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opt.h, init.c, tcpip.c, dhcp.c, dns.h, dns.c: add DNS client for simple name requests with RAW api interface. Initialization is done in lwip_init() with build time options. DNS timer is added in tcpip_thread context. DHCP can set DNS server ip addresses when options are received. You need to set LWIP_DNS=1 in your lwipopts.h file (LWIP_DNS=0 in opt.h). DNS_DEBUG can be set to get some traces with LWIP_DEBUGF. Sanity check have been added. There is a "todo" list with points to improve.

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This commit is contained in:
fbernon 2007-11-14 23:27:13 +00:00
parent a4d14722f3
commit 0c0e8d6544
7 changed files with 791 additions and 1 deletions
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9
CHANGELOG
View File

@ -19,6 +19,15 @@ HISTORY
++ New features:
2007-11-15 Jim Pettinato, Frédéric Bernon
* opt.h, init.c, tcpip.c, dhcp.c, dns.h, dns.c: add DNS client for simple name
requests with RAW api interface. Initialization is done in lwip_init() with
build time options. DNS timer is added in tcpip_thread context. DHCP can set
DNS server ip addresses when options are received. You need to set LWIP_DNS=1
in your lwipopts.h file (LWIP_DNS=0 in opt.h). DNS_DEBUG can be set to get
some traces with LWIP_DEBUGF. Sanity check have been added. There is a "todo"
list with points to improve.
2007-11-06 Simon Goldschmidt
* opt.h, mib2.c: Patch #6215: added ifAdminStatus write support (if explicitly
enabled by defining SNMP_SAFE_REQUESTS to 0); added code to check link status

20
src/api/tcpip.c
View File

@ -48,6 +48,7 @@
#include "lwip/autoip.h"
#include "lwip/dhcp.h"
#include "lwip/igmp.h"
#include "lwip/dns.h"
#include "lwip/tcpip.h"
#include "lwip/init.h"
#include "netif/etharp.h"
@ -202,6 +203,22 @@ igmp_timer(void *arg)
}
#endif /* LWIP_IGMP */
#if LWIP_DNS
/**
* Timer callback function that calls dns_tmr() and reschedules itself.
*
* @param arg unused argument
*/
static void
dns_timer(void *arg)
{
LWIP_UNUSED_ARG(arg);
LWIP_DEBUGF(TCPIP_DEBUG, ("tcpip: dns_tmr()\n"));
dns_tmr();
sys_timeout(DNS_TMR_INTERVAL, dns_timer, NULL);
}
#endif /* LWIP_DNS */
/**
* The main lwIP thread. This thread has exclusive access to lwIP core functions
* (unless access to them is not locked). Other threads communicate with this
@ -234,6 +251,9 @@ tcpip_thread(void *arg)
#if LWIP_IGMP
sys_timeout(IGMP_TMR_INTERVAL, igmp_timer, NULL);
#endif /* LWIP_IGMP */
#if LWIP_DNS
sys_timeout(DNS_TMR_INTERVAL, dns_timer, NULL);
#endif /* LWIP_DNS */
if (tcpip_init_done != NULL) {
tcpip_init_done(tcpip_init_done_arg);

4
src/core/dhcp.c
View File

@ -81,6 +81,7 @@
#include "lwip/sys.h"
#include "lwip/dhcp.h"
#include "lwip/autoip.h"
#include "lwip/dns.h"
#include "netif/etharp.h"
#include <string.h>
@ -517,6 +518,9 @@ static void dhcp_handle_ack(struct netif *netif)
dhcp->dns_count = DHCP_MAX_DNS;
for (n = 0; n < dhcp->dns_count; n++) {
dhcp->offered_dns_addr[n].addr = htonl(dhcp_get_option_long(&option_ptr[2 + n * 4]));
#if LWIP_DNS
dns_setserver( n, (struct ip_addr *)(&(dhcp->offered_dns_addr[n].addr)));
#endif /* LWIP_DNS */
}
}
}

640
src/core/dns.c Normal file
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@ -0,0 +1,640 @@
/**
* @file
* DNS - host name to IP address resolver.
*
*/
/**
* This file implements a DNS host name to IP address resolver.
* Port to lwIP from uIP
* by Jim Pettinato April 2007
* uIP version 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.
*
*
* DNS.C
*
* The lwIP DNS resolver functions are used to lookup a host name and
* map it to a numerical IP address. It maintains a list of resolved
* hostnames that can be queried with the dns_lookup() function.
* New hostnames can be resolved using the dns_query() function.
*
* The lwIP version of the resolver also adds a non-blocking version of
* gethostbyname() that will work with a raw API application. This function
* checks for an IP address string first and converts it if it is valid.
* gethostbyname() then does a dns_lookup() to see if the name is
* already in the table. If so, the IP is returned. If not, a query is
* issued and the function returns with a DNS_QUERY_QUEUED status. The app
* using the dns client must then go into a waiting state.
*
* Once a hostname has been resolved (or found to be non-existent),
* the resolver code calls a specified callback function (which
* must be implemented by the module that uses the resolver).
*/
/** @todo: define good default values (rfc compliance) */
/** @todo: secondary server support */
/** @todo: compressed answer support */
/** @todo: improve answer parsing, more checkings... */
/** @todo: possible alignment problems to access to dns_answer fields? */
/*-----------------------------------------------------------------------------
* RFC 1035 - Domain names - implementation and specification
* RFC 2181 - Clarifications to the DNS Specification
*----------------------------------------------------------------------------*/
/*-----------------------------------------------------------------------------
* Includes
*----------------------------------------------------------------------------*/
#include "lwip/opt.h"
#if LWIP_DNS /* don't build if not configured for use in lwipopts.h */
#include "lwip/udp.h"
#include "lwip/dns.h"
#include <string.h>
/** DNS server IP address */
#ifndef DNS_SERVER_ADDRESS
#define DNS_SERVER_ADDRESS inet_addr("208.67.222.222") /* resolver1.opendns.com */
#endif
/** DNS server port address */
#ifndef DNS_SERVER_PORT
#define DNS_SERVER_PORT 53
#endif
/* The maximum number of table entries to maintain locally */
#ifndef DNS_TABLE_SIZE
#define DNS_TABLE_SIZE 4
#endif
/* The maximum length of a host name supported in the name table. */
#ifndef DNS_MAX_NAME_LENGTH
#define DNS_MAX_NAME_LENGTH 256
#endif
/* The maximum number of retries when asking for a name, before "timeout". */
#ifndef DNS_MAX_RETRIES
#define DNS_MAX_RETRIES 8
#endif
/* DNS entry time to live (in DNS_TMR_INTERVAL ticks) */
#ifndef DNS_TTL_ENTRY
#define DNS_TTL_ENTRY 60
#endif
/* DNS protocol flags */
#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
/* DNS protocol states */
#define DNS_STATE_UNUSED 0
#define DNS_STATE_NEW 1
#define DNS_STATE_ASKING 2
#define DNS_STATE_DONE 3
/* DNS field TYPE used for "Resource Records" */
#define DNS_RRTYPE_A 1 /* a host address */
#define DNS_RRTYPE_NS 2 /* an authoritative name server */
#define DNS_RRTYPE_MD 3 /* a mail destination (Obsolete - use MX) */
#define DNS_RRTYPE_MF 4 /* a mail forwarder (Obsolete - use MX) */
#define DNS_RRTYPE_CNAME 5 /* the canonical name for an alias */
#define DNS_RRTYPE_SOA 6 /* marks the start of a zone of authority */
#define DNS_RRTYPE_MB 7 /* a mailbox domain name (EXPERIMENTAL) */
#define DNS_RRTYPE_MG 8 /* a mail group member (EXPERIMENTAL) */
#define DNS_RRTYPE_MR 9 /* a mail rename domain name (EXPERIMENTAL) */
#define DNS_RRTYPE_NULL 10 /* a null RR (EXPERIMENTAL) */
#define DNS_RRTYPE_WKS 11 /* a well known service description */
#define DNS_RRTYPE_PTR 12 /* a domain name pointer */
#define DNS_RRTYPE_HINFO 13 /* host information */
#define DNS_RRTYPE_MINFO 14 /* mailbox or mail list information */
#define DNS_RRTYPE_MX 15 /* mail exchange */
#define DNS_RRTYPE_TXT 16 /* text strings */
/* DNS field CLASS used for "Resource Records" */
#define DNS_RRCLASS_IN 1 /* the Internet */
#define DNS_RRCLASS_CS 2 /* the CSNET class (Obsolete - used only for examples in some obsolete RFCs) */
#define DNS_RRCLASS_CH 3 /* the CHAOS class */
#define DNS_RRCLASS_HS 4 /* Hesiod [Dyer 87] */
#define DNS_RRCLASS_FLUSH 0x800 /* Flush bit */
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/bpstruct.h"
#endif
PACK_STRUCT_BEGIN
/** DNS message header */
struct dns_hdr {
u16_t id;
u8_t flags1;
u8_t flags2;
u16_t numquestions;
u16_t numanswers;
u16_t numauthrr;
u16_t numextrarr;
} PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/epstruct.h"
#endif
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/bpstruct.h"
#endif
PACK_STRUCT_BEGIN
/** 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;
u32_t ttl;
u16_t len;
struct ip_addr ipaddr;
} PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/epstruct.h"
#endif
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/bpstruct.h"
#endif
PACK_STRUCT_BEGIN
/** DNS table entry */
struct dns_table_entry {
u8_t state;
u8_t tmr;
u8_t retries;
u8_t ttl;
u8_t seqno;
u8_t err;
char name[DNS_MAX_NAME_LENGTH];
struct ip_addr ipaddr;
void (* found)(char *name, struct ip_addr *ipaddr, void *arg); /* pointer to callback on DNS query done */
void *arg;
} PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/epstruct.h"
#endif
/* forward declarations */
static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port);
static void dns_check_entries(void);
/*-----------------------------------------------------------------------------
* Globales
*----------------------------------------------------------------------------*/
/* DNS variables */
static struct udp_pcb *dns_pcb;
static struct dns_table_entry dns_table[DNS_TABLE_SIZE];
static u8_t dns_seqno;
/* DNS request termination sequence: zero(1)+type(2)+class(2) */
static unsigned char dns_endquery[] = {0,0,1,0,1};
/**
* Initialize the resolver and configure which DNS server to use for queries.
*
* param dnsserver A pointer to a 4-byte representation of the IP
* address of the DNS server to be configured.
*/
err_t
dns_init()
{
u8_t i;
struct ip_addr dnsserver = {DNS_SERVER_ADDRESS};
LWIP_DEBUGF(DNS_DEBUG, ("dns_init: initializing\n"));
/* if dns client not yet initialized... */
if (dns_pcb == NULL) {
dns_pcb = udp_new();
if (dns_pcb != NULL) {
/* initialize DNS table */
for (i=0; i<DNS_TABLE_SIZE; ++i) {
dns_table[i].state = DNS_STATE_UNUSED;
dns_table[i].found = NULL;
}
/* initialize DNS client */
udp_bind(dns_pcb, IP_ADDR_ANY, 0);
udp_recv(dns_pcb, dns_recv, NULL);
/* initialize default DNS primary server */
dns_setserver(0, &dnsserver);
}
}
return ERR_OK;
}
/**
* Obtain the currently configured DNS server.
* return unsigned long encoding of the IP address of
* the currently configured DNS server or NULL if no DNS server has
* been configured.
*/
void
dns_setserver(u8_t numdns, struct ip_addr *dnsserver)
{
LWIP_UNUSED_ARG(numdns);
if ((dns_pcb != NULL) && (dnsserver != NULL) && (dnsserver->addr !=0 )) {
udp_connect( dns_pcb, dnsserver, DNS_SERVER_PORT);
}
}
/**
* Obtain the currently configured DNS server.
* return unsigned long encoding of the IP address of
* the currently configured DNS server or NULL if no DNS server has
* been configured.
*/
u32_t
dns_getserver(u8_t numdns)
{
LWIP_UNUSED_ARG(numdns);
return ((dns_pcb != NULL)?dns_pcb->remote_ip.addr:0);
}
/**
* The DNS resolver client timer - handle retries and timeouts
*/
void
dns_tmr(void)
{
if (dns_pcb != NULL) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_tmr: dns_check_entries\n"));
dns_check_entries();
}
}
/**
* 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 dns_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.
*/
u32_t
dns_lookup(char *name)
{
u8_t i;
/* Walk through name list, return entry if found. If not, return NULL. */
for (i=0; i<DNS_TABLE_SIZE; ++i) {
if ( (dns_table[i].state==DNS_STATE_DONE) && (strcmp(name, dns_table[i].name)==0) ) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_lookup: \"%s\": found = ", name));
ip_addr_debug_print(DNS_DEBUG, (&(dns_table[i].ipaddr)));
LWIP_DEBUGF(DNS_DEBUG, ("\n"));
return dns_table[i].ipaddr.addr;
}
}
return 0;
}
/**
* dns_parse_name() - walk through a compact encoded DNS name and return the end
* of the name.
*/
static unsigned char *
dns_parse_name(unsigned char *query)
{
unsigned char n;
do {
n = *query++;
while(n > 0) {
++query;
--n;
};
} while(*query != 0);
return query + 1;
}
/**
* dns_send
*/
static err_t
dns_send( char* name, u8_t id)
{
struct dns_hdr *hdr;
struct pbuf *p;
char *query, *nptr, *pHostname;
u8_t n;
LWIP_DEBUGF(DNS_DEBUG, ("dns_send: \"%s\": request\n", name));
/* if here, we have either a new query or a retry on a previous query to process */
p = pbuf_alloc(PBUF_TRANSPORT, sizeof(struct dns_hdr)+DNS_MAX_NAME_LENGTH+sizeof(dns_endquery), PBUF_RAM);
if (p) {
hdr = (struct dns_hdr *)p->payload;
memset(hdr, 0, sizeof(struct dns_hdr));
hdr->id = htons(id);
hdr->flags1 = DNS_FLAG1_RD;
hdr->numquestions = htons(1);
query = (char *)hdr + sizeof(struct dns_hdr);
pHostname = name;
--pHostname;
/* convert hostname into suitable query format. */
do {
++pHostname;
nptr = query;
++query;
for(n = 0; *pHostname != '.' && *pHostname != 0; ++pHostname) {
*query = *pHostname;
++query;
++n;
}
*nptr = n;
} while(*pHostname != 0);
memcpy( query, dns_endquery, sizeof(dns_endquery));
// resize pbuf to the exact dns query
pbuf_realloc(p, (query+sizeof(dns_endquery))-((char*)(p->payload)));
// send dns packet
udp_send(dns_pcb, p);
// free pbuf
pbuf_free(p);
return ERR_OK;
}
return ERR_BUF;
}
/**
* dns_check_entries() - 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
dns_check_entries(void)
{
u8_t i;
struct dns_table_entry *pEntry;
for (i = 0; i < DNS_TABLE_SIZE; ++i) {
pEntry = &dns_table[i];
switch(pEntry->state) {
case DNS_STATE_NEW:
case DNS_STATE_ASKING: {
if (pEntry->state == DNS_STATE_ASKING) {
if (--pEntry->tmr == 0) {
if (++pEntry->retries == DNS_MAX_RETRIES) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entries: \"%s\": timeout\n", pEntry->name));
/* call specified callback function if provided */
if (pEntry->found)
(*pEntry->found)(pEntry->name, NULL, pEntry->arg);
/* flush this entry */
pEntry->state = DNS_STATE_UNUSED;
pEntry->found = NULL;
continue;
}
/* wait longer for the next retry */
pEntry->tmr = pEntry->retries;
} else {
/* Its timer has not run out, so we move on to next entry. */
continue;
}
} else {
pEntry->state = DNS_STATE_ASKING;
pEntry->tmr = 1;
pEntry->retries = 0;
}
/* send DNS packet for this entry */
dns_send(pEntry->name, i);
break;
}
case DNS_STATE_DONE: {
/* if the time to live is nul */
if (--pEntry->ttl == 0) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entries: \"%s\": flush\n", pEntry->name));
/* flush this entry */
pEntry->state = DNS_STATE_UNUSED;
pEntry->found = NULL;
}
break;
}
}
}
}
/**
* Callback for DNS responses
*/
static void
dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port)
{
u8_t i;
char *pHostname;
struct dns_answer *ans;
struct dns_hdr *hdr;
struct dns_table_entry *pEntry;
u8_t nquestions, nanswers;
hdr = (struct dns_hdr *)p->payload;
/* The ID in the DNS header should be our entry into the name table. */
i = htons(hdr->id);
pEntry = &dns_table[i];
if( (i < DNS_TABLE_SIZE) && (pEntry->state == DNS_STATE_ASKING) ) {
/* This entry is now completed. */
pEntry->state = DNS_STATE_DONE;
pEntry->ttl = DNS_TTL_ENTRY;
pEntry->err = hdr->flags2 & DNS_FLAG2_ERR_MASK;
/* Check for error. If so, call callback to inform. */
if(pEntry->err != 0) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", pEntry->name));
/* call specified callback function if provided */
if (pEntry->found)
(*pEntry->found)(pEntry->name, NULL, pEntry->arg);
/* flush this entry */
pEntry->state = DNS_STATE_UNUSED;
pEntry->found = 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. */
pHostname = (char *) dns_parse_name((unsigned char *)p->payload + sizeof(struct dns_hdr)) + 4/*type(2)+class(2)*/;
while(nanswers > 0) {
/* The first byte in the answer resource record determines if it
is a compressed record or a normal one. */
if(*pHostname & 0xc0) {
/* Compressed name. */
pHostname +=2;
/* printf("Compressed anwser\n");*/
} else {
/* Not compressed name. */
pHostname = (char *) dns_parse_name((unsigned char *)pHostname);
}
/* TODO: isn't it any problem to access to dns_answer fields since pHostname's length can be unaligned? */
ans = (struct dns_answer *)pHostname;
/* 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((ntohs(ans->type) == DNS_RRTYPE_A) && (ntohs(ans->class) == DNS_RRCLASS_IN) && (ntohs(ans->len) == 4/*IPv4 address*/) ) {
/* TODO: we should really check that this IP address is the one we want. */
pEntry->ipaddr = ans->ipaddr;
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", pEntry->name));
ip_addr_debug_print(DNS_DEBUG, (&(pEntry->ipaddr)));
LWIP_DEBUGF(DNS_DEBUG, ("\n"));
/* call specified callback function if provided */
if (pEntry->found)
(*pEntry->found)(pEntry->name, &pEntry->ipaddr, pEntry->arg);
return;
} else {
pHostname = pHostname + 10 + htons(ans->len);
}
--nanswers;
}
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in response\n", pEntry->name));
}
}
/**
* Queues a name so that a question for the name will be sent out.
* param name - The hostname that is to be queried.
*/
static void
dns_query(char *name, void (*found)(char *name, struct ip_addr *addr, void *arg), void *arg)
{
u8_t i;
u8_t lseq, lseqi;
struct dns_table_entry *pEntry;
/* search an unused entry, or the oldest one */
lseq = lseqi = 0;
for (i = 0; i < DNS_TABLE_SIZE; ++i) {
pEntry = &dns_table[i];
/* is it an unused entry ? */
if (pEntry->state == DNS_STATE_UNUSED)
break;
/* check if this is the oldest entry used */
if (dns_seqno - pEntry->seqno > lseq) {
lseq = dns_seqno - pEntry->seqno;
lseqi = i;
}
}
/* if we don't have found an unused entry, use the oldest one */
if (i == DNS_TABLE_SIZE) {
i = lseqi;
pEntry = &dns_table[i];
/* since we replace the previous entry, we "unblock" the caller */
LWIP_DEBUGF(DNS_DEBUG, ("dns_query: \"%s\": replaced by new entry\n", pEntry->name));
/* call specified callback function if provided */
if (pEntry->found)
(*pEntry->found)(pEntry->name, NULL, pEntry->arg);
}
/* fill the entry */
strcpy(pEntry->name, name);
pEntry->found = found;
pEntry->arg = arg;
pEntry->state = DNS_STATE_NEW;
pEntry->seqno = dns_seqno++;
}
/**
* NON-BLOCKING callback version for use with raw API
*/
DNS_RESULT dns_gethostbyname(char *hostname, struct ip_addr *addr,
void (*found)(char *name, struct ip_addr *ipaddr, void *arg),
void *arg
)
{
/* not initialized or no valid server yet, or invalid addr pointer */
if ((dns_pcb == NULL) || (addr == NULL))
return DNS_QUERY_INVALID;
/* invalid hostname */
if ((!hostname) || (!hostname[0]))
return DNS_QUERY_INVALID;
/* invalid hostname length */
if (strlen(hostname) >= DNS_MAX_NAME_LENGTH)
return DNS_QUERY_INVALID;
/* host name already in octet notation? set ip addr and return COMPLETE */
if ((addr->addr = inet_addr(hostname)) != INADDR_NONE)
return DNS_COMPLETE;
/* already have this address cached? */
if ((addr->addr = dns_lookup(hostname)) != 0)
return DNS_COMPLETE;
/* queue query with specified callback */
dns_query(hostname, found, arg);
/* force to send request */
dns_check_entries();
return DNS_QUERY_QUEUED;
}
#endif /* LWIP_DNS */

9
src/core/init.c
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@ -52,6 +52,7 @@
#include "lwip/tcp.h"
#include "lwip/autoip.h"
#include "lwip/igmp.h"
#include "lwip/dns.h"
#include "netif/etharp.h"
/* Compile-time sanity checks for configuration errors.
@ -75,6 +76,9 @@
#if (!LWIP_UDP && LWIP_IGMP)
#error "If you want to use IGMP, you have to define LWIP_UDP=1 in your lwipopts.h"
#endif
#if (!LWIP_UDP && LWIP_DNS)
#error "If you want to use DNS, you have to define LWIP_UDP=1 in your lwipopts.h"
#endif
#if (LWIP_ARP && (ARP_TABLE_SIZE > 0x7f))
#error "If you want to use ARP, ARP_TABLE_SIZE must fit in an s8_t, so, you have to reduce it in your lwipopts.h"
#endif
@ -136,7 +140,7 @@
#error "One and exactly one of LWIP_EVENT_API and LWIP_CALLBACK_API has to be enabled in lwipopts.h"
#endif
/* There must be sufficient timeouts, taking into account requirements of the subsystems. */
#if ((NO_SYS==0) && (MEMP_NUM_SYS_TIMEOUT < (LWIP_TCP + IP_REASSEMBLY + LWIP_ARP + (2*LWIP_DHCP) + LWIP_AUTOIP + LWIP_IGMP + LWIP_PPP)))
#if ((NO_SYS==0) && (MEMP_NUM_SYS_TIMEOUT < (LWIP_TCP + IP_REASSEMBLY + LWIP_ARP + (2*LWIP_DHCP) + LWIP_AUTOIP + LWIP_IGMP + LWIP_DNS + LWIP_PPP)))
#error "MEMP_NUM_SYS_TIMEOUT is too low to accomodate all required timeouts"
#endif
#if (IP_REASSEMBLY && (MEMP_NUM_REASSDATA > IP_REASS_MAX_PBUFS))
@ -233,4 +237,7 @@ lwip_init(void)
#if LWIP_IGMP
igmp_init();
#endif /* LWIP_IGMP */
#if LWIP_DNS
dns_init();
#endif /* LWIP_DNS */
}

90
src/include/lwip/dns.h Normal file
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@ -0,0 +1,90 @@
/**
* lwip DNS resolver header file.
* Author: Jim Pettinato
* April 2007
* ported from uIP resolv.c Copyright (c) 2002-2003, Adam Dunkels.
*
* 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.
*/
#ifndef __LWIP_DNS_H__
#define __LWIP_DNS_H__
#include "lwip/opt.h"
#if LWIP_DNS /* don't build if not configured for use in lwipopts.h */
/** DNS timer period */
#ifndef DNS_TMR_INTERVAL
#define DNS_TMR_INTERVAL 1000
#endif
/* enumerated list of possible result values returned by dns_gethostname() */
typedef enum dns_result {
DNS_QUERY_INVALID,
DNS_QUERY_QUEUED,
DNS_COMPLETE
}DNS_RESULT;
/* initializes the resolver */
err_t dns_init(void);
/* handles requests, retries and timeouts - call every DNS_TMR_INTERVAL tick */
void dns_tmr(void);
/* initializes DNS server IP address */
void dns_setserver(u8_t numdns, struct ip_addr *dnsserver);
/* returns configured DNS server IP address */
u32_t dns_getserver(u8_t numdns);
/* returns IP for host 'name' only if already in table */
u32_t dns_lookup(char *name);
/* resolove a host 'name' in ip address */
DNS_RESULT dns_gethostbyname(char *hostName, struct ip_addr *addr,
void (*found)(char *name, struct ip_addr *ipaddr, void *arg),
void *arg);
/* dns_gethostbyname() - Returns immediately with one of DNS_RESULT return codes
* Return value will be DNS_COMPLETE if hostName is a valid
* IP address string or the host name is already in the local
* names table. Returns DNS_REQUEST_QUEUED and queues a
* request to be sent to the DNS server for resolution if no
* errors are present.
*/
/* dns_found_func() - Callback which is invoked when a hostname is found.
* This function should be implemented by the application using the DNS resolver.
* param 'name' - pointer to the name that was looked up.
* param 'ipaddr' - pointer to a struct ip_addr containing the IP address of the
* hostname, or NULL if the name could not be found.
*/
#endif /* LWIP_DNS */
#endif /* __LWIP_DNS_H__ */

20
src/include/lwip/opt.h
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@ -546,6 +546,19 @@
#define LWIP_IGMP 0
#endif
/*
----------------------------------
---------- DNS options -----------
----------------------------------
*/
/**
* LWIP_DNS==1: Turn on DNS module. UDP must be available for DNS
* transport.
*/
#ifndef LWIP_DNS
#define LWIP_DNS 0
#endif
/*
---------------------------------
---------- UDP options ----------
@ -1515,4 +1528,11 @@
#define SNMP_MIB_DEBUG LWIP_DBG_OFF
#endif
/**
* DNS_DEBUG: Enable debugging for DNS.
*/
#ifndef DNS_DEBUG
#define DNS_DEBUG LWIP_DBG_OFF
#endif
#endif /* __LWIP_OPT_H__ */