networking/nc.c

   1 /* vi: set sw=4 ts=4: */
   2 /*  nc: mini-netcat - built from the ground up for LRP
   3  *
   4  *  Copyright (C) 1998, 1999  Charles P. Wright
   5  *  Copyright (C) 1998  Dave Cinege
   6  *
   7  *  Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
   8  */
   9
  10 #include "libbb.h"
  11
  12 #if ENABLE_DESKTOP
  13 #include "nc_bloaty.c"
  14 #else
  15
  16 /* Lots of small differences in features
  17  * when compared to "standard" nc
  18  */
  19
  20 static void timeout(int signum)
  21 {
  22         bb_error_msg_and_die("timed out");
  23 }
  24
  25 int nc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  26 int nc_main(int argc, char **argv)
  27 {
  28         /* sfd sits _here_ only because of "repeat" option (-l -l). */
  29         int sfd = sfd; /* for gcc */
  30         int cfd = 0;
  31         unsigned lport = 0;
  32         SKIP_NC_SERVER(const) unsigned do_listen = 0;
  33         SKIP_NC_EXTRA (const) unsigned wsecs = 0;
  34         SKIP_NC_EXTRA (const) unsigned delay = 0;
  35         SKIP_NC_EXTRA (const int execparam = 0;)
  36         USE_NC_EXTRA  (char **execparam = NULL;)
  37         len_and_sockaddr *lsa;
  38         fd_set readfds, testfds;
  39         int opt; /* must be signed (getopt returns -1) */
  40
  41         if (ENABLE_NC_SERVER || ENABLE_NC_EXTRA) {
  42                 /* getopt32 is _almost_ usable:
  43                 ** it cannot handle "... -e prog -prog-opt" */
  44                 while ((opt = getopt(argc, argv,
  45                         "" USE_NC_SERVER("lp:") USE_NC_EXTRA("w:i:f:e:") )) > 0
  46                 ) {
  47                         if (ENABLE_NC_SERVER && opt=='l')      USE_NC_SERVER(do_listen++);
  48                         else if (ENABLE_NC_SERVER && opt=='p') {
  49                                 USE_NC_SERVER(lport = bb_lookup_port(optarg, "tcp", 0));
  50                         }
  51                         else if (ENABLE_NC_EXTRA && opt=='w') USE_NC_EXTRA( wsecs = xatou(optarg));
  52                         else if (ENABLE_NC_EXTRA && opt=='i') USE_NC_EXTRA( delay = xatou(optarg));
  53                         else if (ENABLE_NC_EXTRA && opt=='f') USE_NC_EXTRA( cfd = xopen(optarg, O_RDWR));
  54                         else if (ENABLE_NC_EXTRA && opt=='e' && optind<=argc) {
  55                                 /* We cannot just 'break'. We should let getopt finish.
  56                                 ** Or else we won't be able to find where
  57                                 ** 'host' and 'port' params are
  58                                 ** (think "nc -w 60 host port -e prog"). */
  59                                 USE_NC_EXTRA(
  60                                         char **p;
  61                                         // +2: one for progname (optarg) and one for NULL
  62                                         execparam = xzalloc(sizeof(char*) * (argc - optind + 2));
  63                                         p = execparam;
  64                                         *p++ = optarg;
  65                                         while (optind < argc) {
  66                                                 *p++ = argv[optind++];
  67                                         }
  68                                 )
  69                                 /* optind points to argv[arvc] (NULL) now.
