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curl/ares/ares_gethostbyname.c
Daniel Stenberg e3b5673e98 - Phil Blundell: If you ask ares_gethostbyname() to do an AF_INET6 lookup and 
the target host has only A records, it automatically falls back to an
  AF_INET lookup and gives you the A results.  However, if the target host has
  a CNAME record, this behaviour is defeated since the original query does
  return some data even though ares_parse_aaa_reply() doesn't consider it
  relevant. Here's a small patch to make it behave the same with and without
  the CNAME.
2008-07-03 11:32:35 +00:00

460 lines
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C
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/* $Id$ */
/* Copyright 1998 by the Massachusetts Institute of Technology.
*
* Permission to use, copy, modify, and distribute this
* software and its documentation for any purpose and without
* fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright
* notice and this permission notice appear in supporting
* documentation, and that the name of M.I.T. not be used in
* advertising or publicity pertaining to distribution of the
* software without specific, written prior permission.
* M.I.T. makes no representations about the suitability of
* this software for any purpose. It is provided "as is"
* without express or implied warranty.
*/
#include "setup.h"
#if defined(WIN32) && !defined(WATT32)
#include "nameser.h"
#else
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#ifdef HAVE_ARPA_NAMESER_H
#include <arpa/nameser.h>
#endif
#ifdef HAVE_ARPA_NAMESER_COMPAT_H
#include <arpa/nameser_compat.h>
#endif
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif
#include "ares.h"
#include "ares_private.h"
#include "inet_net_pton.h"
#include "bitncmp.h"
#ifdef WATT32
#undef WIN32
#endif
struct host_query {
/* Arguments passed to ares_gethostbyname() */
ares_channel channel;
char *name;
ares_host_callback callback;
void *arg;
int family;
const char *remaining_lookups;
int timeouts;
};
static void next_lookup(struct host_query *hquery, int status_code);
static void host_callback(void *arg, int status, int timeouts,
unsigned char *abuf, int alen);
static void end_hquery(struct host_query *hquery, int status,
struct hostent *host);
static int fake_hostent(const char *name, int family, ares_host_callback callback,
void *arg);
static int file_lookup(const char *name, int family, struct hostent **host);
static void sort_addresses(struct hostent *host, struct apattern *sortlist,
int nsort);
static void sort6_addresses(struct hostent *host, struct apattern *sortlist,
int nsort);
static int get_address_index(struct in_addr *addr, struct apattern *sortlist,
int nsort);
static int get6_address_index(struct in6_addr *addr, struct apattern *sortlist,
int nsort);
void ares_gethostbyname(ares_channel channel, const char *name, int family,
ares_host_callback callback, void *arg)
{
struct host_query *hquery;
/* Right now we only know how to look up Internet addresses. */
if (family != AF_INET && family != AF_INET6)
{
callback(arg, ARES_ENOTIMP, 0, NULL);
return;
}
if (fake_hostent(name, family, callback, arg))
return;
/* Allocate and fill in the host query structure. */
hquery = malloc(sizeof(struct host_query));
if (!hquery)
{
callback(arg, ARES_ENOMEM, 0, NULL);
return;
}
hquery->channel = channel;
hquery->name = strdup(name);
hquery->family = family;
if (!hquery->name)
{
free(hquery);
callback(arg, ARES_ENOMEM, 0, NULL);
return;
}
hquery->callback = callback;
hquery->arg = arg;
hquery->remaining_lookups = channel->lookups;
hquery->timeouts = 0;
/* Start performing lookups according to channel->lookups. */
next_lookup(hquery, ARES_ECONNREFUSED /* initial error code */);
}
static void next_lookup(struct host_query *hquery, int status_code)
{
const char *p;
struct hostent *host;
int status = status_code;
for (p = hquery->remaining_lookups; *p; p++)
{
switch (*p)
{
