current/deps/cares/src/ares_search.c
/* 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 "ares_setup.h"
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif
#include "ares.h"
#include "ares_private.h"
struct search_query {
/* Arguments passed to ares_search */
ares_channel channel;
char *name; /* copied into an allocated buffer */
int dnsclass;
int type;
ares_callback callback;
void *arg;
int status_as_is; /* error status from trying as-is */
int next_domain; /* next search domain to try */
int trying_as_is; /* current query is for name as-is */
int timeouts; /* number of timeouts we saw for this request */
int ever_got_nodata; /* did we ever get ARES_ENODATA along the way? */
};
static void search_callback(void *arg, int status, int timeouts,
unsigned char *abuf, int alen);
static void end_squery(struct search_query *squery, int status,
unsigned char *abuf, int alen);
void ares_search(ares_channel channel, const char *name, int dnsclass,
int type, ares_callback callback, void *arg)
{
struct search_query *squery;
char *s;
const char *p;
int status, ndots;
/* Per RFC 7686, reject queries for ".onion" domain names with NXDOMAIN. */
if (ares__is_onion_domain(name))
{
callback(arg, ARES_ENOTFOUND, 0, NULL, 0);
return;
}
/* If name only yields one domain to search, then we don't have
* to keep extra state, so just do an ares_query().
*/
status = ares__single_domain(channel, name, &s);
if (status != ARES_SUCCESS)
{
callback(arg, status, 0, NULL, 0);
return;
}
if (s)
{
ares_query(channel, s, dnsclass, type, callback, arg);
ares_free(s);
return;
}
/* Allocate a search_query structure to hold the state necessary for
* doing multiple lookups.
*/
squery = ares_malloc(sizeof(struct search_query));
if (!squery)
{
callback(arg, ARES_ENOMEM, 0, NULL, 0);
return;
}
squery->channel = channel;
squery->name = ares_strdup(name);
if (!squery->name)
{
ares_free(squery);
callback(arg, ARES_ENOMEM, 0, NULL, 0);
return;
}
squery->dnsclass = dnsclass;
squery->type = type;
squery->status_as_is = -1;
squery->callback = callback;
squery->arg = arg;
squery->timeouts = 0;
squery->ever_got_nodata = 0;
/* Count the number of dots in name. */
ndots = 0;
for (p = name; *p; p++)
{
if (*p == '.')
ndots++;
}
/* If ndots is at least the channel ndots threshold (usually 1),
* then we try the name as-is first. Otherwise, we try the name
* as-is last.
*/
if (ndots >= channel->ndots)
{
/* Try the name as-is first. */
squery->next_domain = 0;
squery->trying_as_is = 1;
ares_query(channel, name, dnsclass, type, search_callback, squery);
}
else
{
/* Try the name as-is last; start with the first search domain. */
squery->next_domain = 1;
squery->trying_as_is = 0;
status = ares__cat_domain(name, channel->domains[0], &s);
if (status == ARES_SUCCESS)
{
ares_query(channel, s, dnsclass, type, search_callback, squery);
ares_free(s);
}
else
{
/* failed, free the malloc()ed memory */
ares_free(squery->name);
ares_free(squery);
callback(arg, status, 0, NULL, 0);
}
}
}
static void search_callback(void *arg, int status, int timeouts,
unsigned char *abuf, int alen)
{
struct search_query *squery = (struct search_query *) arg;
ares_channel channel = squery->channel;
char *s;
squery->timeouts += timeouts;
/* Stop searching unless we got a non-fatal error. */
if (status != ARES_ENODATA && status != ARES_ESERVFAIL
&& status != ARES_ENOTFOUND)
end_squery(squery, status, abuf, alen);
else
{
/* Save the status if we were trying as-is. */
if (squery->trying_as_is)
squery->status_as_is = status;
/*
* If we ever get ARES_ENODATA along the way, record that; if the search
* should run to the very end and we got at least one ARES_ENODATA,
* then callers like ares_gethostbyname() may want to try a T_A search
* even if the last domain we queried for T_AAAA resource records
* returned ARES_ENOTFOUND.
