Optionally re-introduce bb_info_msg()
[oweals/busybox.git] / networking / tftp.c
index a62c5d8cc6137ba688d24a6f8d0edd283dc2d37b..5ebd221059f8b4782ba3b922d8ade21f2f4ca089 100644 (file)
@@ -1,8 +1,6 @@
 /* vi: set sw=4 ts=4: */
-/* -------------------------------------------------------------------------
- * tftp.c
- *
- * A simple tftp client for busybox.
+/*
+ * A simple tftp client/server for busybox.
  * Tries to follow RFC1350.
  * Only "octet" mode supported.
  * Optional blocksize negotiation (RFC2347 + RFC2348)
  *
  * utftp:  Copyright (C) 1999 Uwe Ohse <uwe@ohse.de>
  *
- * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
- * ------------------------------------------------------------------------- */
-
-#include "busybox.h"
-
-
-#define TFTP_BLOCKSIZE_DEFAULT 512     /* according to RFC 1350, don't change */
-#define TFTP_TIMEOUT 5 /* seconds */
-#define TFTP_NUM_RETRIES 5 /* number of retries */
-
-static const char * const MODE_OCTET = "octet";
-#define MODE_OCTET_LEN 6 /* sizeof(MODE_OCTET)*/
-
-static const char * const OPTION_BLOCKSIZE = "blksize";
-#define OPTION_BLOCKSIZE_LEN 8 /* sizeof(OPTION_BLOCKSIZE) */
+ * tftpd added by Denys Vlasenko & Vladimir Dronnikov
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ */
+//config:config TFTP
+//config:      bool "tftp (11 kb)"
+//config:      default y
+//config:      help
+//config:      Trivial File Transfer Protocol client. TFTP is usually used
+//config:      for simple, small transfers such as a root image
+//config:      for a network-enabled bootloader.
+//config:
+//config:config FEATURE_TFTP_PROGRESS_BAR
+//config:      bool "Enable progress bar"
+//config:      default y
+//config:      depends on TFTP
+//config:
+//config:config TFTPD
+//config:      bool "tftpd (10 kb)"
+//config:      default y
+//config:      help
+//config:      Trivial File Transfer Protocol server.
+//config:      It expects that stdin is a datagram socket and a packet
+//config:      is already pending on it. It will exit after one transfer.
+//config:      In other words: it should be run from inetd in nowait mode,
+//config:      or from udpsvd. Example: "udpsvd -E 0 69 tftpd DIR"
+//config:
+//config:config FEATURE_TFTP_GET
+//config:      bool "Enable 'tftp get' and/or tftpd upload code"
+//config:      default y
+//config:      depends on TFTP || TFTPD
+//config:      help
+//config:      Add support for the GET command within the TFTP client. This allows
+//config:      a client to retrieve a file from a TFTP server.
+//config:      Also enable upload support in tftpd, if tftpd is selected.
+//config:
+//config:      Note: this option does _not_ make tftpd capable of download
+//config:      (the usual operation people need from it)!
+//config:
+//config:config FEATURE_TFTP_PUT
+//config:      bool "Enable 'tftp put' and/or tftpd download code"
+//config:      default y
+//config:      depends on TFTP || TFTPD
+//config:      help
+//config:      Add support for the PUT command within the TFTP client. This allows
+//config:      a client to transfer a file to a TFTP server.
+//config:      Also enable download support in tftpd, if tftpd is selected.
+//config:
+//config:config FEATURE_TFTP_BLOCKSIZE
+//config:      bool "Enable 'blksize' and 'tsize' protocol options"
+//config:      default y
+//config:      depends on TFTP || TFTPD
+//config:      help
+//config:      Allow tftp to specify block size, and tftpd to understand
+//config:      "blksize" and "tsize" options.
+//config:
+//config:config TFTP_DEBUG
+//config:      bool "Enable debug"
+//config:      default n
+//config:      depends on TFTP || TFTPD
+//config:      help
+//config:      Make tftp[d] print debugging messages on stderr.
+//config:      This is useful if you are diagnosing a bug in tftp[d].
+
+//applet:#if ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT
+//applet:IF_TFTP(APPLET(tftp, BB_DIR_USR_BIN, BB_SUID_DROP))
+//applet:IF_TFTPD(APPLET(tftpd, BB_DIR_USR_SBIN, BB_SUID_DROP))
+//applet:#endif
+
+//kbuild:lib-$(CONFIG_TFTP) += tftp.o
+//kbuild:lib-$(CONFIG_TFTPD) += tftp.o
+
+//usage:#define tftp_trivial_usage
+//usage:       "[OPTIONS] HOST [PORT]"
+//usage:#define tftp_full_usage "\n\n"
+//usage:       "Transfer a file from/to tftp server\n"
+//usage:     "\n       -l FILE Local FILE"
+//usage:     "\n       -r FILE Remote FILE"
+//usage:       IF_FEATURE_TFTP_GET(
+//usage:     "\n       -g      Get file"
+//usage:       )
+//usage:       IF_FEATURE_TFTP_PUT(
+//usage:     "\n       -p      Put file"
+//usage:       )
+//usage:       IF_FEATURE_TFTP_BLOCKSIZE(
+//usage:     "\n       -b SIZE Transfer blocks of SIZE octets"
+//usage:       )
+//usage:
+//usage:#define tftpd_trivial_usage
+//usage:       "[-cr] [-u USER] [DIR]"
+//usage:#define tftpd_full_usage "\n\n"
+//usage:       "Transfer a file on tftp client's request\n"
+//usage:       "\n"
+//usage:       "tftpd should be used as an inetd service.\n"
+//usage:       "tftpd's line for inetd.conf:\n"
+//usage:       "       69 dgram udp nowait root tftpd tftpd -l /files/to/serve\n"
+//usage:       "It also can be ran from udpsvd:\n"
+//usage:       "       udpsvd -vE 0.0.0.0 69 tftpd /files/to/serve\n"
+//usage:     "\n       -r      Prohibit upload"
+//usage:     "\n       -c      Allow file creation via upload"
+//usage:     "\n       -u      Access files as USER"
+//usage:     "\n       -l      Log to syslog (inetd mode requires this)"
+
+#include "libbb.h"
+#include "common_bufsiz.h"
+#include <syslog.h>
+
+#if ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT
+
+#define TFTP_BLKSIZE_DEFAULT       512  /* according to RFC 1350, don't change */
+#define TFTP_BLKSIZE_DEFAULT_STR "512"
+/* Was 50 ms but users asked to bump it up a bit */
+#define TFTP_TIMEOUT_MS            100
+#define TFTP_MAXTIMEOUT_MS        2000
+#define TFTP_NUM_RETRIES            12  /* number of backed-off retries */
 
 /* opcodes we support */
 #define TFTP_RRQ   1
@@ -40,80 +138,147 @@ static const char * const OPTION_BLOCKSIZE = "blksize";
 #define TFTP_ERROR 5
 #define TFTP_OACK  6
 
