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contiki/core/net/resolv.c

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/**
* \addtogroup uip
* @{
*/
/**
* \defgroup uipdns uIP hostname resolver functions
* @{
*
* 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.
*
* The event resolv_event_found is posted when a hostname has been
* resolved. It is up to the receiving process to determine if the
* correct hostname has been found by calling the resolv_lookup()
* function with the hostname.
*/
/**
* \file
* DNS host name to IP address resolver.
* \author Adam Dunkels <adam@dunkels.com>
*
* This file implements a DNS host name to IP address resolver.
*/
/*
* 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.
*
* This file is part of the uIP TCP/IP stack.
*
* $Id: resolv.c,v 1.9 2010/05/31 15:22:08 nifi Exp $
*
*/
#include "net/tcpip.h"
#include "net/resolv.h"
#if UIP_UDP
#include <string.h>
#ifndef NULL
#define NULL (void *)0
#endif /* NULL */
#if UIP_CONF_IPV6
/* Currently this implementation only supports IPv4 DNS lookups.
Until support for IPv6 is added, dummy functions are used to
enable compilation with IPv6.
*/
process_event_t resolv_event_found;
PROCESS(resolv_process, "DNS resolver");
void resolv_conf(const uip_ipaddr_t *dnsserver) { }
uip_ipaddr_t *resolv_getserver(void) { return NULL; }
uip_ipaddr_t *resolv_lookup(const char *name) { return NULL; }
void resolv_query(const char *name) { }
PROCESS_THREAD(resolv_process, ev, data)
{
PROCESS_BEGIN();
resolv_event_found = process_alloc_event();
PROCESS_END();
}
#else /* UIP_CONF_IPV6 */
/** \internal The maximum number of retries when asking for a name. */
#define MAX_RETRIES 8
/** \internal The DNS message header. */
struct dns_hdr {
u16_t id;
u8_t flags1, flags2;
#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
u16_t numquestions;
u16_t numanswers;
u16_t numauthrr;
u16_t numextrarr;
};
/** \internal 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. */
u16_t type;
u16_t class;
u16_t ttl[2];
u16_t len;
u8_t ipaddr[4];
};
struct namemap {
#define STATE_UNUSED 0
#define STATE_NEW 1
#define STATE_ASKING 2
#define STATE_DONE 3
#define STATE_ERROR 4
u8_t state;
u8_t tmr;
u8_t retries;
u8_t seqno;
u8_t err;
char name[32];
uip_ipaddr_t ipaddr;
};
#ifndef UIP_CONF_RESOLV_ENTRIES
#define RESOLV_ENTRIES 4
#else /* UIP_CONF_RESOLV_ENTRIES */
#define RESOLV_ENTRIES UIP_CONF_RESOLV_ENTRIES
#endif /* UIP_CONF_RESOLV_ENTRIES */
static struct namemap names[RESOLV_ENTRIES];
static u8_t seqno;
static struct uip_udp_conn *resolv_conn = NULL;
static struct etimer retry;
process_event_t resolv_event_found;
PROCESS(resolv_process, "DNS resolver");
static void resolv_found(char *name, uip_ipaddr_t *ipaddr);
enum {
EVENT_NEW_SERVER=0
};
/*-----------------------------------------------------------------------------------*/
/** \internal
* Walk through a compact encoded DNS name and return the end of it.
*
* \return The end of the name.
*/
/*-----------------------------------------------------------------------------------*/
static unsigned char *
parse_name(unsigned char *query)
{
unsigned char n;
do {
n = *query++;
while(n > 0) {
/* printf("%c", *query);*/
++query;
--n;
};
/* printf(".");*/
} while(*query != 0);
/* printf("\n");*/
return query + 1;
}
/*-----------------------------------------------------------------------------------*/
/** \internal
* 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;
uint8_t i;
uint8_t n;
register struct namemap *namemapptr;
for(i = 0; i < RESOLV_ENTRIES; ++i) {
namemapptr = &names[i];
if(namemapptr->state == STATE_NEW ||
namemapptr->state == STATE_ASKING) {
etimer_set(&retry, CLOCK_SECOND);
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 {
/* printf("Timer %d\n", namemapptr->tmr);*/
/* 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;
}
}
}
/*-----------------------------------------------------------------------------------*/
/** \internal
* Called when new UDP data arrives.
