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lwip/src/core/dns.c
Axel Lin 668d461104 dns: Fix dns_alloc_pcb for reuse an existing one case 
The logic to use an already existing pcb is wrong because the idx never
advanced in the for loop, so it keep checking the same dns_pcbs[idx] for
each loop iteration. Fix it.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
2015-11-16 09:09:31 +01:00

1492 lines
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/**
* @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
* security fixes and more by Simon Goldschmidt
* 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 ERR_INPROGRESS 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).
*/
/*-----------------------------------------------------------------------------
* RFC 1035 - Domain names - implementation and specification
* RFC 2181 - Clarifications to the DNS Specification
*----------------------------------------------------------------------------*/
/** @todo: define good default values (rfc compliance) */
/** @todo: improve answer parsing, more checkings... */
/** @todo: check RFC1035 - 7.3. Processing responses */
/*-----------------------------------------------------------------------------
* 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/mem.h"
#include "lwip/memp.h"
#include "lwip/dns.h"
#include <string.h>
/** Random generator function to create random TXIDs and source ports 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
/** Limits the source port to be >= 1024 by default */
#ifndef DNS_PORT_ALLOWED
#define DNS_PORT_ALLOWED(port) ((port) >= 1024)
#endif
/** DNS server port address */
#ifndef DNS_SERVER_PORT
#define DNS_SERVER_PORT 53
#endif
/** DNS maximum number of retries when asking for a name, before "timeout". */
#ifndef DNS_MAX_RETRIES
#define DNS_MAX_RETRIES 4
#endif
/** DNS resource record max. TTL (one week as default) */
#ifndef DNS_MAX_TTL
#define DNS_MAX_TTL 604800
#endif
/* The number of parallel requests (i.e. calls to dns_gethostbyname
* that cannot be answered from the DNS table.
* This is set to the table size by default.
*/
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
#ifndef DNS_MAX_REQUESTS
#define DNS_MAX_REQUESTS DNS_TABLE_SIZE
#endif
#else
/* In this configuration, both arrays have to have the same size and are used
* like one entry (used/free) */
#define DNS_MAX_REQUESTS DNS_TABLE_SIZE
#endif
/* The number of UDP source ports used in parallel */
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
#ifndef DNS_MAX_SOURCE_PORTS
#define DNS_MAX_SOURCE_PORTS DNS_MAX_REQUESTS
#endif
#else
#ifdef DNS_MAX_SOURCE_PORTS
#undef DNS_MAX_SOURCE_PORTS
#endif
#define DNS_MAX_SOURCE_PORTS 1
#endif
#if LWIP_IPV4 && LWIP_IPV6
#define LWIP_DNS_ADDRTYPE_IS_IPV6(t) (((t) == LWIP_DNS_ADDRTYPE_IPV6_IPV4) || ((t) == LWIP_DNS_ADDRTYPE_IPV6))
#define LWIP_DNS_ADDRTYPE_MATCH_IP(t, ip) (IP_IS_V6_VAL(ip) ? LWIP_DNS_ADDRTYPE_IS_IPV6(t) : (!LWIP_DNS_ADDRTYPE_IS_IPV6(t)))
#define LWIP_DNS_ADDRTYPE_ARG(x) , x
#define LWIP_DNS_ADDRTYPE_ARG_OR_ZERO(x) x
#define LWIP_DNS_SET_ADDRTYPE(x, y) do { x = y; } while(0)
#else
#if LWIP_IPV6
#define LWIP_DNS_ADDRTYPE_IS_IPV6(t) 1
#else
#define LWIP_DNS_ADDRTYPE_IS_IPV6(t) 0
#endif
#define LWIP_DNS_ADDRTYPE_MATCH_IP(t, ip) 1
#define LWIP_DNS_ADDRTYPE_ARG(x)
#define LWIP_DNS_ADDRTYPE_ARG_OR_ZERO(x) 0
#define LWIP_DNS_SET_ADDRTYPE(x, y)
#endif /* LWIP_IPV4 && LWIP_IPV6 */
/** 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 */
#define DNS_RRTYPE_AAAA 28 /* IPv6 address */
/** 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 */
/* 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
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/bpstruct.h"
#endif
PACK_STRUCT_BEGIN
/** DNS message header */
struct dns_hdr {
PACK_STRUCT_FIELD(u16_t id);
PACK_STRUCT_FLD_8(u8_t flags1);
PACK_STRUCT_FLD_8(u8_t flags2);
PACK_STRUCT_FIELD(u16_t numquestions);
PACK_STRUCT_FIELD(u16_t numanswers);
PACK_STRUCT_FIELD(u16_t numauthrr);
PACK_STRUCT_FIELD(u16_t numextrarr);
} PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/epstruct.h"
#endif
#define SIZEOF_DNS_HDR 12
/** DNS query message structure.
No packing needed: only used locally on the stack. */
struct dns_query {
/* DNS query record starts with either a domain name or a pointer
to a name already present somewhere in the packet. */
u16_t type;
u16_t cls;
};
#define SIZEOF_DNS_QUERY 4
/** DNS answer message structure.
