/****************************************************************************
* libc/netdb/lib_dnsquery.c
* DNS host name to IP address resolver.
*
* The DNS resolver functions are used to lookup a hostname and map it to a
* numerical IP address.
*
* Copyright (C) 2007, 2009, 2012, 2014-2016 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Based heavily on portions of uIP:
*
* Author: Adam Dunkels <adam@dunkels.com>
* Copyright (c) 2002-2003, Adam Dunkels.
* All rights reserved.
*
* 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. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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 <string.h>
#include <errno.h>
#include <debug.h>
#include <arpa/inet.h>
#include <nuttx/net/dns.h>
#include "netdb/lib_dns.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* The maximum number of retries when asking for a name */
#define MAX_RETRIES 8
/* Buffer sizes
*
* The SEND_BUFFER_SIZE depends the configured DNS name size,
* sizeof(DNS query0 = Header (12 bytes) + DNS Name (Variable) +
* Query type (2 bytes) + Query Class (2 bytes)
*/
#define SEND_BUFFER_SIZE (32 + CONFIG_NETDB_DNSCLIENT_NAMESIZE)
#define RECV_BUFFER_SIZE CONFIG_NETDB_DNSCLIENT_MAXRESPONSE
/****************************************************************************
* Private Types
****************************************************************************/
struct dns_query_s
{
int sd; /* DNS server socket */
int result; /* Explanation of the failure */
FAR const char *hostname; /* Hostname to lookup */
FAR struct sockaddr *addr; /* Location to return host address */
FAR socklen_t *addrlen; /* Length of the address */
};
/****************************************************************************
* Private Data
****************************************************************************/
static uint8_t g_seqno; /* Sequence number of the next request */
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: dns_parse_name
*
* Description:
* Walk through a compact encoded DNS name and return the end of it.
*
****************************************************************************/
static FAR uint8_t *dns_parse_name(FAR uint8_t *query)
{
uint8_t n;
do
{
n = *query++;
while (n > 0)
{
++query;
--n;
}
}
while (*query != 0);
return query + 1;
}
/****************************************************************************
* Name: dns_send_query
*
* Description:
* Runs through the list of names to see if there are any that have
* not yet been queried and, if so, sends out a query.
*
****************************************************************************/
static int dns_send_query(int sd, FAR const char *name,
FAR union dns_server_u *uaddr, uint16_t rectype)
{
register FAR struct dns_header_s *hdr;
FAR uint8_t *dest;
FAR uint8_t *nptr;
FAR const char *src;
uint8_t buffer[SEND_BUFFER_SIZE];
uint8_t seqno;
socklen_t addrlen;
int errcode;
int ret;
int n;
/* Increment the sequence number */
dns_semtake();
seqno = g_seqno++;
dns_semgive();
/* Initialize the request header */
hdr = (FAR struct dns_header_s *)buffer;
memset(hdr, 0, sizeof(struct dns_header_s));
hdr->id = htons(seqno);
hdr->flags1 = DNS_FLAG1_RD;
