298 строки
7.5 KiB
C
298 строки
7.5 KiB
C
/* Copyright 1998 by the Massachusetts Institute of Technology.
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*
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* Permission to use, copy, modify, and distribute this
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* software and its documentation for any purpose and without
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* fee is hereby granted, provided that the above copyright
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* notice appear in all copies and that both that copyright
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* notice and this permission notice appear in supporting
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* documentation, and that the name of M.I.T. not be used in
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* advertising or publicity pertaining to distribution of the
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* software without specific, written prior permission.
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* M.I.T. makes no representations about the suitability of
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* this software for any purpose. It is provided "as is"
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* without express or implied warranty.
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*/
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static const char rcsid[] = "$Id$";
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#include <sys/types.h>
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#ifdef WIN32
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#include "nameser.h"
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#else
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <arpa/inet.h>
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#include <netdb.h>
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#include <arpa/nameser.h>
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#endif
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <ctype.h>
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#include "ares.h"
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#include "ares_private.h"
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struct host_query {
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/* Arguments passed to ares_gethostbyname() */
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ares_channel channel;
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char *name;
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ares_host_callback callback;
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void *arg;
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const char *remaining_lookups;
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};
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static void next_lookup(struct host_query *hquery);
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static void host_callback(void *arg, int status, unsigned char *abuf,
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int alen);
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static void end_hquery(struct host_query *hquery, int status,
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struct hostent *host);
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static int fake_hostent(const char *name, ares_host_callback callback,
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void *arg);
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static int file_lookup(const char *name, struct hostent **host);
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static void sort_addresses(struct hostent *host, struct apattern *sortlist,
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int nsort);
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static int get_address_index(struct in_addr *addr, struct apattern *sortlist,
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int nsort);
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void ares_gethostbyname(ares_channel channel, const char *name, int family,
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ares_host_callback callback, void *arg)
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{
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struct host_query *hquery;
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/* Right now we only know how to look up Internet addresses. */
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if (family != AF_INET)
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{
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callback(arg, ARES_ENOTIMP, NULL);
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return;
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}
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if (fake_hostent(name, callback, arg))
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return;
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/* Allocate and fill in the host query structure. */
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hquery = malloc(sizeof(struct host_query));
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if (!hquery)
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{
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callback(arg, ARES_ENOMEM, NULL);
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return;
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}
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hquery->channel = channel;
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hquery->name = strdup(name);
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if (!hquery->name)
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{
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free(hquery);
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callback(arg, ARES_ENOMEM, NULL);
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return;
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}
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hquery->callback = callback;
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hquery->arg = arg;
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hquery->remaining_lookups = channel->lookups;
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/* Start performing lookups according to channel->lookups. */
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next_lookup(hquery);
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}
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static void next_lookup(struct host_query *hquery)
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{
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int status;
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const char *p;
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struct hostent *host;
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for (p = hquery->remaining_lookups; *p; p++)
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{
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switch (*p)
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{
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case 'b':
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/* DNS lookup */
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hquery->remaining_lookups = p + 1;
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ares_search(hquery->channel, hquery->name, C_IN, T_A, host_callback,
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hquery);
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return;
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case 'f':
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/* Host file lookup */
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status = file_lookup(hquery->name, &host);
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if (status != ARES_ENOTFOUND)
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{
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end_hquery(hquery, status, host);
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return;
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}
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break;
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}
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}
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end_hquery(hquery, ARES_ENOTFOUND, NULL);
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}
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static void host_callback(void *arg, int status, unsigned char *abuf, int alen)
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{
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struct host_query *hquery = (struct host_query *) arg;
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ares_channel channel = hquery->channel;
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struct hostent *host;
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if (status == ARES_SUCCESS)
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{
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status = ares_parse_a_reply(abuf, alen, &host);
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if (host && channel->nsort)
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sort_addresses(host, channel->sortlist, channel->nsort);
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end_hquery(hquery, status, host);
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}
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else if (status == ARES_EDESTRUCTION)
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end_hquery(hquery, status, NULL);
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else
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next_lookup(hquery);
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}
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static void end_hquery(struct host_query *hquery, int status,
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struct hostent *host)
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{
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hquery->callback(hquery->arg, status, host);
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if (host)
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ares_free_hostent(host);
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free(hquery->name);
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free(hquery);
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}
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/* If the name looks like an IP address, fake up a host entry, end the
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* query immediately, and return true. Otherwise return false.
