src/tftp.c - master - niceSOFT/inetutils

src/tftp.c
1 394 строки30 KB
Simon Josefsson
maint: Run 'make update-copyright'
20 янв 2026, 11:50
20 янв 2026, 11:501ce61cd
/*
  Copyright (C) 1995-2026 Free Software Foundation, Inc.

  This file is part of GNU Inetutils.

  GNU Inetutils is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or (at
  your option) any later version.

  GNU Inetutils is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see `http://www.gnu.org/licenses/'. */

/*
 * Copyright (c) 1983, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/* Many bug fixes are from Jim Guyton <guyton@rand-unix> */

#include <config.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/file.h>
#include <sys/time.h>
#include <time.h>

#include <netinet/in.h>

#include <arpa/tftp.h>
#include <arpa/inet.h>

#include <errno.h>
#include <error.h>
#include <fcntl.h>
#include <netdb.h>
#include <setjmp.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#ifdef HAVE_LOCALE_H
# include <locale.h>
#endif
#if defined HAVE_IDN2_H && defined HAVE_IDN2
# include <idn2.h>
#elif defined HAVE_IDNA_H
# include <idna.h>
#endif

#include <argp.h>
#include <attribute.h>

#include <libinetutils.h>

#include "xalloc.h"
#include "progname.h"
#include "tftpsubs.h"

/* Some systems define PKTSIZE in <arpa/tftp.h>.  */
#ifndef PKTSIZE
# define PKTSIZE    SEGSIZE+4
#endif

char ackbuf[PKTSIZE];
int timeout;
jmp_buf timeoutbuf;

static void nak (int);
static int makerequest (int, const char *, struct tftphdr *, const char *);
static void printstats (const char *, unsigned long);
static void startclock (void);
static void stopclock (void);
static void timer (int);
static void tpacket (const char *, struct tftphdr *, int);

#define TIMEOUT		5	/* secs between rexmt's */

static int rexmtval = TIMEOUT;
static int maxtimeout = 5 * TIMEOUT;

static struct sockaddr_storage peeraddr;	/* filled in by main */
static socklen_t peerlen;
static int f = -1;		/* the opened socket */
static int port;		/* Port number in host byte order of the server. */
static int trace;
static int verbose;
static int connected;
static int fromatty;

char mode[32];
char line[200];
int margc;

#define TFTP_MAX_ARGS 20

char *margv[TFTP_MAX_ARGS];
char *prompt = "tftp";
jmp_buf toplevel;
void intr (int signo);

void get (int, char **);
void help (int, char **);
void modecmd (int, char **);
void put (int, char **);
void quit (int, char **);
void setascii (int, char **);
void setbinary (int, char **);
void setpeer (int, char **);
void setrexmt (int, char **);
void settimeout (int, char **);
void settrace (int, char **);
void setverbose (int, char **);
void status (int, char **);

static void command (void);

static void getusage (char *);
static void makeargv (void);
static void putusage (char *);
static void settftpmode (char *);
static in_port_t get_port (struct sockaddr_storage *);
static void set_port (struct sockaddr_storage *, in_port_t);

#define HELPINDENT (sizeof("connect"))

struct cmd
{
  char *name;
  char *help;
  void (*handler) (int, char **);
};

char vhelp[] = "toggle verbose mode";
char thelp[] = "toggle packet tracing";
char chelp[] = "connect to remote tftp";
char qhelp[] = "exit tftp";
char hhelp[] = "print help information";
char shelp[] = "send file";
char rhelp[] = "receive file";
char mhelp[] = "set file transfer mode";
char sthelp[] = "show current status";
char xhelp[] = "set per-packet retransmission timeout";
char ihelp[] = "set total retransmission timeout";
char ashelp[] = "set mode to netascii";
char bnhelp[] = "set mode to octet";

struct cmd cmdtab[] = {
  {"connect", chelp, setpeer},
  {"mode", mhelp, modecmd},
  {"put", shelp, put},
  {"get", rhelp, get},
  {"quit", qhelp, quit},
  {"verbose", vhelp, setverbose},
  {"trace", thelp, settrace},
  {"status", sthelp, status},
  {"binary", bnhelp, setbinary},
  {"ascii", ashelp, setascii},
  {"rexmt", xhelp, setrexmt},
  {"timeout", ihelp, settimeout},
  {"?", hhelp, help},
  {NULL, NULL, NULL}
};