hdr->numquestions = HTONS(1);
dest = buffer + 12;
/* Convert hostname into suitable query format. */
src = name - 1;
do
{
/* Copy the name string */
src++;
nptr = dest++;
for (n = 0; *src != '.' && *src != 0; src++)
{
*dest++ = *(uint8_t *)src;
n++;
}
/* Pre-pend the name length */
*nptr = n;
}
while (*src != '\0');
/* Add NUL termination, DNS record type, and DNS class */
*dest++ = '\0'; /* NUL termination */
*dest++ = (rectype >> 8); /* DNS record type (big endian) */
*dest++ = (rectype & 0xff);
*dest++ = (DNS_CLASS_IN >> 8); /* DNS record class (big endian) */
*dest++ = (DNS_CLASS_IN & 0xff);
/* Send the request */
#ifdef CONFIG_NET_IPv4
#ifdef CONFIG_NET_IPv6
if (uaddr->ipv4.sin_family == AF_INET)
#endif
{
addrlen = sizeof(struct sockaddr_in);
}
#endif
#ifdef CONFIG_NET_IPv6
#ifdef CONFIG_NET_IPv4
else
#endif
{
addrlen = sizeof(struct sockaddr_in6);
}
#endif
ret = sendto(sd, buffer, dest - buffer, 0, &uaddr->addr, addrlen);
/* Return the negated errno value on sendto failure */
if (ret < 0)
{
errcode = get_errno();
nerr("ERROR: sendto failed: %d\n", errcode);
return -errcode;
}
return OK;
}
/****************************************************************************
* Name: dns_recv_response
*
* Description:
* Called when new UDP data arrives
*
****************************************************************************/
static int dns_recv_response(int sd, FAR struct sockaddr *addr,
FAR socklen_t *addrlen)
{
FAR uint8_t *nameptr;
char buffer[RECV_BUFFER_SIZE];
FAR struct dns_answer_s *ans;
FAR struct dns_header_s *hdr;
#if 0 /* Not used */
uint8_t nquestions;
#endif
uint8_t nanswers;
int errcode;
int ret;
/* Receive the response */
ret = recv(sd, buffer, RECV_BUFFER_SIZE, 0);
if (ret < 0)
{
errcode = get_errno();
nerr("ERROR: recv failed: %d\n", errcode);
return -errcode;
}
hdr = (FAR struct dns_header_s *)buffer;
ninfo("ID %d\n", htons(hdr->id));
ninfo("Query %d\n", hdr->flags1 & DNS_FLAG1_RESPONSE);
ninfo("Error %d\n", hdr->flags2 & DNS_FLAG2_ERR_MASK);
ninfo("Num questions %d, answers %d, authrr %d, extrarr %d\n",
htons(hdr->numquestions), htons(hdr->numanswers),
htons(hdr->numauthrr), htons(hdr->numextrarr));
/* Check for error */
if ((hdr->flags2 & DNS_FLAG2_ERR_MASK) != 0)
{
nerr("ERROR: DNS reported error: flags2=%02x\n", hdr->flags2);
return -EPROTO;
}
/* We only care about the question(s) and the answers. The authrr
* and the extrarr are simply discarded.
*/
#if 0 /* Not used */
nquestions = htons(hdr->numquestions);
#endif
nanswers = htons(hdr->numanswers);
/* Skip the name in the question. TODO: This should really be
* checked against the name in the question, to be sure that they
* match.
*/
#if defined(CONFIG_DEBUG_NET) && defined(CONFIG_DEBUG_INFO)
{
int d = 64;
nameptr = dns_parse_name((uint8_t *)buffer + 12) + 4;
for (; ; )
{
ninfo("%02X %02X %02X %02X %02X %02X %02X %02X \n",
nameptr[0], nameptr[1], nameptr[2], nameptr[3],
nameptr[4], nameptr[5], nameptr[6], nameptr[7]);
nameptr += 8;
d -= 8;
if (d < 0)
{
break;
}
}
}
#endif
nameptr = dns_parse_name((uint8_t *)buffer + 12) + 4;
for (; nanswers > 0; nanswers--)
{
/* The first byte in the answer resource record determines if it
* is a compressed record or a normal one.