No packing needed: only used locally on the stack. */
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 cls;
u32_t ttl;
u16_t len;
};
#define SIZEOF_DNS_ANSWER 10
/* maximum allowed size for the struct due to non-packed */
#define SIZEOF_DNS_ANSWER_ASSERT 12
/** DNS table entry */
struct dns_table_entry {
u32_t ttl;
ip_addr_t ipaddr;
u16_t txid;
u8_t state;
u8_t server_idx;
u8_t tmr;
u8_t retries;
u8_t seqno;
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
u8_t pcb_idx;
#endif
char name[DNS_MAX_NAME_LENGTH];
#if LWIP_IPV4 && LWIP_IPV6
u8_t reqaddrtype;
#endif /* LWIP_IPV4 && LWIP_IPV6 */
};
/** DNS request table entry: used when dns_gehostbyname cannot answer the
* request from the DNS table */
struct dns_req_entry {
/* pointer to callback on DNS query done */
dns_found_callback found;
/* argument passed to the callback function */
void *arg;
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
u8_t dns_table_idx;
#endif
#if LWIP_IPV4 && LWIP_IPV6
u8_t reqaddrtype;
#endif /* LWIP_IPV4 && LWIP_IPV6 */
};
#if DNS_LOCAL_HOSTLIST
#if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
/** Local host-list. For hostnames in this list, no
* external name resolution is performed */
static struct local_hostlist_entry *local_hostlist_dynamic;
#else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
/** Defining this allows the local_hostlist_static to be placed in a different
* linker section (e.g. FLASH) */
#ifndef DNS_LOCAL_HOSTLIST_STORAGE_PRE
#define DNS_LOCAL_HOSTLIST_STORAGE_PRE static
#endif /* DNS_LOCAL_HOSTLIST_STORAGE_PRE */
/** Defining this allows the local_hostlist_static to be placed in a different
* linker section (e.g. FLASH) */
#ifndef DNS_LOCAL_HOSTLIST_STORAGE_POST
#define DNS_LOCAL_HOSTLIST_STORAGE_POST
#endif /* DNS_LOCAL_HOSTLIST_STORAGE_POST */
DNS_LOCAL_HOSTLIST_STORAGE_PRE struct local_hostlist_entry local_hostlist_static[]
DNS_LOCAL_HOSTLIST_STORAGE_POST = DNS_LOCAL_HOSTLIST_INIT;
#endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
static void dns_init_local(void);
#endif /* DNS_LOCAL_HOSTLIST */
/* forward declarations */
static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port);
static void dns_check_entries(void);
static void dns_call_found(u8_t idx, ip_addr_t* addr);
/*-----------------------------------------------------------------------------
* Globals
*----------------------------------------------------------------------------*/
/* DNS variables */
static struct udp_pcb *dns_pcbs[DNS_MAX_SOURCE_PORTS];
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
static u8_t dns_last_pcb_idx;
#endif
static u8_t dns_seqno;
static struct dns_table_entry dns_table[DNS_TABLE_SIZE];
static struct dns_req_entry dns_requests[DNS_MAX_REQUESTS];
static ip_addr_t dns_servers[DNS_MAX_SERVERS];
#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
* (if DNS_SERVER_ADDRESS is set).
*/
void
dns_init(void)
{
#ifdef DNS_SERVER_ADDRESS
/* initialize default DNS server address */
ip_addr_t dnsserver;
DNS_SERVER_ADDRESS(&dnsserver);
dns_setserver(0, &dnsserver);
#endif /* DNS_SERVER_ADDRESS */
LWIP_ASSERT("sanity check SIZEOF_DNS_QUERY",
sizeof(struct dns_query) == SIZEOF_DNS_QUERY);
LWIP_ASSERT("sanity check SIZEOF_DNS_ANSWER",
sizeof(struct dns_answer) <= SIZEOF_DNS_ANSWER_ASSERT);
LWIP_DEBUGF(DNS_DEBUG, ("dns_init: initializing\n"));
/* if dns client not yet initialized... */
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) == 0)
if (dns_pcbs[0] == NULL) {
dns_pcbs[0] = udp_new();
LWIP_ASSERT("dns_pcbs[0] != NULL", dns_pcbs[0] != NULL);
/* initialize DNS table not needed (initialized to zero since it is a
* global variable) */
LWIP_ASSERT("For implicit initialization to work, DNS_STATE_UNUSED needs to be 0",
DNS_STATE_UNUSED == 0);
/* initialize DNS client */
udp_bind(dns_pcbs[0], IP_ADDR_ANY, 0);
udp_recv(dns_pcbs[0], dns_recv, NULL);
}
#endif
#if DNS_LOCAL_HOSTLIST
dns_init_local();
#endif
}
/**
* Initialize one of the DNS servers.
*
* @param numdns the index of the DNS server to set must be < DNS_MAX_SERVERS
* @param dnsserver IP address of the DNS server to set
*/
void
dns_setserver(u8_t numdns, const ip_addr_t *dnsserver)
{
if (numdns < DNS_MAX_SERVERS) {
if (dnsserver != NULL) {
dns_servers[numdns] = (*dnsserver);
} else {
dns_servers[numdns] = *IP_ADDR_ANY;
}
}
}
/**
* Obtain one of the currently configured DNS server.
*
* @param numdns the index of the DNS server
* @return IP address of the indexed DNS server or "ip_addr_any" if the DNS
* server has not been configured.
*/
ip_addr_t
dns_getserver(u8_t numdns)
{
if (numdns < DNS_MAX_SERVERS) {
return dns_servers[numdns];
} else {
return *IP_ADDR_ANY;
}
}
/**
* The DNS resolver client timer - handle retries and timeouts and should
* be called every DNS_TMR_INTERVAL milliseconds (every second by default).