struct cmd *getcmd (char *name);
char *tail (char *filename);


const char args_doc[] = "[HOST [PORT]]";
const char doc[] = "Trivial file transfer protocol client";

static struct argp_option argp_options[] = {
  {"verbose", 'v', NULL, 0, "verbose output", 1},
  {NULL, 0, NULL, 0, NULL, 0}
};

char *hostport_argv[3] = { "connect" };

int hostport_argc = 1;

static in_port_t
get_port (struct sockaddr_storage *ss)
{
  switch (ss->ss_family)
    {
    case AF_INET6:
      return ntohs (((struct sockaddr_in6 *) ss)->sin6_port);
      break;
    case AF_INET:
    default:
      return ntohs (((struct sockaddr_in *) ss)->sin_port);
      break;
    }
}

static void
set_port (struct sockaddr_storage *ss, in_port_t port)
{
  switch (ss->ss_family)
    {
    case AF_INET6:
      ((struct sockaddr_in6 *) ss)->sin6_port = htons (port);
      break;
    case AF_INET:
    default:
      ((struct sockaddr_in *) ss)->sin_port = htons (port);
      break;
    }
}

void recvfile (int, char *, char *);
void tftp_sendfile (int, char *, char *);

static error_t
parse_opt (int key, char *arg, struct argp_state *state)
{
  switch (key)
    {
    case 'v':			/* Verbose.  */
      verbose++;
      break;

    case ARGP_KEY_ARG:
      if (state->arg_num >= 2 || hostport_argc >= 3)
	/* Too many arguments. */
	argp_usage (state);
      hostport_argv[hostport_argc++] = arg;
      break;

    default:
      return ARGP_ERR_UNKNOWN;
    }

  return 0;
}

static struct argp argp =
  { argp_options, parse_opt, args_doc, doc, NULL, NULL, NULL };

int
main (int argc, char *argv[])
{
  struct servent *sp;

  set_program_name (argv[0]);
#ifdef HAVE_SETLOCALE
  setlocale (LC_ALL, "");
#endif
  iu_argp_init ("tftp", default_program_authors);
  argp_parse (&argp, argc, argv, 0, NULL, NULL);

  /* Initiate a default port.  */
  sp = getservbyname ("tftp", "udp");
  if (sp == 0)
    port = 69;
  else
    port = ntohs (sp->s_port);

  fromatty = isatty (STDIN_FILENO);

  strcpy (mode, "netascii");
  signal (SIGINT, intr);
  if (hostport_argc > 1)
    {
      if (setjmp (toplevel) != 0)
	exit (EXIT_SUCCESS);
      setpeer (hostport_argc, hostport_argv);
    }
  if (setjmp (toplevel) != 0)
    putchar ('\n');
  command ();
}

char *hostname;

#define RESOLVE_OK            0
#define RESOLVE_FAIL         -1

/* Resolve NAME. Fill in peeraddr, hostname and set connected on success.
   Return value: RESOLVE_OK success
                 RESOLVE_FAIL error
 */
static int
resolve_name (char *name)
{
  int err;
  char *rname;
  struct sockaddr_storage ss;
  struct addrinfo hints, *ai, *aiptr;

#if defined HAVE_IDN || defined HAVE_IDN2
  err = idna_to_ascii_lz (name, &rname, 0);
  if (err)
    {
      fprintf (stderr, "tftp: %s: %s\n", name, idna_strerror (err));
      return RESOLVE_FAIL;
    }
#else /* !HAVE_IDN && !HAVE_IDN2 */
  rname = name;
#endif

  memset (&hints, 0, sizeof (hints));
  hints.ai_family = AF_UNSPEC;
  hints.ai_socktype = SOCK_DGRAM;
  hints.ai_flags = AI_CANONNAME;
#ifdef AI_IDN
  hints.ai_flags |= AI_IDN;
#endif
#ifdef AI_CANONIDN
  hints.ai_flags |= AI_CANONIDN;
#endif

  err = getaddrinfo (rname, "tftp", &hints, &aiptr);
  if (err)
    {
      fprintf (stderr, "tftp: %s: %s\n", rname, gai_strerror (err));
      return RESOLVE_FAIL;
    }