case 'b':
/* DNS lookup */
hquery->remaining_lookups = p + 1;
if (hquery->family == AF_INET6)
ares_search(hquery->channel, hquery->name, C_IN, T_AAAA,
host_callback, hquery);
else
ares_search(hquery->channel, hquery->name, C_IN, T_A, host_callback,
hquery);
return;
case 'f':
/* Host file lookup */
status = file_lookup(hquery->name, hquery->family, &host);
/* this status check below previously checked for !ARES_ENOTFOUND,
but we should not assume that this single error code is the one
that can occur, as that is in fact no longer the case */
if (status == ARES_SUCCESS)
{
end_hquery(hquery, status, host);
return;
}
status = status_code; /* Use original status code */
break;
}
}
end_hquery(hquery, status, NULL);
}
static void host_callback(void *arg, int status, int timeouts,
unsigned char *abuf, int alen)
{
struct host_query *hquery = (struct host_query *) arg;
ares_channel channel = hquery->channel;
struct hostent *host = NULL;
hquery->timeouts += timeouts;
if (status == ARES_SUCCESS)
{
if (hquery->family == AF_INET)
{
status = ares_parse_a_reply(abuf, alen, &host, NULL, NULL);
if (host && channel->nsort)
sort_addresses(host, channel->sortlist, channel->nsort);
}
else if (hquery->family == AF_INET6)
{
status = ares_parse_aaaa_reply(abuf, alen, &host, NULL, NULL);
if (status == ARES_ENODATA)
{
/* The query returned something (e.g. CNAME) but there were no
AAAA records. Try looking up A instead. */
hquery->family = AF_INET;
ares_search(hquery->channel, hquery->name, C_IN, T_A, host_callback,
hquery);
return;
}
if (host && channel->nsort)
sort6_addresses(host, channel->sortlist, channel->nsort);
}
end_hquery(hquery, status, host);
}
else if (status == ARES_ENODATA && hquery->family == AF_INET6)
{
/* There was no AAAA. Now lookup an A */
hquery->family = AF_INET;
ares_search(hquery->channel, hquery->name, C_IN, T_A, host_callback,
hquery);
}
else if (status == ARES_EDESTRUCTION)
end_hquery(hquery, status, NULL);
else
next_lookup(hquery, status);
}
static void end_hquery(struct host_query *hquery, int status,
struct hostent *host)
{
hquery->callback(hquery->arg, status, hquery->timeouts, host);
if (host)
ares_free_hostent(host);
free(hquery->name);
free(hquery);
}
/* If the name looks like an IP address, fake up a host entry, end the
* query immediately, and return true. Otherwise return false.
*/
static int fake_hostent(const char *name, int family, ares_host_callback callback,
void *arg)
{
struct hostent hostent;
char *aliases[1] = { NULL };
char *addrs[2];
int result = 0;
struct in_addr in;
struct in6_addr in6;
if (family == AF_INET)
{
/* It only looks like an IP address if it's all numbers and dots. */
int numdots = 0;
const char *p;
for (p = name; *p; p++)
{
if (!ISDIGIT(*p) && *p != '.') {
return 0;
} else if (*p == '.') {
numdots++;
}
}
/* if we don't have 3 dots, it is illegal
* (although inet_addr doesn't think so).
*/
if (numdots != 3)
result = 0;
else
result = ((in.s_addr = inet_addr(name)) == INADDR_NONE ? 0 : 1);
}
else if (family == AF_INET6)
result = (ares_inet_pton(AF_INET6, name, &in6) < 1 ? 0 : 1);
if (!result)
return 0;
if (family == AF_INET)
{
hostent.h_length = sizeof(struct in_addr);
addrs[0] = (char *)&in;
}
else if (family == AF_INET6)
{
hostent.h_length = sizeof(struct in6_addr);
addrs[0] = (char *)&in6;
}
/* Duplicate the name, to avoid a constness violation. */
hostent.h_name = strdup(name);
if (!hostent.h_name)
{
callback(arg, ARES_ENOMEM, 0, NULL);
return 1;
}
/* Fill in the rest of the host structure and terminate the query. */
addrs[1] = NULL;
hostent.h_aliases = aliases;
hostent.h_addrtype = family;
hostent.h_addr_list = addrs;
callback(arg, ARES_SUCCESS, 0, &hostent);
free((char *)(hostent.h_name));
return 1;
}
static int file_lookup(const char *name, int family, struct hostent **host)
{
FILE *fp;
char **alias;
int status;
int error;
#ifdef WIN32
char PATH_HOSTS[MAX_PATH];
if (IS_NT()) {
char tmp[MAX_PATH];
HKEY hkeyHosts;
