host.c

很好的命令行下载工具.开发环境为unix/linux

/* Host name resolution and matching.
   Copyright (C) 1995, 1996, 1997, 2000, 2001 Free Software Foundation, Inc.

This file is part of GNU Wget.

GNU Wget 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 2 of the License, or
 (at your option) any later version.

GNU Wget 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 Wget; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

In addition, as a special exception, the Free Software Foundation
gives permission to link the code of its release of Wget with the
OpenSSL project's "OpenSSL" library (or with modified versions of it
that use the same license as the "OpenSSL" library), and distribute
the linked executables.  You must obey the GNU General Public License
in all respects for all of the code used other than "OpenSSL".  If you
modify this file, you may extend this exception to your version of the
file, but you are not obligated to do so.  If you do not wish to do
so, delete this exception statement from your version.  */

#include <config.h>

#include <stdio.h>
#include <stdlib.h>
#ifdef HAVE_STRING_H
# include <string.h>
#else
# include <strings.h>
#endif
#include <assert.h>
#include <sys/types.h>

#ifndef WINDOWS
# include <sys/socket.h>
# include <netinet/in.h>
# ifndef __BEOS__
#  include <arpa/inet.h>
# endif
# include <netdb.h>
# define SET_H_ERRNO(err) ((void)(h_errno = (err)))
#else  /* WINDOWS */
# define SET_H_ERRNO(err) WSASetLastError (err)
#endif /* WINDOWS */

#include <errno.h>

#include "wget.h"
#include "utils.h"
#include "host.h"
#include "url.h"
#include "hash.h"

#ifndef errno
extern int errno;
#endif

#ifndef h_errno
# ifndef __CYGWIN__
extern int h_errno;
# endif
#endif

#ifndef NO_ADDRESS
# define NO_ADDRESS NO_DATA
#endif

/* Lists of IP addresses that result from running DNS queries.  See
   lookup_host for details.  */

struct address_list {
  int count;			/* number of adrresses */
  ip_address *addresses;	/* pointer to the string of addresses */

  int faulty;			/* number of addresses known not to work. */
  int connected;		/* whether we were able to connect to
				   one of the addresses in the list,
				   at least once. */

  int refcount;			/* reference count; when it drops to
				   0, the entry is freed. */
};

/* Get the bounds of the address list.  */

void
address_list_get_bounds (const struct address_list *al, int *start, int *end)
{
  *start = al->faulty;
  *end   = al->count;
}

/* Return a pointer to the address at position POS.  */

const ip_address *
address_list_address_at (const struct address_list *al, int pos)
{
  assert (pos >= al->faulty && pos < al->count);
  return al->addresses + pos;
}

/* Return non-zero if AL contains IP, zero otherwise.  */

int
address_list_contains (const struct address_list *al, const ip_address *ip)
{
  int i;
  switch (ip->type)
    {
    case IPV4_ADDRESS:
      for (i = 0; i < al->count; i++)
	{
	  ip_address *cur = al->addresses + i;
	  if (cur->type == IPV4_ADDRESS
	      && (ADDRESS_IPV4_IN_ADDR (cur).s_addr
		  ==
		  ADDRESS_IPV4_IN_ADDR (ip).s_addr))
	    return 1;
	}
      return 0;
#ifdef ENABLE_IPV6
    case IPV6_ADDRESS:
      for (i = 0; i < al->count; i++)
	{
	  ip_address *cur = al->addresses + i;
	  if (cur->type == IPV6_ADDRESS
#ifdef HAVE_SOCKADDR_IN6_SCOPE_ID
	      && ADDRESS_IPV6_SCOPE (cur) == ADDRESS_IPV6_SCOPE (ip)
#endif
	      && IN6_ARE_ADDR_EQUAL (&ADDRESS_IPV6_IN6_ADDR (cur),
				     &ADDRESS_IPV6_IN6_ADDR (ip)))
	    return 1;
	}
      return 0;
#endif /* ENABLE_IPV6 */
    default:
      abort ();
    }
}

/* Mark the INDEXth element of AL as faulty, so that the next time
   this address list is used, the faulty element will be skipped.  */

void
address_list_set_faulty (struct address_list *al, int index)
{
  /* We assume that the address list is traversed in order, so that a
     "faulty" attempt is always preceded with all-faulty addresses,
     and this is how Wget uses it.  */
  assert (index == al->faulty);