#if defined HAVE_IDN || defined HAVE_IDN2
  free (rname);
#endif

  if (f >= 0)
    {
      close (f);
      f = -1;
    }

  for (ai = aiptr; ai; ai = ai->ai_next)
    {
      f = socket (ai->ai_family, ai->ai_socktype, ai->ai_protocol);
      if (f < 0)
	continue;

      memset (&ss, 0, sizeof (ss));
      ss.ss_family = ai->ai_family;
#if HAVE_STRUCT_SOCKADDR_STORAGE_SS_LEN
      ss.ss_len = ai->ai_addrlen;
#endif
      if (bind (f, (struct sockaddr *) &ss, ai->ai_addrlen))
	{
	  close (f);
	  f = -1;
	  continue;
	}

      /* Successfully resolved hostname. */
      peerlen = ai->ai_addrlen;
      memcpy (&peeraddr, ai->ai_addr, ai->ai_addrlen);
      connected = 1;
      free (hostname);
      if (ai->ai_canonname)
	hostname = xstrdup (ai->ai_canonname);
      else
	hostname = xstrdup ("<dummy>");
      break;
    }

  freeaddrinfo (aiptr);

  if (ai == NULL)
    return RESOLVE_FAIL;
  else
    return RESOLVE_OK;
}

/* Prompt for more arguments from the user with PROMPT, putting the results
   into ARGC & ARGV, with an initial argument of ARG0.  Global variables
   LINE, MARGC, and MARGV are changed.  */
static void
get_args (char *arg0, char *prompt, int *argc, char ***argv)
{
  size_t arg0_len = strlen (arg0);

  strcpy (line, arg0);
  strcat (line, " ");

  printf ("%s", prompt);
  if (fgets (line + arg0_len + 1, sizeof line - arg0_len - 1, stdin))
    {
      makeargv ();
      *argc = margc;
      *argv = margv;
    }
  else
    {
      *argv[0] = arg0;
      *argc = 1;		/* Will produce a usage printout.  */
    }
}

void
setpeer (int argc, char *argv[])
{
  if (argc < 2)
    get_args ("Connect", "(to) ", &argc, &argv);

  if (argc < 2 || argc > 3)
    {
      printf ("usage: %s host-name [port]\n", argv[0]);
      return;
    }

  switch (resolve_name (argv[1]))
    {
    case RESOLVE_OK:
      break;

    case RESOLVE_FAIL:
      return;
    }

  if (argc == 3)
    {
      /* Take a user-specified port number.  */
      port = atoi (argv[2]);
      if (port <= 0)
	{
	  printf ("%s: bad port number\n", argv[2]);
	  connected = 0;
	  return;
	}
    }
  else
    {
      /* Use the standard TFTP port.  */
      struct servent *sp;
      sp = getservbyname ("tftp", "udp");
      if (sp == 0)
	error (EXIT_FAILURE, 0, "udp/tftp: unknown service\n");
      port = ntohs (sp->s_port);
    }
  connected = 1;
}

struct modes
{
  char *m_name;
  char *m_mode;
} modes[] = {
  {"ascii", "netascii"},
  {"netascii", "netascii"},
  {"binary", "octet"},
  {"image", "octet"},
  {"octet", "octet"},
  {0, 0}
};

void
modecmd (int argc, char *argv[])
{
  struct modes *p;
  char *sep;

  if (argc < 2)
    {
      printf ("Using %s mode to transfer files.\n", mode);
      return;
    }
  if (argc == 2)
    {
      for (p = modes; p->m_name; p++)
	if (strcmp (argv[1], p->m_name) == 0)
	  break;
      if (p->m_name)
	{
	  settftpmode (p->m_mode);
	  return;
	}
      printf ("%s: unknown mode\n", argv[1]);
      /* drop through and print usage message */
    }

  printf ("usage: %s [", argv[0]);
  sep = " ";
  for (p = modes; p->m_name; p++)
    {
      printf ("%s%s", sep, p->m_name);
      if (*sep == ' ')
	sep = " | ";
    }
  printf (" ]\n");
  return;
}

void
setbinary (int argc MAYBE_UNUSED, MAYBE_UNUSED char *argv[])
{
  settftpmode ("octet");
}

void
setascii (int argc MAYBE_UNUSED, MAYBE_UNUSED char *argv[])
{
  settftpmode ("netascii");
}

static void
settftpmode (char *newmode)
{
  strcpy (mode, newmode);
  if (verbose)
    printf ("mode set to %s\n", mode);
}

