networking/tftp.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * A simple tftp client/server for busybox.
   4  * Tries to follow RFC1350.
   5  * Only "octet" mode supported.
   6  * Optional blocksize negotiation (RFC2347 + RFC2348)
   7  *
   8  * Copyright (C) 2001 Magnus Damm <damm@opensource.se>
   9  *
  10  * Parts of the code based on:
  11  *
  12  * atftp:  Copyright (C) 2000 Jean-Pierre Lefebvre <helix@step.polymtl.ca>
  13  *                        and Remi Lefebvre <remi@debian.org>
  14  *
  15  * utftp:  Copyright (C) 1999 Uwe Ohse <uwe@ohse.de>
  16  *
  17  * tftpd added by Denys Vlasenko & Vladimir Dronnikov
  18  *
  19  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  20  */
  21
  22 //usage:#define tftp_trivial_usage
  23 //usage:       "[OPTIONS] HOST [PORT]"
  24 //usage:#define tftp_full_usage "\n\n"
  25 //usage:       "Transfer a file from/to tftp server\n"
  26 //usage:     "\nOptions:"
  27 //usage:     "\n        -l FILE Local FILE"
  28 //usage:     "\n        -r FILE Remote FILE"
  29 //usage:        IF_FEATURE_TFTP_GET(
  30 //usage:     "\n        -g      Get file"
  31 //usage:        )
  32 //usage:        IF_FEATURE_TFTP_PUT(
  33 //usage:     "\n        -p      Put file"
  34 //usage:        )
  35 //usage:        IF_FEATURE_TFTP_BLOCKSIZE(
  36 //usage:     "\n        -b SIZE Transfer blocks of SIZE octets"
  37 //usage:        )
  38 //usage:
  39 //usage:#define tftpd_trivial_usage
  40 //usage:       "[-cr] [-u USER] [DIR]"
  41 //usage:#define tftpd_full_usage "\n\n"
  42 //usage:       "Transfer a file on tftp client's request\n"
  43 //usage:       "\n"
  44 //usage:       "tftpd should be used as an inetd service.\n"
  45 //usage:       "tftpd's line for inetd.conf:\n"
  46 //usage:       "        69 dgram udp nowait root tftpd tftpd -l /files/to/serve\n"
  47 //usage:       "It also can be ran from udpsvd:\n"
  48 //usage:       "        udpsvd -vE 0.0.0.0 69 tftpd /files/to/serve\n"
  49 //usage:     "\nOptions:"
  50 //usage:     "\n        -r      Prohibit upload"
  51 //usage:     "\n        -c      Allow file creation via upload"
  52 //usage:     "\n        -u      Access files as USER"
  53 //usage:     "\n        -l      Log to syslog (inetd mode requires this)"
  54
  55 #include "libbb.h"
  56 #include <syslog.h>
  57
  58 #if ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT
  59
  60 #define TFTP_BLKSIZE_DEFAULT       512  /* according to RFC 1350, don't change */
  61 #define TFTP_BLKSIZE_DEFAULT_STR "512"
  62 /* Was 50 ms but users asked to bump it up a bit */
  63 #define TFTP_TIMEOUT_MS            100
  64 #define TFTP_MAXTIMEOUT_MS        2000
  65 #define TFTP_NUM_RETRIES            12  /* number of backed-off retries */
  66
  67 /* opcodes we support */
  68 #define TFTP_RRQ   1
  69 #define TFTP_WRQ   2
  70 #define TFTP_DATA  3
  71 #define TFTP_ACK   4
  72 #define TFTP_ERROR 5
  73 #define TFTP_OACK  6
  74
  75 /* error codes sent over network (we use only 0, 1, 3 and 8) */
  76 /* generic (error message is included in the packet) */
  77 #define ERR_UNSPEC   0
  78 #define ERR_NOFILE   1
  79 #define ERR_ACCESS   2
  80 /* disk full or allocation exceeded */
  81 #define ERR_WRITE    3
  82 #define ERR_OP       4
  83 #define ERR_BAD_ID   5
  84 #define ERR_EXIST    6
  85 #define ERR_BAD_USER 7
  86 #define ERR_BAD_OPT  8
  87
  88 /* masks coming from getopt32 */
  89 enum {
  90         TFTP_OPT_GET = (1 << 0),
  91         TFTP_OPT_PUT = (1 << 1),
  92         /* pseudo option: if set, it's tftpd */
  93         TFTPD_OPT = (1 << 7) * ENABLE_TFTPD,
  94         TFTPD_OPT_r = (1 << 8) * ENABLE_TFTPD,
  95         TFTPD_OPT_c = (1 << 9) * ENABLE_TFTPD,
  96         TFTPD_OPT_u = (1 << 10) * ENABLE_TFTPD,
  97         TFTPD_OPT_l = (1 << 11) * ENABLE_TFTPD,
  98 };
  99
 100 #if ENABLE_FEATURE_TFTP_GET && !ENABLE_FEATURE_TFTP_PUT
 101 #define IF_GETPUT(...)
