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fixed bug #42987 lwIP is vulnerable to DNS cache poisoning due to non-randomized TXIDs

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This commit is contained in:
Simon Goldschmidt 2014-08-31 20:29:56 +02:00
parent 63038e0305
commit a5e06ed5b7
2 changed files with 217 additions and 64 deletions
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3
CHANGELOG
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@ -168,6 +168,9 @@ HISTORY
++ Bugfixes: ++ Bugfixes:
2014-08-20: Simon Goldschmidt
* dns.c: fixed bug #42987 lwIP is vulnerable to DNS cache poisoning due to
non-randomized TXIDs
2014-06-03: Simon Goldschmidt 2014-06-03: Simon Goldschmidt
* tcp_impl.h, tcp_in.c: fixed bug #37969 SYN packet dropped as short packet in * tcp_impl.h, tcp_in.c: fixed bug #37969 SYN packet dropped as short packet in

278
src/core/dns.c
View File

@ -49,13 +49,13 @@
* The lwIP version of the resolver also adds a non-blocking version of * The lwIP version of the resolver also adds a non-blocking version of
* gethostbyname() that will work with a raw API application. This function * 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. * 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 * 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 * already in the table. If so, the IP is returned. If not, a query is
* issued and the function returns with a ERR_INPROGRESS status. The app * issued and the function returns with a ERR_INPROGRESS status. The app
* using the dns client must then go into a waiting state. * using the dns client must then go into a waiting state.
* *
* Once a hostname has been resolved (or found to be non-existent), * Once a hostname has been resolved (or found to be non-existent),
* the resolver code calls a specified callback function (which * the resolver code calls a specified callback function (which
* must be implemented by the module that uses the resolver). * must be implemented by the module that uses the resolver).
*/ */
@ -83,6 +83,26 @@
#include <string.h> #include <string.h>
/* A list of DNS security features follows */
#define LWIP_DNS_SECURE_RAND_XID 1
#define LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING 2
/** Use all DNS security features by default.
* This is overridable but should only be needed by very small targets
* or when using against non standard DNS servers. */
#ifndef LWIP_DNS_SECURE
#define LWIP_DNS_SECURE (LWIP_DNS_SECURE_RAND_XID | LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING)
#endif
/** Random generator function to create random TXIDs for queries */
#ifndef DNS_RAND_TXID
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_XID) != 0)
#define DNS_RAND_TXID LWIP_RAND
#else
static u16_t dns_txid;
#define DNS_RAND_TXID() (++dns_txid)
#endif
#endif
/** DNS server IP address */ /** DNS server IP address */
#ifndef DNS_SERVER_ADDRESS #ifndef DNS_SERVER_ADDRESS
#define DNS_SERVER_ADDRESS(ipaddr) (ip4_addr_set_u32(ipaddr, ipaddr_addr("208.67.222.222"))) /* resolver1.opendns.com */ #define DNS_SERVER_ADDRESS(ipaddr) (ip4_addr_set_u32(ipaddr, ipaddr_addr("208.67.222.222"))) /* resolver1.opendns.com */
@ -117,10 +137,13 @@
#define DNS_FLAG2_ERR_NAME 0x03 #define DNS_FLAG2_ERR_NAME 0x03
/* DNS protocol states */ /* DNS protocol states */
#define DNS_STATE_UNUSED 0 #define DNS_STATE_UNUSED 0
#define DNS_STATE_NEW 1 #define DNS_STATE_NEW 1
#define DNS_STATE_ASKING 2 #define DNS_STATE_ASKING 2
#define DNS_STATE_DONE 3 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
#define DNS_STATE_DUPLICATE_PENDING 3
#endif
#define DNS_STATE_DONE 4
#ifdef PACK_STRUCT_USE_INCLUDES #ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/bpstruct.h" # include "arch/bpstruct.h"
@ -172,6 +195,7 @@ struct dns_table_entry {
u8_t retries; u8_t retries;
u8_t seqno; u8_t seqno;
u8_t err; u8_t err;
u16_t txid;
u32_t ttl; u32_t ttl;
char name[DNS_MAX_NAME_LENGTH]; char name[DNS_MAX_NAME_LENGTH];
ip_addr_t ipaddr; ip_addr_t ipaddr;
@ -212,7 +236,7 @@ static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *ad
static void dns_check_entries(void); static void dns_check_entries(void);
/*----------------------------------------------------------------------------- /*-----------------------------------------------------------------------------
* Globales * Globals
*----------------------------------------------------------------------------*/ *----------------------------------------------------------------------------*/
/* DNS variables */ /* DNS variables */
@ -224,6 +248,40 @@ static ip_addr_t dns_servers[DNS_MAX_SERVERS];
static u8_t dns_payload_buffer[LWIP_MEM_ALIGN_BUFFER(DNS_MSG_SIZE)]; static u8_t dns_payload_buffer[LWIP_MEM_ALIGN_BUFFER(DNS_MSG_SIZE)];
static u8_t* dns_payload; static u8_t* dns_payload;
#ifndef LWIP_DNS_STRICMP
#define LWIP_DNS_STRICMP(str1, str2) dns_stricmp(str1, str2)
/**
* A small but sufficient implementation for case insensitive strcmp.