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*/
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static int fake_hostent(const char *name, ares_host_callback callback,
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void *arg)
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{
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struct in_addr addr;
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struct hostent hostent;
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const char *p;
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char *aliases[1] = { NULL };
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char *addrs[2];
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/* It only looks like an IP address if it's all numbers and dots. */
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for (p = name; *p; p++)
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{
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if (!isdigit((unsigned char)*p) && *p != '.')
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return 0;
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}
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/* It also only looks like an IP address if it's non-zero-length and
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* doesn't end with a dot.
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*/
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if (p == name || *(p - 1) == '.')
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return 0;
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/* It looks like an IP address. Figure out what IP address it is. */
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addr.s_addr = inet_addr(name);
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if (addr.s_addr == INADDR_NONE)
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{
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callback(arg, ARES_EBADNAME, NULL);
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return 1;
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}
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/* Duplicate the name, to avoid a constness violation. */
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hostent.h_name = strdup(name);
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if (!hostent.h_name)
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{
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callback(arg, ARES_ENOMEM, NULL);
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return 1;
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}
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/* Fill in the rest of the host structure and terminate the query. */
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addrs[0] = (char *) &addr;
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addrs[1] = NULL;
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hostent.h_aliases = aliases;
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hostent.h_addrtype = AF_INET;
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hostent.h_length = sizeof(struct in_addr);
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hostent.h_addr_list = addrs;
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callback(arg, ARES_SUCCESS, &hostent);
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free(hostent.h_name);
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return 1;
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}
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static int file_lookup(const char *name, struct hostent **host)
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{
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FILE *fp;
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char **alias;
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int status;
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#ifdef WIN32
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char PATH_HOSTS[MAX_PATH];
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if (IsNT) {
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GetSystemDirectory(PATH_HOSTS, MAX_PATH);
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strcat(PATH_HOSTS, PATH_HOSTS_NT);
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} else {
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GetWindowsDirectory(PATH_HOSTS, MAX_PATH);
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strcat(PATH_HOSTS, PATH_HOSTS_9X);
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}
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#endif
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fp = fopen(PATH_HOSTS, "r");
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if (!fp)
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return ARES_ENOTFOUND;
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while ((status = ares__get_hostent(fp, host)) == ARES_SUCCESS)
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{
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if (strcasecmp((*host)->h_name, name) == 0)
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break;
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for (alias = (*host)->h_aliases; *alias; alias++)
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{
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if (strcasecmp(*alias, name) == 0)
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break;
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}
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if (*alias)
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break;
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ares_free_hostent(*host);
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}
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fclose(fp);
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if (status == ARES_EOF)
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status = ARES_ENOTFOUND;
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if (status != ARES_SUCCESS)
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*host = NULL;
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return status;
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}
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static void sort_addresses(struct hostent *host, struct apattern *sortlist,
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int nsort)
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{
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struct in_addr a1, a2;
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int i1, i2, ind1, ind2;
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/* This is a simple insertion sort, not optimized at all. i1 walks
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* through the address list, with the loop invariant that everything
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* to the left of i1 is sorted. In the loop body, the value at i1 is moved
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* back through the list (via i2) until it is in sorted order.
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*/
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for (i1 = 0; host->h_addr_list[i1]; i1++)
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{
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memcpy(&a1, host->h_addr_list[i1], sizeof(struct in_addr));
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ind1 = get_address_index(&a1, sortlist, nsort);
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for (i2 = i1 - 1; i2 >= 0; i2--)
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{
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memcpy(&a2, host->h_addr_list[i2], sizeof(struct in_addr));
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ind2 = get_address_index(&a2, sortlist, nsort);
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if (ind2 <= ind1)
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break;
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memcpy(host->h_addr_list[i2 + 1], &a2, sizeof(struct in_addr));
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}
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memcpy(host->h_addr_list[i2 + 1], &a1, sizeof(struct in_addr));
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}
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}
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/* Find the first entry in sortlist which matches addr. Return nsort
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* if none of them match.
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*/
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static int get_address_index(struct in_addr *addr, struct apattern *sortlist,
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int nsort)
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{
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int i;
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for (i = 0; i < nsort; i++)
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{
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if ((addr->s_addr & sortlist[i].mask.s_addr) == sortlist[i].addr.s_addr)
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break;
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}
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return i;
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}
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