-static const char *const tftp_bb_error_msg[] = {
-       "Undefined error",
-       "File not found",
-       "Access violation",
-       "Disk full or allocation error",
-       "Illegal TFTP operation",
-       "Unknown transfer ID",
-       "File already exists",
-       "No such user"
+/* error codes sent over network (we use only 0, 1, 3 and 8) */
+/* generic (error message is included in the packet) */
+#define ERR_UNSPEC   0
+#define ERR_NOFILE   1
+#define ERR_ACCESS   2
+/* disk full or allocation exceeded */
+#define ERR_WRITE    3
+#define ERR_OP       4
+#define ERR_BAD_ID   5
+#define ERR_EXIST    6
+#define ERR_BAD_USER 7
+#define ERR_BAD_OPT  8
+
+/* masks coming from getopt32 */
+enum {
+       TFTP_OPT_GET = (1 << 0),
+       TFTP_OPT_PUT = (1 << 1),
+       /* pseudo option: if set, it's tftpd */
+       TFTPD_OPT = (1 << 7) * ENABLE_TFTPD,
+       TFTPD_OPT_r = (1 << 8) * ENABLE_TFTPD,
+       TFTPD_OPT_c = (1 << 9) * ENABLE_TFTPD,
+       TFTPD_OPT_u = (1 << 10) * ENABLE_TFTPD,
+       TFTPD_OPT_l = (1 << 11) * ENABLE_TFTPD,
 };
 
-#define tftp_cmd_get ENABLE_FEATURE_TFTP_GET
-
-#if ENABLE_FEATURE_TFTP_PUT
-# define tftp_cmd_put (tftp_cmd_get+ENABLE_FEATURE_TFTP_PUT)
+#if ENABLE_FEATURE_TFTP_GET && !ENABLE_FEATURE_TFTP_PUT
+#define IF_GETPUT(...)
+#define CMD_GET(cmd) 1
+#define CMD_PUT(cmd) 0
+#elif !ENABLE_FEATURE_TFTP_GET && ENABLE_FEATURE_TFTP_PUT
+#define IF_GETPUT(...)
+#define CMD_GET(cmd) 0
+#define CMD_PUT(cmd) 1
 #else
-# define tftp_cmd_put 0
+#define IF_GETPUT(...) __VA_ARGS__
+#define CMD_GET(cmd) ((cmd) & TFTP_OPT_GET)
+#define CMD_PUT(cmd) ((cmd) & TFTP_OPT_PUT)
+#endif
+/* NB: in the code below
+ * CMD_GET(cmd) and CMD_PUT(cmd) are mutually exclusive
+ */
+
+
+struct globals {
+       /* u16 TFTP_ERROR; u16 reason; both network-endian, then error text: */
+       uint8_t error_pkt[4 + 32];
+       struct passwd *pw;
+       /* Used in tftpd_main() for initial packet */
+       /* Some HP PA-RISC firmware always sends fixed 516-byte requests */
+       char block_buf[516];
+       char block_buf_tail[1];
+#if ENABLE_FEATURE_TFTP_PROGRESS_BAR
+       off_t pos;
+       off_t size;
+       const char *file;
+       bb_progress_t pmt;
+#endif
+} FIX_ALIASING;
+#define G (*(struct globals*)bb_common_bufsiz1)
+#define INIT_G() do { \
+       setup_common_bufsiz(); \
+       BUILD_BUG_ON(sizeof(G) > COMMON_BUFSIZE); \
+} while (0)
+
+#define G_error_pkt_reason (G.error_pkt[3])
+#define G_error_pkt_str    ((char*)(G.error_pkt + 4))
+
+#if ENABLE_FEATURE_TFTP_PROGRESS_BAR && ENABLE_FEATURE_TFTP_BLOCKSIZE
+static void tftp_progress_update(void)
+{
+       bb_progress_update(&G.pmt, 0, G.pos, G.size);
+}
+static void tftp_progress_init(void)
+{
+       bb_progress_init(&G.pmt, G.file);
+       tftp_progress_update();
+}
+static void tftp_progress_done(void)
+{
+       if (is_bb_progress_inited(&G.pmt)) {
+               tftp_progress_update();
+               bb_putchar_stderr('\n');
+               bb_progress_free(&G.pmt);
+       }
+}
+#else
+# define tftp_progress_update() ((void)0)
+# define tftp_progress_init() ((void)0)
+# define tftp_progress_done() ((void)0)
 #endif
-
 
 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
 
-static int tftp_blocksize_check(int blocksize, int bufsize)
+static int tftp_blksize_check(const char *blksize_str, int maxsize)
 {
-       /* Check if the blocksize is valid:
+       /* Check if the blksize is valid:
         * RFC2348 says between 8 and 65464,
         * but our implementation makes it impossible
-        * to use blocksizes smaller than 22 octets.
-        */
-
-       if ((bufsize && (blocksize > bufsize)) ||
-               (blocksize < 8) || (blocksize > 65564)) {
-               bb_error_msg("bad blocksize");
-               return 0;
+        * to use blksizes smaller than 22 octets. */
+       unsigned blksize = bb_strtou(blksize_str, NULL, 10);
+       if (errno
+        || (blksize < 24) || (blksize > maxsize)
+       ) {
+               bb_error_msg("bad blocksize '%s'", blksize_str);
+               return -1;
        }
-
-       return blocksize;
+# if ENABLE_TFTP_DEBUG
+       bb_info_msg("using blksize %u", blksize);
+# endif
+       return blksize;
 }
 
-static char *tftp_option_get(char *buf, int len, const char * const option)
+static char *tftp_get_option(const char *option, char *buf, int len)
 {
        int opt_val = 0;
        int opt_found = 0;
        int k;
 
-       while (len > 0) {
-
-               /* Make sure the options are terminated correctly */
+       /* buf points to:
+        * "opt_name<NUL>opt_val<NUL>opt_name2<NUL>opt_val2<NUL>..." */
 
+       while (len > 0) {
+               /* Make sure options are terminated correctly */
                for (k = 0; k < len; k++) {
                        if (buf[k] == '\0') {
-                               break;
+                               goto nul_found;
                        }
                }
-
-               if (k >= len) {
-                       break;
-               }
-
-               if (opt_val == 0) {
+               return NULL;
+ nul_found:
+               if (opt_val == 0) { /* it's "name" part */
                        if (strcasecmp(buf, option) == 0) {
                                opt_found = 1;
                        }
-               } else {
-                       if (opt_found) {
-                               return buf;
-                       }
+               } else if (opt_found) {
+                       return buf;
                }
 
                k++;
-
                buf += k;
                len -= k;
-
                opt_val ^= 1;
        }
 
@@ -122,440 +287,674 @@ static char *tftp_option_get(char *buf, int len, const char * const option)
 