*/
void
dns_tmr(void)
{
LWIP_DEBUGF(DNS_DEBUG, ("dns_tmr: dns_check_entries\n"));
dns_check_entries();
}
#if DNS_LOCAL_HOSTLIST
static void
dns_init_local(void)
{
#if DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT)
size_t i;
struct local_hostlist_entry *entry;
/* Dynamic: copy entries from DNS_LOCAL_HOSTLIST_INIT to list */
struct local_hostlist_entry local_hostlist_init[] = DNS_LOCAL_HOSTLIST_INIT;
size_t namelen;
for (i = 0; i < sizeof(local_hostlist_init) / sizeof(struct local_hostlist_entry); i++) {
struct local_hostlist_entry *init_entry = &local_hostlist_init[i];
LWIP_ASSERT("invalid host name (NULL)", init_entry->name != NULL);
namelen = strlen(init_entry->name);
LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN);
entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST);
LWIP_ASSERT("mem-error in dns_init_local", entry != NULL);
if (entry != NULL) {
char* entry_name = (char*)entry + sizeof(struct local_hostlist_entry);
MEMCPY(entry_name, init_entry->name, namelen);
entry_name[namelen] = 0;
entry->name = entry_name;
entry->addr = init_entry->addr;
entry->next = local_hostlist_dynamic;
local_hostlist_dynamic = entry;
}
}
#endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT) */
}
/**
* Scans the local host-list for a hostname.
*
* @param hostname Hostname to look for in the local host-list
* @param addr the first IP address for the hostname in the local host-list or
* IPADDR_NONE if not found.
* @return ERR_OK if found, ERR_ARG if not found
*/
static err_t
dns_lookup_local(const char *hostname, ip_addr_t *addr LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype))
{
#if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
struct local_hostlist_entry *entry = local_hostlist_dynamic;
while (entry != NULL) {
if ((LWIP_DNS_STRICMP(entry->name, hostname) == 0) &&
LWIP_DNS_ADDRTYPE_MATCH_IP(dns_addrtype, entry->addr)) {
if (addr) {
ip_addr_copy(*addr, entry->addr);
}
return ERR_OK;
}
entry = entry->next;
}
#else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
size_t i;
for (i = 0; i < sizeof(local_hostlist_static) / sizeof(struct local_hostlist_entry); i++) {
if ((LWIP_DNS_STRICMP(local_hostlist_static[i].name, hostname) == 0) &&
LWIP_DNS_ADDRTYPE_MATCH_IP(dns_addrtype, local_hostlist_static[i].addr)) {
if (addr) {
ip_addr_copy(*addr, local_hostlist_static[i].addr);
}
return ERR_OK;
}
}
#endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
return ERR_ARG;
}
#if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
/** Remove all entries from the local host-list for a specific hostname
* and/or IP address
*
* @param hostname hostname for which entries shall be removed from the local
* host-list
* @param addr address for which entries shall be removed from the local host-list
* @return the number of removed entries
*/
int
dns_local_removehost(const char *hostname, const ip_addr_t *addr)
{
int removed = 0;
struct local_hostlist_entry *entry = local_hostlist_dynamic;
struct local_hostlist_entry *last_entry = NULL;
while (entry != NULL) {
if (((hostname == NULL) || !LWIP_DNS_STRICMP(entry->name, hostname)) &&
((addr == NULL) || ip_addr_cmp(&entry->addr, addr))) {
struct local_hostlist_entry *free_entry;
if (last_entry != NULL) {
last_entry->next = entry->next;
} else {
local_hostlist_dynamic = entry->next;
}
free_entry = entry;
entry = entry->next;
memp_free(MEMP_LOCALHOSTLIST, free_entry);
removed++;
} else {
last_entry = entry;
entry = entry->next;
}
}
return removed;
}
/**
* Add a hostname/IP address pair to the local host-list.
* Duplicates are not checked.
*
* @param hostname hostname of the new entry
* @param addr IP address of the new entry
* @return ERR_OK if succeeded or ERR_MEM on memory error
*/
err_t
dns_local_addhost(const char *hostname, const ip_addr_t *addr)
{
struct local_hostlist_entry *entry;
size_t namelen;
char* entry_name;
LWIP_ASSERT("invalid host name (NULL)", hostname != NULL);
namelen = strlen(hostname);
LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN);
entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST);
if (entry == NULL) {
return ERR_MEM;
}
entry_name = (char*)entry + sizeof(struct local_hostlist_entry);
MEMCPY(entry_name, hostname, namelen);
entry_name[namelen] = 0;
entry->name = entry_name;
ip_addr_copy(entry->addr, *addr);
entry->next = local_hostlist_dynamic;
local_hostlist_dynamic = entry;
return ERR_OK;
}
#endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC*/
#endif /* DNS_LOCAL_HOSTLIST */
/**
* 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_enqueue() can be used to send a query
* for a hostname.
*
* @param name the hostname to look up
* @param addr the hostname's IP address, as u32_t (instead of ip_addr_t to
* better check for failure: != IPADDR_NONE) or IPADDR_NONE if the hostname
* was not found in the cached dns_table.
* @return ERR_OK if found, ERR_ARG if not found
*/
static err_t
dns_lookup(const char *name, ip_addr_t *addr LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype))
{
u8_t i;
#if DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN)
#endif /* DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN) */
#if DNS_LOCAL_HOSTLIST
if (dns_lookup_local(name, addr LWIP_DNS_ADDRTYPE_ARG(dns_addrtype)) == ERR_OK) {
return ERR_OK;
}
#endif /* DNS_LOCAL_HOSTLIST */
#ifdef DNS_LOOKUP_LOCAL_EXTERN
if (DNS_LOOKUP_LOCAL_EXTERN(name, addr, LWIP_DNS_ADDRTYPE_ARG_OR_ZERO(dns_addrtype))) {
return ERR_OK;
}
#endif /* DNS_LOOKUP_LOCAL_EXTERN */
/* 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) &&
(LWIP_DNS_STRICMP(name, dns_table[i].name) == 0) &&
LWIP_DNS_ADDRTYPE_MATCH_IP(dns_addrtype, dns_table[i].ipaddr)) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_lookup: \"%s\": found = ", name));
ip_addr_debug_print(DNS_DEBUG, &(dns_table[i].ipaddr));
LWIP_DEBUGF(DNS_DEBUG, ("\n"));
if (addr) {
ip_addr_copy(*addr, dns_table[i].ipaddr);
}
return ERR_OK;
}
}
return ERR_ARG;
}
/**
* Compare the "dotted" name "query" with the encoded name "response"
* to make sure an answer from the DNS server matches the current dns_table
* entry (otherwise, answers might arrive late for hostname not on the list
* any more).