/*
 * Send file(s).
 */
void
put (int argc, char *argv[])
{
  int fd;
  int n;
  char *cp, *targ;

  if (argc < 2)
    get_args ("send", "(file) ", &argc, &argv);

  if (argc < 2)
    {
      putusage (argv[0]);
      return;
    }
  targ = argv[argc - 1];
  if (strchr (argv[argc - 1], ':'))
    {
      char *cp;

      for (n = 1; n < argc - 1; n++)
	if (strchr (argv[n], ':'))
	  {
	    putusage (argv[0]);
	    return;
	  }
      cp = argv[argc - 1];
      /* Is host string escaped using square brackets?  */
      if (cp[0] == '[')
	{			/* Locate far end.  */
	  cp = strchr (cp, ']');
	  if (cp == NULL)
	    return;		/* Unpaired bracket.  Fail!  */

	  /* Erase far end and capture valid host string.  */
	  *cp = 0;
	  targ = cp + 1;	/* Position beyond bracket.  */
	  cp = argv[argc - 1] + 1;
	  /* Verify presence of a colon. Else backup
	   * in order to accept a strange file name.  */
	  if (targ[0] == ':')
	    ++targ;
	  else
	    {
	      targ = argv[argc - 1];
	      cp = NULL;	/* Invalidate host name string.  */
	    }
	}
      else
	{
	  targ = strchr (cp, ':');
	  *targ++ = 0;
	  /* Test whether host string lacks content.
	   * Then the host string will be ignored.  */
	  if (strlen (cp) == 0)
	    cp = NULL;		/* Invalidate host name string.  */
	}
      /* If a remote host was stated, resolve it!  */
      if (cp != NULL && resolve_name (cp) != RESOLVE_OK)
	return;
    }
  if (!connected)
    {
      printf ("No target machine specified.\n");
      return;
    }
  if (argc < 4)
    {
      cp = argc == 2 ? tail (targ) : argv[1];
      fd = open (cp, O_RDONLY);
      if (fd < 0)
	{
	  fprintf (stderr, "tftp: ");
	  perror (cp);
	  return;
	}
      if (verbose)
	printf ("putting %s to %s:%s [%s]\n", cp, hostname, targ, mode);
      set_port (&peeraddr, port);
      tftp_sendfile (fd, targ, mode);
      return;
    }
  /* this assumes the target is a directory */
  /* on a remote unix system.  hmmmm.  */
  cp = strchr (targ, '\0');
  *cp++ = '/';
  for (n = 1; n < argc - 1; n++)
    {
      strcpy (cp, tail (argv[n]));
      fd = open (argv[n], O_RDONLY);
      if (fd < 0)
	{
	  fprintf (stderr, "tftp: ");
	  perror (argv[n]);
	  continue;
	}
      if (verbose)
	printf ("putting %s to %s:%s [%s]\n", argv[n], hostname, targ, mode);
      set_port (&peeraddr, port);
      tftp_sendfile (fd, targ, mode);
    }
}

static void
putusage (char *s)
{
  printf ("usage: %s file ... host:target, or\n", s);
  printf ("       %s file ... target (when already connected)\n", s);
}

/*
 * Receive file(s).
 */
void
get (int argc, char *argv[])
{
  int fd;
  int n;
  char *cp;
  char *src;

  if (argc < 2)
    get_args ("get", "(files) ", &argc, &argv);

  if (argc < 2)
    {
      getusage (argv[0]);
      return;
    }
  if (!connected)
    {
      for (n = 1; n < argc; n++)
	if (strchr (argv[n], ':') == 0)
	  {
	    getusage (argv[0]);
	    return;
	  }
    }
  for (n = 1; n < argc; n++)
    {
      src = strchr (argv[n], ':');
      if (src == NULL)
	src = argv[n];
      else if (src == argv[n])
	{
	  /* Degenerate case: silently drop initial colon.
	   * No usable host name.  */
	  ++src;
	}
      else
	{			/* Parse the host name string; remove square brackets.  */
	  cp = argv[n];

	  if (cp[0] == '[')
	    {
	      cp = strchr (argv[n], ']');
	      if (cp)
		{
		  /* Calculate host string and source file name.  */
		  src = cp + 1;
		  *cp = 0;
		  if (*src == ':')
		    ++src;
		  cp = argv[n] + 1;
		}
	    }
	  else
	    {			/* No escaping; break string at first colon.  */
	      *src++ = 0;
	    }
	  if (cp != NULL && resolve_name (cp) != RESOLVE_OK)
	    continue;
	}