*/
if (*nameptr & 0xc0)
{
/* Compressed name. */
nameptr += 2;
ninfo("Compressed answer\n");
}
else
{
/* Not compressed name. */
nameptr = dns_parse_name(nameptr);
}
ans = (FAR struct dns_answer_s *)nameptr;
ninfo("Answer: type=%04x, class=%04x, ttl=%06x, length=%04x \n",
htons(ans->type), htons(ans->class),
(htons(ans->ttl[0]) << 16) | htons(ans->ttl[1]),
htons(ans->len));
/* Check for IPv4/6 address type and Internet class. Others are discarded. */
#ifdef CONFIG_NET_IPv4
if (ans->type == HTONS(DNS_RECTYPE_A) &&
ans->class == HTONS(DNS_CLASS_IN) &&
ans->len == HTONS(4))
{
ans->u.ipv4.s_addr = *(FAR uint32_t *)(nameptr + 10);
ninfo("IPv4 address: %d.%d.%d.%d\n",
(ans->u.ipv4.s_addr ) & 0xff,
(ans->u.ipv4.s_addr >> 8 ) & 0xff,
(ans->u.ipv4.s_addr >> 16) & 0xff,
(ans->u.ipv4.s_addr >> 24) & 0xff);
if (*addrlen >= sizeof(struct sockaddr_in))
{
FAR struct sockaddr_in *inaddr;
inaddr = (FAR struct sockaddr_in *)addr;
inaddr->sin_family = AF_INET;
inaddr->sin_port = 0;
inaddr->sin_addr.s_addr = ans->u.ipv4.s_addr;
*addrlen = sizeof(struct sockaddr_in);
return OK;
}
else
{
return -ERANGE;
}
}
else
#endif
#ifdef CONFIG_NET_IPv6
if (ans->type == HTONS(DNS_RECTYPE_AAAA) &&
ans->class == HTONS(DNS_CLASS_IN) &&
ans->len == HTONS(16))
{
memcpy(&ans->u.ipv6.s6_addr, nameptr + 10, 16);
ninfo("IPv6 address: %04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x\n",
htons(ans->u.ipv6.s6_addr[7]), htons(ans->u.ipv6.s6_addr[6]),
htons(ans->u.ipv6.s6_addr[5]), htons(ans->u.ipv6.s6_addr[4]),
htons(ans->u.ipv6.s6_addr[3]), htons(ans->u.ipv6.s6_addr[2]),
htons(ans->u.ipv6.s6_addr[1]), htons(ans->u.ipv6.s6_addr[0]));
if (*addrlen >= sizeof(struct sockaddr_in6))
{
FAR struct sockaddr_in6 *inaddr;
inaddr = (FAR struct sockaddr_in6 *)addr;
inaddr->sin6_family = AF_INET;
inaddr->sin6_port = 0;
memcpy(inaddr->sin6_addr.s6_addr, ans->u.ipv6.s6_addr, 16);
*addrlen = sizeof(struct sockaddr_in6);
return OK;
}
else
{
return -ERANGE;
}
}
else
#endif
{
nameptr = nameptr + 10 + htons(ans->len);
}
}
return -EADDRNOTAVAIL;
}
/****************************************************************************
* Name: dns_query_callback
*
* Description:
* Using the DNS information and this DNS server address, look up the
* hostname.
*
* Input Parameters:
* arg - Query arguements
* addr - DNS name server address
* addrlen - Length of the DNS name server address.
*
* Returned Value:
* Returns one (1) if the query was successful. Zero is returned in all
* other cases. The result field of the query structure is set to a
* negated errno value indicate the reason for the last failure (only).
*
****************************************************************************/
static int dns_query_callback(FAR void *arg, FAR struct sockaddr *addr,
FAR socklen_t addrlen)
{
FAR struct dns_query_s *query = (FAR struct dns_query_s *)arg;
int retries;
int ret;
/* Loop while receive timeout errors occur and there are remaining retries */
for (retries = 0; retries < 3; retries++)
{
#ifdef CONFIG_NET_IPv4
/* Is this an IPv4 address? */
if (addr->sa_family == AF_INET)
{
/* Yes.. verify the address size */
if (addrlen < sizeof(struct sockaddr_in))
{
/* Return zero to skip this address and try the next
* namserver address in resolv.conf.
*/
nerr("ERROR: Invalid IPv4 address size: %d\n", addrlen);
query->result = -EINVAL;
return 0;
}
/* Send the IPv4 query */
ret = dns_send_query(query->sd, query->hostname,
(FAR union dns_server_u *)addr,
DNS_RECTYPE_A);
if (ret < 0)
{
/* Return zero to skip this address and try the next
* namserver address in resolv.conf.
*/
nerr("ERROR: IPv4 dns_send_query failed: %d\n", ret);
query->result = ret;
return 0;
}
/* Obtain the IPv4 response */
ret = dns_recv_response(query->sd, query->addr, query->addrlen);
if (ret >= 0)
{
/* IPv4 response received successfully */
#if CONFIG_NETDB_DNSCLIENT_ENTRIES > 0
/* Save the answer in the DNS cache */
dns_save_answer(query->hostname, query->addr, *query->addrlen);
#endif
/* Return 1 to indicate to (1) stop the traversal, and (2)
* indicate that the address was found.