 102 #define CMD_GET(cmd) 1
 103 #define CMD_PUT(cmd) 0
 104 #elif !ENABLE_FEATURE_TFTP_GET && ENABLE_FEATURE_TFTP_PUT
 105 #define IF_GETPUT(...)
 106 #define CMD_GET(cmd) 0
 107 #define CMD_PUT(cmd) 1
 108 #else
 109 #define IF_GETPUT(...) __VA_ARGS__
 110 #define CMD_GET(cmd) ((cmd) & TFTP_OPT_GET)
 111 #define CMD_PUT(cmd) ((cmd) & TFTP_OPT_PUT)
 112 #endif
 113 /* NB: in the code below
 114  * CMD_GET(cmd) and CMD_PUT(cmd) are mutually exclusive
 115  */
 116
 117
 118 struct globals {
 119         /* u16 TFTP_ERROR; u16 reason; both network-endian, then error text: */
 120         uint8_t error_pkt[4 + 32];
 121         char *user_opt;
 122         /* used in tftpd_main(), a bit big for stack: */
 123         char block_buf[TFTP_BLKSIZE_DEFAULT];
 124 #if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 125         off_t pos;
 126         off_t size;
 127         const char *file;
 128         bb_progress_t pmt;
 129 #endif
 130 } FIX_ALIASING;
 131 #define G (*(struct globals*)&bb_common_bufsiz1)
 132 struct BUG_G_too_big {
 133         char BUG_G_too_big[sizeof(G) <= COMMON_BUFSIZE ? 1 : -1];
 134 };
 135 #define block_buf        (G.block_buf   )
 136 #define user_opt         (G.user_opt    )
 137 #define error_pkt        (G.error_pkt   )
 138 #define INIT_G() do { } while (0)
 139
 140 #define error_pkt_reason (error_pkt[3])
 141 #define error_pkt_str    (error_pkt + 4)
 142
 143 #if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 144 static void tftp_progress_update(void)
 145 {
 146         bb_progress_update(&G.pmt, 0, G.pos, G.size);
 147 }
 148 static void tftp_progress_init(void)
 149 {
 150         bb_progress_init(&G.pmt, G.file);
 151         tftp_progress_update();
 152 }
 153 static void tftp_progress_done(void)
 154 {
 155         if (is_bb_progress_inited(&G.pmt)) {
 156                 tftp_progress_update();
 157                 bb_putchar_stderr('\n');
 158                 bb_progress_free(&G.pmt);
 159         }
 160 }
 161 #else
 162 # define tftp_progress_init() ((void)0)
 163 # define tftp_progress_done() ((void)0)
 164 #endif
 165
 166 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 167
 168 static int tftp_blksize_check(const char *blksize_str, int maxsize)
 169 {
 170         /* Check if the blksize is valid:
 171          * RFC2348 says between 8 and 65464,
 172          * but our implementation makes it impossible
 173          * to use blksizes smaller than 22 octets. */
 174         unsigned blksize = bb_strtou(blksize_str, NULL, 10);
 175         if (errno
 176          || (blksize < 24) || (blksize > maxsize)
 177         ) {
 178                 bb_error_msg("bad blocksize '%s'", blksize_str);
 179                 return -1;
 180         }
 181 # if ENABLE_TFTP_DEBUG
 182         bb_error_msg("using blksize %u", blksize);
 183 # endif
 184         return blksize;
 185 }
 186
 187 static char *tftp_get_option(const char *option, char *buf, int len)
 188 {
 189         int opt_val = 0;
 190         int opt_found = 0;
 191         int k;
 192
 193         /* buf points to:
 194          * "opt_name<NUL>opt_val<NUL>opt_name2<NUL>opt_val2<NUL>..." */
 195
 196         while (len > 0) {
 197                 /* Make sure options are terminated correctly */
 198                 for (k = 0; k < len; k++) {
 199                         if (buf[k] == '\0') {
 200                                 goto nul_found;
 201                         }
 202                 }
 203                 return NULL;
 204  nul_found:
 205                 if (opt_val == 0) { /* it's "name" part */
 206                         if (strcasecmp(buf, option) == 0) {
 207                                 opt_found = 1;
 208                         }
 209                 } else if (opt_found) {
 210                         return buf;
 211                 }
 212
 213                 k++;
 214                 buf += k;
 215                 len -= k;
 216                 opt_val ^= 1;
 217         }
 218
 219         return NULL;
 220 }
 221
 222 #endif
 223
 224 static int tftp_protocol(
 225                 /* NULL if tftp, !NULL if tftpd: */
 226                 len_and_sockaddr *our_lsa,
 227                 len_and_sockaddr *peer_lsa,
 228                 const char *local_file
 229                 IF_TFTP(, const char *remote_file)
 230 #if !ENABLE_TFTP
 231 # define remote_file NULL
 232 #endif
 233                 /* 1 for tftp; 1/0 for tftpd depending whether client asked about it: */
 234                 IF_FEATURE_TFTP_BLOCKSIZE(, int want_transfer_size)
 235                 IF_FEATURE_TFTP_BLOCKSIZE(, int blksize))
 236 {
 237 #if !ENABLE_FEATURE_TFTP_BLOCKSIZE
 238         enum { blksize = TFTP_BLKSIZE_DEFAULT };
 239 #endif
 240
 241         struct pollfd pfd[1];
 242 #define socket_fd (pfd[0].fd)
 243         int len;
 244         int send_len;
 245         IF_FEATURE_TFTP_BLOCKSIZE(smallint expect_OACK = 0;)
 246         smallint finished = 0;
 247         uint16_t opcode;
 248         uint16_t block_nr;
 249         uint16_t recv_blk;
 250         int open_mode, local_fd;
 251         int retries, waittime_ms;
 252         int io_bufsize = blksize + 4;
 253         char *cp;
 254         /* Can't use RESERVE_CONFIG_BUFFER here since the allocation
 255          * size varies meaning BUFFERS_GO_ON_STACK would fail.