 #endif
 
-static int tftp(const int cmd, const struct hostent *host,
-                  const char *remotefile, const int localfd,
-                  const unsigned short port, int tftp_bufsize)
+static int tftp_protocol(
+               /* NULL if tftp, !NULL if tftpd: */
+               len_and_sockaddr *our_lsa,
+               len_and_sockaddr *peer_lsa,
+               const char *local_file
+               IF_TFTP(, const char *remote_file)
+#if !ENABLE_TFTP
+# define remote_file NULL
+#endif
+               /* 1 for tftp; 1/0 for tftpd depending whether client asked about it: */
+               IF_FEATURE_TFTP_BLOCKSIZE(, int want_transfer_size)
+               IF_FEATURE_TFTP_BLOCKSIZE(, int blksize))
 {
-       struct sockaddr_in sa;
-       struct sockaddr_in from;
-       struct timeval tv;
-       socklen_t fromlen;
-       fd_set rfds;
-       int socketfd;
+#if !ENABLE_FEATURE_TFTP_BLOCKSIZE
+       enum { blksize = TFTP_BLKSIZE_DEFAULT };
+#endif
+
+       struct pollfd pfd[1];
+#define socket_fd (pfd[0].fd)
        int len;
-       int opcode = 0;
-       int finished = 0;
-       int timeout = TFTP_NUM_RETRIES;
-       unsigned short block_nr = 1;
-       unsigned short tmp;
+       int send_len;
+       IF_FEATURE_TFTP_BLOCKSIZE(smallint expect_OACK = 0;)
+       smallint finished = 0;
+       uint16_t opcode;
+       uint16_t block_nr;
+       uint16_t recv_blk;
+       int open_mode, local_fd;
+       int retries, waittime_ms;
+       int io_bufsize = blksize + 4;
        char *cp;
-
-       USE_FEATURE_TFTP_BLOCKSIZE(int want_option_ack = 0;)
-
        /* Can't use RESERVE_CONFIG_BUFFER here since the allocation
-        * size varies meaning BUFFERS_GO_ON_STACK would fail */
-       char *buf=xmalloc(tftp_bufsize += 4);
-
-       if ((socketfd = socket(PF_INET, SOCK_DGRAM, 0)) < 0) {
-               /* need to unlink the localfile, so don't use xsocket here. */
-               bb_perror_msg("socket");
-               return EXIT_FAILURE;
+        * size varies meaning BUFFERS_GO_ON_STACK would fail.
+        *
+        * We must keep the transmit and receive buffers separate
+        * in case we rcv a garbage pkt - we need to rexmit the last pkt.
+        */
+       char *xbuf = xmalloc(io_bufsize);
+       char *rbuf = xmalloc(io_bufsize);
+
+       socket_fd = xsocket(peer_lsa->u.sa.sa_family, SOCK_DGRAM, 0);
+       setsockopt_reuseaddr(socket_fd);
+
+       if (!ENABLE_TFTP || our_lsa) { /* tftpd */
+               /* Create a socket which is:
+                * 1. bound to IP:port peer sent 1st datagram to,
+                * 2. connected to peer's IP:port
+                * This way we will answer from the IP:port peer
+                * expects, will not get any other packets on
+                * the socket, and also plain read/write will work. */
+               xbind(socket_fd, &our_lsa->u.sa, our_lsa->len);
+               xconnect(socket_fd, &peer_lsa->u.sa, peer_lsa->len);
+
+               /* Is there an error already? Send pkt and bail out */
+               if (G_error_pkt_reason || G_error_pkt_str[0])
+                       goto send_err_pkt;
+
+               if (G.pw) {
+                       change_identity(G.pw); /* initgroups, setgid, setuid */
+               }
        }
 
-       len = sizeof(sa);
-
-       memset(&sa, 0, len);
-       xbind(socketfd, (struct sockaddr *)&sa, len);
-
-       sa.sin_family = host->h_addrtype;
-       sa.sin_port = port;
-       memcpy(&sa.sin_addr, (struct in_addr *) host->h_addr,
-                  sizeof(sa.sin_addr));
-
-       /* build opcode */
-       if (cmd & tftp_cmd_get) {
-               opcode = TFTP_RRQ;
-       }
-       if (cmd & tftp_cmd_put) {
-               opcode = TFTP_WRQ;
+       /* Prepare open mode */
+       if (CMD_PUT(option_mask32)) {
+               open_mode = O_RDONLY;
+       } else {
+               open_mode = O_WRONLY | O_TRUNC | O_CREAT;
+#if ENABLE_TFTPD
+               if ((option_mask32 & (TFTPD_OPT+TFTPD_OPT_c)) == TFTPD_OPT) {
+                       /* tftpd without -c */
+                       open_mode = O_WRONLY | O_TRUNC;
+               }
+#endif
        }
 