* This can be defined to e.g. stricmp for windows or strcasecmp for linux. */
static int
dns_stricmp(const char* str1, const char* str2)
{
char c1, c2;
do {
c1 = *str1++;
c2 = *str2++;
if (c1 != c2) {
char c1_upc = c1 | 0x20;
if ((c1_upc >= 'a') && (c1_upc <= 'z')) {
/* characters are not equal an one is in the alphabet range:
downcase both chars and check again */
char c2_upc = c2 | 0x20;
if (c1_upc != c2_upc) {
/* still not equal */
/* don't care for < or > */
return 1;
}
} else {
/* characters are not equal but none is in the alphabet range */
return 1;
}
}
} while (c1 != 0);
return 0;
}
#endif /* LWIP_DNS_STRICMP */
/** /**
* Initialize the resolver: set up the UDP pcb and configure the default server * Initialize the resolver: set up the UDP pcb and configure the default server
* (DNS_SERVER_ADDRESS). * (DNS_SERVER_ADDRESS).
@ -234,7 +292,7 @@ dns_init()
ip_addr_t dnsserver; ip_addr_t dnsserver;
dns_payload = (u8_t *)LWIP_MEM_ALIGN(dns_payload_buffer); dns_payload = (u8_t *)LWIP_MEM_ALIGN(dns_payload_buffer);
/* initialize default DNS server address */ /* initialize default DNS server address */
DNS_SERVER_ADDRESS(&dnsserver); DNS_SERVER_ADDRESS(&dnsserver);
@ -350,7 +408,7 @@ dns_lookup_local(const char *hostname)
#if DNS_LOCAL_HOSTLIST_IS_DYNAMIC #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
struct local_hostlist_entry *entry = local_hostlist_dynamic; struct local_hostlist_entry *entry = local_hostlist_dynamic;
while(entry != NULL) { while(entry != NULL) {
if(strcmp(entry->name, hostname) == 0) { if (LWIP_DNS_STRICMP(entry->name, hostname) == 0) {
return ip4_addr_get_u32(&entry->addr); return ip4_addr_get_u32(&entry->addr);
} }
entry = entry->next; entry = entry->next;
@ -358,7 +416,7 @@ dns_lookup_local(const char *hostname)
#else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
int i; int i;
for (i = 0; i < sizeof(local_hostlist_static) / sizeof(struct local_hostlist_entry); i++) { for (i = 0; i < sizeof(local_hostlist_static) / sizeof(struct local_hostlist_entry); i++) {
if(strcmp(local_hostlist_static[i].name, hostname) == 0) { if (LWIP_DNS_STRICMP(local_hostlist_static[i].name, hostname) == 0) {
return ip4_addr_get_u32(&local_hostlist_static[i].addr); return ip4_addr_get_u32(&local_hostlist_static[i].addr);
} }
} }
@ -467,7 +525,7 @@ dns_lookup(const char *name)
/* Walk through name list, return entry if found. If not, return NULL. */ /* Walk through name list, return entry if found. If not, return NULL. */
for (i = 0; i < DNS_TABLE_SIZE; ++i) { for (i = 0; i < DNS_TABLE_SIZE; ++i) {
if ((dns_table[i].state == DNS_STATE_DONE) && if ((dns_table[i].state == DNS_STATE_DONE) &&
(strcmp(name, dns_table[i].name) == 0)) { (LWIP_DNS_STRICMP(name, dns_table[i].name) == 0)) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_lookup: \"%s\": found = ", name)); LWIP_DEBUGF(DNS_DEBUG, ("dns_lookup: \"%s\": found = ", name));
ip_addr_debug_print(DNS_DEBUG, &(dns_table[i].ipaddr)); ip_addr_debug_print(DNS_DEBUG, &(dns_table[i].ipaddr));