if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, KEY_READ, &hkeyHosts)
== ERROR_SUCCESS)
{
DWORD dwLength = MAX_PATH;
RegQueryValueEx(hkeyHosts, DATABASEPATH, NULL, NULL, (LPBYTE)tmp,
&dwLength);
ExpandEnvironmentStrings(tmp, PATH_HOSTS, MAX_PATH);
RegCloseKey(hkeyHosts);
}
}
else
GetWindowsDirectory(PATH_HOSTS, MAX_PATH);
strcat(PATH_HOSTS, WIN_PATH_HOSTS);
#elif defined(WATT32)
extern const char *_w32_GetHostsFile (void);
const char *PATH_HOSTS = _w32_GetHostsFile();
if (!PATH_HOSTS)
return ARES_ENOTFOUND;
#endif
fp = fopen(PATH_HOSTS, "r");
if (!fp)
{
error = ERRNO;
switch(error)
{
case ENOENT:
case ESRCH:
return ARES_ENOTFOUND;
default:
DEBUGF(fprintf(stderr, "fopen() failed with error: %d %s\n",
error, strerror(error)));
DEBUGF(fprintf(stderr, "Error opening file: %s\n",
PATH_HOSTS));
*host = NULL;
return ARES_EFILE;
}
}
while ((status = ares__get_hostent(fp, family, host)) == ARES_SUCCESS)
{
if (strcasecmp((*host)->h_name, name) == 0)
break;
for (alias = (*host)->h_aliases; *alias; alias++)
{
if (strcasecmp(*alias, name) == 0)
break;
}
if (*alias)
break;
ares_free_hostent(*host);
}
fclose(fp);
if (status == ARES_EOF)
status = ARES_ENOTFOUND;
if (status != ARES_SUCCESS)
*host = NULL;
return status;
}
static void sort_addresses(struct hostent *host, struct apattern *sortlist,
int nsort)
{
struct in_addr a1, a2;
int i1, i2, ind1, ind2;
/* This is a simple insertion sort, not optimized at all. i1 walks
* through the address list, with the loop invariant that everything
* to the left of i1 is sorted. In the loop body, the value at i1 is moved
* back through the list (via i2) until it is in sorted order.
*/
for (i1 = 0; host->h_addr_list[i1]; i1++)
{
memcpy(&a1, host->h_addr_list[i1], sizeof(struct in_addr));
ind1 = get_address_index(&a1, sortlist, nsort);
for (i2 = i1 - 1; i2 >= 0; i2--)
{
memcpy(&a2, host->h_addr_list[i2], sizeof(struct in_addr));
ind2 = get_address_index(&a2, sortlist, nsort);
if (ind2 <= ind1)
break;
memcpy(host->h_addr_list[i2 + 1], &a2, sizeof(struct in_addr));
}
memcpy(host->h_addr_list[i2 + 1], &a1, sizeof(struct in_addr));
}
}
/* Find the first entry in sortlist which matches addr. Return nsort
* if none of them match.
*/
static int get_address_index(struct in_addr *addr, struct apattern *sortlist,
int nsort)
{
int i;
for (i = 0; i < nsort; i++)
{
if (sortlist[i].family != AF_INET)
continue;
if (sortlist[i].type == PATTERN_MASK)
{
if ((addr->s_addr & sortlist[i].mask.addr.addr4.s_addr)
== sortlist[i].addr.addr4.s_addr)
break;
}
else
{
if (!ares_bitncmp(&addr->s_addr, &sortlist[i].addr.addr4.s_addr,
sortlist[i].mask.bits))
break;
}
}
return i;
}
static void sort6_addresses(struct hostent *host, struct apattern *sortlist,
int nsort)
{
struct in6_addr a1, a2;
int i1, i2, ind1, ind2;
/* This is a simple insertion sort, not optimized at all. i1 walks
* through the address list, with the loop invariant that everything
* to the left of i1 is sorted. In the loop body, the value at i1 is moved
* back through the list (via i2) until it is in sorted order.
*/
for (i1 = 0; host->h_addr_list[i1]; i1++)
{
memcpy(&a1, host->h_addr_list[i1], sizeof(struct in6_addr));
ind1 = get6_address_index(&a1, sortlist, nsort);
for (i2 = i1 - 1; i2 >= 0; i2--)
{
memcpy(&a2, host->h_addr_list[i2], sizeof(struct in6_addr));
ind2 = get6_address_index(&a2, sortlist, nsort);
if (ind2 <= ind1)
break;
memcpy(host->h_addr_list[i2 + 1], &a2, sizeof(struct in6_addr));
}
memcpy(host->h_addr_list[i2 + 1], &a1, sizeof(struct in6_addr));
}
}
/* Find the first entry in sortlist which matches addr. Return nsort
* if none of them match.
*/
static int get6_address_index(struct in6_addr *addr, struct apattern *sortlist,
int nsort)
{
int i;
for (i = 0; i < nsort; i++)
{
if (sortlist[i].family != AF_INET6)
continue;
if (!ares_bitncmp(&addr->s6_addr, &sortlist[i].addr.addr6.s6_addr, sortlist[i].mask.bits))
break;
}
return i;
}
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