-       while (1) {
-
-               cp = buf;
-
-               /* first create the opcode part */
-               *((unsigned short *) cp) = htons(opcode);
-               cp += 2;
-
-               /* add filename and mode */
-               if (((cmd & tftp_cmd_get) && (opcode == TFTP_RRQ)) ||
-                       ((cmd & tftp_cmd_put) && (opcode == TFTP_WRQ)))
-               {
-                       int too_long = 0;
-
-                       /* see if the filename fits into buf
-                        * and fill in packet.  */
-                       len = strlen(remotefile) + 1;
-
-                       if ((cp + len) >= &buf[tftp_bufsize - 1]) {
-                               too_long = 1;
-                       } else {
-                               safe_strncpy(cp, remotefile, len);
-                               cp += len;
-                       }
-
-                       if (too_long || ((&buf[tftp_bufsize - 1] - cp) < MODE_OCTET_LEN)) {
-                               bb_error_msg("remote filename too long");
-                               break;
-                       }
-
-                       /* add "mode" part of the package */
-                       memcpy(cp, MODE_OCTET, MODE_OCTET_LEN);
-                       cp += MODE_OCTET_LEN;
-
+       /* Examples of network traffic.
+        * Note two cases when ACKs with block# of 0 are sent.
+        *
+        * Download without options:
+        * tftp -> "\0\1FILENAME\0octet\0"
+        *         "\0\3\0\1FILEDATA..." <- tftpd
+        * tftp -> "\0\4\0\1"
+        * ...
+        * Download with option of blksize 16384:
+        * tftp -> "\0\1FILENAME\0octet\0blksize\00016384\0"
+        *         "\0\6blksize\00016384\0" <- tftpd
+        * tftp -> "\0\4\0\0"
+        *         "\0\3\0\1FILEDATA..." <- tftpd
+        * tftp -> "\0\4\0\1"
+        * ...
+        * Upload without options:
+        * tftp -> "\0\2FILENAME\0octet\0"
+        *         "\0\4\0\0" <- tftpd
+        * tftp -> "\0\3\0\1FILEDATA..."
+        *         "\0\4\0\1" <- tftpd
+        * ...
+        * Upload with option of blksize 16384:
+        * tftp -> "\0\2FILENAME\0octet\0blksize\00016384\0"
+        *         "\0\6blksize\00016384\0" <- tftpd
+        * tftp -> "\0\3\0\1FILEDATA..."
+        *         "\0\4\0\1" <- tftpd
+        * ...
+        */
+       block_nr = 1;
+       cp = xbuf + 2;
+
+       if (!ENABLE_TFTP || our_lsa) { /* tftpd */
+               /* Open file (must be after changing user) */
+               local_fd = open(local_file, open_mode, 0666);
+               if (local_fd < 0) {
+                       G_error_pkt_reason = ERR_NOFILE;
+                       strcpy(G_error_pkt_str, "can't open file");
+                       goto send_err_pkt;
+               }
+/* gcc 4.3.1 would NOT optimize it out as it should! */
 #if ENABLE_FEATURE_TFTP_BLOCKSIZE
-
-                       len = tftp_bufsize - 4; /* data block size */
-
-                       if (len != TFTP_BLOCKSIZE_DEFAULT) {
-
-                               if ((&buf[tftp_bufsize - 1] - cp) < 15) {
-                                       bb_error_msg("remote filename too long");
-                                       break;
-                               }
-
-                               /* add "blksize" + number of blocks  */
-                               memcpy(cp, OPTION_BLOCKSIZE, OPTION_BLOCKSIZE_LEN);
-                               cp += OPTION_BLOCKSIZE_LEN;
-                               cp += snprintf(cp, 6, "%d", len) + 1;
-
-                               want_option_ack = 1;
-                       }
+               if (blksize != TFTP_BLKSIZE_DEFAULT || want_transfer_size) {
+                       /* Create and send OACK packet. */
+                       /* For the download case, block_nr is still 1 -
+                        * we expect 1st ACK from peer to be for (block_nr-1),
+                        * that is, for "block 0" which is our OACK pkt */
+                       opcode = TFTP_OACK;
+                       goto add_blksize_opt;
+               }
 #endif
+               if (CMD_GET(option_mask32)) {
+                       /* It's upload and we don't send OACK.
+                        * We must ACK 1st packet (with filename)
+                        * as if it is "block 0" */
+                       block_nr = 0;
                }
+       } else { /* tftp */
+               /* Open file (must be after changing user) */
+               local_fd = CMD_GET(option_mask32) ? STDOUT_FILENO : STDIN_FILENO;
+               if (NOT_LONE_DASH(local_file))
+                       local_fd = xopen(local_file, open_mode);
+/* Removing #if, or using if() statement instead of #if may lead to
+ * "warning: null argument where non-null required": */
+#if ENABLE_TFTP
+               /* tftp */
+
+               /* We can't (and don't really need to) bind the socket:
+                * we don't know from which local IP datagrams will be sent,
+                * but kernel will pick the same IP every time (unless routing
+                * table is changed), thus peer will see dgrams consistently
+                * coming from the same IP.
+                * We would like to connect the socket, but since peer's
+                * UDP code can be less perfect than ours, _peer's_ IP:port
+                * in replies may differ from IP:port we used to send
+                * our first packet. We can connect() only when we get
+                * first reply. */
+
+               /* build opcode */
+               opcode = TFTP_WRQ;
+               if (CMD_GET(option_mask32)) {
+                       opcode = TFTP_RRQ;
+               }
+               /* add filename and mode */
+               /* fill in packet if the filename fits into xbuf */
+               len = strlen(remote_file) + 1;
+               if (2 + len + sizeof("octet") >= io_bufsize) {
+                       bb_error_msg("remote filename is too long");
+                       goto ret;
+               }
+               strcpy(cp, remote_file);
+               cp += len;
+               /* add "mode" part of the packet */
+               strcpy(cp, "octet");
+               cp += sizeof("octet");
+
+# if ENABLE_FEATURE_TFTP_BLOCKSIZE
+               if (blksize == TFTP_BLKSIZE_DEFAULT && !want_transfer_size)
+                       goto send_pkt;
+
+               /* Need to add option to pkt */
+               if ((&xbuf[io_bufsize - 1] - cp) < sizeof("blksize NNNNN tsize ") + sizeof(off_t)*3) {
+                       bb_error_msg("remote filename is too long");
+                       goto ret;
+               }
+               expect_OACK = 1;
+# endif
+#endif /* ENABLE_TFTP */
 
-               /* add ack and data */
-
-               if (((cmd & tftp_cmd_get) && (opcode == TFTP_ACK)) ||
-                       ((cmd & tftp_cmd_put) && (opcode == TFTP_DATA))) {
-
-                       *((unsigned short *) cp) = htons(block_nr);
-
-                       cp += 2;
-
-                       block_nr++;
-
-                       if ((cmd & tftp_cmd_put) && (opcode == TFTP_DATA)) {
-                               len = full_read(localfd, cp, tftp_bufsize - 4);
-
-                               if (len < 0) {
-                                       bb_perror_msg(bb_msg_read_error);
-                                       break;
-                               }
-
-                               if (len != (tftp_bufsize - 4)) {
-                                       finished++;
-                               }
+#if ENABLE_FEATURE_TFTP_BLOCKSIZE
+ add_blksize_opt:
+               if (blksize != TFTP_BLKSIZE_DEFAULT) {
+                       /* add "blksize", <nul>, blksize, <nul> */
+                       strcpy(cp, "blksize");
+                       cp += sizeof("blksize");
+                       cp += snprintf(cp, 6, "%d", blksize) + 1;
+               }
+               if (want_transfer_size) {
+                       /* add "tsize", <nul>, size, <nul> (see RFC2349) */
+                       /* if tftp and downloading, we send "0" (since we opened local_fd with O_TRUNC)
+                        * and this makes server to send "tsize" option with the size */
+                       /* if tftp and uploading, we send file size (maybe dont, to not confuse old servers???) */
+                       /* if tftpd and downloading, we are answering to client's request */
+                       /* if tftpd and uploading: !want_transfer_size, this code is not executed */
+                       struct stat st;
+                       strcpy(cp, "tsize");
+                       cp += sizeof("tsize");
+                       st.st_size = 0;
+                       fstat(local_fd, &st);
+                       cp += sprintf(cp, "%"OFF_FMT"u", (off_t)st.st_size) + 1;
+# if ENABLE_FEATURE_TFTP_PROGRESS_BAR
+                       /* Save for progress bar. If 0 (tftp downloading),
+                        * we look at server's reply later */
+                       G.size = st.st_size;
+                       if (remote_file && st.st_size)
+                               tftp_progress_init();
+# endif
+               }
+#endif
+               /* First packet is built, so skip packet generation */
+               goto send_pkt;
+       }
 
