server_to_client_buffer);

safe_close_pair(c->client_to_server_buffer);

sd_resolve_query_unref(c->resolve_query);

free(c);

}

static void context_free(Context *context) {

sd_event_source *es;

Connection *c;

assert(context);

while ((es = set_steal_first(context->listen)))

sd_event_source_unref(es);

while ((c = set_first(context->connections)))

connection_free(c);

set_free(context->listen);

set_free(context->connections);

sd_event_unref(context->event);

sd_resolve_unref(context->resolve);

}

static int connection_create_pipes(Connection *c, int buffer[2], size_t *sz) {

int r;

assert(c);

assert(buffer);

assert(sz);

if (buffer[0] >= 0)

return 0;

r = pipe2(buffer, O_CLOEXEC|O_NONBLOCK);

if (r < 0)

return log_error_errno(errno, "Failed to allocate pipe buffer: %m");

(void) fcntl(buffer[0], F_SETPIPE_SZ, BUFFER_SIZE);

r = fcntl(buffer[0], F_GETPIPE_SZ);

if (r < 0)

return log_error_errno(errno, "Failed to get pipe buffer size: %m");

assert(r > 0);

*sz = r;

return 0;

}

static int connection_shovel(

Connection *c,

int *from, int buffer[2], int *to,

size_t *full, size_t *sz,

sd_event_source **from_source, sd_event_source **to_source) {

bool shoveled;

assert(c);

assert(from);

assert(buffer);

assert(buffer[0] >= 0);

assert(buffer[1] >= 0);

assert(to);

assert(full);

assert(sz);

assert(from_source);

assert(to_source);

do {

ssize_t z;

shoveled = false;

if (*full < *sz && *from >= 0 && *to >= 0) {

z = splice(*from, NULL, buffer[1], NULL, *sz - *full, SPLICE_F_MOVE|SPLICE_F_NONBLOCK);

if (z > 0) {

*full += z;

shoveled = true;

} else if (z == 0 || errno == EPIPE || errno == ECONNRESET) {

*from_source = sd_event_source_unref(*from_source);

*from = safe_close(*from);

} else if (errno != EAGAIN && errno != EINTR)

return log_error_errno(errno, "Failed to splice: %m");

}

if (*full > 0 && *to >= 0) {

z = splice(buffer[0], NULL, *to, NULL, *full, SPLICE_F_MOVE|SPLICE_F_NONBLOCK);

if (z > 0) {

*full -= z;

shoveled = true;

} else if (z == 0 || errno == EPIPE || errno == ECONNRESET) {

*to_source = sd_event_source_unref(*to_source);

*to = safe_close(*to);

} else if (errno != EAGAIN && errno != EINTR)

return log_error_errno(errno, "Failed to splice: %m");

}

} while (shoveled);

return 0;

}

static int connection_enable_event_sources(Connection *c);

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

Connection *c = userdata;

int r;

assert(s);

assert(fd >= 0);

assert(c);

r = connection_shovel(c,

&c->server_fd, c->server_to_client_buffer, &c->client_fd,

&c->server_to_client_buffer_full, &c->server_to_client_buffer_size,

&c->server_event_source, &c->client_event_source);

if (r < 0)

goto quit;

r = connection_shovel(c,

&c->client_fd, c->client_to_server_buffer, &c->server_fd,

&c->client_to_server_buffer_full, &c->client_to_server_buffer_size,

&c->client_event_source, &c->server_event_source);

if (r < 0)

goto quit;

/* EOF on both sides? */

if (c->server_fd == -1 && c->client_fd == -1)

goto quit;

/* Server closed, and all data written to client? */

if (c->server_fd == -1 && c->server_to_client_buffer_full <= 0)

goto quit;

/* Client closed, and all data written to server? */

if (c->client_fd == -1 && c->client_to_server_buffer_full <= 0)

goto quit;

r = connection_enable_event_sources(c);

if (r < 0)

goto quit;

return 1;

quit:

connection_free(c);

return 0; /* ignore errors, continue serving */

}

static int connection_enable_event_sources(Connection *c) {

uint32_t a = 0, b = 0;

int r;

assert(c);

if (c->server_to_client_buffer_full > 0)

b |= EPOLLOUT;

if (c->server_to_client_buffer_full < c->server_to_client_buffer_size)

a |= EPOLLIN;

if (c->client_to_server_buffer_full > 0)

a |= EPOLLOUT;

if (c->client_to_server_buffer_full < c->client_to_server_buffer_size)

b |= EPOLLIN;

if (c->server_event_source)

r = sd_event_source_set_io_events(c->server_event_source, a);

else if (c->server_fd >= 0)

r = sd_event_add_io(c->context->event, &c->server_event_source, c->server_fd, a, traffic_cb, c);

else

r = 0;

if (r < 0)

return log_error_errno(r, "Failed to set up server event source: %m");

if (c->client_event_source)

r = sd_event_source_set_io_events(c->client_event_source, b);

else if (c->client_fd >= 0)

r = sd_event_add_io(c->context->event, &c->client_event_source, c->client_fd, b, traffic_cb, c);

else

r = 0;

if (r < 0)

return log_error_errno(r, "Failed to set up client event source: %m");

return 0;