LWIP_DEBUGF(DNS_DEBUG, ("\n")); LWIP_DEBUGF(DNS_DEBUG, ("\n"));
@ -478,7 +536,6 @@ dns_lookup(const char *name)
return IPADDR_NONE; return IPADDR_NONE;
} }
#if DNS_DOES_NAME_CHECK
/** /**
* Compare the "dotted" name "query" with the encoded name "response" * Compare the "dotted" name "query" with the encoded name "response"
* to make sure an answer from the DNS server matches the current dns_table * to make sure an answer from the DNS server matches the current dns_table
@ -489,8 +546,8 @@ dns_lookup(const char *name)
* @param response encoded hostname in the DNS response * @param response encoded hostname in the DNS response
* @return 0: names equal; 1: names differ * @return 0: names equal; 1: names differ
*/ */
static u8_t static char*
dns_compare_name(unsigned char *query, unsigned char *response) dns_compare_name(char *query, char *response)
{ {
unsigned char n; unsigned char n;
@ -498,13 +555,13 @@ dns_compare_name(unsigned char *query, unsigned char *response)
n = *response++; n = *response++;
/** @see RFC 1035 - 4.1.4. Message compression */ /** @see RFC 1035 - 4.1.4. Message compression */
if ((n & 0xc0) == 0xc0) { if ((n & 0xc0) == 0xc0) {
/* Compressed name */ /* Compressed name: cannot be equal since we don't send them */
break; return NULL;
} else { } else {
/* Not compressed name */ /* Not compressed name */
while (n > 0) { while (n > 0) {
if ((*query) != (*response)) { if ((*query) != (*response)) {
return 1; return NULL;
} }
++response; ++response;
++query; ++query;
@ -514,9 +571,8 @@ dns_compare_name(unsigned char *query, unsigned char *response)
} }
} while (*response != 0); } while (*response != 0);
return 0; return response + 1;
} }
#endif /* DNS_DOES_NAME_CHECK */
/** /**
* Walk through a compact encoded DNS name and return the end of the name. * Walk through a compact encoded DNS name and return the end of the name.
@ -524,13 +580,13 @@ dns_compare_name(unsigned char *query, unsigned char *response)
* @param query encoded DNS name in the DNS server response * @param query encoded DNS name in the DNS server response
* @return end of the name * @return end of the name
*/ */
static unsigned char * static char *
dns_parse_name(unsigned char *query) dns_parse_name(char *query)
{ {
unsigned char n; unsigned char n;
do { do {
n = *query++; n = (unsigned char) *query++;
/** @see RFC 1035 - 4.1.4. Message compression */ /** @see RFC 1035 - 4.1.4. Message compression */
if ((n & 0xc0) == 0xc0) { if ((n & 0xc0) == 0xc0) {
/* Compressed name */ /* Compressed name */
@ -552,12 +608,11 @@ dns_parse_name(unsigned char *query)
* *
* @param numdns index of the DNS server in the dns_servers table * @param numdns index of the DNS server in the dns_servers table
* @param name hostname to query * @param name hostname to query
* @param id index of the hostname in dns_table, used as transaction ID in the * @param txid transmission id for the query
* DNS query packet