      if (argc < 4)
	{
	  cp = argc == 3 ? argv[2] : tail (src);
	  fd = creat (cp, 0644);
	  if (fd < 0)
	    {
	      fprintf (stderr, "tftp: ");
	      perror (cp);
	      return;
	    }
	  if (verbose)
	    printf ("getting from %s:%s to %s [%s]\n",
		    hostname, src, cp, mode);
	  set_port (&peeraddr, port);
	  recvfile (fd, src, mode);
	  break;
	}
      cp = tail (src);		/* new .. jdg */
      fd = creat (cp, 0644);
      if (fd < 0)
	{
	  fprintf (stderr, "tftp: ");
	  perror (cp);
	  continue;
	}
      if (verbose)
	printf ("getting from %s:%s to %s [%s]\n", hostname, src, cp, mode);
      set_port (&peeraddr, port);
      recvfile (fd, src, mode);
    }
}

static void
getusage (char *s)
{
  printf ("usage: %s host:file host:file ... file, or\n", s);
  printf ("       %s file file ... file if connected\n", s);
}

void
setrexmt (int argc, char *argv[])
{
  int t;

  if (argc < 2)
    get_args ("Rexmt-timeout", "(value) ", &argc, &argv);

  if (argc != 2)
    {
      printf ("usage: %s value\n", argv[0]);
      return;
    }
  t = atoi (argv[1]);
  if (t < 0)
    printf ("%s: bad value\n", argv[1]);
  else
    rexmtval = t;
}

void
settimeout (int argc, char *argv[])
{
  int t;

  if (argc < 2)
    get_args ("Maximum-timeout", "(value) ", &argc, &argv);

  if (argc != 2)
    {
      printf ("usage: %s value\n", argv[0]);
      return;
    }
  t = atoi (argv[1]);
  if (t < 0)
    printf ("%s: bad value\n", argv[1]);
  else
    maxtimeout = t;
}

void
status (int argc MAYBE_UNUSED, MAYBE_UNUSED char *argv[])
{
  if (connected)
    printf ("Connected to %s.\n", hostname);
  else
    printf ("Not connected.\n");
  printf ("Mode: %s Verbose: %s Tracing: %s\n", mode,
	  verbose ? "on" : "off", trace ? "on" : "off");
  printf ("Rexmt-interval: %d seconds, Max-timeout: %d seconds\n",
	  rexmtval, maxtimeout);
}

void
intr (int signo MAYBE_UNUSED)
{
  signal (SIGALRM, SIG_IGN);
  alarm (0);
  longjmp (toplevel, -1);
}

char *
tail (char *filename)
{
  char *s;

  while (*filename)
    {
      s = strrchr (filename, '/');
      if (s == NULL)
	break;
      if (s[1])
	return (s + 1);
      *s = '\0';
    }
  return filename;
}

/*
 * Command parser.
 */
static void
command (void)
{
  struct cmd *c;

  for (;;)
    {
      if (fromatty)
	printf ("%s> ", prompt);
      if (fgets (line, sizeof line, stdin) == 0)
	{
	  if (feof (stdin))
	    exit (EXIT_SUCCESS);
	  else
	    continue;
	}
      if (line[0] == 0)
	continue;
      makeargv ();
      if (margc == 0)
	continue;
      c = getcmd (margv[0]);
      if (c == (struct cmd *) -1)
	{
	  printf ("?Ambiguous command\n");
	  continue;
	}
      if (c == 0)
	{
	  printf ("?Invalid command\n");
	  continue;
	}
      (*c->handler) (margc, margv);
    }
}

struct cmd *
getcmd (char *name)
{
  char *p, *q;
  struct cmd *c, *found;
  int nmatches, longest;

  longest = 0;
  nmatches = 0;
  found = 0;
  for (c = cmdtab; (p = c->name) != NULL; c++)
    {
      for (q = name; *q == *p++; q++)
	if (*q == 0)		/* exact match? */
	  return (c);

      if (!*q)
	{			/* the name was a prefix */
	  if (q - name > longest)
	    {
	      longest = q - name;
	      nmatches = 1;
	      found = c;
	    }
	  else if (q - name == longest)
	    nmatches++;
	}
    }
  if (nmatches > 1)
    return (struct cmd *) -1;
  return found;
}