*/
return 1;
}
/* Handle errors */
nerr("ERROR: IPv4 dns_recv_response failed: %d\n", ret);
if (ret == -EADDRNOTAVAIL)
{
/* The IPv4 address is not available. Return zero to
* continue the tranversal with the next nameserver
* address in resolv.conf.
*/
query->result = -EADDRNOTAVAIL;
return 0;
}
else if (ret != -EAGAIN)
{
/* Some failure other than receive timeout occurred. Return
* zero to skip this address and try the next namserver
* address in resolv.conf.
*/
query->result = ret;
return 0;
}
}
else
#endif /* CONFIG_NET_IPv4 */
#ifdef CONFIG_NET_IPv6
/* Is this an IPv4 address? */
if (query->addr->sa_family == AF_INET6)
{
/* Yes.. verify the address size */
if (addrlen < sizeof(struct sockaddr_in6))
{
/* Return zero to skip this address and try the next
* namserver address in resolv.conf.
*/
nerr("ERROR: Invalid IPv6 address size: %d\n", addrlen);
query->result = -EINVAL;
return 0;
}
/* Send the IPv6 query */
ret = dns_send_query(query->sd, query->hostname,
(FAR union dns_server_u *)addr,
DNS_RECTYPE_AAAA);
if (ret < 0)
{
/* Return zero to skip this address and try the next
* namserver address in resolv.conf.
*/
nerr("ERROR: IPv6 dns_send_query failed: %d\n", ret);
query->result = ret;
return 0;
}
/* Obtain the IPv6 response */
ret = dns_recv_response(query->sd, query->addr, query->addrlen);
if (ret >= 0)
{
/* IPv6 response received successfully */
#if CONFIG_NETDB_DNSCLIENT_ENTRIES > 0
/* Save the answer in the DNS cache */
dns_save_answer(query->hostname, query->addr, *query->addrlen);
#endif
/* Return 1 to indicate to (1) stop the traversal, and (2)
* indicate that the address was found.
*/
return 1;
}
/* Handle errors */
nerr("ERROR: IPv6 dns_recv_response failed: %d\n", ret);
if (ret == -EADDRNOTAVAIL)
{
/* The IPv6 address is not available. Return zero to
* continue the tranversal with the next nameserver
* address in resolv.conf.
*/
query->result = -EADDRNOTAVAIL;
return 0;
}
else if (ret != -EAGAIN)
{
/* Some failure other than receive timeout occurred. Return
* zero to skip this address and try the next namserver
* address in resolv.conf.
*/
query->result = ret;
return 0;
}
}
else
#endif
{
/* Unsupported address family. Return zero to continue the
* tranversal with the next nameserver address in resolv.conf.
*/
return 0;
}
}
/* We tried three times and could not communicate with this nameserver.
* Perhaps it is down? Return zero to continue with the next address
* in the resolv.conf file.
*/
query->result = -ETIMEDOUT;
return 0;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: dns_query
*
* Description:
* Using the DNS resolver socket (sd), look up the 'hostname', and
* return its IP address in 'ipaddr'
*
* Input Parameters:
* sd - The socket descriptor previously initialized by dsn_bind().
* 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:
* Returns zero (OK) if the query was successful.
*
****************************************************************************/
int dns_query(int sd, FAR const char *hostname, FAR struct sockaddr *addr,
FAR socklen_t *addrlen)
{
FAR struct dns_query_s query;
int ret;
/* Set up the query info structure */
query.sd = sd;
query.result = -EADDRNOTAVAIL;
query.hostname = hostname;
query.addr = addr;
query.addrlen = addrlen;
/* Perform the query. dns_foreach_nameserver() will return:
*
* 1 - The query was successful.
* 0 - Look up failed
* <0 - Some other failure (?, shouldn't happen)
*/
ret = dns_foreach_nameserver(dns_query_callback, &query);
if (ret > 0)
{
/* The lookup was successful */
ret = OK;
}
else if (ret == 0)
{
ret = query.result;
}
return ret;
}