465 lines
13 KiB
C
465 lines
13 KiB
C
/**
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* \addtogroup apps
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* @{
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*/
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/**
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* \defgroup resolv DNS resolver
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* @{
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*
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* The uIP DNS resolver functions are used to lookup a hostname and
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* map it to a numerical IP address. It maintains a list of resolved
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* hostnames that can be queried with the resolv_lookup()
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* function. New hostnames can be resolved using the resolv_query()
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* function.
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*
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* When a hostname has been resolved (or found to be non-existant),
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* the resolver code calls a callback function called resolv_found()
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* that must be implemented by the module that uses the resolver.
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*/
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/**
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* \file
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* DNS host name to IP address resolver.
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* \author Adam Dunkels <adam@dunkels.com>
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*
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* This file implements a DNS host name to IP address resolver.
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*/
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/*
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* Copyright (c) 2002-2003, Adam Dunkels.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote
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* products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
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* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
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* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* This file is part of the uIP TCP/IP stack.
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*
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* $Id: resolv.c,v 1.5 2006/06/11 21:46:37 adam Exp $
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*
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*/
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#include "resolv.h"
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#include "uip.h"
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#include <string.h>
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#ifndef NULL
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#define NULL (void *)0
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#endif /* NULL */
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/** \internal The maximum number of retries when asking for a name. */
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#define MAX_RETRIES 8
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/** \internal The DNS message header. */
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struct dns_hdr {
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u16_t id;
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u8_t flags1, flags2;
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#define DNS_FLAG1_RESPONSE 0x80
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#define DNS_FLAG1_OPCODE_STATUS 0x10
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#define DNS_FLAG1_OPCODE_INVERSE 0x08
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#define DNS_FLAG1_OPCODE_STANDARD 0x00
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#define DNS_FLAG1_AUTHORATIVE 0x04
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#define DNS_FLAG1_TRUNC 0x02
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#define DNS_FLAG1_RD 0x01
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#define DNS_FLAG2_RA 0x80
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#define DNS_FLAG2_ERR_MASK 0x0f
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#define DNS_FLAG2_ERR_NONE 0x00
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#define DNS_FLAG2_ERR_NAME 0x03
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u16_t numquestions;
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u16_t numanswers;
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u16_t numauthrr;
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u16_t numextrarr;
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};
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/** \internal The DNS answer message structure. */
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struct dns_answer {
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/* DNS answer record starts with either a domain name or a pointer
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to a name already present somewhere in the packet. */
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u16_t type;
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u16_t class;
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u16_t ttl[2];
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u16_t len;
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uip_ipaddr_t ipaddr;
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};
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struct namemap {
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#define STATE_UNUSED 0
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#define STATE_NEW 1
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#define STATE_ASKING 2
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#define STATE_DONE 3
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#define STATE_ERROR 4
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u8_t state;
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u8_t tmr;
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u8_t retries;
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u8_t seqno;
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u8_t err;
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char name[32];
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uip_ipaddr_t ipaddr;
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};
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#ifndef UIP_CONF_RESOLV_ENTRIES
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#define RESOLV_ENTRIES 4
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#else /* UIP_CONF_RESOLV_ENTRIES */
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#define RESOLV_ENTRIES UIP_CONF_RESOLV_ENTRIES
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#endif /* UIP_CONF_RESOLV_ENTRIES */
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static struct namemap names[RESOLV_ENTRIES];
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static u8_t seqno;
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static struct uip_udp_conn *resolv_conn = NULL;
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/*---------------------------------------------------------------------------*/
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/** \internal
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* Walk through a compact encoded DNS name and return the end of it.
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*
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* \return The end of the name.
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*/
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/*---------------------------------------------------------------------------*/
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static unsigned char *
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parse_name(unsigned char *query)
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{
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unsigned char n;
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do {
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n = *query++;
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while(n > 0) {
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/* printf("%c", *query);*/
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++query;
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--n;
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};
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/* printf(".");*/
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} while(*query != 0);
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/* printf("\n");*/
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return query + 1;
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}
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/*---------------------------------------------------------------------------*/
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/** \internal
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* Runs through the list of names to see if there are any that have
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* not yet been queried and, if so, sends out a query.
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*/
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/*---------------------------------------------------------------------------*/
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static void
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check_entries(void)
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{
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register struct dns_hdr *hdr;
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char *query, *nptr, *nameptr;
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static u8_t i;
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static u8_t n;
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register struct namemap *namemapptr;
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for(i = 0; i < RESOLV_ENTRIES; ++i) {
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namemapptr = &names[i];
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if(namemapptr->state == STATE_NEW ||
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namemapptr->state == STATE_ASKING) {
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if(namemapptr->state == STATE_ASKING) {
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if(--namemapptr->tmr == 0) {
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if(++namemapptr->retries == MAX_RETRIES) {
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namemapptr->state = STATE_ERROR;
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resolv_found(namemapptr->name, NULL);
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continue;
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}
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namemapptr->tmr = namemapptr->retries;
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} else {
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/* printf("Timer %d\n", namemapptr->tmr);*/
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/* Its timer has not run out, so we move on to next
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entry. */
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continue;
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}
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} else {
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namemapptr->state = STATE_ASKING;
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namemapptr->tmr = 1;
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namemapptr->retries = 0;
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}
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hdr = (struct dns_hdr *)uip_appdata;
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memset(hdr, 0, sizeof(struct dns_hdr));
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hdr->id = htons(i);
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hdr->flags1 = DNS_FLAG1_RD;
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hdr->numquestions = HTONS(1);
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query = (char *)uip_appdata + 12;
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nameptr = namemapptr->name;
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--nameptr;
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/* Convert hostname into suitable query format. */
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do {
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++nameptr;
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nptr = query;
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++query;
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for(n = 0; *nameptr != '.' && *nameptr != 0; ++nameptr) {
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*query = *nameptr;
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++query;
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++n;
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}
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*nptr = n;
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} while(*nameptr != 0);
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{
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static unsigned char endquery[] =
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{0,0,1,0,1};
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memcpy(query, endquery, 5);
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}
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uip_udp_send((unsigned char)(query + 5 - (char *)uip_appdata));
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break;
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}
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}
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}
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/*---------------------------------------------------------------------------*/
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/** \internal
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* Called when new UDP data arrives.
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*/
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/*---------------------------------------------------------------------------*/
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static void
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newdata(void)
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{
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char *nameptr;
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struct dns_answer *ans;
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struct dns_hdr *hdr;
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static u8_t nquestions, nanswers;
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static u8_t i;
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register struct namemap *namemapptr;
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hdr = (struct dns_hdr *)uip_appdata;
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/* printf("ID %d\n", htons(hdr->id));
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printf("Query %d\n", hdr->flags1 & DNS_FLAG1_RESPONSE);
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printf("Error %d\n", hdr->flags2 & DNS_FLAG2_ERR_MASK);
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printf("Num questions %d, answers %d, authrr %d, extrarr %d\n",
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htons(hdr->numquestions),
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htons(hdr->numanswers),
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htons(hdr->numauthrr),
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htons(hdr->numextrarr));
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*/
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/* The ID in the DNS header should be our entry into the name
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table. */
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i = htons(hdr->id);
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namemapptr = &names[i];
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if(i < RESOLV_ENTRIES &&
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namemapptr->state == STATE_ASKING) {
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/* This entry is now finished. */
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namemapptr->state = STATE_DONE;
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namemapptr->err = hdr->flags2 & DNS_FLAG2_ERR_MASK;
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/* Check for error. If so, call callback to inform. */
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if(namemapptr->err != 0) {
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namemapptr->state = STATE_ERROR;
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resolv_found(namemapptr->name, NULL);
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return;
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}
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/* We only care about the question(s) and the answers. The authrr
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and the extrarr are simply discarded. */
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nquestions = htons(hdr->numquestions);
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nanswers = htons(hdr->numanswers);
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/* Skip the name in the question. XXX: This should really be
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checked agains the name in the question, to be sure that they
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match. */
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nameptr = parse_name((char *)uip_appdata + 12) + 4;
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while(nanswers > 0) {
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/* The first byte in the answer resource record determines if it
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is a compressed record or a normal one. */
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if(*nameptr & 0xc0) {
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/* Compressed name. */
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nameptr +=2;
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/* printf("Compressed anwser\n");*/
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} else {
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/* Not compressed name. */
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nameptr = parse_name((char *)nameptr);
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}
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ans = (struct dns_answer *)nameptr;
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/* printf("Answer: type %x, class %x, ttl %x, length %x\n",
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htons(ans->type), htons(ans->class), (htons(ans->ttl[0])
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<< 16) | htons(ans->ttl[1]), htons(ans->len));*/
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/* Check for IP address type and Internet class. Others are
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discarded. */
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if(ans->type == HTONS(1) &&
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ans->class == HTONS(1) &&
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ans->len == HTONS(4)) {
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/* printf("IP address %d.%d.%d.%d\n",
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htons(ans->ipaddr[0]) >> 8,
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htons(ans->ipaddr[0]) & 0xff,
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htons(ans->ipaddr[1]) >> 8,
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htons(ans->ipaddr[1]) & 0xff);*/
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/* XXX: we should really check that this IP address is the one
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we want. */
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namemapptr->ipaddr[0] = ans->ipaddr[0];
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namemapptr->ipaddr[1] = ans->ipaddr[1];
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resolv_found(namemapptr->name, namemapptr->ipaddr);
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return;
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} else {
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nameptr = nameptr + 10 + htons(ans->len);
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}
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--nanswers;
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}
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}
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}
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/*---------------------------------------------------------------------------*/
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/** \internal
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* The main UDP function.
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*/
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/*---------------------------------------------------------------------------*/
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void
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resolv_appcall(void)
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{
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if(uip_udp_conn->rport == HTONS(53)) {
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if(uip_poll()) {
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check_entries();
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}
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if(uip_newdata()) {
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newdata();
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}
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}
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}
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/*---------------------------------------------------------------------------*/
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/**
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* Queues a name so that a question for the name will be sent out.
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*
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* \param name The hostname that is to be queried.
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*/
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/*---------------------------------------------------------------------------*/
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void
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resolv_query(char *name)
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{
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static u8_t i;
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static u8_t lseq, lseqi;
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register struct namemap *nameptr;
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lseq = lseqi = 0;
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for(i = 0; i < RESOLV_ENTRIES; ++i) {
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nameptr = &names[i];
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if(nameptr->state == STATE_UNUSED) {
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break;
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}
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if(seqno - nameptr->seqno > lseq) {
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lseq = seqno - nameptr->seqno;
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lseqi = i;
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}
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}
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if(i == RESOLV_ENTRIES) {
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i = lseqi;
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nameptr = &names[i];
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}
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/* printf("Using entry %d\n", i);*/
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strcpy(nameptr->name, name);
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nameptr->state = STATE_NEW;
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nameptr->seqno = seqno;
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++seqno;
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}
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/*---------------------------------------------------------------------------*/
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/**
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* Look up a hostname in the array of known hostnames.
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*
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* \note This function only looks in the internal array of known
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* hostnames, it does not send out a query for the hostname if none
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* was found. The function resolv_query() can be used to send a query
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* for a hostname.
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*
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* \return A pointer to a 4-byte representation of the hostname's IP
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* address, or NULL if the hostname was not found in the array of
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* hostnames.
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*/
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/*---------------------------------------------------------------------------*/
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u16_t *
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resolv_lookup(char *name)
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{
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static u8_t i;
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struct namemap *nameptr;
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/* Walk through the list to see if the name is in there. If it is
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not, we return NULL. */
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for(i = 0; i < RESOLV_ENTRIES; ++i) {
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nameptr = &names[i];
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if(nameptr->state == STATE_DONE &&
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strcmp(name, nameptr->name) == 0) {
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return nameptr->ipaddr;
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}
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}
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return NULL;
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}
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/*---------------------------------------------------------------------------*/
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/**
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* Obtain the currently configured DNS server.
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*
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* \return A pointer to a 4-byte representation of the IP address of
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* the currently configured DNS server or NULL if no DNS server has
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* been configured.
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*/
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/*---------------------------------------------------------------------------*/
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u16_t *
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resolv_getserver(void)
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{
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if(resolv_conn == NULL) {
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return NULL;
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}
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return resolv_conn->ripaddr;
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}
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/*---------------------------------------------------------------------------*/
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/**
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* Configure which DNS server to use for queries.
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*
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* \param dnsserver A pointer to a 4-byte representation of the IP
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* address of the DNS server to be configured.
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*/
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/*---------------------------------------------------------------------------*/
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void
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resolv_conf(u16_t *dnsserver)
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{
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if(resolv_conn != NULL) {
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uip_udp_remove(resolv_conn);
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}
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resolv_conn = uip_udp_new(dnsserver, HTONS(53));
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}
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/*---------------------------------------------------------------------------*/
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/**
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* Initalize the resolver.
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*/
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/*---------------------------------------------------------------------------*/
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void
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resolv_init(void)
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{
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static u8_t i;
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for(i = 0; i < RESOLV_ENTRIES; ++i) {
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names[i].state = STATE_DONE;
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}
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}
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/*---------------------------------------------------------------------------*/
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/** @} */
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/** @} */
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