/* uip-resolv.c
* DNS host name to IP address resolver.
*
* The uIP DNS resolver functions are used to lookup a hostname and
* map it to a numerical IP address. It maintains a list of resolved
* hostnames that can be queried with the resolv_lookup()
* function. New hostnames can be resolved using the resolv_query()
* function.
*
* When a hostname has been resolved (or found to be non-existant),
* the resolver code calls a callback function called resolv_found()
* that must be implemented by the module that uses the resolver.
*
* Copyright (C) 2007 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* 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 <sys/types.h>
#include <string.h>
#include <unistd.h>
#include <time.h>
#include <errno.h>
#include <debug.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <net/uip/resolv.h>
/****************************************************************************
* Definitions
****************************************************************************/
#ifndef CONFIG_NET_RESOLV_ENTRIES
#define RESOLV_ENTRIES 4
#else /* CONFIG_NET_RESOLV_ENTRIES */
#define RESOLV_ENTRIES CONFIG_NET_RESOLV_ENTRIES
#endif /* CONFIG_NET_RESOLV_ENTRIES */
#ifndef NULL
#define NULL (void *)0
#endif /* NULL */
/* The maximum number of retries when asking for a name */
#define MAX_RETRIES 8
#define DNS_FLAG1_RESPONSE 0x80
#define DNS_FLAG1_OPCODE_STATUS 0x10
#define DNS_FLAG1_OPCODE_INVERSE 0x08
#define DNS_FLAG1_OPCODE_STANDARD 0x00
#define DNS_FLAG1_AUTHORATIVE 0x04
#define DNS_FLAG1_TRUNC 0x02
#define DNS_FLAG1_RD 0x01
#define DNS_FLAG2_RA 0x80
#define DNS_FLAG2_ERR_MASK 0x0f
#define DNS_FLAG2_ERR_NONE 0x00
#define DNS_FLAG2_ERR_NAME 0x03
#define SEND_BUFFER_SIZE 64
#define RECV_BUFFER_SIZE 64
#ifdef CONFIG_NET_IPv6
#define ADDRLEN sizeof(struct sockaddr_in6)
#else
#define ADDRLEN sizeof(struct sockaddr_in)
#endif
/****************************************************************************
* Private Types
****************************************************************************/
/* The DNS message header */
struct dns_hdr
{
uint16 id;
uint8 flags1, flags2;
uint16 numquestions;
uint16 numanswers;
uint16 numauthrr;
uint16 numextrarr;
};
/* The DNS answer message structure */
struct dns_answer
{
/* DNS answer record starts with either a domain name or a pointer
* to a name already present somewhere in the packet.
*/
uint16 type;
uint16 class;
uint16 ttl[2];
uint16 len;
#ifdef CONFIG_NET_IPv6
#else
uint16 ipaddr[2];
#endif
};
struct namemap
{
uint8 state;
uint8 tmr;
uint8 retries;
uint8 seqno;
uint8 err;
char name[32];
#ifdef CONFIG_NET_IPv6
#else
uint16 ipaddr[2];
#endif
};
/****************************************************************************
* Private Data
****************************************************************************/
static uint8 g_seqno;
static int g_sockfd = -1;
#ifdef CONFIG_NET_IPv6
static struct sockaddr_in6 g_dnsserver;
#else
static struct sockaddr_in g_dnsserver;
#endif
/****************************************************************************
* Private Functions
****************************************************************************/
/* Walk through a compact encoded DNS name and return the end of it. */
static unsigned char *parse_name(unsigned char *query)
{
unsigned char n;
do
{
n = *query++;
while(n > 0)
{
++query;
--n;
}
}
while(*query != 0);
return query + 1;
}
/* 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.