*
* @param query hostname (not encoded) from the dns_table
* @param p pbuf containing the encoded hostname in the DNS response
* @param start_offset offset into p where the name starts
* @return 0xFFFF: names differ, other: names equal -> offset behind name
*/
static u16_t
dns_compare_name(char *query, struct pbuf* p, u16_t start_offset)
{
unsigned char n;
u16_t response_offset = start_offset;
do {
n = pbuf_get_at(p, response_offset++);
/** @see RFC 1035 - 4.1.4. Message compression */
if ((n & 0xc0) == 0xc0) {
/* Compressed name: cannot be equal since we don't send them */
return 0xFFFF;
} else {
/* Not compressed name */
while (n > 0) {
if ((*query) != pbuf_get_at(p, response_offset)) {
return 0xFFFF;
}
++response_offset;
++query;
--n;
}
++query;
}
} while (pbuf_get_at(p, response_offset) != 0);
return response_offset + 1;
}
/**
* Walk through a compact encoded DNS name and return the end of the name.
*
* @param p pbuf containing the name
* @param query_idx start index into p pointing to encoded DNS name in the DNS server response
* @return index to end of the name
*/
static u16_t
dns_parse_name(struct pbuf* p, u16_t query_idx)
{
unsigned char n;
do {
n = pbuf_get_at(p, query_idx++);
/** @see RFC 1035 - 4.1.4. Message compression */
if ((n & 0xc0) == 0xc0) {
/* Compressed name */
break;
} else {
/* Not compressed name */
while (n > 0) {
++query_idx;
--n;
}
}
} while (pbuf_get_at(p, query_idx) != 0);
return query_idx + 1;
}
/**
* Send a DNS query packet.
*
* @param idx the DNS table entry index for which to send a request
* @return ERR_OK if packet is sent; an err_t indicating the problem otherwise
*/
static err_t
dns_send(u8_t idx)
{
err_t err;
struct dns_hdr hdr;
struct dns_query qry;
struct pbuf *p;
u16_t query_idx, copy_len;
const char *hostname, *hostname_part;
u8_t n;
u8_t pcb_idx;
struct dns_table_entry* entry = &dns_table[idx];
LWIP_DEBUGF(DNS_DEBUG, ("dns_send: dns_servers[%"U16_F"] \"%s\": request\n",
(u16_t)(entry->server_idx), entry->name));
LWIP_ASSERT("dns server out of array", entry->server_idx < DNS_MAX_SERVERS);
if (ip_addr_isany_val(dns_servers[entry->server_idx])) {
/* DNS server not valid anymore, e.g. PPP netif has been shut down */
/* call specified callback function if provided */
dns_call_found(idx, NULL);
/* flush this entry */
entry->state = DNS_STATE_UNUSED;
return ERR_OK;
}
/* if here, we have either a new query or a retry on a previous query to process */
p = pbuf_alloc(PBUF_TRANSPORT, (u16_t)(SIZEOF_DNS_HDR + strlen(entry->name) + 2 +
SIZEOF_DNS_QUERY), PBUF_RAM);
if (p != NULL) {
/* fill dns header */
memset(&hdr, 0, SIZEOF_DNS_HDR);
hdr.id = htons(entry->txid);
hdr.flags1 = DNS_FLAG1_RD;
hdr.numquestions = PP_HTONS(1);
pbuf_take(p, &hdr, SIZEOF_DNS_HDR);
hostname = entry->name;
--hostname;
/* convert hostname into suitable query format. */
query_idx = SIZEOF_DNS_HDR;
do {
++hostname;
hostname_part = hostname;
for (n = 0; *hostname != '.' && *hostname != 0; ++hostname) {
++n;
}
copy_len = (u16_t)(hostname - hostname_part);
pbuf_put_at(p, query_idx, n);
pbuf_take_at(p, hostname_part, copy_len, query_idx + 1);
query_idx += n + 1;
} while (*hostname != 0);
pbuf_put_at(p, query_idx, 0);
query_idx++;
/* fill dns query */
if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype)) {
qry.type = PP_HTONS(DNS_RRTYPE_AAAA);
} else {
qry.type = PP_HTONS(DNS_RRTYPE_A);
}
qry.cls = PP_HTONS(DNS_RRCLASS_IN);
pbuf_take_at(p, &qry, SIZEOF_DNS_QUERY, query_idx);
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
pcb_idx = entry->pcb_idx;
#else
pcb_idx = 0;
#endif
/* send dns packet */
LWIP_DEBUGF(DNS_DEBUG, ("sending DNS request ID %d for name \"%s\" to server %d\r\n",
entry->txid, entry->name, entry->server_idx));
err = udp_sendto(dns_pcbs[pcb_idx], p, &dns_servers[entry->server_idx], DNS_SERVER_PORT);
/* free pbuf */
pbuf_free(p);
} else {
err = ERR_MEM;
}
return err;
}
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
static struct udp_pcb*
dns_alloc_random_port(void)
{
err_t err;
struct udp_pcb* ret;
ret = udp_new();
if (ret == NULL) {
/* out of memory, have to reuse an existing pcb */
return NULL;
}
do {
u16_t port = (u16_t)DNS_RAND_TXID();
if (!DNS_PORT_ALLOWED(port)) {
/* this port is not allowed, try again */
err = ERR_USE;
continue;
}
err = udp_bind(ret, IP_ADDR_ANY, port);
} while (err == ERR_USE);
if ((err != ERR_OK) && (err != ERR_USE)) {
udp_remove(ret);
return NULL;
}
udp_recv(ret, dns_recv, NULL);
return ret;
}
/**
* dns_alloc_pcb() - allocates a new pcb (or reuses an existing one) to be used
* for sending a request
*
* @return an index into dns_pcbs
*/
static u8_t
dns_alloc_pcb(void)
{
u8_t i;
u8_t idx;
for (i = 0; i < DNS_MAX_SOURCE_PORTS; i++) {
if (dns_pcbs[i] == NULL) {
break;
}
}
if (i < DNS_MAX_SOURCE_PORTS) {
dns_pcbs[i] = dns_alloc_random_port();