-                               cp += len;
+       /* Using mostly goto's - continue/break will be less clear
+        * in where we actually jump to */
+       while (1) {
+               /* Build ACK or DATA */
+               cp = xbuf + 2;
+               *((uint16_t*)cp) = htons(block_nr);
+               cp += 2;
+               block_nr++;
+               opcode = TFTP_ACK;
+               if (CMD_PUT(option_mask32)) {
+                       opcode = TFTP_DATA;
+                       len = full_read(local_fd, cp, blksize);
+                       if (len < 0) {
+                               goto send_read_err_pkt;
                        }
+                       if (len != blksize) {
+                               finished = 1;
+                       }
+                       cp += len;
+                       IF_FEATURE_TFTP_PROGRESS_BAR(G.pos += len;)
                }
+ send_pkt:
+               /* Send packet */
+               *((uint16_t*)xbuf) = htons(opcode); /* fill in opcode part */
+               send_len = cp - xbuf;
+               /* NB: send_len value is preserved in code below
+                * for potential resend */
+
+               retries = TFTP_NUM_RETRIES;  /* re-initialize */
+               waittime_ms = TFTP_TIMEOUT_MS;
+
+ send_again:
+#if ENABLE_TFTP_DEBUG
+               fprintf(stderr, "sending %u bytes\n", send_len);
+               for (cp = xbuf; cp < &xbuf[send_len]; cp++)
+                       fprintf(stderr, "%02x ", (unsigned char) *cp);
+               fprintf(stderr, "\n");
+#endif
+               xsendto(socket_fd, xbuf, send_len, &peer_lsa->u.sa, peer_lsa->len);
 
-
-               /* send packet */
-
-
-               timeout = TFTP_NUM_RETRIES;     /* re-initialize */
-               do {
-
-                       len = cp - buf;
-
-#if ENABLE_DEBUG_TFTP
-                       fprintf(stderr, "sending %u bytes\n", len);
-                       for (cp = buf; cp < &buf[len]; cp++)
-                               fprintf(stderr, "%02x ", (unsigned char) *cp);
-                       fprintf(stderr, "\n");
+#if ENABLE_FEATURE_TFTP_PROGRESS_BAR
+               if (is_bb_progress_inited(&G.pmt))
+                       tftp_progress_update();
 #endif
-                       if (sendto(socketfd, buf, len, 0,
-                                          (struct sockaddr *) &sa, sizeof(sa)) < 0) {
-                               bb_perror_msg("send");
-                               len = -1;
-                               break;
+               /* Was it final ACK? then exit */
+               if (finished && (opcode == TFTP_ACK))
+                       goto ret;
+
+ recv_again:
+               /* Receive packet */
+               /*pfd[0].fd = socket_fd;*/
+               pfd[0].events = POLLIN;
+               switch (safe_poll(pfd, 1, waittime_ms)) {
+               default:
+                       /*bb_perror_msg("poll"); - done in safe_poll */
+                       goto ret;
+               case 0:
+                       retries--;
+                       if (retries == 0) {
+                               tftp_progress_done();
+                               bb_error_msg("timeout");
+                               goto ret; /* no err packet sent */
                        }
 
-
-                       if (finished && (opcode == TFTP_ACK)) {
-                               break;
+                       /* exponential backoff with limit */
+                       waittime_ms += waittime_ms/2;
+                       if (waittime_ms > TFTP_MAXTIMEOUT_MS) {
+                               waittime_ms = TFTP_MAXTIMEOUT_MS;
                        }
 
-                       /* receive packet */
-
-                       memset(&from, 0, sizeof(from));
-                       fromlen = sizeof(from);
-
-                       tv.tv_sec = TFTP_TIMEOUT;
-                       tv.tv_usec = 0;
-
-                       FD_ZERO(&rfds);
-                       FD_SET(socketfd, &rfds);
-
-                       switch (select(socketfd + 1, &rfds, NULL, NULL, &tv)) {
-                       case 1:
-                               len = recvfrom(socketfd, buf, tftp_bufsize, 0,
-                                                          (struct sockaddr *) &from, &fromlen);
-
-                               if (len < 0) {
-                                       bb_perror_msg("recvfrom");
-                                       break;
-                               }
-
-                               timeout = 0;
-
-                               if (sa.sin_port == port) {
-                                       sa.sin_port = from.sin_port;
-                               }
-                               if (sa.sin_port == from.sin_port) {
-                                       break;
-                               }
-
-                               /* fall-through for bad packets! */
-                               /* discard the packet - treat as timeout */
-                               timeout = TFTP_NUM_RETRIES;
-                       case 0:
-                               bb_error_msg("timeout");
-
-                               timeout--;
-                               if (timeout == 0) {
-                                       len = -1;
-                                       bb_error_msg("last timeout");
-                               }
-                               break;
-                       default:
-                               bb_perror_msg("select");
-                               len = -1;
+                       goto send_again; /* resend last sent pkt */
+               case 1:
+                       if (!our_lsa) {
+                               /* tftp (not tftpd!) receiving 1st packet */
+                               our_lsa = ((void*)(ptrdiff_t)-1); /* not NULL */
+                               len = recvfrom(socket_fd, rbuf, io_bufsize, 0,
+                                               &peer_lsa->u.sa, &peer_lsa->len);
+                               /* Our first dgram went to port 69
+                                * but reply may come from different one.
+                                * Remember and use this new port (and IP) */
+                               if (len >= 0)
+                                       xconnect(socket_fd, &peer_lsa->u.sa, peer_lsa->len);
+                       } else {
+                               /* tftpd, or not the very first packet:
+                                * socket is connect()ed, can just read from it. */
+                               /* Don't full_read()!
+                                * This is not TCP, one read == one pkt! */
+                               len = safe_read(socket_fd, rbuf, io_bufsize);
+                       }
+                       if (len < 0) {
+                               goto send_read_err_pkt;
+                       }
+                       if (len < 4) { /* too small? */
+                               goto recv_again;
                        }
-
-               } while (timeout && (len >= 0));
-
-               if ((finished) || (len < 0)) {
-                       break;
                }
 