}

static int connection_complete(Connection *c) {

int r;

assert(c);

r = connection_create_pipes(c, c->server_to_client_buffer, &c->server_to_client_buffer_size);

if (r < 0)

goto fail;

r = connection_create_pipes(c, c->client_to_server_buffer, &c->client_to_server_buffer_size);

if (r < 0)

goto fail;

r = connection_enable_event_sources(c);

if (r < 0)

goto fail;

return 0;

fail:

connection_free(c);

return 0; /* ignore errors, continue serving */

}

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

Connection *c = userdata;

socklen_t solen;

int error, r;

assert(s);

assert(fd >= 0);

assert(c);

solen = sizeof(error);

r = getsockopt(fd, SOL_SOCKET, SO_ERROR, &error, &solen);

if (r < 0) {

log_error_errno(errno, "Failed to issue SO_ERROR: %m");

goto fail;

}

if (error != 0) {

log_error_errno(error, "Failed to connect to remote host: %m");

goto fail;

}

c->client_event_source = sd_event_source_unref(c->client_event_source);

return connection_complete(c);

fail:

connection_free(c);

return 0; /* ignore errors, continue serving */

}

static int connection_start(Connection *c, struct sockaddr *sa, socklen_t salen) {

int r;

assert(c);

assert(sa);

assert(salen);

c->client_fd = socket(sa->sa_family, SOCK_STREAM|SOCK_NONBLOCK|SOCK_CLOEXEC, 0);

if (c->client_fd < 0) {

log_error_errno(errno, "Failed to get remote socket: %m");

goto fail;

}

r = connect(c->client_fd, sa, salen);

if (r < 0) {

if (errno == EINPROGRESS) {

r = sd_event_add_io(c->context->event, &c->client_event_source, c->client_fd, EPOLLOUT, connect_cb, c);

if (r < 0) {

log_error_errno(r, "Failed to add connection socket: %m");

goto fail;

}

r = sd_event_source_set_enabled(c->client_event_source, SD_EVENT_ONESHOT);

if (r < 0) {

log_error_errno(r, "Failed to enable oneshot event source: %m");

goto fail;

}

} else {

log_error_errno(errno, "Failed to connect to remote host: %m");

goto fail;

}

} else {

r = connection_complete(c);

if (r < 0)

goto fail;

}

return 0;

fail:

connection_free(c);

return 0; /* ignore errors, continue serving */

}

static int resolve_cb(sd_resolve_query *q, int ret, const struct addrinfo *ai, void *userdata) {

Connection *c = userdata;

assert(q);

assert(c);

if (ret != 0) {

log_error("Failed to resolve host: %s", gai_strerror(ret));

goto fail;

}

c->resolve_query = sd_resolve_query_unref(c->resolve_query);

return connection_start(c, ai->ai_addr, ai->ai_addrlen);

fail:

connection_free(c);

return 0; /* ignore errors, continue serving */

}

static int resolve_remote(Connection *c) {

static const struct addrinfo hints = {

.ai_family = AF_UNSPEC,

.ai_socktype = SOCK_STREAM,

.ai_flags = AI_ADDRCONFIG

};

union sockaddr_union sa = {};

const char *node, *service;

socklen_t salen;

int r;

if (path_is_absolute(arg_remote_host)) {

sa.un.sun_family = AF_UNIX;

strncpy(sa.un.sun_path, arg_remote_host, sizeof(sa.un.sun_path)-1);

sa.un.sun_path[sizeof(sa.un.sun_path)-1] = 0;

salen = offsetof(union sockaddr_union, un.sun_path) + strlen(sa.un.sun_path);

return connection_start(c, &sa.sa, salen);

}

if (arg_remote_host[0] == '@') {

sa.un.sun_family = AF_UNIX;

sa.un.sun_path[0] = 0;

strncpy(sa.un.sun_path+1, arg_remote_host+1, sizeof(sa.un.sun_path)-2);

sa.un.sun_path[sizeof(sa.un.sun_path)-1] = 0;

salen = offsetof(union sockaddr_union, un.sun_path) + 1 + strlen(sa.un.sun_path + 1);

return connection_start(c, &sa.sa, salen);

}

service = strrchr(arg_remote_host, ':');

if (service) {

node = strndupa(arg_remote_host, service - arg_remote_host);

service ++;

} else {

node = arg_remote_host;

service = "80";

}

log_debug("Looking up address info for %s:%s", node, service);

r = sd_resolve_getaddrinfo(c->context->resolve, &c->resolve_query, node, service, &hints, resolve_cb, c);

if (r < 0) {

log_error_errno(r, "Failed to resolve remote host: %m");

goto fail;

}

return 0;

fail:

connection_free(c);

return 0; /* ignore errors, continue serving */

}

static int add_connection_socket(Context *context, int fd) {

Connection *c;

int r;

assert(context);

assert(fd >= 0);

if (set_size(context->connections) > CONNECTIONS_MAX) {

log_warning("Hit connection limit, refusing connection.");

safe_close(fd);

return 0;

