/* 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 <net/uip/uip.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 STATE_UNUSED 0
#define STATE_NEW 1
#define STATE_ASKING 2
#define STATE_DONE 3
#define STATE_ERROR 4
/****************************************************************************
* 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;
uip_ipaddr_t ipaddr;
};
struct namemap
{
uint8 state;
uint8 tmr;
uint8 retries;
uint8 seqno;
uint8 err;
char name[32];
uip_ipaddr_t ipaddr;
};
/****************************************************************************
* Private Data
****************************************************************************/
static struct namemap names[RESOLV_ENTRIES];
static uint8 seqno;
static struct uip_udp_conn *resolv_conn = NULL;
/****************************************************************************
* 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.
*/
static void check_entries(void)
{
register struct dns_hdr *hdr;
char *query, *nptr, *nameptr;
static uint8 i;
static uint8 n;
register struct namemap *namemapptr;
for(i = 0; i < RESOLV_ENTRIES; ++i)
{
namemapptr = &names[i];
if (namemapptr->state == STATE_NEW ||
namemapptr->state == STATE_ASKING)
{
if (namemapptr->state == STATE_ASKING)
{
if (--namemapptr->tmr == 0)
{
if (++namemapptr->retries == MAX_RETRIES)
{
namemapptr->state = STATE_ERROR;
resolv_found(namemapptr->name, NULL);
continue;
}
namemapptr->tmr = namemapptr->retries;
}
else
{
/* Its timer has not run out, so we move on to next entry. */
continue;
}
}
else
{
namemapptr->state = STATE_ASKING;
namemapptr->tmr = 1;
namemapptr->retries = 0;
}
hdr = (struct dns_hdr *)uip_appdata;
memset(hdr, 0, sizeof(struct dns_hdr));
hdr->id = htons(i);
hdr->flags1 = DNS_FLAG1_RD;
hdr->numquestions = HTONS(1);
query = (char *)uip_appdata + 12;
nameptr = namemapptr->name;
--nameptr;
/* Convert hostname into suitable query format. */
do
{
++nameptr;
nptr = query;
++query;
for (n = 0; *nameptr != '.' && *nameptr != 0; ++nameptr)
{
*query = *nameptr;
++query;
++n;
}
*nptr = n;
}
while(*nameptr != 0);
{
static unsigned char endquery[] = {0,0,1,0,1};
memcpy(query, endquery, 5);
}
uip_udp_send((unsigned char)(query + 5 - (char *)uip_appdata));
break;
}
}
}
/* Called when new UDP data arrives */
static void newdata(void)
{
unsigned char *nameptr;
struct dns_answer *ans;
struct dns_hdr *hdr;
static uint8 nquestions, nanswers;
static uint8 i;
register struct namemap *namemapptr;
hdr = (struct dns_hdr *)uip_appdata;
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));
/* The ID in the DNS header should be our entry into the name
* table.
*/
i = htons(hdr->id);
namemapptr = &names[i];
if (i < RESOLV_ENTRIES && namemapptr->state == STATE_ASKING)
{
/* This entry is now finished */
namemapptr->state = STATE_DONE;
namemapptr->err = hdr->flags2 & DNS_FLAG2_ERR_MASK;
/* Check for error. If so, call callback to inform */
if (namemapptr->err != 0)
{
namemapptr->state = STATE_ERROR;
resolv_found(namemapptr->name, NULL);
return;
}
/* 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 *)uip_appdata + 12) + 4;
while(nanswers > 0)
{
/* 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.
*/
namemapptr->ipaddr[0] = ans->ipaddr[0];
namemapptr->ipaddr[1] = ans->ipaddr[1];
resolv_found(namemapptr->name, namemapptr->ipaddr);
return;
}
else
{
nameptr = nameptr + 10 + htons(ans->len);
}
--nanswers;
}
}
}
/****************************************************************************
* Private Functions
****************************************************************************/
/* This function is called by the UIP interrupt handling logic whenevent an
* event of interest occurs.
*/
void uip_interrupt_udp_event(void)
{
if (uip_udp_conn->rport == HTONS(53))
{
if (uip_poll())
{
check_entries();
}
if (uip_newdata())
{
newdata();
}
}
}
/* Queues a name so that a question for the name will be sent out. */
void resolv_query(char *name)
{
static uint8 i;
static uint8 lseq, lseqi;
register struct namemap *nameptr;
lseq = lseqi = 0;
for(i = 0; i < RESOLV_ENTRIES; ++i)
{
nameptr = &names[i];
if (nameptr->state == STATE_UNUSED)
{
break;
}
if (seqno - nameptr->seqno > lseq)
{
lseq = seqno - nameptr->seqno;
lseqi = i;
}
}
if (i == RESOLV_ENTRIES)
{
i = lseqi;
nameptr = &names[i];
}
dbg("Using entry %d\n", i);
strcpy(nameptr->name, name);
nameptr->state = STATE_NEW;
nameptr->seqno = seqno;
++seqno;
}
/* Look up a hostname in the array of known hostnames.
*
* Note: This function only looks in the internal array of known
* hostnames, it does not send out a query for the hostname if none
* was found. The function resolv_query() can be used to send a query
* for a hostname.
*
* Return A pointer to a 4-byte representation of the hostname's IP
* address, or NULL if the hostname was not found in the array of
* hostnames.
*/
uint16 *resolv_lookup(char *name)
{
static uint8 i;
struct namemap *nameptr;
/* Walk through the list to see if the name is in there. If it is
* not, we return NULL.
*/
for(i = 0; i < RESOLV_ENTRIES; ++i)
{
nameptr = &names[i];
if (nameptr->state == STATE_DONE && strcmp(name, nameptr->name) == 0)
{
return nameptr->ipaddr;
}
}
return NULL;
}
/* Obtain the currently configured DNS server.
*
* Return: A pointer to a 4-byte representation of the IP address of
* the currently configured DNS server or NULL if no DNS server has
* been configured.
*/
uint16 *resolv_getserver(void)
{
if (resolv_conn == NULL)
{
return NULL;
}
return resolv_conn->ripaddr;
}
/* Configure which DNS server to use for queries.
*
* dnsserver A pointer to a 4-byte representation of the IP
* address of the DNS server to be configured.
*/
void resolv_conf(uint16 *dnsserver)
{
if (resolv_conn != NULL)
{
uip_udp_remove(resolv_conn);
}
resolv_conn = uip_udp_new(dnsserver, HTONS(53));
}
/* Initalize the resolver. */
void resolv_init(void)
{
static uint8 i;
for(i = 0; i < RESOLV_ENTRIES; ++i)
{
names[i].state = STATE_DONE;
}
}