*/
if (status == ARES_ENODATA)
squery->ever_got_nodata = 1;
if (squery->next_domain < channel->ndomains)
{
/* Try the next domain. */
status = ares__cat_domain(squery->name,
channel->domains[squery->next_domain], &s);
if (status != ARES_SUCCESS)
end_squery(squery, status, NULL, 0);
else
{
squery->trying_as_is = 0;
squery->next_domain++;
ares_query(channel, s, squery->dnsclass, squery->type,
search_callback, squery);
ares_free(s);
}
}
else if (squery->status_as_is == -1)
{
/* Try the name as-is at the end. */
squery->trying_as_is = 1;
ares_query(channel, squery->name, squery->dnsclass, squery->type,
search_callback, squery);
}
else {
if (squery->status_as_is == ARES_ENOTFOUND && squery->ever_got_nodata) {
end_squery(squery, ARES_ENODATA, NULL, 0);
}
else
end_squery(squery, squery->status_as_is, NULL, 0);
}
}
}
static void end_squery(struct search_query *squery, int status,
unsigned char *abuf, int alen)
{
squery->callback(squery->arg, status, squery->timeouts, abuf, alen);
ares_free(squery->name);
ares_free(squery);
}
/* Concatenate two domains. */
int ares__cat_domain(const char *name, const char *domain, char **s)
{
size_t nlen = strlen(name);
size_t dlen = strlen(domain);
*s = ares_malloc(nlen + 1 + dlen + 1);
if (!*s)
return ARES_ENOMEM;
memcpy(*s, name, nlen);
(*s)[nlen] = '.';
memcpy(*s + nlen + 1, domain, dlen);
(*s)[nlen + 1 + dlen] = 0;
return ARES_SUCCESS;
}
/* Determine if this name only yields one query. If it does, set *s to
* the string we should query, in an allocated buffer. If not, set *s
* to NULL.
*/
int ares__single_domain(ares_channel channel, const char *name, char **s)
{
size_t len = strlen(name);
const char *hostaliases;
FILE *fp;
char *line = NULL;
int status;
size_t linesize;
const char *p, *q;
int error;
/* If the name contains a trailing dot, then the single query is the name
* sans the trailing dot.
*/
if ((len > 0) && (name[len - 1] == '.'))
{
*s = ares_strdup(name);
return (*s) ? ARES_SUCCESS : ARES_ENOMEM;
}
if (!(channel->flags & ARES_FLAG_NOALIASES) && !strchr(name, '.'))
{
/* The name might be a host alias. */
hostaliases = getenv("HOSTALIASES");
if (hostaliases)
{
fp = fopen(hostaliases, "r");
if (fp)
{
while ((status = ares__read_line(fp, &line, &linesize))
== ARES_SUCCESS)
{
if (strncasecmp(line, name, len) != 0 ||
!ISSPACE(line[len]))
continue;
p = line + len;
while (ISSPACE(*p))
p++;
if (*p)
{
q = p + 1;
while (*q && !ISSPACE(*q))
q++;
*s = ares_malloc(q - p + 1);
if (*s)
{
memcpy(*s, p, q - p);
(*s)[q - p] = 0;
}
ares_free(line);
fclose(fp);
return (*s) ? ARES_SUCCESS : ARES_ENOMEM;
}
}
ares_free(line);
fclose(fp);
if (status != ARES_SUCCESS && status != ARES_EOF)
return status;
}
else
{
error = ERRNO;
switch(error)
{
case ENOENT:
case ESRCH:
break;
default:
DEBUGF(fprintf(stderr, "fopen() failed with error: %d %s\n",
error, strerror(error)));
DEBUGF(fprintf(stderr, "Error opening file: %s\n",
hostaliases));
*s = NULL;
return ARES_EFILE;
}
}
}
}
if (channel->flags & ARES_FLAG_NOSEARCH || channel->ndomains == 0)
{
/* No domain search to do; just try the name as-is. */
*s = ares_strdup(name);
return (*s) ? ARES_SUCCESS : ARES_ENOMEM;
}
*s = NULL;
return ARES_SUCCESS;
}