  ++al->faulty;
  if (al->faulty >= al->count)
    /* All addresses have been proven faulty.  Since there's not much
       sense in returning the user an empty address list the next
       time, we'll rather make them all clean, so that they can be
       retried anew.  */
    al->faulty = 0;
}

/* Set the "connected" flag to true.  This flag used by connect.c to
   see if the host perhaps needs to be resolved again.  */

void
address_list_set_connected (struct address_list *al)
{
  al->connected = 1;
}

/* Return the value of the "connected" flag. */

int
address_list_connected_p (const struct address_list *al)
{
  return al->connected;
}

#ifdef ENABLE_IPV6

/* Create an address_list from the addresses in the given struct
   addrinfo.  */

static struct address_list *
address_list_from_addrinfo (const struct addrinfo *ai)
{
  struct address_list *al;
  const struct addrinfo *ptr;
  int cnt;
  ip_address *ip;

  cnt = 0;
  for (ptr = ai; ptr != NULL ; ptr = ptr->ai_next)
    if (ptr->ai_family == AF_INET || ptr->ai_family == AF_INET6)
      ++cnt;
  if (cnt == 0)
    return NULL;

  al = xnew0 (struct address_list);
  al->addresses = xnew_array (ip_address, cnt);
  al->count     = cnt;
  al->refcount  = 1;

  ip = al->addresses;
  for (ptr = ai; ptr != NULL; ptr = ptr->ai_next)
    if (ptr->ai_family == AF_INET6) 
      {
	const struct sockaddr_in6 *sin6 =
	  (const struct sockaddr_in6 *)ptr->ai_addr;
	ip->type = IPV6_ADDRESS;
	ADDRESS_IPV6_IN6_ADDR (ip) = sin6->sin6_addr;
#ifdef HAVE_SOCKADDR_IN6_SCOPE_ID
	ADDRESS_IPV6_SCOPE (ip) = sin6->sin6_scope_id;
#endif
	++ip;
      } 
    else if (ptr->ai_family == AF_INET)
      {
	const struct sockaddr_in *sin =
	  (const struct sockaddr_in *)ptr->ai_addr;
	ip->type = IPV4_ADDRESS;
	ADDRESS_IPV4_IN_ADDR (ip) = sin->sin_addr;
	++ip;
      }
  assert (ip - al->addresses == cnt);
  return al;
}

#define IS_IPV4(addr) (((const ip_address *) addr)->type == IPV4_ADDRESS)

/* Compare two IP addresses by type, giving preference to the IPv4
   address (sorting it first).  In other words, return -1 if ADDR1 is
   IPv4 and ADDR2 is IPv6, +1 if ADDR1 is IPv6 and ADDR2 is IPv4, and
   0 otherwise.

   This is intended to be used as the comparator arg to a qsort-like
   sorting function, which is why it accepts generic pointers.  */

static int
cmp_prefer_ipv4 (const void *addr1, const void *addr2)
{
  return !IS_IPV4 (addr1) - !IS_IPV4 (addr2);
}

#define IS_IPV6(addr) (((const ip_address *) addr)->type == IPV6_ADDRESS)

/* Like the above, but give preference to the IPv6 address.  */

static int
cmp_prefer_ipv6 (const void *addr1, const void *addr2)
{
  return !IS_IPV6 (addr1) - !IS_IPV6 (addr2);
}

#else  /* not ENABLE_IPV6 */

/* Create an address_list from a NULL-terminated vector of IPv4
   addresses.  This kind of vector is returned by gethostbyname.  */

static struct address_list *
address_list_from_ipv4_addresses (char **vec)
{
  int count, i;
  struct address_list *al = xnew0 (struct address_list);

  count = 0;
  while (vec[count])
    ++count;
  assert (count > 0);

  al->addresses = xnew_array (ip_address, count);
  al->count     = count;
  al->refcount  = 1;

  for (i = 0; i < count; i++)
    {
      ip_address *ip = &al->addresses[i];
      ip->type = IPV4_ADDRESS;
      memcpy (ADDRESS_IPV4_DATA (ip), vec[i], 4);
    }

  return al;
}

#endif /* not ENABLE_IPV6 */

static void
address_list_delete (struct address_list *al)
{
  xfree (al->addresses);
  xfree (al);
}

/* Mark the address list as being no longer in use.  This will reduce
   its reference count which will cause the list to be freed when the
   count reaches 0.  */

void
address_list_release (struct address_list *al)
{
  --al->refcount;
  DEBUGP (("Releasing 0x%0*lx (new refcount %d).\n", PTR_FORMAT (al),
	   al->refcount));
  if (al->refcount <= 0)
    {
      DEBUGP (("Deleting unused 0x%0*lx.\n", PTR_FORMAT (al)));
      address_list_delete (al);
    }
}