*/
#ifdef CONFIG_NET_IPv6
static int send_query(const char *name, struct sockaddr_in6 *addr)
#else
static int send_query(const char *name, struct sockaddr_in *addr)
#endif
{
register struct dns_hdr *hdr;
char *query;
char *nptr;
const char *nameptr;
uint8 seqno = g_seqno++;
static unsigned char endquery[] = {0,0,1,0,1};
char buffer[SEND_BUFFER_SIZE];
int n;
hdr = (struct dns_hdr*)buffer;
memset(hdr, 0, sizeof(struct dns_hdr));
hdr->id = htons(seqno);
hdr->flags1 = DNS_FLAG1_RD;
hdr->numquestions = HTONS(1);
query = buffer + 12;
/* Convert hostname into suitable query format. */
nameptr = name - 1;
do
{
nameptr++;
nptr = query++;
for (n = 0; *nameptr != '.' && *nameptr != 0; nameptr++)
{
*query++ = *nameptr;
n++;
}
*nptr = n;
}
while(*nameptr != 0);
memcpy(query, endquery, 5);
return sendto(g_sockfd, buffer, query + 5 - buffer, 0, (struct sockaddr*)addr, ADDRLEN);
}
/* Called when new UDP data arrives */
#ifdef CONFIG_NET_IPv6
#error "Not implemented
#else
int recv_response(struct sockaddr_in *addr)
#endif
{
unsigned char *nameptr;
char buffer[RECV_BUFFER_SIZE];
struct dns_answer *ans;
struct dns_hdr *hdr;
uint8 nquestions;
uint8 nanswers;
int ret;
/* Receive the response */
ret = recv(g_sockfd, buffer, RECV_BUFFER_SIZE, 0);
if (ret < 0)
{
return ret;
}
hdr = (struct dns_hdr *)buffer;
dbg( "ID %d\n", htons(hdr->id));
dbg( "Query %d\n", hdr->flags1 & DNS_FLAG1_RESPONSE);
dbg( "Error %d\n", hdr->flags2 & DNS_FLAG2_ERR_MASK);
dbg( "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 so, call callback to inform */
if ((hdr->flags2 & DNS_FLAG2_ERR_MASK) != 0)
{
return ERROR;
}
/* We only care about the question(s) and the answers. The authrr
* and the extrarr are simply discarded.
*/
nquestions = htons(hdr->numquestions);
nanswers = htons(hdr->numanswers);
/* Skip the name in the question. XXX: This should really be
* checked agains the name in the question, to be sure that they
* match.
*/
nameptr = parse_name((unsigned char *)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;
dbg("Compressed anwser\n");
}
else
{
/* Not compressed name. */
nameptr = parse_name(nameptr);
}
ans = (struct dns_answer *)nameptr;
dbg("Answer: type %x, class %x, ttl %x, length %x\n",
htons(ans->type), htons(ans->class), (htons(ans->ttl[0]) << 16) | htons(ans->ttl[1]),
htons(ans->len));
/* Check for IP address type and Internet class. Others are discarded. */
if (ans->type == HTONS(1) && ans->class == HTONS(1) && ans->len == HTONS(4))
{
dbg("IP address %d.%d.%d.%d\n",
htons(ans->ipaddr[0]) >> 8, htons(ans->ipaddr[0]) & 0xff,
htons(ans->ipaddr[1]) >> 8, htons(ans->ipaddr[1]) & 0xff);
/* XXX: we should really check that this IP address is the one
* we want.
*/
addr->sin_addr.s_addr = ((uint32)ans->ipaddr[0] << 16) | (uint32)ans->ipaddr[1];
return OK;
}
else
{
nameptr = nameptr + 10 + htons(ans->len);
}
}
return ERROR;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/* Get the binding for name. */
#ifdef CONFIG_NET_IPv6
int resolv_query(const char *name, struct sockaddr_in6 *addr)
#else
int resolv_query(const char *name, struct sockaddr_in *addr)
#endif
{
int retries;
int ret;
// Loop while receive timeout errors occur and there are remaining retries
for (retries = 0; retries < 3; retries++)
{
if (send_query(name, addr) < 0)
{
return ERROR;
}
ret = recv_response(addr);
if (ret >= 0)
{
/* Response received successfully */
return OK;
}
else if (*get_errno_ptr() != EAGAIN)
{
/* Some failure other than receive timeout occurred */
return ERROR;
}
}
return ret;
}
/* Obtain the currently configured DNS server. */
#ifdef CONFIG_NET_IPv6
void resolv_getserver(struct sockaddr_in6 *dnsserver)
#else
void resolv_getserver(struct sockaddr_in *dnsserver)
#endif
{
memcpy(dnsserver, &g_dnsserver, ADDRLEN);
}
/* Configure which DNS server to use for queries */
#ifdef CONFIG_NET_IPv6
void resolv_conf(const struct sockaddr_in6 *dnsserver)
#else
void resolv_conf(const struct sockaddr_in *dnsserver)
#endif
{
memcpy(&g_dnsserver, dnsserver, ADDRLEN);
}
/* Initalize the resolver. */
int resolv_init(void)
{
struct timeval tv;
g_sockfd = socket(PF_INET, SOCK_DGRAM, 0);
if (g_sockfd < 0)
{
return ERROR;
}
/* Set up a receive timeout */
tv.tv_sec = 30;
tv.tv_usec = 0;
if (setsockopt(g_sockfd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(struct timeval)) < 0)
{
close(g_sockfd);
g_sockfd = -1;
return ERROR;
}
return OK;
}