* @return ERR_OK if packet is sent; an err_t indicating the problem otherwise * @return ERR_OK if packet is sent; an err_t indicating the problem otherwise
*/ */
static err_t static err_t
dns_send(u8_t numdns, const char* name, u8_t id) dns_send(u8_t numdns, const char* name, u16_t txid)
{ {
err_t err; err_t err;
struct dns_hdr *hdr; struct dns_hdr *hdr;
@ -581,7 +636,7 @@ dns_send(u8_t numdns, const char* name, u8_t id)
/* fill dns header */ /* fill dns header */
hdr = (struct dns_hdr*)p->payload; hdr = (struct dns_hdr*)p->payload;
memset(hdr, 0, SIZEOF_DNS_HDR); memset(hdr, 0, SIZEOF_DNS_HDR);
hdr->id = htons(id); hdr->id = htons(txid);
hdr->flags1 = DNS_FLAG1_RD; hdr->flags1 = DNS_FLAG1_RD;
hdr->numquestions = PP_HTONS(1); hdr->numquestions = PP_HTONS(1);
query = (char*)hdr + SIZEOF_DNS_HDR; query = (char*)hdr + SIZEOF_DNS_HDR;
@ -615,6 +670,7 @@ dns_send(u8_t numdns, const char* name, u8_t id)
/* connect to the server for faster receiving */ /* connect to the server for faster receiving */
udp_connect(dns_pcb, &dns_servers[numdns], DNS_SERVER_PORT); udp_connect(dns_pcb, &dns_servers[numdns], DNS_SERVER_PORT);
/* send dns packet */ /* send dns packet */
LWIP_DEBUGF(DNS_DEBUG, ("sending DNS request ID %d for name \"%s\" to server %d\r\n", txid, name, numdns));
err = udp_sendto(dns_pcb, p, &dns_servers[numdns], DNS_SERVER_PORT); err = udp_sendto(dns_pcb, p, &dns_servers[numdns], DNS_SERVER_PORT);
/* free pbuf */ /* free pbuf */
@ -626,6 +682,61 @@ dns_send(u8_t numdns, const char* name, u8_t id)
return err; return err;
} }
/**
* dns_call_found() - call the found callback and check if there are duplicate
* entries for the given hostname. If there are any, their found callback will
* be called and they will be removed.
*
* @param pEntry entry that is resolved or removed
* @param addr IP address for the hostname (or NULL on error or memory shortage)
*/
static void
dns_call_found(struct dns_table_entry* pEntry, ip_addr_t* addr)
{
if (pEntry->found) {
(*pEntry->found)(pEntry->name, addr, pEntry->arg);
}
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
{
u8_t i;
for (i = 0; i < DNS_TABLE_SIZE; i++) {
if ((dns_table[i].state == DNS_STATE_DUPLICATE_PENDING) &&
(LWIP_DNS_STRICMP(dns_table[i].name, pEntry->name) == 0)) {
if (dns_table[i].found) {
(*dns_table[i].found)(dns_table[i].name, addr, dns_table[i].arg);
}
/* flush this entry */
dns_table[i].state = DNS_STATE_UNUSED;
dns_table[i].found = NULL;
}
}
}
#endif
}
/* Create a query transmission ID that is unique for all outstanding queries */
static u16_t
dns_create_txid(void)
{
u16_t txid;
u8_t i;
again:
txid = DNS_RAND_TXID();
/* check whether the ID is unique */
for (i = 0; i < DNS_TABLE_SIZE; i++) {
if ((dns_table[i].state == DNS_STATE_ASKING) &&
(dns_table[i].txid == txid)) {
/* ID already used by another pending query */
goto again;
}
}
return txid;
}
/** /**
* dns_check_entry() - see if pEntry has not yet been queried and, if so, sends out a query. * dns_check_entry() - see if pEntry has not yet been queried and, if so, sends out a query.