 256          *
 257          * We must keep the transmit and receive buffers separate
 258          * in case we rcv a garbage pkt - we need to rexmit the last pkt.
 259          */
 260         char *xbuf = xmalloc(io_bufsize);
 261         char *rbuf = xmalloc(io_bufsize);
 262
 263         socket_fd = xsocket(peer_lsa->u.sa.sa_family, SOCK_DGRAM, 0);
 264         setsockopt_reuseaddr(socket_fd);
 265
 266         if (!ENABLE_TFTP || our_lsa) { /* tftpd */
 267                 /* Create a socket which is:
 268                  * 1. bound to IP:port peer sent 1st datagram to,
 269                  * 2. connected to peer's IP:port
 270                  * This way we will answer from the IP:port peer
 271                  * expects, will not get any other packets on
 272                  * the socket, and also plain read/write will work. */
 273                 xbind(socket_fd, &our_lsa->u.sa, our_lsa->len);
 274                 xconnect(socket_fd, &peer_lsa->u.sa, peer_lsa->len);
 275
 276                 /* Is there an error already? Send pkt and bail out */
 277                 if (error_pkt_reason || error_pkt_str[0])
 278                         goto send_err_pkt;
 279
 280                 if (user_opt) {
 281                         struct passwd *pw = xgetpwnam(user_opt);
 282                         change_identity(pw); /* initgroups, setgid, setuid */
 283                 }
 284         }
 285
 286         /* Prepare open mode */
 287         if (CMD_PUT(option_mask32)) {
 288                 open_mode = O_RDONLY;
 289         } else {
 290                 open_mode = O_WRONLY | O_TRUNC | O_CREAT;
 291 #if ENABLE_TFTPD
 292                 if ((option_mask32 & (TFTPD_OPT+TFTPD_OPT_c)) == TFTPD_OPT) {
 293                         /* tftpd without -c */
 294                         open_mode = O_WRONLY | O_TRUNC;
 295                 }
 296 #endif
 297         }
 298
 299         /* Examples of network traffic.
 300          * Note two cases when ACKs with block# of 0 are sent.
 301          *
 302          * Download without options:
 303          * tftp -> "\0\1FILENAME\0octet\0"
 304          *         "\0\3\0\1FILEDATA..." <- tftpd
 305          * tftp -> "\0\4\0\1"
 306          * ...
 307          * Download with option of blksize 16384:
 308          * tftp -> "\0\1FILENAME\0octet\0blksize\00016384\0"
 309          *         "\0\6blksize\00016384\0" <- tftpd
 310          * tftp -> "\0\4\0\0"
 311          *         "\0\3\0\1FILEDATA..." <- tftpd
 312          * tftp -> "\0\4\0\1"
 313          * ...
 314          * Upload without options:
 315          * tftp -> "\0\2FILENAME\0octet\0"
 316          *         "\0\4\0\0" <- tftpd
 317          * tftp -> "\0\3\0\1FILEDATA..."
 318          *         "\0\4\0\1" <- tftpd
 319          * ...
 320          * Upload with option of blksize 16384:
 321          * tftp -> "\0\2FILENAME\0octet\0blksize\00016384\0"
 322          *         "\0\6blksize\00016384\0" <- tftpd
 323          * tftp -> "\0\3\0\1FILEDATA..."
 324          *         "\0\4\0\1" <- tftpd
 325          * ...