if (dns_pcbs[i] != NULL) {
/* succeeded */
dns_last_pcb_idx = i;
return i;
}
}
/* if we come here, creating a new UDP pcb failed, so we have to use
an already existing one */
for (i = 0, idx = dns_last_pcb_idx + 1; i < DNS_MAX_SOURCE_PORTS; i++, idx++) {
if (idx >= DNS_MAX_SOURCE_PORTS) {
idx = 0;
}
if (dns_pcbs[idx] != NULL) {
dns_last_pcb_idx = idx;
return idx;
}
}
return DNS_MAX_SOURCE_PORTS;
}
#endif /* ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0) */
/**
* 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 idx dns table index of the 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(u8_t idx, ip_addr_t* addr)
{
#if ((LWIP_DNS_SECURE & (LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING | LWIP_DNS_SECURE_RAND_SRC_PORT)) != 0)
u8_t i;
#endif
#if LWIP_IPV4 && LWIP_IPV6
if (addr != NULL) {
/* check that address type matches the request and adapt the table entry */
if (IP_IS_V6_VAL(*addr)) {
LWIP_ASSERT("invalid response", LWIP_DNS_ADDRTYPE_IS_IPV6(dns_table[idx].reqaddrtype));
dns_table[idx].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV6;
} else {
LWIP_ASSERT("invalid response", !LWIP_DNS_ADDRTYPE_IS_IPV6(dns_table[idx].reqaddrtype));
dns_table[idx].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV4;
}
}
#endif /* LWIP_IPV4 && LWIP_IPV6 */
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
for (i = 0; i < DNS_MAX_REQUESTS; i++) {
if (dns_requests[i].found && (dns_requests[i].dns_table_idx == idx)) {
(*dns_requests[i].found)(dns_table[idx].name, addr, dns_requests[i].arg);
/* flush this entry */
dns_requests[i].found = NULL;
}
}
#else
if (dns_requests[idx].found) {
(*dns_requests[idx].found)(dns_table[idx].name, addr, dns_requests[idx].arg);
}
dns_requests[idx].found = NULL;
#endif
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
/* close the pcb used unless other request are using it */
for (i = 0; i < DNS_MAX_REQUESTS; i++) {
if (i == idx) {
continue; /* only check other requests */
}
if (dns_table[i].state == DNS_STATE_ASKING) {
if (dns_table[i].pcb_idx == dns_table[idx].pcb_idx) {
/* another request is still using the same pcb */
dns_table[idx].pcb_idx = DNS_MAX_SOURCE_PORTS;
break;
}
}
}
if (dns_table[idx].pcb_idx < DNS_MAX_SOURCE_PORTS) {
/* if we come here, the pcb is not used any more and can be removed */
udp_remove(dns_pcbs[dns_table[idx].pcb_idx]);
dns_pcbs[dns_table[idx].pcb_idx] = NULL;
dns_table[idx].pcb_idx = DNS_MAX_SOURCE_PORTS;
}
#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 = (u16_t)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 entry has not yet been queried and, if so, sends out a query.
* Check an entry in the dns_table:
* - send out query for new entries
* - retry old pending entries on timeout (also with different servers)
* - remove completed entries from the table if their TTL has expired
*
* @param i index of the dns_table entry to check
*/
static void
dns_check_entry(u8_t i)
{
err_t err;
struct dns_table_entry *entry = &dns_table[i];
LWIP_ASSERT("array index out of bounds", i < DNS_TABLE_SIZE);
switch (entry->state) {
case DNS_STATE_NEW: {
u16_t txid;
/* initialize new entry */
txid = dns_create_txid();
entry->txid = txid;
entry->state = DNS_STATE_ASKING;
entry->server_idx = 0;
entry->tmr = 1;
entry->retries = 0;
/* send DNS packet for this entry */
err = dns_send(i);
if (err != ERR_OK) {
LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING,
("dns_send returned error: %s\n", lwip_strerr(err)));
}
break;
}
case DNS_STATE_ASKING:
if (--entry->tmr == 0) {
if (++entry->retries == DNS_MAX_RETRIES) {
if ((entry->server_idx + 1 < DNS_MAX_SERVERS) && !ip_addr_isany_val(dns_servers[entry->server_idx + 1])) {
/* change of server */
entry->server_idx++;
entry->tmr = 1;
entry->retries = 0;
} else {
LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": timeout\n", entry->name));
/* call specified callback function if provided */
dns_call_found(i, NULL);
/* flush this entry */
entry->state = DNS_STATE_UNUSED;
break;
}
} else {
/* wait longer for the next retry */
entry->tmr = entry->retries;
}
/* send DNS packet for this entry */
err = dns_send(i);
if (err != ERR_OK) {
LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING,
("dns_send returned error: %s\n", lwip_strerr(err)));
}
}
break;
case DNS_STATE_DONE:
/* if the time to live is nul */
if ((entry->ttl == 0) || (--entry->ttl == 0)) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": flush\n", entry->name));
/* flush this entry, there cannot be any related pending entries in this state */
entry->state = DNS_STATE_UNUSED;
}
break;
case DNS_STATE_UNUSED:
/* nothing to do */
break;
default:
LWIP_ASSERT("unknown dns_table entry state:", 0);
break;
}
}
/**
* Call dns_check_entry for each entry in dns_table - check all entries.
