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 static void timeout(int signum)
  13 {
  14         bb_error_msg_and_die("timed out");
  15 }
  16
  17 int nc_main(int argc, char **argv)
  18 {
  19         int sfd = 0;
  20         int cfd = 0;
  21         SKIP_NC_SERVER(const) unsigned do_listen = 0;
  22         SKIP_NC_SERVER(const) unsigned lport = 0;
  23         SKIP_NC_EXTRA (const) unsigned wsecs = 0;
  24         SKIP_NC_EXTRA (const) unsigned delay = 0;
  25         SKIP_NC_EXTRA (const int execparam = 0;)
  26         USE_NC_EXTRA  (char **execparam = NULL;)
  27         struct sockaddr_in address;
  28         fd_set readfds, testfds;
  29         int opt; /* must be signed (getopt returns -1) */
  30
  31         memset(&address, 0, sizeof(address));
  32
  33         if (ENABLE_NC_SERVER || ENABLE_NC_EXTRA) {
  34                 /* getopt32 is _almost_ usable:
  35                 ** it cannot handle "... -e prog -prog-opt" */
  36                 while ((opt = getopt(argc, argv,
  37                         "" USE_NC_SERVER("lp:") USE_NC_EXTRA("w:i:f:e:") )) > 0
  38                 ) {
  39                         if (ENABLE_NC_SERVER && opt=='l')      USE_NC_SERVER(do_listen++);
  40                         else if (ENABLE_NC_SERVER && opt=='p') {
  41                                 USE_NC_SERVER(lport = bb_lookup_port(optarg, "tcp", 0));
  42                                 USE_NC_SERVER(lport = htons(lport));
  43                         }
  44                         else if (ENABLE_NC_EXTRA  && opt=='w') USE_NC_EXTRA( wsecs = xatou(optarg));
  45                         else if (ENABLE_NC_EXTRA  && opt=='i') USE_NC_EXTRA( delay = xatou(optarg));
  46                         else if (ENABLE_NC_EXTRA  && opt=='f') USE_NC_EXTRA( cfd = xopen(optarg, O_RDWR));
  47                         else if (ENABLE_NC_EXTRA  && opt=='e' && optind<=argc) {
  48                                 /* We cannot just 'break'. We should let getopt finish.
  49                                 ** Or else we won't be able to find where
  50                                 ** 'host' and 'port' params are
  51                                 ** (think "nc -w 60 host port -e prog"). */
  52                                 USE_NC_EXTRA(
  53                                         char **p;
  54                                         // +2: one for progname (optarg) and one for NULL
  55                                         execparam = xzalloc(sizeof(char*) * (argc - optind + 2));
  56                                         p = execparam;
  57                                         *p++ = optarg;
  58                                         while (optind < argc) {
  59                                                 *p++ = argv[optind++];
  60                                         }
  61                                 )
  62                                 /* optind points to argv[arvc] (NULL) now.
  63                                 ** FIXME: we assume that getopt will not count options
  64                                 ** possibly present on "-e prog args" and will not
  65                                 ** include them into final value of optind
  66                                 ** which is to be used ...  */
  67                         } else bb_show_usage();
  68                 }
  69                 argv += optind; /* ... here! */
  70                 argc -= optind;
  71                 // -l and -f don't mix
  72                 if (do_listen && cfd) bb_show_usage();
  73                 // Listen or file modes need zero arguments, client mode needs 2
  74                 opt = ((do_listen || cfd) ? 0 : 2);
  75                 if (argc != opt)
  76                         bb_show_usage();
  77         } else {
  78                 if (argc != 3) bb_show_usage();
  79                 argc--;
  80                 argv++;
  81         }
  82
  83         if (wsecs) {
  84                 signal(SIGALRM, timeout);
  85                 alarm(wsecs);
  86         }
  87
  88         if (!cfd) {
  89                 sfd = xsocket(AF_INET, SOCK_STREAM, 0);
  90                 fcntl(sfd, F_SETFD, FD_CLOEXEC);
  91                 setsockopt_reuseaddr(sfd);
  92                 address.sin_family = AF_INET;
  93
  94                 // Set local port.