 326          */
 327         block_nr = 1;
 328         cp = xbuf + 2;
 329
 330         if (!ENABLE_TFTP || our_lsa) { /* tftpd */
 331                 /* Open file (must be after changing user) */
 332                 local_fd = open(local_file, open_mode, 0666);
 333                 if (local_fd < 0) {
 334                         error_pkt_reason = ERR_NOFILE;
 335                         strcpy((char*)error_pkt_str, "can't open file");
 336                         goto send_err_pkt;
 337                 }
 338 /* gcc 4.3.1 would NOT optimize it out as it should! */
 339 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 340                 if (blksize != TFTP_BLKSIZE_DEFAULT || want_transfer_size) {
 341                         /* Create and send OACK packet. */
 342                         /* For the download case, block_nr is still 1 -
 343                          * we expect 1st ACK from peer to be for (block_nr-1),
 344                          * that is, for "block 0" which is our OACK pkt */
 345                         opcode = TFTP_OACK;
 346                         goto add_blksize_opt;
 347                 }
 348 #endif
 349                 if (CMD_GET(option_mask32)) {
 350                         /* It's upload and we don't send OACK.
 351                          * We must ACK 1st packet (with filename)
 352                          * as if it is "block 0" */
 353                         block_nr = 0;
 354                 }
 355
 356         } else { /* tftp */
 357                 /* Open file (must be after changing user) */
 358                 local_fd = CMD_GET(option_mask32) ? STDOUT_FILENO : STDIN_FILENO;
 359                 if (NOT_LONE_DASH(local_file))
 360                         local_fd = xopen(local_file, open_mode);
 361 /* Removing #if, or using if() statement instead of #if may lead to
 362  * "warning: null argument where non-null required": */
 363 #if ENABLE_TFTP
 364                 /* tftp */
 365
 366                 /* We can't (and don't really need to) bind the socket:
 367                  * we don't know from which local IP datagrams will be sent,
 368                  * but kernel will pick the same IP every time (unless routing
 369                  * table is changed), thus peer will see dgrams consistently
 370                  * coming from the same IP.
 371                  * We would like to connect the socket, but since peer's
 372                  * UDP code can be less perfect than ours, _peer's_ IP:port
 373                  * in replies may differ from IP:port we used to send
 374                  * our first packet. We can connect() only when we get
 375                  * first reply. */
 376
 377                 /* build opcode */
 378                 opcode = TFTP_WRQ;
 379                 if (CMD_GET(option_mask32)) {
 380                         opcode = TFTP_RRQ;
 381                 }
 382                 /* add filename and mode */
 383                 /* fill in packet if the filename fits into xbuf */
 384                 len = strlen(remote_file) + 1;
 385                 if (2 + len + sizeof("octet") >= io_bufsize) {
 386                         bb_error_msg("remote filename is too long");
 387                         goto ret;
 388                 }
 389                 strcpy(cp, remote_file);
 390                 cp += len;
 391                 /* add "mode" part of the packet */
 392                 strcpy(cp, "octet");
 393                 cp += sizeof("octet");
 394
 395 # if ENABLE_FEATURE_TFTP_BLOCKSIZE
 396                 if (blksize == TFTP_BLKSIZE_DEFAULT && !want_transfer_size)
 397                         goto send_pkt;
 398
 399                 /* Need to add option to pkt */
 400                 if ((&xbuf[io_bufsize - 1] - cp) < sizeof("blksize NNNNN tsize ") + sizeof(off_t)*3) {
 401                         bb_error_msg("remote filename is too long");
 402                         goto ret;
 403                 }
 404                 expect_OACK = 1;
 405 # endif
 406 #endif /* ENABLE_TFTP */
 407
 408 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 409  add_blksize_opt:
 410                 if (blksize != TFTP_BLKSIZE_DEFAULT) {
 411                         /* add "blksize", <nul>, blksize, <nul> */
 412                         strcpy(cp, "blksize");
 413                         cp += sizeof("blksize");
 414                         cp += snprintf(cp, 6, "%d", blksize) + 1;
 415                 }
 416                 if (want_transfer_size) {
 417                         /* add "tsize", <nul>, size, <nul> (see RFC2349) */
 418                         /* if tftp and downloading, we send "0" (since we opened local_fd with O_TRUNC)
 419                          * and this makes server to send "tsize" option with the size */
 420                         /* if tftp and uploading, we send file size (maybe dont, to not confuse old servers???) */
 421                         /* if tftpd and downloading, we are answering to client's request */
 422                         /* if tftpd and uploading: !want_transfer_size, this code is not executed */