-               /* process received packet */
-
-               opcode = ntohs(*((unsigned short *) buf));
-               tmp = ntohs(*((unsigned short *) &buf[2]));
-
-#if ENABLE_DEBUG_TFTP
-               fprintf(stderr, "received %d bytes: %04x %04x\n", len, opcode, tmp);
+               /* Process recv'ed packet */
+               opcode = ntohs( ((uint16_t*)rbuf)[0] );
+               recv_blk = ntohs( ((uint16_t*)rbuf)[1] );
+#if ENABLE_TFTP_DEBUG
+               fprintf(stderr, "received %d bytes: %04x %04x\n", len, opcode, recv_blk);
 #endif
-
                if (opcode == TFTP_ERROR) {
-                       const char *msg = NULL;
-
-                       if (buf[4] != '\0') {
-                               msg = &buf[4];
-                               buf[tftp_bufsize - 1] = '\0';
-                       } else if (tmp < (sizeof(tftp_bb_error_msg)
-                                                         / sizeof(char *))) {
-
-                               msg = tftp_bb_error_msg[tmp];
-                       }
-
-                       if (msg) {
-                               bb_error_msg("server says: %s", msg);
+                       static const char errcode_str[] ALIGN1 =
+                               "\0"
+                               "file not found\0"
+                               "access violation\0"
+                               "disk full\0"
+                               "bad operation\0"
+                               "unknown transfer id\0"
+                               "file already exists\0"
+                               "no such user\0"
+                               "bad option";
+
+                       const char *msg = "";
+
+                       if (len > 4 && rbuf[4] != '\0') {
+                               msg = &rbuf[4];
+                               rbuf[io_bufsize - 1] = '\0'; /* paranoia */
+                       } else if (recv_blk <= 8) {
+                               msg = nth_string(errcode_str, recv_blk);
                        }
-
-                       break;
+                       bb_error_msg("server error: (%u) %s", recv_blk, msg);
+                       goto ret;
                }
-#if ENABLE_FEATURE_TFTP_BLOCKSIZE
-               if (want_option_ack) {
-
-                       want_option_ack = 0;
 
+#if ENABLE_FEATURE_TFTP_BLOCKSIZE
+               if (expect_OACK) {
+                       expect_OACK = 0;
                        if (opcode == TFTP_OACK) {
-
                                /* server seems to support options */
-
                                char *res;
 
-                               res = tftp_option_get(&buf[2], len - 2, OPTION_BLOCKSIZE);
-
+                               res = tftp_get_option("blksize", &rbuf[2], len - 2);
                                if (res) {
-                                       int blksize = xatoi_u(res);
-
-                                       if (tftp_blocksize_check(blksize, tftp_bufsize - 4)) {
-
-                                               if (cmd & tftp_cmd_put) {
-                                                       opcode = TFTP_DATA;
-                                               } else {
-                                                       opcode = TFTP_ACK;
-                                               }
-#if ENABLE_DEBUG_TFTP
-                                               fprintf(stderr, "using %s %u\n", OPTION_BLOCKSIZE,
-                                                               blksize);
-#endif
-                                               tftp_bufsize = blksize + 4;
-                                               block_nr = 0;
-                                               continue;
+                                       blksize = tftp_blksize_check(res, blksize);
+                                       if (blksize < 0) {
+                                               G_error_pkt_reason = ERR_BAD_OPT;
+                                               goto send_err_pkt;
                                        }
+                                       io_bufsize = blksize + 4;
                                }
-                               /* FIXME:
-                                * we should send ERROR 8 */
-                               bb_error_msg("bad server option");
-                               break;
+# if ENABLE_FEATURE_TFTP_PROGRESS_BAR
+                               if (remote_file && G.size == 0) { /* if we don't know it yet */
+                                       res = tftp_get_option("tsize", &rbuf[2], len - 2);
+                                       if (res) {
+                                               G.size = bb_strtoull(res, NULL, 10);
+                                               if (G.size)
+                                                       tftp_progress_init();
+                                       }
+                               }
+# endif
+                               if (CMD_GET(option_mask32)) {
+                                       /* We'll send ACK for OACK,
+                                        * such ACK has "block no" of 0 */
+                                       block_nr = 0;
+                               }
+                               continue;
                        }
-
-                       bb_error_msg("warning: blksize not supported by server"
-                                                " - reverting to 512");
-
-                       tftp_bufsize = TFTP_BLOCKSIZE_DEFAULT + 4;
+                       /* rfc2347:
+                        * "An option not acknowledged by the server
+                        * must be ignored by the client and server
+                        * as if it were never requested." */
+                       if (blksize != TFTP_BLKSIZE_DEFAULT)
+                               bb_error_msg("falling back to blocksize "TFTP_BLKSIZE_DEFAULT_STR);
+                       blksize = TFTP_BLKSIZE_DEFAULT;
+                       io_bufsize = TFTP_BLKSIZE_DEFAULT + 4;
                }
 #endif
-
-               if ((cmd & tftp_cmd_get) && (opcode == TFTP_DATA)) {
-
-                       if (tmp == block_nr) {
-
-                               len = full_write(localfd, &buf[4], len - 4);
-
-                               if (len < 0) {
-                                       bb_perror_msg(bb_msg_write_error);
-                                       break;
+               /* block_nr is already advanced to next block# we expect
+                * to get / block# we are about to send next time */
+
+               if (CMD_GET(option_mask32) && (opcode == TFTP_DATA)) {
+                       if (recv_blk == block_nr) {
+                               int sz = full_write(local_fd, &rbuf[4], len - 4);
+                               if (sz != len - 4) {
+                                       strcpy(G_error_pkt_str, bb_msg_write_error);
+                                       G_error_pkt_reason = ERR_WRITE;
+                                       goto send_err_pkt;
                                }
-
-                               if (len != (tftp_bufsize - 4)) {
-                                       finished++;
+                               if (sz != blksize) {
+                                       finished = 1;
                                }
-
-                               opcode = TFTP_ACK;
-                               continue;
+                               IF_FEATURE_TFTP_PROGRESS_BAR(G.pos += sz;)
+                               continue; /* send ACK */
                        }
-                       /* in case the last ack disappeared into the ether */
-                       if (tmp == (block_nr - 1)) {
-                               --block_nr;
-                               opcode = TFTP_ACK;
-                               continue;
-                       } else if (tmp + 1 == block_nr) {
+/* Disabled to cope with servers with Sorcerer's Apprentice Syndrome */
+#if 0
+                       if (recv_blk == (block_nr - 1)) {
                                /* Server lost our TFTP_ACK.  Resend it */
-                               block_nr = tmp;
-                               opcode = TFTP_ACK;
+                               block_nr = recv_blk;
                                continue;
                        }
+#endif
                }
 