  70                                 ** FIXME: we assume that getopt will not count options
  71                                 ** possibly present on "-e prog args" and will not
  72                                 ** include them into final value of optind
  73                                 ** which is to be used ...  */
  74                         } else bb_show_usage();
  75                 }
  76                 argv += optind; /* ... here! */
  77                 argc -= optind;
  78                 // -l and -f don't mix
  79                 if (do_listen && cfd) bb_show_usage();
  80                 // Listen or file modes need zero arguments, client mode needs 2
  81                 if (do_listen || cfd) {
  82                         if (argc) bb_show_usage();
  83                 } else {
  84                         if (!argc || argc > 2) bb_show_usage();
  85                 }
  86         } else {
  87                 if (argc != 3) bb_show_usage();
  88                 argc--;
  89                 argv++;
  90         }
  91
  92         if (wsecs) {
  93                 signal(SIGALRM, timeout);
  94                 alarm(wsecs);
  95         }
  96
  97         if (!cfd) {
  98                 if (do_listen) {
  99                         /* create_and_bind_stream_or_die(NULL, lport)
 100                          * would've work wonderfully, but we need
 101                          * to know lsa */
 102                         sfd = xsocket_stream(&lsa);
 103                         if (lport)
 104                                 set_nport(lsa, htons(lport));
 105                         setsockopt_reuseaddr(sfd);
 106                         xbind(sfd, &lsa->sa, lsa->len);
 107                         xlisten(sfd, do_listen); /* can be > 1 */
 108                         /* If we didn't specify a port number,
 109                          * query and print it after listen() */
 110                         if (!lport) {
 111                                 socklen_t addrlen = lsa->len;
 112                                 getsockname(sfd, &lsa->sa, &addrlen);
 113                                 lport = get_nport(&lsa->sa);
 114                                 fdprintf(2, "%d\n", ntohs(lport));
 115                         }
 116                         close_on_exec_on(sfd);
 117  accept_again:
 118                         cfd = accept(sfd, NULL, 0);
 119                         if (cfd < 0)
 120                                 bb_perror_msg_and_die("accept");
 121                         if (!execparam)
 122                                 close(sfd);
 123                 } else {
 124                         cfd = create_and_connect_stream_or_die(argv[0],
 125                                 argv[1] ? bb_lookup_port(argv[1], "tcp", 0) : 0);
 126                 }
 127         }
 128
 129         if (wsecs) {
 130                 alarm(0);
 131                 signal(SIGALRM, SIG_DFL);
 132         }
 133
 134         /* -e given? */
 135         if (execparam) {
 136                 signal(SIGCHLD, SIG_IGN);
 137                 // With more than one -l, repeatedly act as server.
 138                 if (do_listen > 1 && vfork()) {
 139                         /* parent */
 140                         // This is a bit weird as cleanup goes, since we wind up with no
 141                         // stdin/stdout/stderr.  But it's small and shouldn't hurt anything.
 142                         // We check for cfd == 0 above.
 143                         logmode = LOGMODE_NONE;
 144                         close(0);
 145                         close(1);
 146                         close(2);
 147                         goto accept_again;
 148                 }
 149                 /* child (or main thread if no multiple -l) */
 150                 if (cfd) {
 151                         dup2(cfd, 0);
 152                         close(cfd);
 153                 }
 154                 dup2(0, 1);
 155                 dup2(0, 2);
 156                 USE_NC_EXTRA(BB_EXECVP(execparam[0], execparam);)
 157                 /* Don't print stuff or it will go over the wire.... */
 158                 _exit(127);
 159         }
 160
 161         // Select loop copying stdin to cfd, and cfd to stdout.
 162
 163         FD_ZERO(&readfds);
 164         FD_SET(cfd, &readfds);
 165         FD_SET(STDIN_FILENO, &readfds);
 166
 167         for (;;) {
 168                 int fd;
 169                 int ofd;
 170                 int nread;
 171
 172                 testfds = readfds;
 173
 174                 if (select(FD_SETSIZE, &testfds, NULL, NULL, NULL) < 0)
 175                         bb_perror_msg_and_die("select");
 176
 177 #define iobuf bb_common_bufsiz1
 178                 for (fd = 0; fd < FD_SETSIZE; fd++) {
 179                         if (FD_ISSET(fd, &testfds)) {
 180                                 nread = safe_read(fd, iobuf, sizeof(iobuf));
 181                                 if (fd == cfd) {
 182                                         if (nread < 1)
 183                                                 exit(0);
 184                                         ofd = STDOUT_FILENO;
 185                                 } else {
 186                                         if (nread<1) {
 187                                                 // Close outgoing half-connection so they get EOF, but
 188                                                 // leave incoming alone so we can see response.
 189                                                 shutdown(cfd, 1);
 190                                                 FD_CLR(STDIN_FILENO, &readfds);
 191                                         }
 192                                         ofd = cfd;
 193                                 }
 194                                 xwrite(ofd, iobuf, nread);
 195                                 if (delay > 0) sleep(delay);
 196                         }
 197                 }
 198         }
 199 }
 200 #endif