*/
/*-----------------------------------------------------------------------------------*/
static void
newdata(void)
{
unsigned char *nameptr;
struct dns_answer *ans;
struct dns_hdr *hdr;
static u8_t nquestions, nanswers;
static u8_t i;
register struct namemap *namemapptr;
hdr = (struct dns_hdr *)uip_appdata;
/* printf("ID %d\n", htons(hdr->id));
printf("Query %d\n", hdr->flags1 & DNS_FLAG1_RESPONSE);
printf("Error %d\n", hdr->flags2 & DNS_FLAG2_ERR_MASK);
printf("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 = (u8_t)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 = (u8_t)htons(hdr->numquestions);
nanswers = (u8_t)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((uint8_t *)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;
/* printf("Compressed anwser\n");*/
} else {
/* Not compressed name. */
nameptr = parse_name((uint8_t *)nameptr);
}
ans = (struct dns_answer *)nameptr;
/* printf("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)) {
/* printf("IP address %d.%d.%d.%d\n",
ans->ipaddr[0],
ans->ipaddr[1],
ans->ipaddr[2],
ans->ipaddr[3]);*/
/* XXX: we should really check that this IP address is the one
we want. */
for(i = 0; i < 4; i++) {
namemapptr->ipaddr.u8[i] = ans->ipaddr[i];
}
resolv_found(namemapptr->name, &namemapptr->ipaddr);
return;
} else {
nameptr = nameptr + 10 + htons(ans->len);
}
--nanswers;
}
}
}
/*-----------------------------------------------------------------------------------*/
/** \internal
* The main UDP function.
*/
/*-----------------------------------------------------------------------------------*/
PROCESS_THREAD(resolv_process, ev, data)
{
int i;
PROCESS_BEGIN();
for(i = 0; i < RESOLV_ENTRIES; ++i) {
names[i].state = STATE_UNUSED;
}
resolv_conn = NULL;
resolv_event_found = process_alloc_event();
while(1) {
PROCESS_WAIT_EVENT();
if(ev == PROCESS_EVENT_TIMER) {
if(resolv_conn != NULL) {
tcpip_poll_udp(resolv_conn);
}
} else if(ev == EVENT_NEW_SERVER) {
if(resolv_conn != NULL) {
uip_udp_remove(resolv_conn);
}
resolv_conn = udp_new((uip_ipaddr_t *)data, HTONS(53), NULL);
} else if(ev == tcpip_event) {
if(uip_udp_conn->rport == HTONS(53)) {
if(uip_poll()) {
check_entries();
}
if(uip_newdata()) {
newdata();
}
}
}
}
PROCESS_END();
}
/*-----------------------------------------------------------------------------------*/
/**
* Queues a name so that a question for the name will be sent out.
*
* \param name The hostname that is to be queried.
*/
/*-----------------------------------------------------------------------------------*/
void
resolv_query(const char *name)
{
static u8_t i;
static u8_t lseq, lseqi;
register struct namemap *nameptr;
lseq = lseqi = 0;
nameptr = 0; //compiler warning if not initialized
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];
}
strncpy(nameptr->name, name, sizeof(nameptr->name));
nameptr->state = STATE_NEW;
nameptr->seqno = seqno;
++seqno;
if(resolv_conn != NULL) {
tcpip_poll_udp(resolv_conn);
}
}
/*-----------------------------------------------------------------------------------*/
/**
* 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.
*/
/*-----------------------------------------------------------------------------------*/
uip_ipaddr_t *
resolv_lookup(const char *name)
{
static u8_t 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.
*/
/*-----------------------------------------------------------------------------------*/
uip_ipaddr_t *
resolv_getserver(void)
{
if(resolv_conn == NULL) {
return NULL;
}
return &resolv_conn->ripaddr;
}
/*-----------------------------------------------------------------------------------*/
/**
* Configure a DNS server.
*
* \param dnsserver A pointer to a 4-byte representation of the IP
* address of the DNS server to be configured.
*/
/*-----------------------------------------------------------------------------------*/
void
resolv_conf(const uip_ipaddr_t *dnsserver)
{
static uip_ipaddr_t server;
uip_ipaddr_copy(&server, dnsserver);
process_post(&resolv_process, EVENT_NEW_SERVER, &server);
/* if(resolv_conn != NULL) {
uip_udp_remove(resolv_conn);
}
resolv_conn = udp_new(dnsserver, 53, NULL);*/
}
/*-----------------------------------------------------------------------------------*/
/** \internal
* Callback function which is called when a hostname is found.
*
*/
/*-----------------------------------------------------------------------------------*/
static void
resolv_found(char *name, uip_ipaddr_t *ipaddr)
{
process_post(PROCESS_BROADCAST, resolv_event_found, name);
}
/*-----------------------------------------------------------------------------------*/
#endif /* UIP_CONF_IPV6 */
#endif /* UIP_UDP */
/** @} */
/** @} */
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