/*
 * Slice a string up into argc/argv.
 */
static void
makeargv (void)
{
  char *cp;
  char **argp = margv;

  margc = 0;
  for (cp = line; *cp;)
    {
      while (isspace (*cp))
	cp++;
      if (*cp == '\0')
	break;
      if (margc + 1 >= TFTP_MAX_ARGS)
	{
	  fprintf (stderr, "Ignoring excess arguments.\n");
	  break;
	}
      *argp++ = cp;
      margc += 1;
      while (*cp != '\0' && !isspace (*cp))
	cp++;
      if (*cp == '\0')
	break;
      *cp++ = '\0';
    }
  *argp++ = 0;
}

void
quit (int argc MAYBE_UNUSED, MAYBE_UNUSED char *argv[])
{
  exit (EXIT_SUCCESS);
}

/*
 * Help command.
 */
void
help (int argc, char *argv[])
{
  struct cmd *c;

  if (argc == 1)
    {
      printf ("Commands may be abbreviated.  Commands are:\n\n");
      for (c = cmdtab; c->name; c++)
	printf ("%-*s\t%s\n", (int) HELPINDENT, c->name, c->help);
      return;
    }

  while (--argc > 0)
    {
      char *arg;

      arg = *++argv;
      c = getcmd (arg);
      if (c == (struct cmd *) -1)
	printf ("?Ambiguous help command %s\n", arg);
      else if (c == (struct cmd *) 0)
	printf ("?Invalid help command %s\n", arg);
      else
	printf ("%s\n", c->help);
    }
}

void
settrace (int argc MAYBE_UNUSED, MAYBE_UNUSED char *argv[])
{
  trace = !trace;
  printf ("Packet tracing %s.\n", trace ? "on" : "off");
}

void
setverbose (int argc MAYBE_UNUSED, MAYBE_UNUSED char *argv[])
{
  verbose = !verbose;
  printf ("Verbose mode %s.\n", verbose ? "on" : "off");
}

/*
 * Send the requested file.
 */
void
tftp_sendfile (int fd, char *name, char *mode)
{
  struct tftphdr *ap;		/* data and ack packets */
  struct tftphdr *r_init (void), *dp;
  int n;
  volatile int block, size, convert;
  volatile unsigned long amount;
  struct sockaddr_storage from;
  socklen_t fromlen;
  FILE *file;

  startclock ();		/* start stat's clock */
  dp = r_init ();		/* reset fillbuf/read-ahead code */
  ap = (struct tftphdr *) ackbuf;
  file = fdopen (fd, "r");
  convert = !strcmp (mode, "netascii");
  block = 0;
  amount = 0;

  signal (SIGALRM, timer);
  do
    {
      if (block == 0)
	size = makerequest (WRQ, name, dp, mode) - 4;
      else
	{
	  /*      size = read(fd, dp->th_data, SEGSIZE);   */
	  size = readit (file, &dp, convert);
	  if (size < 0)
	    {
	      nak (errno + 100);
	      break;
	    }
	  dp->th_opcode = htons ((unsigned short) DATA);
	  dp->th_block = htons ((unsigned short) block);
	}
      timeout = 0;
      setjmp (timeoutbuf);

    send_data:
      if (trace)
	tpacket ("sent", dp, size + 4);
      n = sendto (f, (const char *) dp, size + 4, 0,
		  (struct sockaddr *) &peeraddr, peerlen);
      if (n != size + 4)
	{
	  perror ("tftp: sendto");
	  goto abort;
	}
      read_ahead (file, convert);

      for (;;)
	{
	  alarm (rexmtval);
	  do
	    {
	      fromlen = sizeof (from);
	      n = recvfrom (f, ackbuf, sizeof (ackbuf), 0,
			    (struct sockaddr *) &from, &fromlen);
	    }
	  while (n <= 0);
	  alarm (0);
	  if (n < 0)
	    {
	      perror ("tftp: recvfrom");
	      goto abort;
	    }
	  set_port (&peeraddr, get_port (&from));
	  if (trace)
	    tpacket ("received", ap, n);
	  /* should verify packet came from server */
	  ap->th_opcode = ntohs (ap->th_opcode);
	  ap->th_block = ntohs (ap->th_block);
	  if (ap->th_opcode == ERROR)
	    {
	      printf ("Error code %d: %s\n", ap->th_code, ap->th_msg);
	      goto abort;
	    }
	  if (ap->th_opcode == ACK)
	    {
	      int j;

	      if (ap->th_block == block)
		break;