* Check an entry in the dns_table: * Check an entry in the dns_table:
@ -646,14 +757,17 @@ dns_check_entry(u8_t i)
switch(pEntry->state) { switch(pEntry->state) {
case DNS_STATE_NEW: { case DNS_STATE_NEW: {
u16_t txid;
/* initialize new entry */ /* initialize new entry */
txid = dns_create_txid();
pEntry->txid = txid;
pEntry->state = DNS_STATE_ASKING; pEntry->state = DNS_STATE_ASKING;
pEntry->numdns = 0; pEntry->numdns = 0;
pEntry->tmr = 1; pEntry->tmr = 1;
pEntry->retries = 0; pEntry->retries = 0;
/* send DNS packet for this entry */ /* send DNS packet for this entry */
err = dns_send(pEntry->numdns, pEntry->name, i); err = dns_send(pEntry->numdns, pEntry->name, txid);
if (err != ERR_OK) { if (err != ERR_OK) {
LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING, LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING,
("dns_send returned error: %s\n", lwip_strerr(err))); ("dns_send returned error: %s\n", lwip_strerr(err)));
@ -673,8 +787,7 @@ dns_check_entry(u8_t i)
} else { } else {
LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": timeout\n", pEntry->name)); LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": timeout\n", pEntry->name));
/* call specified callback function if provided */ /* call specified callback function if provided */
if (pEntry->found) dns_call_found(pEntry, NULL);
(*pEntry->found)(pEntry->name, NULL, pEntry->arg);
/* flush this entry */ /* flush this entry */
pEntry->state = DNS_STATE_UNUSED; pEntry->state = DNS_STATE_UNUSED;
pEntry->found = NULL; pEntry->found = NULL;
@ -686,7 +799,7 @@ dns_check_entry(u8_t i)
pEntry->tmr = pEntry->retries; pEntry->tmr = pEntry->retries;
/* send DNS packet for this entry */ /* send DNS packet for this entry */
err = dns_send(pEntry->numdns, pEntry->name, i); err = dns_send(pEntry->numdns, pEntry->name, pEntry->txid);
if (err != ERR_OK) { if (err != ERR_OK) {
LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING, LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING,
("dns_send returned error: %s\n", lwip_strerr(err))); ("dns_send returned error: %s\n", lwip_strerr(err)));
@ -694,12 +807,16 @@ dns_check_entry(u8_t i)
} }
break; break;
} }
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
case DNS_STATE_DUPLICATE_PENDING:
/* nothing to do */
break;
#endif
case DNS_STATE_DONE: { case DNS_STATE_DONE: {
/* if the time to live is nul */ /* if the time to live is nul */
if ((pEntry->ttl == 0) || (--pEntry->ttl == 0)) { if ((pEntry->ttl == 0) || (--pEntry->ttl == 0)) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": flush\n", pEntry->name)); LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": flush\n", pEntry->name));
/* flush this entry */ /* flush this entry, there cannot be any related pending entries in this state */
pEntry->state = DNS_STATE_UNUSED; pEntry->state = DNS_STATE_UNUSED;
pEntry->found = NULL; pEntry->found = NULL;
} }
@ -735,16 +852,17 @@ dns_check_entries(void)
static void static void
dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port) dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port)
{ {
u16_t i; u8_t i;
char *pHostname; u16_t txid;
char *ptr;
struct dns_hdr *hdr; struct dns_hdr *hdr;
struct dns_answer ans; struct dns_answer ans;
struct dns_table_entry *pEntry; struct dns_table_entry *pEntry;
struct dns_query qry;
u16_t nquestions, nanswers; u16_t nquestions, nanswers;
LWIP_UNUSED_ARG(arg); LWIP_UNUSED_ARG(arg);
LWIP_UNUSED_ARG(pcb); LWIP_UNUSED_ARG(pcb);
LWIP_UNUSED_ARG(addr);
LWIP_UNUSED_ARG(port); LWIP_UNUSED_ARG(port);
/* is the dns message too big ? */ /* is the dns message too big ? */
@ -761,14 +879,15 @@ dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t
goto memerr; goto memerr;
} }
/* copy dns payload inside static buffer for processing */ /* copy dns payload inside static buffer for processing */