 423                         struct stat st;
 424                         strcpy(cp, "tsize");
 425                         cp += sizeof("tsize");
 426                         st.st_size = 0;
 427                         fstat(local_fd, &st);
 428                         cp += sprintf(cp, "%"OFF_FMT"u", (off_t)st.st_size) + 1;
 429 # if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 430                         /* Save for progress bar. If 0 (tftp downloading),
 431                          * we look at server's reply later */
 432                         G.size = st.st_size;
 433                         if (remote_file && st.st_size)
 434                                 tftp_progress_init();
 435 # endif
 436                 }
 437 #endif
 438                 /* First packet is built, so skip packet generation */
 439                 goto send_pkt;
 440         }
 441
 442         /* Using mostly goto's - continue/break will be less clear
 443          * in where we actually jump to */
 444         while (1) {
 445                 /* Build ACK or DATA */
 446                 cp = xbuf + 2;
 447                 *((uint16_t*)cp) = htons(block_nr);
 448                 cp += 2;
 449                 block_nr++;
 450                 opcode = TFTP_ACK;
 451                 if (CMD_PUT(option_mask32)) {
 452                         opcode = TFTP_DATA;
 453                         len = full_read(local_fd, cp, blksize);
 454                         if (len < 0) {
 455                                 goto send_read_err_pkt;
 456                         }
 457                         if (len != blksize) {
 458                                 finished = 1;
 459                         }
 460                         cp += len;
 461                         IF_FEATURE_TFTP_PROGRESS_BAR(G.pos += len;)
 462                 }
 463  send_pkt:
 464                 /* Send packet */
 465                 *((uint16_t*)xbuf) = htons(opcode); /* fill in opcode part */
 466                 send_len = cp - xbuf;
 467                 /* NB: send_len value is preserved in code below
 468                  * for potential resend */
 469
 470                 retries = TFTP_NUM_RETRIES;  /* re-initialize */
 471                 waittime_ms = TFTP_TIMEOUT_MS;
 472
 473  send_again:
 474 #if ENABLE_TFTP_DEBUG
 475                 fprintf(stderr, "sending %u bytes\n", send_len);
 476                 for (cp = xbuf; cp < &xbuf[send_len]; cp++)
 477                         fprintf(stderr, "%02x ", (unsigned char) *cp);
 478                 fprintf(stderr, "\n");
 479 #endif
 480                 xsendto(socket_fd, xbuf, send_len, &peer_lsa->u.sa, peer_lsa->len);
 481
 482 #if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 483                 if (is_bb_progress_inited(&G.pmt))
 484                         tftp_progress_update();
 485 #endif
 486                 /* Was it final ACK? then exit */
 487                 if (finished && (opcode == TFTP_ACK))
 488                         goto ret;
 489
 490  recv_again:
 491                 /* Receive packet */
 492                 /*pfd[0].fd = socket_fd;*/
 493                 pfd[0].events = POLLIN;
 494                 switch (safe_poll(pfd, 1, waittime_ms)) {
 495                 default:
 496                         /*bb_perror_msg("poll"); - done in safe_poll */
 497                         goto ret;
 498                 case 0:
 499                         retries--;
 500                         if (retries == 0) {
 501                                 tftp_progress_done();
 502                                 bb_error_msg("timeout");
 503                                 goto ret; /* no err packet sent */
 504                         }
 505
 506                         /* exponential backoff with limit */
 507                         waittime_ms += waittime_ms/2;
 508                         if (waittime_ms > TFTP_MAXTIMEOUT_MS) {
 509                                 waittime_ms = TFTP_MAXTIMEOUT_MS;
 510                         }
 511
 512                         goto send_again; /* resend last sent pkt */
 513                 case 1:
 514                         if (!our_lsa) {
 515                                 /* tftp (not tftpd!) receiving 1st packet */
 516                                 our_lsa = ((void*)(ptrdiff_t)-1); /* not NULL */
 517                                 len = recvfrom(socket_fd, rbuf, io_bufsize, 0,
 518                                                 &peer_lsa->u.sa, &peer_lsa->len);
 519                                 /* Our first dgram went to port 69
 520                                  * but reply may come from different one.
 521                                  * Remember and use this new port (and IP) */
 522                                 if (len >= 0)
 523                                         xconnect(socket_fd, &peer_lsa->u.sa, peer_lsa->len);
 524                         } else {
 525                                 /* tftpd, or not the very first packet:
 526                                  * socket is connect()ed, can just read from it. */
 527                                 /* Don't full_read()!