-               if ((cmd & tftp_cmd_put) && (opcode == TFTP_ACK)) {
-
-                       if (tmp == (unsigned short) (block_nr - 1)) {
-                               if (finished) {
-                                       break;
-                               }
-
-                               opcode = TFTP_DATA;
-                               continue;
+               if (CMD_PUT(option_mask32) && (opcode == TFTP_ACK)) {
+                       /* did peer ACK our last DATA pkt? */
+                       if (recv_blk == (uint16_t) (block_nr - 1)) {
+                               if (finished)
+                                       goto ret;
+                               continue; /* send next block */
                        }
                }
+               /* Awww... recv'd packet is not recognized! */
+               goto recv_again;
+               /* why recv_again? - rfc1123 says:
+                * "The sender (i.e., the side originating the DATA packets)
+                *  must never resend the current DATA packet on receipt
+                *  of a duplicate ACK".
+                * DATA pkts are resent ONLY on timeout.
+                * Thus "goto send_again" will ba a bad mistake above.
+                * See:
+                * http://en.wikipedia.org/wiki/Sorcerer's_Apprentice_Syndrome
+                */
+       } /* end of "while (1)" */
+ ret:
+       if (ENABLE_FEATURE_CLEAN_UP) {
+               close(local_fd);
+               close(socket_fd);
+               free(xbuf);
+               free(rbuf);
        }
-
-#if ENABLE_FEATURE_CLEAN_UP
-       close(socketfd);
-       free(buf);
-#endif
-
-       return finished ? EXIT_SUCCESS : EXIT_FAILURE;
+       return finished == 0; /* returns 1 on failure */
+
+ send_read_err_pkt:
+       strcpy(G_error_pkt_str, bb_msg_read_error);
+ send_err_pkt:
+       if (G_error_pkt_str[0])
+               bb_error_msg("%s", G_error_pkt_str);
+       G.error_pkt[1] = TFTP_ERROR;
+       xsendto(socket_fd, G.error_pkt, 4 + 1 + strlen(G_error_pkt_str),
+                       &peer_lsa->u.sa, peer_lsa->len);
+       return EXIT_FAILURE;
+#undef remote_file
 }
 
-int tftp_main(int argc, char **argv)
+#if ENABLE_TFTP
+
+int tftp_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int tftp_main(int argc UNUSED_PARAM, char **argv)
 {
-       struct hostent *host = NULL;
-       const char *localfile = NULL;
-       const char *remotefile = NULL;
-       int port;
-       int cmd = 0;
-       int fd = -1;
-       int flags = 0;
+       len_and_sockaddr *peer_lsa;
+       const char *local_file = NULL;
+       const char *remote_file = NULL;
+# if ENABLE_FEATURE_TFTP_BLOCKSIZE
+       const char *blksize_str = TFTP_BLKSIZE_DEFAULT_STR;
+       int blksize;
+# endif
        int result;
-       int blocksize = TFTP_BLOCKSIZE_DEFAULT;
-
-       /* figure out what to pass to getopt */
-
-#if ENABLE_FEATURE_TFTP_BLOCKSIZE
-       char *sblocksize = NULL;
+       int port;
+       IF_GETPUT(int opt;)
+
+       INIT_G();
+
+       IF_GETPUT(opt =) getopt32(argv, "^"
+                       IF_FEATURE_TFTP_GET("g") IF_FEATURE_TFTP_PUT("p")
+                       "l:r:" IF_FEATURE_TFTP_BLOCKSIZE("b:")
+                       "\0"
+                       /* -p or -g is mandatory, and they are mutually exclusive */
+                       IF_FEATURE_TFTP_GET("g:") IF_FEATURE_TFTP_PUT("p:")
+                       IF_GETPUT("g--p:p--g:"),
+                       &local_file, &remote_file
+                       IF_FEATURE_TFTP_BLOCKSIZE(, &blksize_str)
+       );
+       argv += optind;
+
+# if ENABLE_FEATURE_TFTP_BLOCKSIZE
+       /* Check if the blksize is valid:
+        * RFC2348 says between 8 and 65464 */
+       blksize = tftp_blksize_check(blksize_str, 65564);
+       if (blksize < 0) {
+               //bb_error_msg("bad block size");
+               return EXIT_FAILURE;
+       }
+# endif
 
-#define BS "b:"
-#define BS_ARG , &sblocksize
-#else
-#define BS
-#define BS_ARG
-#endif
+       if (remote_file) {
+               if (!local_file) {
+                       const char *slash = strrchr(remote_file, '/');
+                       local_file = slash ? slash + 1 : remote_file;
+               }
+       } else {
+               remote_file = local_file;
+       }
 
-#if ENABLE_FEATURE_TFTP_GET
-#define GET "g"
-#define GET_COMPL ":g"
-#else
-#define GET
-#define GET_COMPL
-#endif
+       /* Error if filename or host is not known */
+       if (!remote_file || !argv[0])
+               bb_show_usage();
 
-#if ENABLE_FEATURE_TFTP_PUT
-#define PUT "p"
-#define PUT_COMPL ":p"
-#else
-#define PUT
-#define PUT_COMPL
-#endif
+       port = bb_lookup_port(argv[1], "udp", 69);
+       peer_lsa = xhost2sockaddr(argv[0], port);
+
+# if ENABLE_TFTP_DEBUG
+       fprintf(stderr, "using server '%s', remote_file '%s', local_file '%s'\n",
+                       xmalloc_sockaddr2dotted(&peer_lsa->u.sa),
+                       remote_file, local_file);
+# endif
+
+# if ENABLE_FEATURE_TFTP_PROGRESS_BAR
+       G.file = remote_file;
+# endif
+       result = tftp_protocol(
+               NULL /*our_lsa*/, peer_lsa,
+               local_file, remote_file
+               IF_FEATURE_TFTP_BLOCKSIZE(, 1 /* want_transfer_size */)
+               IF_FEATURE_TFTP_BLOCKSIZE(, blksize)
+       );
+       tftp_progress_done();
+
+       if (result != EXIT_SUCCESS && NOT_LONE_DASH(local_file) && CMD_GET(opt)) {
+               unlink(local_file);
+       }
+       return result;
+}
 
-#if defined(CONFIG_FEATURE_TFTP_GET) && defined(CONFIG_FEATURE_TFTP_PUT)
-       opt_complementary = GET_COMPL PUT_COMPL ":?g--p:p--g";
-#elif defined(CONFIG_FEATURE_TFTP_GET) || defined(CONFIG_FEATURE_TFTP_PUT)
-       opt_complementary = GET_COMPL PUT_COMPL;
-#endif
+#endif /* ENABLE_TFTP */
 
-       cmd = getopt32(argc, argv, GET PUT "l:r:" BS, &localfile, &remotefile BS_ARG);
+#if ENABLE_TFTPD
+int tftpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int tftpd_main(int argc UNUSED_PARAM, char **argv)
+{
+       len_and_sockaddr *our_lsa;
+       len_and_sockaddr *peer_lsa;
+       char *mode, *user_opt;
+       char *local_file = local_file;
+       const char *error_msg;
+       int opt, result, opcode;
+       IF_FEATURE_TFTP_BLOCKSIZE(int blksize = TFTP_BLKSIZE_DEFAULT;)
+       IF_FEATURE_TFTP_BLOCKSIZE(int want_transfer_size = 0;)
+
+       INIT_G();
+
+       our_lsa = get_sock_lsa(STDIN_FILENO);
+       if (!our_lsa) {
+               /* This is confusing:
+                *bb_error_msg_and_die("stdin is not a socket");
+                * Better: */
+               bb_show_usage();
+               /* Help text says that tftpd must be used as inetd service,
+                * which is by far the most usual cause of get_sock_lsa
+                * failure */
+       }
+       peer_lsa = xzalloc(LSA_LEN_SIZE + our_lsa->len);
+       peer_lsa->len = our_lsa->len;
+
+       /* Shifting to not collide with TFTP_OPTs */
+       opt = option_mask32 = TFTPD_OPT | (getopt32(argv, "rcu:l", &user_opt) << 8);
+       argv += optind;
+       if (opt & TFTPD_OPT_l) {
+               openlog(applet_name, LOG_PID, LOG_DAEMON);
+               logmode = LOGMODE_SYSLOG;
+       }
+       if (opt & TFTPD_OPT_u) {
+               /* Must be before xchroot */
+               G.pw = xgetpwnam(user_opt);
+       }
+       if (argv[0]) {
+               xchroot(argv[0]);
+       }
 