if (pbuf_copy_partial(p, dns_payload, p->tot_len, 0) == p->tot_len) { 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. */ /* Match the ID in the DNS header with the name table. */
hdr = (struct dns_hdr*)dns_payload; hdr = (struct dns_hdr*)dns_payload;
i = htons(hdr->id); txid = htons(hdr->id);
if (i < DNS_TABLE_SIZE) { for (i = 0; i < DNS_TABLE_SIZE; i++) {
pEntry = &dns_table[i]; pEntry = &dns_table[i];
if(pEntry->state == DNS_STATE_ASKING) { if ((pEntry->state == DNS_STATE_ASKING) &&
(pEntry->txid == txid)) {
/* This entry is now completed. */ /* This entry is now completed. */
pEntry->state = DNS_STATE_DONE; pEntry->state = DNS_STATE_DONE;
pEntry->err = hdr->flags2 & DNS_FLAG2_ERR_MASK; pEntry->err = hdr->flags2 & DNS_FLAG2_ERR_MASK;
@ -785,24 +904,38 @@ dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t
goto responseerr; goto responseerr;
} }
#if DNS_DOES_NAME_CHECK /* Check whether response comes from the same network address to which the
/* Check if the name in the "question" part match with the name in the entry. */ question was sent. (RFC 5452) */
if (dns_compare_name((unsigned char *)(pEntry->name), (unsigned char *)dns_payload + SIZEOF_DNS_HDR) != 0) { if (!ip_addr_cmp(addr, &dns_servers[pEntry->numdns])) {
/* call callback to indicate error, clean up memory and return */
goto responseerr;
}
/* Check if the name in the "question" part match with the name in the entry and
skip it if equal. */
ptr = dns_compare_name(pEntry->name, (char*)dns_payload + SIZEOF_DNS_HDR);
if (ptr == NULL) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", pEntry->name)); LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", pEntry->name));
/* call callback to indicate error, clean up memory and return */ /* call callback to indicate error, clean up memory and return */
goto responseerr; goto responseerr;
} }
#endif /* DNS_DOES_NAME_CHECK */
/* Skip the name in the "question" part */ /* check if "question" part matches the request */
pHostname = (char *) dns_parse_name((unsigned char *)dns_payload + SIZEOF_DNS_HDR) + SIZEOF_DNS_QUERY; SMEMCPY(&qry, ptr, SIZEOF_DNS_QUERY);
if((qry.type != PP_HTONS(DNS_RRTYPE_A)) || (qry.cls != PP_HTONS(DNS_RRCLASS_IN))) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", pEntry->name));
/* call callback to indicate error, clean up memory and return */
goto responseerr;
}
/* skip the rest of the "question" part */
ptr += SIZEOF_DNS_QUERY;
while (nanswers > 0) { while (nanswers > 0) {
/* skip answer resource record's host name */ /* skip answer resource record's host name */
pHostname = (char *) dns_parse_name((unsigned char *)pHostname); ptr = dns_parse_name(ptr);
/* Check for IP address type and Internet class. Others are discarded. */ /* Check for IP address type and Internet class. Others are discarded. */
SMEMCPY(&ans, pHostname, SIZEOF_DNS_ANSWER); SMEMCPY(&ans, ptr, SIZEOF_DNS_ANSWER);
if((ans.type == PP_HTONS(DNS_RRTYPE_A)) && (ans.cls == PP_HTONS(DNS_RRCLASS_IN)) && if((ans.type == PP_HTONS(DNS_RRTYPE_A)) && (ans.cls == PP_HTONS(DNS_RRCLASS_IN)) &&
(ans.len == PP_HTONS(sizeof(ip_addr_t))) ) { (ans.len == PP_HTONS(sizeof(ip_addr_t))) ) {
/* read the answer resource record's TTL, and maximize it if needed */ /* read the answer resource record's TTL, and maximize it if needed */
@ -811,14 +944,12 @@ dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t
pEntry->ttl = DNS_MAX_TTL; pEntry->ttl = DNS_MAX_TTL;
} }
/* read the IP address after answer resource record's header */ /* read the IP address after answer resource record's header */
SMEMCPY(&(pEntry->ipaddr), (pHostname+SIZEOF_DNS_ANSWER), sizeof(ip_addr_t)); SMEMCPY(&(pEntry->ipaddr), (ptr + SIZEOF_DNS_ANSWER), sizeof(ip_addr_t));
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", pEntry->name)); LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", pEntry->name));
ip_addr_debug_print(DNS_DEBUG, (&(pEntry->ipaddr))); ip_addr_debug_print(DNS_DEBUG, (&(pEntry->ipaddr)));