/* Versions of gethostbyname and getaddrinfo that support timeout. */

#ifndef ENABLE_IPV6

struct ghbnwt_context {
  const char *host_name;
  struct hostent *hptr;
};

static void
gethostbyname_with_timeout_callback (void *arg)
{
  struct ghbnwt_context *ctx = (struct ghbnwt_context *)arg;
  ctx->hptr = gethostbyname (ctx->host_name);
}

/* Just like gethostbyname, except it times out after TIMEOUT seconds.
   In case of timeout, NULL is returned and errno is set to ETIMEDOUT.
   The function makes sure that when NULL is returned for reasons
   other than timeout, errno is reset.  */

static struct hostent *
gethostbyname_with_timeout (const char *host_name, double timeout)
{
  struct ghbnwt_context ctx;
  ctx.host_name = host_name;
  if (run_with_timeout (timeout, gethostbyname_with_timeout_callback, &ctx))
    {
      SET_H_ERRNO (HOST_NOT_FOUND);
      errno = ETIMEDOUT;
      return NULL;
    }
  if (!ctx.hptr)
    errno = 0;
  return ctx.hptr;
}

/* Print error messages for host errors.  */
static char *
host_errstr (int error)
{
  /* Can't use switch since some of these constants can be equal,
     which makes the compiler complain about duplicate case
     values.  */
  if (error == HOST_NOT_FOUND
      || error == NO_RECOVERY
      || error == NO_DATA
      || error == NO_ADDRESS)
    return _("Unknown host");
  else if (error == TRY_AGAIN)
    /* Message modeled after what gai_strerror returns in similar
       circumstances.  */
    return _("Temporary failure in name resolution");
  else
    return _("Unknown error");
}

#else  /* ENABLE_IPV6 */

struct gaiwt_context {
  const char *node;
  const char *service;
  const struct addrinfo *hints;
  struct addrinfo **res;
  int exit_code;
};

static void
getaddrinfo_with_timeout_callback (void *arg)
{
  struct gaiwt_context *ctx = (struct gaiwt_context *)arg;
  ctx->exit_code = getaddrinfo (ctx->node, ctx->service, ctx->hints, ctx->res);
}

/* Just like getaddrinfo, except it times out after TIMEOUT seconds.
   In case of timeout, the EAI_SYSTEM error code is returned and errno
   is set to ETIMEDOUT.  */

static int
getaddrinfo_with_timeout (const char *node, const char *service,
			  const struct addrinfo *hints, struct addrinfo **res,
			  double timeout)
{
  struct gaiwt_context ctx;
  ctx.node = node;
  ctx.service = service;
  ctx.hints = hints;
  ctx.res = res;

  if (run_with_timeout (timeout, getaddrinfo_with_timeout_callback, &ctx))
    {
      errno = ETIMEDOUT;
      return EAI_SYSTEM;
    }
  return ctx.exit_code;
}

#endif /* ENABLE_IPV6 */

/* Pretty-print ADDR.  When compiled without IPv6, this is the same as
   inet_ntoa.  With IPv6, it either prints an IPv6 address or an IPv4
   address.  */

const char *
pretty_print_address (const ip_address *addr)
{
  switch (addr->type) 
    {
    case IPV4_ADDRESS:
      return inet_ntoa (ADDRESS_IPV4_IN_ADDR (addr));
#ifdef ENABLE_IPV6
    case IPV6_ADDRESS:
      {
        static char buf[128];
	inet_ntop (AF_INET6, &ADDRESS_IPV6_IN6_ADDR (addr), buf, sizeof (buf));
#if 0
#ifdef HAVE_SOCKADDR_IN6_SCOPE_ID
	{
	  /* append "%SCOPE_ID" for all ?non-global? addresses */
	  char *p = buf + strlen (buf);
	  *p++ = '%';
	  number_to_string (p, ADDRESS_IPV6_SCOPE (addr));
	}
#endif
#endif
        buf[sizeof (buf) - 1] = '\0';
        return buf;
      }
#endif
    }
  abort ();
}

/* The following two functions were adapted from glibc. */

static int
is_valid_ipv4_address (const char *str, const char *end)
{
  int saw_digit = 0;
  int octets = 0;
  int val = 0;

  while (str < end)
    {