*/
static void
dns_check_entries(void)
{
u8_t i;
for (i = 0; i < DNS_TABLE_SIZE; ++i) {
dns_check_entry(i);
}
}
/**
* Receive input function for DNS response packets arriving for the dns UDP pcb.
*
* @params see udp.h
*/
static void
dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port)
{
u8_t i, entry_idx = DNS_TABLE_SIZE;
u16_t txid;
u16_t res_idx;
struct dns_hdr hdr;
struct dns_answer ans;
struct dns_query qry;
u16_t nquestions, nanswers;
LWIP_UNUSED_ARG(arg);
LWIP_UNUSED_ARG(pcb);
LWIP_UNUSED_ARG(port);
/* is the dns message big enough ? */
if (p->tot_len < (SIZEOF_DNS_HDR + SIZEOF_DNS_QUERY)) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too small\n"));
/* free pbuf and return */
goto memerr;
}
/* copy dns payload inside static buffer for processing */
if (pbuf_copy_partial(p, &hdr, SIZEOF_DNS_HDR, 0) == SIZEOF_DNS_HDR) {
/* Match the ID in the DNS header with the name table. */
txid = htons(hdr.id);
for (i = 0; i < DNS_TABLE_SIZE; i++) {
struct dns_table_entry *entry = &dns_table[i];
entry_idx = i;
if ((entry->state == DNS_STATE_ASKING) &&
(entry->txid == txid)) {
u8_t dns_err;
/* This entry is now completed. */
entry->state = DNS_STATE_DONE;
dns_err = hdr.flags2 & DNS_FLAG2_ERR_MASK;
/* 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);
/* Check for error. If so, call callback to inform. */
if (((hdr.flags1 & DNS_FLAG1_RESPONSE) == 0) || (dns_err != 0) || (nquestions != 1)) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", entry->name));
/* call callback to indicate error, clean up memory and return */
goto responseerr;
}
/* Check whether response comes from the same network address to which the
question was sent. (RFC 5452) */
if (!ip_addr_cmp(addr, &dns_servers[entry->server_idx])) {
/* 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. */
res_idx = dns_compare_name(entry->name, p, SIZEOF_DNS_HDR);
if (res_idx == 0xFFFF) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
/* call callback to indicate error, clean up memory and return */
goto responseerr;
}
/* check if "question" part matches the request */
pbuf_copy_partial(p, &qry, SIZEOF_DNS_QUERY, res_idx);
if ((qry.cls != PP_HTONS(DNS_RRCLASS_IN)) ||
(LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype) && (qry.type != PP_HTONS(DNS_RRTYPE_AAAA))) ||
(!LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype) && (qry.type != PP_HTONS(DNS_RRTYPE_A)))) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
/* call callback to indicate error, clean up memory and return */
goto responseerr;
}
/* skip the rest of the "question" part */
res_idx += SIZEOF_DNS_QUERY;
while (nanswers > 0) {
/* skip answer resource record's host name */
res_idx = dns_parse_name(p, res_idx);
/* Check for IP address type and Internet class. Others are discarded. */
pbuf_copy_partial(p, &ans, SIZEOF_DNS_ANSWER, res_idx);
if (ans.cls == PP_HTONS(DNS_RRCLASS_IN)) {
#if LWIP_IPV4
if ((ans.type == PP_HTONS(DNS_RRTYPE_A)) && (ans.len == PP_HTONS(sizeof(ip4_addr_t)))) {
#if LWIP_IPV4 && LWIP_IPV6
if (!LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype))
#endif /* LWIP_IPV4 && LWIP_IPV6 */
{
ip4_addr_t ip4addr;
res_idx += SIZEOF_DNS_ANSWER;
/* read the answer resource record's TTL, and maximize it if needed */
entry->ttl = ntohl(ans.ttl);
if (entry->ttl > DNS_MAX_TTL) {
entry->ttl = DNS_MAX_TTL;
}
/* read the IP address after answer resource record's header */
pbuf_copy_partial(p, &ip4addr, sizeof(ip4_addr_t), res_idx);
ip_addr_copy_from_ip4(entry->ipaddr, ip4addr);
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", entry->name));
ip_addr_debug_print(DNS_DEBUG, (&(entry->ipaddr)));
LWIP_DEBUGF(DNS_DEBUG, ("\n"));
/* call specified callback function if provided */
dns_call_found(entry_idx, &entry->ipaddr);
if (entry->ttl == 0) {
/* RFC 883, page 29: "Zero values are
interpreted to mean that the RR can only be used for the
transaction in progress, and should not be cached."
-> flush this entry now */
goto flushentry;
}
/* deallocate memory and return */
goto memerr;
}
}
#endif /* LWIP_IPV4 */
#if LWIP_IPV6
if ((ans.type == PP_HTONS(DNS_RRTYPE_AAAA)) && (ans.len == PP_HTONS(sizeof(ip6_addr_t)))) {
#if LWIP_IPV4 && LWIP_IPV6
if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype))
#endif /* LWIP_IPV4 && LWIP_IPV6 */
{
ip6_addr_t ip6addr;
res_idx += SIZEOF_DNS_ANSWER;
/* read the answer resource record's TTL, and maximize it if needed */
entry->ttl = ntohl(ans.ttl);
if (entry->ttl > DNS_MAX_TTL) {
entry->ttl = DNS_MAX_TTL;
}
/* read the IP address after answer resource record's header */
pbuf_copy_partial(p, &ip6addr, sizeof(ip6_addr_t), res_idx);
ip_addr_copy_from_ip6(entry->ipaddr, ip6addr);
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", entry->name));
ip_addr_debug_print(DNS_DEBUG, (&(entry->ipaddr)));
LWIP_DEBUGF(DNS_DEBUG, (" AAAA\n"));
/* call specified callback function if provided */
dns_call_found(entry_idx, &entry->ipaddr);
if (entry->ttl == 0) {
/* RFC 883, page 29: "Zero values are
interpreted to mean that the RR can only be used for the
transaction in progress, and should not be cached."