 528                                  * This is not TCP, one read == one pkt! */
 529                                 len = safe_read(socket_fd, rbuf, io_bufsize);
 530                         }
 531                         if (len < 0) {
 532                                 goto send_read_err_pkt;
 533                         }
 534                         if (len < 4) { /* too small? */
 535                                 goto recv_again;
 536                         }
 537                 }
 538
 539                 /* Process recv'ed packet */
 540                 opcode = ntohs( ((uint16_t*)rbuf)[0] );
 541                 recv_blk = ntohs( ((uint16_t*)rbuf)[1] );
 542 #if ENABLE_TFTP_DEBUG
 543                 fprintf(stderr, "received %d bytes: %04x %04x\n", len, opcode, recv_blk);
 544 #endif
 545                 if (opcode == TFTP_ERROR) {
 546                         static const char errcode_str[] ALIGN1 =
 547                                 "\0"
 548                                 "file not found\0"
 549                                 "access violation\0"
 550                                 "disk full\0"
 551                                 "bad operation\0"
 552                                 "unknown transfer id\0"
 553                                 "file already exists\0"
 554                                 "no such user\0"
 555                                 "bad option";
 556
 557                         const char *msg = "";
 558
 559                         if (len > 4 && rbuf[4] != '\0') {
 560                                 msg = &rbuf[4];
 561                                 rbuf[io_bufsize - 1] = '\0'; /* paranoia */
 562                         } else if (recv_blk <= 8) {
 563                                 msg = nth_string(errcode_str, recv_blk);
 564                         }
 565                         bb_error_msg("server error: (%u) %s", recv_blk, msg);
 566                         goto ret;
 567                 }
 568
 569 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 570                 if (expect_OACK) {
 571                         expect_OACK = 0;
 572                         if (opcode == TFTP_OACK) {
 573                                 /* server seems to support options */
 574                                 char *res;
 575
 576                                 res = tftp_get_option("blksize", &rbuf[2], len - 2);
 577                                 if (res) {
 578                                         blksize = tftp_blksize_check(res, blksize);
 579                                         if (blksize < 0) {
 580                                                 error_pkt_reason = ERR_BAD_OPT;
 581                                                 goto send_err_pkt;
 582                                         }
 583                                         io_bufsize = blksize + 4;
 584                                 }
 585 # if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 586                                 if (remote_file && G.size == 0) { /* if we don't know it yet */
 587                                         res = tftp_get_option("tsize", &rbuf[2], len - 2);
 588                                         if (res) {
 589                                                 G.size = bb_strtoull(res, NULL, 10);
 590                                                 if (G.size)
 591                                                         tftp_progress_init();
 592                                         }
 593                                 }
 594 # endif
 595                                 if (CMD_GET(option_mask32)) {
 596                                         /* We'll send ACK for OACK,
 597                                          * such ACK has "block no" of 0 */
 598                                         block_nr = 0;
 599                                 }
 600                                 continue;
 601                         }
 602                         /* rfc2347:
 603                          * "An option not acknowledged by the server
 604                          * must be ignored by the client and server
 605                          * as if it were never requested." */
 606                         if (blksize != TFTP_BLKSIZE_DEFAULT)
 607                                 bb_error_msg("falling back to blocksize "TFTP_BLKSIZE_DEFAULT_STR);
 608                         blksize = TFTP_BLKSIZE_DEFAULT;
 609                         io_bufsize = TFTP_BLKSIZE_DEFAULT + 4;
 610                 }
 611 #endif
 612                 /* block_nr is already advanced to next block# we expect
 613                  * to get / block# we are about to send next time */
 614
 615                 if (CMD_GET(option_mask32) && (opcode == TFTP_DATA)) {
 616                         if (recv_blk == block_nr) {
 617                                 int sz = full_write(local_fd, &rbuf[4], len - 4);
 618                                 if (sz != len - 4) {
 619                                         strcpy((char*)error_pkt_str, bb_msg_write_error);
 620                                         error_pkt_reason = ERR_WRITE;
 621                                         goto send_err_pkt;
 622                                 }
 623                                 if (sz != blksize) {
 624                                         finished = 1;
 625                                 }
 626                                 IF_FEATURE_TFTP_PROGRESS_BAR(G.pos += sz;)
 627                                 continue; /* send ACK */
 628                         }
 629 /* Disabled to cope with servers with Sorcerer's Apprentice Syndrome */
 630 #if 0
 631                         if (recv_blk == (block_nr - 1)) {
 632                                 /* Server lost our TFTP_ACK.  Resend it */
 633                                 block_nr = recv_blk;
 634                                 continue;
 635                         }
 636 #endif
 637                 }
 638
 639                 if (CMD_PUT(option_mask32) && (opcode == TFTP_ACK)) {
 640                         /* did peer ACK our last DATA pkt? */
 641                         if (recv_blk == (uint16_t) (block_nr - 1)) {
 642                                 if (finished)
 643                                         goto ret;
 644                                 continue; /* send next block */
 645                         }
 646                 }
 647                 /* Awww... recv'd packet is not recognized! */
 648                 goto recv_again;
 649                 /* why recv_again? - rfc1123 says:
 650                  * "The sender (i.e., the side originating the DATA packets)
 651                  *  must never resend the current DATA packet on receipt
 652                  *  of a duplicate ACK".
 653                  * DATA pkts are resent ONLY on timeout.
 654                  * Thus "goto send_again" will ba a bad mistake above.