	      /* On an error, try to synchronize
	       * both sides.
	       */
	      j = synchnet (f);
	      if (j && trace)
		printf ("discarded %d packets\n", j);

	      if (ap->th_block == (block - 1))
		goto send_data;
	    }
	}
      if (block > 0)
	amount += size;
      block++;
    }
  while (size == SEGSIZE || block == 1);

abort:
  fclose (file);
  stopclock ();
  if (amount > 0)
    printstats ("Sent", amount);
}

/*
 * Receive a file.
 */
void
recvfile (int fd, char *name, char *mode)
{
  struct tftphdr *ap;
  struct tftphdr *dp, *w_init (void);
  int n;
  volatile int block, size, firsttrip;
  volatile unsigned long amount;
  struct sockaddr_storage from;
  socklen_t fromlen;
  FILE *file;
  volatile int convert;		/* true if converting crlf -> lf */

  startclock ();
  dp = w_init ();
  ap = (struct tftphdr *) ackbuf;
  file = fdopen (fd, "w");
  convert = !strcmp (mode, "netascii");
  block = 1;
  firsttrip = 1;
  amount = 0;

  signal (SIGALRM, timer);
  do
    {
      if (firsttrip)
	{
	  size = makerequest (RRQ, name, ap, mode);
	  firsttrip = 0;
	}
      else
	{
	  ap->th_opcode = htons ((unsigned short) ACK);
	  ap->th_block = htons ((unsigned short) (block));
	  size = 4;
	  block++;
	}
      timeout = 0;
      setjmp (timeoutbuf);

    send_ack:
      if (trace)
	tpacket ("sent", ap, size);
      if (sendto (f, ackbuf, size, 0, (struct sockaddr *) &peeraddr,
		  peerlen) != size)
	{
	  alarm (0);
	  perror ("tftp: sendto");
	  goto abort;
	}
      write_behind (file, convert);

      for (;;)
	{
	  alarm (rexmtval);
	  do
	    {
	      fromlen = sizeof (from);
	      n = recvfrom (f, (char *) dp, PKTSIZE, 0,
			    (struct sockaddr *) &from, &fromlen);
	    }
	  while (n <= 0);

	  alarm (0);
	  if (n < 0)
	    {
	      perror ("tftp: recvfrom");
	      goto abort;
	    }
	  set_port (&peeraddr, get_port (&from));
	  if (trace)
	    tpacket ("received", dp, n);
	  /* should verify client address */
	  dp->th_opcode = ntohs (dp->th_opcode);
	  dp->th_block = ntohs (dp->th_block);
	  if (dp->th_opcode == ERROR)
	    {
	      printf ("Error code %d: %s\n", dp->th_code, dp->th_msg);
	      goto abort;
	    }
	  if (dp->th_opcode == DATA)
	    {
	      int j;

	      if (dp->th_block == block)
		break;		/* have next packet */

	      /* On an error, try to synchronize
	       * both sides.
	       */
	      j = synchnet (f);
	      if (j && trace)
		printf ("discarded %d packets\n", j);

	      if (dp->th_block == (block - 1))
		goto send_ack;	/* resend ack */
	    }
	}
      /*      size = write(fd, dp->th_data, n - 4); */
      size = writeit (file, &dp, n - 4, convert);
      if (size < 0)
	{
	  nak (errno + 100);
	  break;
	}
      amount += size;
    }
  while (size == SEGSIZE);

abort:				/* ok to ack, since user */
  ap->th_opcode = htons ((unsigned short) ACK);	/* has seen err msg */
  ap->th_block = htons ((unsigned short) block);
  sendto (f, ackbuf, 4, 0, (struct sockaddr *) &peeraddr, peerlen);
  write_behind (file, convert);	/* flush last buffer */
  fclose (file);
  stopclock ();
  if (amount > 0)
    printstats ("Received", amount);
}

static int
makerequest (int request, const char *name, struct tftphdr *tp,
	     const char *mode)
{
  char *cp;
  size_t arglen, len;

  tp->th_opcode = htons ((unsigned short) request);
#if HAVE_STRUCT_TFTPHDR_TH_U
  /*
   * GNU and BSD essentially, i.e. modulo a macro, define
   * 'tftphdr.th_stuff' as a character array of length
   * naught with GNU, and one with BSD!
   *
   * When compiling with stack protectors, like during
   * hardened builds in Debian, every useful file name
   * will overflow that limit.  However, our code ensures
   * '*tp' to be of length PKTSIZE.  Assigning CP via an
   * offset calculation avoids this issue.
   */
  cp = (char *) tp + (tp->th_stuff - (char *) tp);
#else
  cp = (char *) &(tp->th_stuff);
#endif