-> flush this entry now */
goto flushentry;
}
/* deallocate memory and return */
goto memerr;
}
}
#endif /* LWIP_IPV6 */
}
/* skip this answer */
res_idx += SIZEOF_DNS_ANSWER + htons(ans.len);
--nanswers;
}
#if LWIP_IPV4 && LWIP_IPV6
if ((entry->reqaddrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) ||
(entry->reqaddrtype == LWIP_DNS_ADDRTYPE_IPV6_IPV4)) {
if (entry->reqaddrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) {
/* IPv4 failed, try IPv6 */
entry->reqaddrtype = LWIP_DNS_ADDRTYPE_IPV6;
} else {
/* IPv6 failed, try IPv4 */
entry->reqaddrtype = LWIP_DNS_ADDRTYPE_IPV4;
}
pbuf_free(p);
entry->state = DNS_STATE_NEW;
dns_check_entry(entry_idx);
return;
}
#endif /* LWIP_IPV4 && LWIP_IPV6 */
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in response\n", entry->name));
/* call callback to indicate error, clean up memory and return */
goto responseerr;
}
}
}
/* deallocate memory and return */
goto memerr;
responseerr:
/* ERROR: call specified callback function with NULL as name to indicate an error */
dns_call_found(entry_idx, NULL);
flushentry:
/* flush this entry */
dns_table[entry_idx].state = DNS_STATE_UNUSED;
memerr:
/* free pbuf */
pbuf_free(p);
return;
}
/**
* Queues a new hostname to resolve and sends out a DNS query for that hostname
*
* @param name the hostname that is to be queried
* @param hostnamelen length of the hostname
* @param found a callback function to be called on success, failure or timeout
* @param callback_arg argument to pass to the callback function
* @return @return a err_t return code.
*/
static err_t
dns_enqueue(const char *name, size_t hostnamelen, dns_found_callback found,
void *callback_arg LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype))
{
u8_t i;
u8_t lseq, lseqi;
struct dns_table_entry *entry = NULL;
size_t namelen;
struct dns_req_entry* req;
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
u8_t r;
/* check for duplicate entries */
for (i = 0; i < DNS_TABLE_SIZE; i++) {
if ((dns_table[i].state == DNS_STATE_ASKING) &&
(LWIP_DNS_STRICMP(name, dns_table[i].name) == 0)) {
#if LWIP_IPV4 && LWIP_IPV6
if (dns_table[i].reqaddrtype != dns_addrtype) {
/* requested address types don't match
this can lead to 2 concurrent requests, but mixing the address types
for the same host should not be that common */
continue;
}
#endif /* LWIP_IPV4 && LWIP_IPV6 */
/* this is a duplicate entry, find a free request entry */
for (r = 0; r < DNS_MAX_REQUESTS; r++) {
if (dns_requests[r].found == 0) {
dns_requests[r].found = found;
dns_requests[r].arg = callback_arg;
dns_requests[r].dns_table_idx = i;
LWIP_DNS_SET_ADDRTYPE(dns_requests[r].reqaddrtype, dns_addrtype);
LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": duplicate request\n", name));
return ERR_INPROGRESS;
}
}
}
}
/* no duplicate entries found */
#endif
/* search an unused entry, or the oldest one */
lseq = 0;
lseqi = DNS_TABLE_SIZE;
for (i = 0; i < DNS_TABLE_SIZE; ++i) {
entry = &dns_table[i];
/* is it an unused entry ? */
if (entry->state == DNS_STATE_UNUSED) {
break;
}
/* check if this is the oldest completed entry */
if (entry->state == DNS_STATE_DONE) {
if ((u8_t)(dns_seqno - entry->seqno) > lseq) {
lseq = dns_seqno - entry->seqno;
lseqi = i;
}
}
}
/* if we don't have found an unused entry, use the oldest completed one */
if (i == DNS_TABLE_SIZE) {
if ((lseqi >= DNS_TABLE_SIZE) || (dns_table[lseqi].state != DNS_STATE_DONE)) {
/* no entry can be used now, table is full */
LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS entries table is full\n", name));
return ERR_MEM;
} else {
/* use the oldest completed one */
i = lseqi;
entry = &dns_table[i];
}
}
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
/* find a free request entry */
req = NULL;
for (r = 0; r < DNS_MAX_REQUESTS; r++) {
if (dns_requests[r].found == NULL) {
req = &dns_requests[r];
break;
}
}
if (req == NULL) {
/* no request entry can be used now, table is full */
LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS request entries table is full\n", name));
return ERR_MEM;
}
req->dns_table_idx = i;
#else
/* in this configuration, the entry index is the same as the request index */
req = &dns_requests[i];
#endif
/* use this entry */
LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS entry %"U16_F"\n", name, (u16_t)(i)));
/* fill the entry */
entry->state = DNS_STATE_NEW;
entry->seqno = dns_seqno;
LWIP_DNS_SET_ADDRTYPE(entry->reqaddrtype, dns_addrtype);
LWIP_DNS_SET_ADDRTYPE(req->reqaddrtype, dns_addrtype);
req->found = found;
req->arg = callback_arg;
namelen = LWIP_MIN(hostnamelen, DNS_MAX_NAME_LENGTH-1);
MEMCPY(entry->name, name, namelen);
entry->name[namelen] = 0;
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
entry->pcb_idx = dns_alloc_pcb();
if (entry->pcb_idx >= DNS_MAX_SOURCE_PORTS) {
/* failed to get a UDP pcb */
LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": failed to allocate a pcb\n", name));
entry->state = DNS_STATE_UNUSED;
req->found = NULL;
return ERR_MEM;
}
LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS pcb %"U16_F"\n", name, (u16_t)(entry->pcb_idx)));
#endif
dns_seqno++;
/* force to send query without waiting timer */
dns_check_entry(i);
/* dns query is enqueued */
return ERR_INPROGRESS;
}
/**
* Resolve a hostname (string) into an IP address.