}

r = set_ensure_allocated(&context->connections, NULL);

if (r < 0) {

log_oom();

return 0;

}

c = new0(Connection, 1);

if (!c) {

log_oom();

return 0;

}

c->context = context;

c->server_fd = fd;

c->client_fd = -1;

c->server_to_client_buffer[0] = c->server_to_client_buffer[1] = -1;

c->client_to_server_buffer[0] = c->client_to_server_buffer[1] = -1;

r = set_put(context->connections, c);

if (r < 0) {

free(c);

log_oom();

return 0;

}

return resolve_remote(c);

}

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

_cleanup_free_ char *peer = NULL;

Context *context = userdata;

int nfd = -1, r;

assert(s);

assert(fd >= 0);

assert(revents & EPOLLIN);

assert(context);

nfd = accept4(fd, NULL, NULL, SOCK_NONBLOCK|SOCK_CLOEXEC);

if (nfd < 0) {

if (errno != -EAGAIN)

log_warning_errno(errno, "Failed to accept() socket: %m");

} else {

getpeername_pretty(nfd, true, &peer);

log_debug("New connection from %s", strna(peer));

r = add_connection_socket(context, nfd);

if (r < 0) {

log_error_errno(r, "Failed to accept connection, ignoring: %m");

safe_close(fd);

}

}

r = sd_event_source_set_enabled(s, SD_EVENT_ONESHOT);

if (r < 0) {

log_error_errno(r, "Error while re-enabling listener with ONESHOT: %m");

sd_event_exit(context->event, r);

return r;

}

return 1;

}

static int add_listen_socket(Context *context, int fd) {

sd_event_source *source;

int r;

assert(context);

assert(fd >= 0);

r = set_ensure_allocated(&context->listen, NULL);

if (r < 0) {

log_oom();

return r;

}

r = sd_is_socket(fd, 0, SOCK_STREAM, 1);

if (r < 0)

return log_error_errno(r, "Failed to determine socket type: %m");

if (r == 0) {

log_error("Passed in socket is not a stream socket.");

return -EINVAL;

}

r = fd_nonblock(fd, true);

if (r < 0)

return log_error_errno(r, "Failed to mark file descriptor non-blocking: %m");

r = sd_event_add_io(context->event, &source, fd, EPOLLIN, accept_cb, context);

if (r < 0)

return log_error_errno(r, "Failed to add event source: %m");

r = set_put(context->listen, source);

if (r < 0) {

log_error_errno(r, "Failed to add source to set: %m");

sd_event_source_unref(source);

return r;

}

/* Set the watcher to oneshot in case other processes are also

r = sd_event_source_set_enabled(source, SD_EVENT_ONESHOT);

if (r < 0)

return log_error_errno(r, "Failed to enable oneshot mode: %m");

return 0;

}

static void help(void) {

printf("%1$s [HOST:PORT]\n"

"%1$s [SOCKET]\n\n"

"Bidirectionally proxy local sockets to another (possibly remote) socket.\n\n"

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

" --version Show package version\n",

program_invocation_short_name);

}

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

enum {

ARG_VERSION = 0x100,

ARG_IGNORE_ENV

};

static const struct option options[] = {

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

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

{}

};

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 ARG_VERSION:

return version();

case '?':

return -EINVAL;

default:

assert_not_reached("Unhandled option");

}

if (optind >= argc) {

log_error("Not enough parameters.");

return -EINVAL;

}

if (argc != optind+1) {

log_error("Too many parameters.");

return -EINVAL;

}

arg_remote_host = argv[optind];

return 1;

}

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

Context context = {};

int r, n, fd;

log_parse_environment();

log_open();

r = parse_argv(argc, argv);

if (r <= 0)

goto finish;

r = sd_event_default(&context.event);

if (r < 0) {

log_error_errno(r, "Failed to allocate event loop: %m");

goto finish;

}

r = sd_resolve_default(&context.resolve);

if (r < 0) {

log_error_errno(r, "Failed to allocate resolver: %m");

goto finish;

}

r = sd_resolve_attach_event(context.resolve, context.event, 0);

if (r < 0) {

log_error_errno(r, "Failed to attach resolver: %m");

goto finish;

}

sd_event_set_watchdog(context.event, true);

n = sd_listen_fds(1);

if (n < 0) {

log_error("Failed to receive sockets from parent.");

r = n;

goto finish;

} else if (n == 0) {

log_error("Didn't get any sockets passed in.");

r = -EINVAL;

goto finish;

}

for (fd = SD_LISTEN_FDS_START; fd < SD_LISTEN_FDS_START + n; fd++) {

r = add_listen_socket(&context, fd);

if (r < 0)

goto finish;

}

r = sd_event_loop(context.event);

if (r < 0) {

log_error_errno(r, "Failed to run event loop: %m");

goto finish;

}

finish:

context_free(&context);

return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;

}