-       cmd &= (tftp_cmd_get | tftp_cmd_put);
-#if ENABLE_FEATURE_TFTP_GET
-       if (cmd == tftp_cmd_get)
-               flags = O_WRONLY | O_CREAT | O_TRUNC;
-#endif
-#if ENABLE_FEATURE_TFTP_PUT
-       if (cmd == tftp_cmd_put)
-               flags = O_RDONLY;
-#endif
+       result = recv_from_to(STDIN_FILENO,
+                       G.block_buf, sizeof(G.block_buf) + 1,
+                       /* ^^^ sizeof+1 to reliably detect oversized input */
+                       0 /* flags */,
+                       &peer_lsa->u.sa, &our_lsa->u.sa, our_lsa->len);
+
+       error_msg = "malformed packet";
+       opcode = ntohs(*(uint16_t*)G.block_buf);
+       if (result < 4 || result > sizeof(G.block_buf)
+       /*|| G.block_buf[result-1] != '\0' - bug compatibility, see below */
+        || (IF_FEATURE_TFTP_PUT(opcode != TFTP_RRQ) /* not download */
+            IF_GETPUT(&&)
+            IF_FEATURE_TFTP_GET(opcode != TFTP_WRQ) /* not upload */
+           )
+       ) {
+               goto err;
+       }
+       /* Some HP PA-RISC firmware always sends fixed 516-byte requests,
+        * with trailing garbage.
+        * Support that by not requiring NUL to be the last byte (see above).
+        * To make strXYZ() ops safe, force NUL termination:
+        */
+       G.block_buf_tail[0] = '\0';
 
-#if ENABLE_FEATURE_TFTP_BLOCKSIZE
-       if (sblocksize) {
-               blocksize = xatoi_u(sblocksize);
-               if (!tftp_blocksize_check(blocksize, 0)) {
-                       return EXIT_FAILURE;
+       local_file = G.block_buf + 2;
+       if (local_file[0] == '.' || strstr(local_file, "/.")) {
+               error_msg = "dot in file name";
+               goto err;
+       }
+       mode = local_file + strlen(local_file) + 1;
+       /* RFC 1350 says mode string is case independent */
+       if (mode >= G.block_buf + result || strcasecmp(mode, "octet") != 0) {
+               goto err;
+       }
+# if ENABLE_FEATURE_TFTP_BLOCKSIZE
+       {
+               char *res;
+               char *opt_str = mode + sizeof("octet");
+               int opt_len = G.block_buf + result - opt_str;
+               if (opt_len > 0) {
+                       res = tftp_get_option("blksize", opt_str, opt_len);
+                       if (res) {
+                               blksize = tftp_blksize_check(res, 65564);
+                               if (blksize < 0) {
+                                       G_error_pkt_reason = ERR_BAD_OPT;
+                                       /* will just send error pkt */
+                                       goto do_proto;
+                               }
+                       }
+                       if (opcode != TFTP_WRQ /* download? */
+                       /* did client ask us about file size? */
+                        && tftp_get_option("tsize", opt_str, opt_len)
+                       ) {
+                               want_transfer_size = 1;
+                       }
                }
        }
-#endif
-
-       if (localfile == NULL)
-               localfile = remotefile;
-       if (remotefile == NULL)
-               remotefile = localfile;
-       if ((localfile == NULL && remotefile == NULL) || (argv[optind] == NULL))
-               bb_show_usage();
-
-       if (localfile == NULL || LONE_DASH(localfile)) {
-               fd = (cmd == tftp_cmd_get) ? STDOUT_FILENO : STDIN_FILENO;
+# endif
+
+       if (!ENABLE_FEATURE_TFTP_PUT || opcode == TFTP_WRQ) {
+               if (opt & TFTPD_OPT_r) {
+                       /* This would mean "disk full" - not true */
+                       /*G_error_pkt_reason = ERR_WRITE;*/
+                       error_msg = bb_msg_write_error;
+                       goto err;
+               }
+               IF_GETPUT(option_mask32 |= TFTP_OPT_GET;) /* will receive file's data */
        } else {
-               fd = open(localfile, flags, 0644); /* fail below */
+               IF_GETPUT(option_mask32 |= TFTP_OPT_PUT;) /* will send file's data */
        }
-       if (fd < 0) {
-               bb_perror_msg_and_die("local file");
-       }
-
-       host = xgethostbyname(argv[optind]);
-       port = bb_lookup_port(argv[optind + 1], "udp", 69);
 
-#if ENABLE_DEBUG_TFTP
-       fprintf(stderr, "using server \"%s\", remotefile \"%s\", "
-                       "localfile \"%s\".\n",
-                       inet_ntoa(*((struct in_addr *) host->h_addr)),
-                       remotefile, localfile);
-#endif
+       /* NB: if G_error_pkt_str or G_error_pkt_reason is set up,
+        * tftp_protocol() just sends one error pkt and returns */
 
-       result = tftp(cmd, host, remotefile, fd, port, blocksize);
+ do_proto:
+       close(STDIN_FILENO); /* close old, possibly wildcard socket */
+       /* tftp_protocol() will create new one, bound to particular local IP */
+       result = tftp_protocol(
+               our_lsa, peer_lsa,
+               local_file IF_TFTP(, NULL /*remote_file*/)
+               IF_FEATURE_TFTP_BLOCKSIZE(, want_transfer_size)
+               IF_FEATURE_TFTP_BLOCKSIZE(, blksize)
+       );
 
-       if (!(fd == STDOUT_FILENO || fd == STDIN_FILENO)) {
-               if (ENABLE_FEATURE_CLEAN_UP)
-                       close(fd);
-               if (cmd == tftp_cmd_get && result != EXIT_SUCCESS)
-                       unlink(localfile);
-       }
        return result;
+ err:
+       strcpy(G_error_pkt_str, error_msg);
+       goto do_proto;
 }
+
+#endif /* ENABLE_TFTPD */
+
+#endif /* ENABLE_FEATURE_TFTP_GET || ENABLE_FEATURE_TFTP_PUT */