* NON-BLOCKING callback version for use with raw API!!!
*
* Returns immediately with one of err_t return codes:
* - ERR_OK if hostname is a valid IP address string or the host
* name is already in the local names table.
* - ERR_INPROGRESS enqueue a request to be sent to the DNS server
* for resolution if no errors are present.
* - ERR_ARG: dns client not initialized or invalid hostname
*
* @param hostname the hostname that is to be queried
* @param addr pointer to a ip_addr_t where to store the address if it is already
* cached in the dns_table (only valid if ERR_OK is returned!)
* @param found a callback function to be called on success, failure or timeout (only if
* ERR_INPROGRESS is returned!)
* @param callback_arg argument to pass to the callback function
* @return a err_t return code.
*/
err_t
dns_gethostbyname(const char *hostname, ip_addr_t *addr, dns_found_callback found,
void *callback_arg)
{
#if LWIP_IPV4 && LWIP_IPV6
return dns_gethostbyname_addrtype(hostname, addr, found, callback_arg, LWIP_DNS_ADDRTYPE_DEFAULT);
}
/** Like dns_gethostbyname, but returned address type can be controlled:
* @param dns_addrtype: - LWIP_DNS_ADDRTYPE_IPV4_IPV6: try to resolve IPv4 first, try IPv6 if IPv4 fails only
* - LWIP_DNS_ADDRTYPE_IPV6_IPV4: try to resolve IPv6 first, try IPv4 if IPv6 fails only
* - LWIP_DNS_ADDRTYPE_IPV4: try to resolve IPv4 only
* - LWIP_DNS_ADDRTYPE_IPV6: try to resolve IPv6 only
*/
err_t
dns_gethostbyname_addrtype(const char *hostname, ip_addr_t *addr, dns_found_callback found,
void *callback_arg, u8_t dns_addrtype)
{
#endif /* LWIP_IPV4 && LWIP_IPV6 */
size_t hostnamelen;
/* not initialized or no valid server yet, or invalid addr pointer
* or invalid hostname or invalid hostname length */
if ((addr == NULL) ||
(!hostname) || (!hostname[0])) {
return ERR_ARG;
}
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) == 0)
if (dns_pcbs[0] == NULL) {
return ERR_ARG;
}
#endif
hostnamelen = strlen(hostname);
if (hostnamelen >= DNS_MAX_NAME_LENGTH) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_gethostbyname: name too long to resolve"));
return ERR_ARG;
}
#if LWIP_HAVE_LOOPIF
if (strcmp(hostname, "localhost") == 0) {
ip_addr_set_loopback(LWIP_DNS_ADDRTYPE_IS_IPV6(dns_addrtype), addr);
return ERR_OK;
}
#endif /* LWIP_HAVE_LOOPIF */
/* host name already in octet notation? set ip addr and return ERR_OK */
if (ipaddr_aton(hostname, addr)) {
#if LWIP_IPV4 && LWIP_IPV6
if ((IP_IS_V6(addr) && (dns_addrtype != LWIP_DNS_ADDRTYPE_IPV4)) ||
(!IP_IS_V6(addr) && (dns_addrtype != LWIP_DNS_ADDRTYPE_IPV6)))
#endif /* LWIP_IPV4 && LWIP_IPV6 */
{
return ERR_OK;
}
}
/* already have this address cached? */
if (dns_lookup(hostname, addr LWIP_DNS_ADDRTYPE_ARG(dns_addrtype)) == ERR_OK) {
return ERR_OK;
}
#if LWIP_IPV4 && LWIP_IPV6
if ((dns_addrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) || (dns_addrtype == LWIP_DNS_ADDRTYPE_IPV6_IPV4)) {
/* fallback to 2nd IP type and try again to lookup */
u8_t fallback;
if (dns_addrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) {
fallback = LWIP_DNS_ADDRTYPE_IPV6;
} else {
fallback = LWIP_DNS_ADDRTYPE_IPV4;
}
if (dns_lookup(hostname, addr LWIP_DNS_ADDRTYPE_ARG(fallback)) == ERR_OK) {
return ERR_OK;
}
}
#endif /* LWIP_IPV4 && LWIP_IPV6 */
/* queue query with specified callback */
return dns_enqueue(hostname, hostnamelen, found, callback_arg LWIP_DNS_ADDRTYPE_ARG(dns_addrtype));
}
#if !LWIP_IPV4 || !LWIP_IPV6
err_t
dns_gethostbyname_addrtype(const char *hostname, ip_addr_t *addr, dns_found_callback found,
void *callback_arg, u8_t dns_addrtype)
{
LWIP_UNUSED_ARG(dns_addrtype);
return dns_gethostbyname(hostname, addr, found, callback_arg);
}
#endif /* LWIP_IPV4 && LWIP_IPV6 */
#endif /* LWIP_DNS */
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