LWIP_DEBUGF(DNS_DEBUG, ("\n")); LWIP_DEBUGF(DNS_DEBUG, ("\n"));
/* call specified callback function if provided */ /* call specified callback function if provided */
if (pEntry->found) { dns_call_found(pEntry, &pEntry->ipaddr);
(*pEntry->found)(pEntry->name, &pEntry->ipaddr, pEntry->arg);
}
if (pEntry->ttl == 0) { if (pEntry->ttl == 0) {
/* RFC 883, page 29: "Zero values are /* RFC 883, page 29: "Zero values are
interpreted to mean that the RR can only be used for the interpreted to mean that the RR can only be used for the
@ -829,7 +960,7 @@ dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t
/* deallocate memory and return */ /* deallocate memory and return */
goto memerr; goto memerr;
} else { } else {
pHostname = pHostname + SIZEOF_DNS_ANSWER + htons(ans.len); ptr = ptr + SIZEOF_DNS_ANSWER + htons(ans.len);
} }
--nanswers; --nanswers;
} }
@ -845,9 +976,7 @@ dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t
responseerr: responseerr:
/* ERROR: call specified callback function with NULL as name to indicate an error */ /* ERROR: call specified callback function with NULL as name to indicate an error */
if (pEntry->found) { dns_call_found(pEntry, NULL);
(*pEntry->found)(pEntry->name, NULL, pEntry->arg);
}
flushentry: flushentry:
/* flush this entry */ /* flush this entry */
pEntry->state = DNS_STATE_UNUSED; pEntry->state = DNS_STATE_UNUSED;
@ -878,13 +1007,14 @@ dns_enqueue(const char *name, size_t hostnamelen, dns_found_callback found,
size_t namelen; size_t namelen;
/* search an unused entry, or the oldest one */ /* search an unused entry, or the oldest one */
lseq = lseqi = 0; lseq = 0;
lseqi = DNS_TABLE_SIZE;
for (i = 0; i < DNS_TABLE_SIZE; ++i) { for (i = 0; i < DNS_TABLE_SIZE; ++i) {
pEntry = &dns_table[i]; pEntry = &dns_table[i];
/* is it an unused entry ? */ /* is it an unused entry ? */
if (pEntry->state == DNS_STATE_UNUSED) if (pEntry->state == DNS_STATE_UNUSED) {
break; break;
}
/* check if this is the oldest completed entry */ /* check if this is the oldest completed entry */
if (pEntry->state == DNS_STATE_DONE) { if (pEntry->state == DNS_STATE_DONE) {
if ((dns_seqno - pEntry->seqno) > lseq) { if ((dns_seqno - pEntry->seqno) > lseq) {
@ -912,13 +1042,33 @@ dns_enqueue(const char *name, size_t hostnamelen, dns_found_callback found,
/* fill the entry */ /* fill the entry */
pEntry->state = DNS_STATE_NEW; pEntry->state = DNS_STATE_NEW;
pEntry->seqno = dns_seqno++; pEntry->seqno = dns_seqno;
pEntry->found = found; pEntry->found = found;
pEntry->arg = callback_arg; pEntry->arg = callback_arg;
namelen = LWIP_MIN(hostnamelen, DNS_MAX_NAME_LENGTH-1); namelen = LWIP_MIN(hostnamelen, DNS_MAX_NAME_LENGTH-1);
MEMCPY(pEntry->name, name, namelen); MEMCPY(pEntry->name, name, namelen);
pEntry->name[namelen] = 0; pEntry->name[namelen] = 0;
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
/* check for duplicate entries */
{
u8_t n;
for (n = 0; n < DNS_TABLE_SIZE; n++) {
if ((dns_table[n].state == DNS_STATE_ASKING) &&
(LWIP_DNS_STRICMP(name, dns_table[n].name) == 0)) {
/* this is a duplicate entry */
struct dns_table_entry *orig = &dns_table[n];
pEntry->state = DNS_STATE_DUPLICATE_PENDING;
pEntry->seqno = orig->seqno;
/* don't send a query for this entry, only for the original */
return ERR_INPROGRESS;
}
}
}
/* no duplicate entries found */
#endif
dns_seqno++;
/* force to send query without waiting timer */ /* force to send query without waiting timer */
dns_check_entry(i); dns_check_entry(i);
@ -961,10 +1111,10 @@ dns_gethostbyname(const char *hostname, ip_addr_t *addr, dns_found_callback foun
if (hostnamelen >= DNS_MAX_NAME_LENGTH) { if (hostnamelen >= DNS_MAX_NAME_LENGTH) {
return ERR_ARG; return ERR_ARG;
} }
#if LWIP_HAVE_LOOPIF #if LWIP_HAVE_LOOPIF
if (strcmp(hostname, "localhost")==0) { if (strcmp(hostname, "localhost") == 0) {
ip_addr_set_loopback(addr); ip_addr_set_loopback(addr);
return ERR_OK; return ERR_OK;
} }