  /* Available space for naming the target file.  */
  len = PKTSIZE - sizeof (struct tftphdr) - sizeof ("netascii");
  arglen = strlen (name);

  strncpy (cp, name, len);

  cp += (arglen < len) ? arglen : len;
  *cp++ = '\0';

  /* Mode is either "netascii" or "octet", so is always fits
   * based on our choice of LEN.  */
  strcpy (cp, mode);
  cp += strlen (mode);
  *cp++ = '\0';
  return cp - (char *) tp;
}

struct errmsg
{
  int e_code;
  const char *e_msg;
} errmsgs[] = {
  {EUNDEF, "Undefined error code"},
  {ENOTFOUND, "File not found"},
  {EACCESS, "Access violation"},
  {ENOSPACE, "Disk full or allocation exceeded"},
  {EBADOP, "Illegal TFTP operation"},
  {EBADID, "Unknown transfer ID"},
  {EEXISTS, "File already exists"},
  {ENOUSER, "No such user"},
  {-1, 0}
};

/*
 * Send a nak packet (error message).
 * Error code passed in is one of the
 * standard TFTP codes, or a UNIX errno
 * offset by 100.
 */
static void
nak (int error)
{
  struct errmsg *pe;
  struct tftphdr *tp;
  int length;

  tp = (struct tftphdr *) ackbuf;
  tp->th_opcode = htons ((unsigned short) ERROR);
  tp->th_code = htons ((unsigned short) error);
  for (pe = errmsgs; pe->e_code >= 0; pe++)
    if (pe->e_code == error)
      break;

  if (pe->e_code < 0)
    {
      pe->e_msg = strerror (error - 100);
      tp->th_code = EUNDEF;
    }
  length = strlen (pe->e_msg) + 4;
  memcpy (tp->th_msg, pe->e_msg, length - 3);
  if (trace)
    tpacket ("sent", tp, length);
  if (sendto (f, ackbuf, length, 0, (struct sockaddr *) &peeraddr,
	      peerlen) != length)
    perror ("nak");
}

static void
tpacket (const char *s, struct tftphdr *tp, int n)
{
  static char *opcodes[] = { "#0", "RRQ", "WRQ", "DATA", "ACK", "ERROR" };
  char *cp, *file;
  unsigned short op = ntohs (tp->th_opcode);

  if (op < RRQ || op > ERROR)
    printf ("%s opcode=%x ", s, op);
  else
    printf ("%s %s ", s, opcodes[op]);
  switch (op)
    {
    case RRQ:
    case WRQ:
      n -= 2;
#if HAVE_STRUCT_TFTPHDR_TH_U
      file = cp = tp->th_stuff;
#else
      file = cp = (char *) &(tp->th_stuff);
#endif
      cp = strchr (cp, '\0');
      printf ("<file=%s, mode=%s>\n", file, cp + 1);
      break;

    case DATA:
      printf ("<block=%d, %d bytes>\n", ntohs (tp->th_block), n - 4);
      break;

    case ACK:
      printf ("<block=%d>\n", ntohs (tp->th_block));
      break;

    case ERROR:
      printf ("<code=%d, msg=%s>\n", ntohs (tp->th_code), tp->th_msg);
      break;
    }
}

struct timeval tstart;
struct timeval tstop;

static void
startclock (void)
{
  gettimeofday (&tstart, NULL);
}

static void
stopclock (void)
{
  gettimeofday (&tstop, NULL);
}

static void
printstats (const char *direction, unsigned long amount)
{
  double delta;

  /* compute delta in 1/10's second units */
  delta = ((tstop.tv_sec * 10.) + (tstop.tv_usec / 100000)) -
    ((tstart.tv_sec * 10.) + (tstart.tv_usec / 100000));
  delta = delta / 10.;		/* back to seconds */
  printf ("%s %d bytes in %.1f seconds", direction, (int) amount, delta);
  if (verbose)
    printf (" [%.0f bits/sec]", (amount * 8.) / delta);
  putchar ('\n');
}

static void
timer (int sig MAYBE_UNUSED)
{
  timeout += rexmtval;
  if (timeout >= maxtimeout)
    {
      printf ("Transfer timed out.\n");
      longjmp (toplevel, -1);
    }
  longjmp (timeoutbuf, 1);
}