/****************************************************************************
* libc/netdb/lib_dnscache.c
*
* Copyright (C) 2007, 2009, 2012, 2014-2016 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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 NuttX 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 COPYRIGHT HOLDERS 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
* COPYRIGHT OWNER 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.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/time.h>
#include <string.h>
#include <time.h>
#include <errno.h>
#include <debug.h>
#include "netdb/lib_dns.h"
#if CONFIG_NETDB_DNSCLIENT_ENTRIES > 0
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Use clock monotonic, if possible */
#ifdef CONFIG_CLOCK_MONOTONIC
# define DNS_CLOCK CLOCK_MONOTONIC
#else
# define DNS_CLOCK CLOCK_REALTIME
#endif
/****************************************************************************
* Private Types
****************************************************************************/
/* This described one entry in the cache of resolved hostnames */
struct dns_cache_s
{
#if CONFIG_NETDB_DNSCLIENT_LIFESEC > 0
time_t ctime; /* Creation time */
#endif
char name[CONFIG_NETDB_DNSCLIENT_NAMESIZE];
union dns_server_u addr; /* Resolved address */
};
/****************************************************************************
* Private Data
****************************************************************************/
static uint8_t g_dns_head; /* Head of the circular, DNS resolver cache */
static uint8_t g_dns_tail; /* Tail of the circular, DNS resolver cache */
/* This is the DNS resolver cache */
static struct dns_cache_s g_dns_cache[CONFIG_NETDB_DNSCLIENT_ENTRIES];
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: dns_save_answer
*
* Description:
* Same the last resolved hostname in the DNS cache
*
* Input Parameters:
* hostname - The hostname string to be cached.
* addr - The IP address associated with the hostname
* addrlen - The size of the of the IP address.
*
* Returned Value:
* None
*
****************************************************************************/
void dns_save_answer(FAR const char *hostname,
FAR const struct sockaddr *addr, socklen_t addrlen)
{
FAR struct dns_cache_s *entry;
#if CONFIG_NETDB_DNSCLIENT_LIFESEC > 0
struct timespec now;
#endif
int next;
int ndx;
/* Get exclusive access to the DNS cache */
dns_semtake();
/* Get the index to the new head of the list */
ndx = g_dns_head;
next = ndx + 1;
if (next >= CONFIG_NETDB_DNSCLIENT_ENTRIES)
{
next = 0;
}
/* If the next head pointer would match the tail index, then increment
* the tail index, discarding the oldest mapping in the cache.
*/
if (next == g_dns_tail)
{
int tmp = g_dns_tail + 1;
if (tmp >= CONFIG_NETDB_DNSCLIENT_ENTRIES)
{
tmp = 0;
}
g_dns_tail = tmp;
}
/* Save the answer in the cache */
entry = &g_dns_cache[ndx];
#if CONFIG_NETDB_DNSCLIENT_LIFESEC > 0
/* Get the current time, using CLOCK_MONOTONIC if possible */
(void)clock_gettime(DNS_CLOCK, &now);
entry->ctime = (time_t)now.tv_sec;
#endif
strncpy(entry->name, hostname, CONFIG_NETDB_DNSCLIENT_NAMESIZE);
memcpy(&entry->addr.addr, addr, addrlen);
/* Save the updated head index */
g_dns_head = next;
dns_semgive();
}
/****************************************************************************
* Name: dns_find_answer
*
* Description:
* Check if we already have the resolved hostname address in the cache.
*
* Input Parameters:
* hostname - The hostname string to be resolved.
* addr - The location to return the IP address associated with the
* hostname
* addrlen - On entry, the size of the buffer backing up the 'addr'
* pointer. On return, this location will hold the actual size of
* the returned address.
*
* Returned Value:
* If the host name was successfully found in the DNS name resolution
* cache, zero (OK) will be returned. Otherwise, some negated errno
* value will be returned, typically -ENOENT meaning that the hostname
* was not found in the cache.
*
****************************************************************************/
int dns_find_answer(FAR const char *hostname, FAR struct sockaddr *addr,
FAR socklen_t *addrlen)
{
FAR struct dns_cache_s *entry;
#if CONFIG_NETDB_DNSCLIENT_LIFESEC > 0
struct timespec now;
uint32_t elapsed;
int ret;
#endif
int next;
int ndx;
/* If DNS not initialized, no need to proceed */
if (!dns_initialize())
{
nerr("ERROR: DNS failed to initialize\n");
return -EAGAIN;
}
/* Get exclusive access to the DNS cache */
dns_semtake();
#if CONFIG_NETDB_DNSCLIENT_LIFESEC > 0
/* Get the current time, using CLOCK_MONOTONIC if possible */
ret = clock_gettime(DNS_CLOCK, &now);
#endif
/* REVISIT: This is not thread safe */
for (ndx = g_dns_tail; ndx != g_dns_head; ndx = next)
{
entry = &g_dns_cache[ndx];
/* Advance the index for the next time through the loop, handling
* wrapping to the beginning of the circular buffer.
*/
next = ndx + 1;
if (next >= CONFIG_NETDB_DNSCLIENT_ENTRIES)
{
next = 0;
}
#if CONFIG_NETDB_DNSCLIENT_LIFESEC > 0
/* Check if this entry has expired
* REVISIT: Does not this calculation assume that the sizeof(time_t)
* is equal to the sizeof(uint32_t)?
*/
elapsed = (uint32_t)now.tv_sec - (uint32_t)entry->ctime;
if (ret >= 0 && elapsed > CONFIG_NETDB_DNSCLIENT_LIFESEC)
{
/* This entry has expired. Increment the tail index to exclude
* this entry on future traversals.
*/
g_dns_tail = next;
}
else
#endif
{
/* The entry has not expired, check for a name match. Notice that
* because the names are truncated to CONFIG_NETDB_DNSCLIENT_NAMESIZE,
* this has the possibility of aliasing two names and returning
* the wrong entry from the cache.
*/
if (strncmp(hostname, entry->name, CONFIG_NETDB_DNSCLIENT_NAMESIZE) == 0)
{
socklen_t inlen;
/* We have a match. Return the resolved host address */
#ifdef CONFIG_NET_IPv4
#ifdef CONFIG_NET_IPv6
if (entry->addr.addr.sa_family == AF_INET)
#endif
{
inlen = sizeof(struct sockaddr_in);
}
#endif
#ifdef CONFIG_NET_IPv6
#ifdef CONFIG_NET_IPv4
else
#endif
{
inlen = sizeof(struct sockaddr_in6);
}
#endif
/* Make sure that the address will fit in the caller-provided
* buffer.
*/
if (*addrlen < inlen)
{
ret = -ERANGE;
goto errout_with_sem;
}
/* Return the address information */
memcpy(addr, &entry->addr.addr, inlen);
*addrlen = inlen;
dns_semgive();
return OK;
}
}
}
ret = -ENOENT;
errout_with_sem:
dns_semgive();
return ret;
}
#endif /* CONFIG_NETDB_DNSCLIENT_ENTRIES > 0 */