 655                  * See:
 656                  * http://en.wikipedia.org/wiki/Sorcerer's_Apprentice_Syndrome
 657                  */
 658         } /* end of "while (1)" */
 659  ret:
 660         if (ENABLE_FEATURE_CLEAN_UP) {
 661                 close(local_fd);
 662                 close(socket_fd);
 663                 free(xbuf);
 664                 free(rbuf);
 665         }
 666         return finished == 0; /* returns 1 on failure */
 667
 668  send_read_err_pkt:
 669         strcpy((char*)error_pkt_str, bb_msg_read_error);
 670  send_err_pkt:
 671         if (error_pkt_str[0])
 672                 bb_error_msg("%s", (char*)error_pkt_str);
 673         error_pkt[1] = TFTP_ERROR;
 674         xsendto(socket_fd, error_pkt, 4 + 1 + strlen((char*)error_pkt_str),
 675                         &peer_lsa->u.sa, peer_lsa->len);
 676         return EXIT_FAILURE;
 677 #undef remote_file
 678 }
 679
 680 #if ENABLE_TFTP
 681
 682 int tftp_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 683 int tftp_main(int argc UNUSED_PARAM, char **argv)
 684 {
 685         len_and_sockaddr *peer_lsa;
 686         const char *local_file = NULL;
 687         const char *remote_file = NULL;
 688 # if ENABLE_FEATURE_TFTP_BLOCKSIZE
 689         const char *blksize_str = TFTP_BLKSIZE_DEFAULT_STR;
 690         int blksize;
 691 # endif
 692         int result;
 693         int port;
 694         IF_GETPUT(int opt;)
 695
 696         INIT_G();
 697
 698         /* -p or -g is mandatory, and they are mutually exclusive */
 699         opt_complementary = "" IF_FEATURE_TFTP_GET("g:") IF_FEATURE_TFTP_PUT("p:")
 700                         IF_GETPUT("g--p:p--g:");
 701
 702         IF_GETPUT(opt =) getopt32(argv,
 703                         IF_FEATURE_TFTP_GET("g") IF_FEATURE_TFTP_PUT("p")
 704                                 "l:r:" IF_FEATURE_TFTP_BLOCKSIZE("b:"),
 705                         &local_file, &remote_file
 706                         IF_FEATURE_TFTP_BLOCKSIZE(, &blksize_str));
 707         argv += optind;
 708
 709 # if ENABLE_FEATURE_TFTP_BLOCKSIZE
 710         /* Check if the blksize is valid:
 711          * RFC2348 says between 8 and 65464 */
 712         blksize = tftp_blksize_check(blksize_str, 65564);
 713         if (blksize < 0) {
 714                 //bb_error_msg("bad block size");
 715                 return EXIT_FAILURE;
 716         }
 717 # endif
 718
 719         if (remote_file) {
 720                 if (!local_file) {
 721                         const char *slash = strrchr(remote_file, '/');
 722                         local_file = slash ? slash + 1 : remote_file;
 723                 }
 724         } else {
 725                 remote_file = local_file;
 726         }
 727
 728         /* Error if filename or host is not known */
 729         if (!remote_file || !argv[0])
 730                 bb_show_usage();
 731
 732         port = bb_lookup_port(argv[1], "udp", 69);
 733         peer_lsa = xhost2sockaddr(argv[0], port);
 734
 735 # if ENABLE_TFTP_DEBUG
 736         fprintf(stderr, "using server '%s', remote_file '%s', local_file '%s'\n",
 737                         xmalloc_sockaddr2dotted(&peer_lsa->u.sa),
 738                         remote_file, local_file);
 739 # endif
 740
 741 # if ENABLE_FEATURE_TFTP_PROGRESS_BAR
 742         G.file = remote_file;
 743 # endif
 744         result = tftp_protocol(
 745                 NULL /*our_lsa*/, peer_lsa,
 746                 local_file, remote_file
 747                 IF_FEATURE_TFTP_BLOCKSIZE(, 1 /* want_transfer_size */)
 748                 IF_FEATURE_TFTP_BLOCKSIZE(, blksize)
 749         );
 750         tftp_progress_done();
 751
 752         if (result != EXIT_SUCCESS && NOT_LONE_DASH(local_file) && CMD_GET(opt)) {
 753                 unlink(local_file);
 754         }
 755         return result;
 756 }
 757
 758 #endif /* ENABLE_TFTP */
 759
 760 #if ENABLE_TFTPD
 761 int tftpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 762 int tftpd_main(int argc UNUSED_PARAM, char **argv)
 763 {
 764         len_and_sockaddr *our_lsa;
 765         len_and_sockaddr *peer_lsa;
 766         char *local_file, *mode;
 767         const char *error_msg;
 768         int opt, result, opcode;
 769         IF_FEATURE_TFTP_BLOCKSIZE(int blksize = TFTP_BLKSIZE_DEFAULT;)
 770         IF_FEATURE_TFTP_BLOCKSIZE(int want_transfer_size = 0;)
 771
 772         INIT_G();
 773
 774         our_lsa = get_sock_lsa(STDIN_FILENO);
 775         if (!our_lsa) {
 776                 /* This is confusing:
 777                  *bb_error_msg_and_die("stdin is not a socket");
 778                  * Better: */
 779                 bb_show_usage();
 780                 /* Help text says that tftpd must be used as inetd service,
 781                  * which is by far the most usual cause of get_sock_lsa
 782                  * failure */
 783         }
 784         peer_lsa = xzalloc(LSA_LEN_SIZE + our_lsa->len);
 785         peer_lsa->len = our_lsa->len;
 786
 787         /* Shifting to not collide with TFTP_OPTs */
 788         opt = option_mask32 = TFTPD_OPT | (getopt32(argv, "rcu:l", &user_opt) << 8);
 789         argv += optind;
 790         if (opt & TFTPD_OPT_l) {
 791                 openlog(applet_name, LOG_PID, LOG_DAEMON);
 792                 logmode = LOGMODE_SYSLOG;
 793         }
 794         if (argv[0])
 795                 xchdir(argv[0]);
 796
 797         result = recv_from_to(STDIN_FILENO, block_buf, sizeof(block_buf),
 798                         0 /* flags */,
 799                         &peer_lsa->u.sa, &our_lsa->u.sa, our_lsa->len);
 800
 801         error_msg = "malformed packet";
 802         opcode = ntohs(*(uint16_t*)block_buf);
 803         if (result < 4 || result >= sizeof(block_buf)
 804          || block_buf[result-1] != '\0'
 805          || (IF_FEATURE_TFTP_PUT(opcode != TFTP_RRQ) /* not download */
 806              IF_GETPUT(&&)
 807              IF_FEATURE_TFTP_GET(opcode != TFTP_WRQ) /* not upload */
 808             )
 809         ) {
 810                 goto err;
 811         }
 812         local_file = block_buf + 2;
 813         if (local_file[0] == '.' || strstr(local_file, "/.")) {
 814                 error_msg = "dot in file name";
 815                 goto err;
 816         }
 817         mode = local_file + strlen(local_file) + 1;
 818         if (mode >= block_buf + result || strcmp(mode, "octet") != 0) {
 819                 goto err;
 820         }
 821 # if ENABLE_FEATURE_TFTP_BLOCKSIZE
 822         {
 823                 char *res;
 824                 char *opt_str = mode + sizeof("octet");
 825                 int opt_len = block_buf + result - opt_str;
 826                 if (opt_len > 0) {
 827                         res = tftp_get_option("blksize", opt_str, opt_len);
 828                         if (res) {
 829                                 blksize = tftp_blksize_check(res, 65564);
 830                                 if (blksize < 0) {
 831                                         error_pkt_reason = ERR_BAD_OPT;
 832                                         /* will just send error pkt */
 833                                         goto do_proto;
 834                                 }
 835                         }
 836                         if (opcode != TFTP_WRQ /* download? */
 837                         /* did client ask us about file size? */
 838                          && tftp_get_option("tsize", opt_str, opt_len)
 839                         ) {
 840                                 want_transfer_size = 1;
 841                         }
 842                 }
 843         }
 844 # endif
 845
 846         if (!ENABLE_FEATURE_TFTP_PUT || opcode == TFTP_WRQ) {
 847                 if (opt & TFTPD_OPT_r) {
 848                         /* This would mean "disk full" - not true */
 849                         /*error_pkt_reason = ERR_WRITE;*/
 850                         error_msg = bb_msg_write_error;
 851                         goto err;
 852                 }
 853                 IF_GETPUT(option_mask32 |= TFTP_OPT_GET;) /* will receive file's data */
 854         } else {
 855                 IF_GETPUT(option_mask32 |= TFTP_OPT_PUT;) /* will send file's data */
 856         }
 857
 858         /* NB: if error_pkt_str or error_pkt_reason is set up,
 859          * tftp_protocol() just sends one error pkt and returns */
 860
 861  do_proto:
 862         close(STDIN_FILENO); /* close old, possibly wildcard socket */
 863         /* tftp_protocol() will create new one, bound to particular local IP */
 864         result = tftp_protocol(
 865                 our_lsa, peer_lsa,
 866                 local_file IF_TFTP(, NULL /*remote_file*/)
 867                 IF_FEATURE_TFTP_BLOCKSIZE(, want_transfer_size)
 868                 IF_FEATURE_TFTP_BLOCKSIZE(, blksize)
 869         );
 870
 871         return result;
 872  err:
 873         strcpy((char*)error_pkt_str, error_msg);
 874         goto do_proto;
 875 }
 876
 877 #endif /* ENABLE_TFTPD */
 878
 879 #endif /* ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT */