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api_msg.c, dns.h, dns.c: Implement DNS_DOES_NAME_CHECK option (check if name received match the name query), implement DNS_USES_STATIC_BUF (the place where copy dns payload to parse the response), return an error if there is no place for a new query, and fix some minor problems.

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This commit is contained in:
fbernon 2007-11-19 22:42:01 +00:00
parent da4df1f414
commit f58515b51e
4 changed files with 209 additions and 88 deletions
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6
CHANGELOG
View File

@ -19,6 +19,12 @@ HISTORY
++ New features:
2007-11-19 Frédéric Bernon
* api_msg.c, dns.h, dns.c: Implement DNS_DOES_NAME_CHECK option (check if name
received match the name query), implement DNS_USES_STATIC_BUF (the place where
copy dns payload to parse the response), return an error if there is no place
for a new query, and fix some minor problems.
2007-11-16 Simon Goldschmidt
* new files: ipv4/inet.c, ipv4/inet_chksum.c, ipv6/inet6.c
removed files: core/inet.c, core/inet6.c

3
src/api/api_msg.c
View File

@ -1032,6 +1032,9 @@ do_gethostbyname(void *arg)
if (res == DNS_COMPLETE) {
/* name was already in octet notation or cached */
*msg->err = ERR_OK;
} else if (res == DNS_ERR_MEM) {
/* memory allocation error */
*msg->err = ERR_MEM;
} else {
/* some error occurred */
*msg->err = ERR_ARG;

287
src/core/dns.c
View File

@ -77,6 +77,7 @@
#if LWIP_DNS /* don't build if not configured for use in lwipopts.h */
#include "lwip/udp.h"
#include "lwip/mem.h"
#include "lwip/dns.h"
#include <string.h>
@ -91,20 +92,31 @@
#define DNS_SERVER_PORT 53
#endif
/* The maximum number of table entries to maintain locally */
/* DNS maximum number of 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. */
/** DNS maximum host name length 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". */
/** DNS maximum number of retries when asking for a name, before "timeout". */
#ifndef DNS_MAX_RETRIES
#define DNS_MAX_RETRIES 4
#endif
#endif
/** DNS do a name checking between the query and the response. */
#ifndef DNS_DOES_NAME_CHECK
#define DNS_DOES_NAME_CHECK 1
#endif
/** DNS use a local buffer if DNS_USES_STATIC_BUF=0, a static one if
DNS_USES_STATIC_BUF=1, or a dynamic one if DNS_USES_STATIC_BUF=2. */
#ifndef DNS_USES_STATIC_BUF
#define DNS_USES_STATIC_BUF 1
#endif
/* DNS protocol flags */
#define DNS_FLAG1_RESPONSE 0x80
@ -214,7 +226,10 @@ static struct udp_pcb *dns_pcb;
static u8_t dns_seqno;
static struct dns_table_entry dns_table[DNS_TABLE_SIZE];
static struct ip_addr dns_servers[DNS_MAX_SERVERS];
#if (DNS_USES_STATIC_BUF == 1)
static u8_t dns_payload[DNS_MSG_SIZE];
#endif /* (DNS_USES_STATIC_BUF == 1) */
/**
* Initialize the resolver and configure which DNS server to use for queries.
@ -253,10 +268,7 @@ dns_init()
}
/**
* 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.
* Initialize one if the DNS server.
*/
void
dns_setserver(u8_t numdns, struct ip_addr *dnsserver)
@ -267,10 +279,9 @@ dns_setserver(u8_t numdns, struct ip_addr *dnsserver)
}
/**
* 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.
* Obtain one of the currently configured DNS server.
* return IP address of one of the currently configured DNS server or "ip_addr_any"
* if the DNS server has not been configured.
*/
struct ip_addr
dns_getserver(u8_t numdns)
@ -320,6 +331,40 @@ dns_lookup(const char *name)
return 0;
}
#if DNS_DOES_NAME_CHECK
/**
* dns_compare_name: compare the "dotted" name "query" with the
* encoded name "response"
*/
static u8_t
dns_compare_name(unsigned char *query, unsigned char *response)
{
unsigned char n;
do {
n = *response++;
/** @see RFC 1035 - 4.1.4. Message compression */
if ((n & 0xc0)==0xc0) {
/* Compressed name */
break;
} else {
/* Not compressed name */
while(n > 0) {
if ((*query)!=(*response)) {
return 1;
}
++response;
++query;
--n;
};
++query;
}
} while(*response != 0);
return 0;
}
#endif /* DNS_DOES_NAME_CHECK */
/**
* dns_parse_name() - walk through a compact encoded DNS name and return the end
* of the name.
@ -409,6 +454,71 @@ dns_send(u8_t numdns, const char* name, u8_t id)
return ERR_BUF;
}
/**
* dns_check_entry() - see if pEntry has not yet been queried and, if so, sends out a query.
*/
static void
dns_check_entry(u8_t i)
{
struct dns_table_entry *pEntry = &dns_table[i];
switch(pEntry->state) {
case DNS_STATE_NEW: {
/* initialize new entry */
pEntry->state = DNS_STATE_ASKING;
pEntry->numdns = 0;
pEntry->tmr = 1;
pEntry->retries = 0;
/* send DNS packet for this entry */
dns_send(pEntry->numdns, pEntry->name, i);
break;
}
case DNS_STATE_ASKING: {
if (--pEntry->tmr == 0) {
if (++pEntry->retries == DNS_MAX_RETRIES) {
if ((pEntry->numdns+1<DNS_MAX_SERVERS) && (dns_servers[pEntry->numdns+1].addr!=0)) {
/* change of server */
pEntry->numdns++;
pEntry->tmr = 1;
pEntry->retries = 0;
break;
} else {
LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%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;
break;
}
}
/* wait longer for the next retry */
pEntry->tmr = pEntry->retries;
/* send DNS packet for this entry */
dns_send(pEntry->numdns, 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_entry: \"%s\": flush\n", pEntry->name));
/* flush this entry */
pEntry->state = DNS_STATE_UNUSED;
pEntry->found = NULL;
}
break;
}
}
}
/**
* 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.
@ -417,62 +527,9 @@ 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) {
if ((pEntry->numdns+1<DNS_MAX_SERVERS) && (dns_servers[pEntry->numdns+1].addr!=0)) {
/* change of server */
pEntry->numdns++;
pEntry->tmr = 1;
pEntry->retries = 0;
continue;
} else {
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->numdns = 0;
pEntry->tmr = 1;
pEntry->retries = 0;
}
/* send DNS packet for this entry */
dns_send(pEntry->numdns, 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;
}
}
dns_check_entry(i);
}
}
@ -488,6 +545,12 @@ dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16
struct dns_answer *ans;
struct dns_table_entry *pEntry;
u8_t nquestions, nanswers;
#if (DNS_USES_STATIC_BUF == 0)
u8_t dns_payload[DNS_MSG_SIZE];
#endif /* (DNS_USES_STATIC_BUF == 0) */
#if (DNS_USES_STATIC_BUF == 2)
u8_t* dns_payload;
#endif /* (DNS_USES_STATIC_BUF == 2) */
/* is the dns message too big ? */
if (p->tot_len > DNS_MSG_SIZE) {
@ -503,6 +566,15 @@ dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16
return;
}
#if (DNS_USES_STATIC_BUF == 2)
dns_payload = mem_malloc(p->tot_len);
if (dns_payload == NULL) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: mem_malloc error\n"));
pbuf_free(p);
return;
}
#endif /* (DNS_USES_STATIC_BUF == 2) */
/* copy dns payload inside static buffer for processing */
if (pbuf_copy_partial(p, dns_payload, p->tot_len, 0) == p->tot_len) {
/* The ID in the DNS header should be our entry into the name table. */
@ -531,11 +603,34 @@ dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16
pEntry->found = NULL;
/* free pbuf */
pbuf_free(p);
#if (DNS_USES_STATIC_BUF == 2)
/* free dns buffer */
mem_free(dns_payload);
#endif /* (DNS_USES_STATIC_BUF == 2) */
return;
}
/* Skip the name in the "question" part. This should really be checked
agains the name in the question, to be sure that they match. */
#if DNS_DOES_NAME_CHECK
/* Check if the name in the "question" part match with the name in the entry. */
if (dns_compare_name(pEntry->name, (unsigned char *)dns_payload + sizeof(struct dns_hdr)) != 0) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\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;
/* free pbuf */
pbuf_free(p);
#if (DNS_USES_STATIC_BUF == 2)
/* free dns buffer */
mem_free(dns_payload);
#endif /* (DNS_USES_STATIC_BUF == 2) */
return;
}
#endif /* DNS_DOES_NAME_CHECK */
/* Skip the name in the "question" part */
pHostname = (char *) dns_parse_name((unsigned char *)dns_payload + sizeof(struct dns_hdr)) + sizeof(struct dns_query);
while(nanswers > 0) {
@ -560,6 +655,10 @@ dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16
(*pEntry->found)(pEntry->name, &pEntry->ipaddr, pEntry->arg);
/* free pbuf */
pbuf_free(p);
#if (DNS_USES_STATIC_BUF == 2)
/* free dns buffer */
mem_free(dns_payload);
#endif /* (DNS_USES_STATIC_BUF == 2) */
return;
} else {
pHostname = pHostname + sizeof(struct dns_answer) + htons(ans->len);
@ -572,14 +671,18 @@ dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16
}
/* free pbuf */
pbuf_free(p);
#if (DNS_USES_STATIC_BUF == 2)
/* free dns buffer */
mem_free(dns_payload);
#endif /* (DNS_USES_STATIC_BUF == 2) */
}
/**
* 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(const char *name, void (*found)(const char *name, struct ip_addr *addr, void *arg), void *arg)
static DNS_RESULT
dns_enqueue(const char *name, void (*found)(const char *name, struct ip_addr *addr, void *arg), void *arg)
{
u8_t i;
u8_t lseq, lseqi;
@ -593,30 +696,43 @@ dns_query(const char *name, void (*found)(const char *name, struct ip_addr *addr
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;
/* check if this is the oldest completed entry */
if (pEntry->state == DNS_STATE_DONE) {
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 we don't have found an unused entry, use the oldest completed 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);
if ((lseqi >= DNS_TABLE_SIZE) || (dns_table[lseqi].state != DNS_STATE_DONE)) {
/* no entry can't be used now, table is full */
LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS entries table is full\n", name));
return DNS_ERR_MEM;
} else {
/* use the oldest completed one */
i = lseqi;
pEntry = &dns_table[i];
}
}
/* use this entry */
LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS entry %"U16_F"\n", name, (u16_t)(i)));
/* fill the entry */
pEntry->state = DNS_STATE_NEW;
pEntry->seqno = dns_seqno++;
pEntry->found = found;
pEntry->arg = arg;
strcpy( pEntry->name, name);
/* force to send query without waiting timer */
dns_check_entry(i);
/* dns query is enqueued */
return DNS_QUERY_QUEUED;
}
/**
@ -648,12 +764,7 @@ DNS_RESULT dns_gethostbyname(const char *hostname, struct ip_addr *addr,
return DNS_COMPLETE;
/* queue query with specified callback */
dns_query(hostname, found, arg);
/* force to send request */
dns_check_entries();
return DNS_QUERY_QUEUED;
return dns_enqueue(hostname, found, arg);
}
#endif /* LWIP_DNS */

1
src/include/lwip/dns.h
View File

@ -81,6 +81,7 @@
/* enumerated list of possible result values returned by dns_gethostname() */
typedef enum dns_result {
DNS_ERR_MEM,
DNS_QUERY_INVALID,
DNS_QUERY_QUEUED,
DNS_COMPLETE