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