  95
  96                 if (lport != 0) {
  97                         address.sin_port = lport;
  98                         xbind(sfd, (struct sockaddr *) &address, sizeof(address));
  99                 }
 100
 101                 if (do_listen) {
 102                         socklen_t addrlen = sizeof(address);
 103
 104                         xlisten(sfd, do_listen);
 105
 106                         // If we didn't specify a port number, query and print it to stderr.
 107
 108                         if (!lport) {
 109                                 socklen_t len = sizeof(address);
 110                                 getsockname(sfd, (struct sockaddr *) &address, &len);
 111                                 fdprintf(2, "%d\n", SWAP_BE16(address.sin_port));
 112                         }
 113  repeatyness:
 114                         cfd = accept(sfd, (struct sockaddr *) &address, &addrlen);
 115                         if (cfd < 0)
 116                                 bb_perror_msg_and_die("accept");
 117
 118                         if (!execparam) close(sfd);
 119                 } else {
 120                         struct hostent *hostinfo;
 121                         hostinfo = xgethostbyname(argv[0]);
 122
 123                         address.sin_addr = *(struct in_addr *) *hostinfo->h_addr_list;
 124                         address.sin_port = bb_lookup_port(argv[1], "tcp", 0);
 125                         address.sin_port = htons(address.sin_port);
 126
 127                         xconnect(sfd, (struct sockaddr *) &address, sizeof(address));
 128                         cfd = sfd;
 129                 }
 130         }
 131
 132         if (wsecs) {
 133                 alarm(0);
 134                 signal(SIGALRM, SIG_DFL);
 135         }
 136
 137         /* -e given? */
 138         if (execparam) {
 139                 if (cfd) {
 140                         signal(SIGCHLD, SIG_IGN);
 141                         dup2(cfd, 0);
 142                         close(cfd);
 143                 }
 144                 dup2(0, 1);
 145                 dup2(0, 2);
 146
 147                 // With more than one -l, repeatedly act as server.
 148
 149                 if (do_listen > 1 && vfork()) {
 150                         // This is a bit weird as cleanup goes, since we wind up with no
 151                         // stdin/stdout/stderr.  But it's small and shouldn't hurt anything.
 152                         // We check for cfd == 0 above.
 153                         logmode = LOGMODE_NONE;
 154                         close(0);
 155                         close(1);
 156                         close(2);
 157
 158                         goto repeatyness;
 159                 }
 160                 USE_NC_EXTRA(execvp(execparam[0], execparam);)
 161                 /* Don't print stuff or it will go over the wire.... */
 162                 _exit(127);
 163         }
 164
 165         // Select loop copying stdin to cfd, and cfd to stdout.
 166
 167         FD_ZERO(&readfds);
 168         FD_SET(cfd, &readfds);
 169         FD_SET(STDIN_FILENO, &readfds);
 170
 171         for (;;) {
 172                 int fd;
 173                 int ofd;
 174                 int nread;
 175
 176                 testfds = readfds;
 177
 178                 if (select(FD_SETSIZE, &testfds, NULL, NULL, NULL) < 0)
 179                         bb_perror_msg_and_die("select");
 180
 181                 for (fd = 0; fd < FD_SETSIZE; fd++) {
 182                         if (FD_ISSET(fd, &testfds)) {
 183                                 nread = safe_read(fd, bb_common_bufsiz1,
 184                                                         sizeof(bb_common_bufsiz1));
 185
 186                                 if (fd == cfd) {
 187                                         if (nread<1) exit(0);
 188                                         ofd = STDOUT_FILENO;
 189                                 } else {
 190                                         if (nread<1) {
 191                                                 // Close outgoing half-connection so they get EOF, but
 192                                                 // leave incoming alone so we can see response.
 193                                                 shutdown(cfd, 1);
 194                                                 FD_CLR(STDIN_FILENO, &readfds);
 195                                         }
 196                                         ofd = cfd;
 197                                 }
 198
 199                                 xwrite(ofd, bb_common_bufsiz1, nread);
 200                                 if (delay > 0) sleep(delay);
 201                         }
 202                 }
 203         }
 204 }