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/**
* @file
* DNS - host name to IP address resolver.
*
* @defgroup dns DNS
* @ingroup callbackstyle_api
*
* Implements a DNS host name to IP address resolver.
*
* 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).
*
* Multicast DNS queries are supported for names ending on ".local".
* However, only "One-Shot Multicast DNS Queries" are supported (RFC 6762
* chapter 5.1), this is not a fully compliant implementation of continuous
* mDNS querying!
*
* All functions must be called from TCPIP thread.
*
* @see DNS_MAX_SERVERS
* @see LWIP_DHCP_MAX_DNS_SERVERS
* @see @ref netconn_common for thread-safe access.
*/
/*
* 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.
*/
/*-----------------------------------------------------------------------------
* 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 */
/** @todo: one-shot mDNS: dual-stack fallback to another IP version */
/*-----------------------------------------------------------------------------
* Includes
*----------------------------------------------------------------------------*/
#include "lwip/opt.h"
#if LWIP_DNS /* don't build if not configured for use in lwipopts.h */
#include "lwip/def.h"
#include "lwip/udp.h"
#include "lwip/mem.h"
#include "lwip/memp.h"
#include "lwip/dns.h"
#include "lwip/prot/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 resource record max. TTL (one week as default) */
#ifndef DNS_MAX_TTL
#define DNS_MAX_TTL 604800
#elif DNS_MAX_TTL > 0x7FFFFFFF
#error DNS_MAX_TTL must be a positive 32-bit value
#endif
#if DNS_TABLE_SIZE > 255
#error DNS_TABLE_SIZE must fit into an u8_t
#endif
#if DNS_MAX_SERVERS > 255
#error DNS_MAX_SERVERS must fit into an u8_t
#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
#else
#if DNS_MAX_REQUESTS > 255
#error DNS_MAX_REQUESTS must fit into an u8_t
#endif
#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
#else
#if DNS_MAX_SOURCE_PORTS > 255
#error DNS_MAX_SOURCE_PORTS must fit into an u8_t
#endif
#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 */
#if LWIP_DNS_SUPPORT_MDNS_QUERIES
#define LWIP_DNS_ISMDNS_ARG(x) , x
#else
#define LWIP_DNS_ISMDNS_ARG(x)
#endif
/** 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 states */
typedef enum {
DNS_STATE_UNUSED = 0,
DNS_STATE_NEW = 1,
DNS_STATE_ASKING = 2,
DNS_STATE_DONE = 3
} dns_state_enum_t;
/** 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 */
#if LWIP_DNS_SUPPORT_MDNS_QUERIES
u8_t is_mdns;
#endif
};
/** 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);
static err_t dns_lookup_local(const char *hostname, ip_addr_t *addr LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype));
#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];
#if LWIP_IPV4
const ip_addr_t dns_mquery_v4group = DNS_MQUERY_IPV4_GROUP_INIT;
#endif /* LWIP_IPV4 */
#if LWIP_IPV6
const ip_addr_t dns_mquery_v6group = DNS_MQUERY_IPV6_GROUP_INIT;
#endif /* LWIP_IPV6 */
/**
* 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_ip_type(IPADDR_TYPE_ANY);
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_ANY_TYPE, 0);
udp_recv(dns_pcbs[0], dns_recv, NULL);
}
#endif
#if DNS_LOCAL_HOSTLIST
dns_init_local();
#endif
}
/**
* @ingroup dns
* 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;
}
}
}
/**
* @ingroup dns
* 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.
*/
const 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 < LWIP_ARRAYSIZE(local_hostlist_init); 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) */
}
/**
* @ingroup dns
* Iterate the local host-list for a hostname.
*
* @param iterator_fn a function that is called for every entry in the local host-list
* @param iterator_arg 3rd argument passed to iterator_fn
* @return the number of entries in the local host-list
*/
size_t
dns_local_iterate(dns_found_callback iterator_fn, void *iterator_arg)
{
size_t i;
#if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
struct local_hostlist_entry *entry = local_hostlist_dynamic;
i = 0;
while (entry != NULL) {
if (iterator_fn != NULL) {
iterator_fn(entry->name, &entry->addr, iterator_arg);
}
i++;
entry = entry->next;
}
#else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
for (i = 0; i < LWIP_ARRAYSIZE(local_hostlist_static); i++) {
if (iterator_fn != NULL) {
iterator_fn(local_hostlist_static[i].name, &local_hostlist_static[i].addr, iterator_arg);
}
}
#endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
return i;
}
/**
* @ingroup dns
* 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.
* @param dns_addrtype - LWIP_DNS_ADDRTYPE_IPV4_IPV6: try to resolve IPv4 (ATTENTION: no fallback here!)
* - LWIP_DNS_ADDRTYPE_IPV6_IPV4: try to resolve IPv6 (ATTENTION: no fallback here!)
* - LWIP_DNS_ADDRTYPE_IPV4: try to resolve IPv4 only
* - LWIP_DNS_ADDRTYPE_IPV6: try to resolve IPv6 only
* @return ERR_OK if found, ERR_ARG if not found
*/
err_t
dns_local_lookup(const char *hostname, ip_addr_t *addr, u8_t dns_addrtype)
{
LWIP_UNUSED_ARG(dns_addrtype);
return dns_lookup_local(hostname, addr LWIP_DNS_ADDRTYPE_ARG(dns_addrtype));
}
/* Internal implementation for dns_local_lookup and dns_lookup */
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_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 < LWIP_ARRAYSIZE(local_hostlist_static); i++) {
if ((lwip_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
/**
* @ingroup dns
* 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_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;
}
/**
* @ingroup dns
* 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 */
/**
* @ingroup dns
* 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
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)) == ERR_OK) {
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_strnicmp(name, dns_table[i].name, sizeof(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_val(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).
*
* For now, this function compares case-insensitive to cope with all kinds of
* servers. This also means that "dns 0x20 bit encoding" must be checked
* externally, if we want to implement it.
* Currently, the request is sent exactly as passed in by he user request.
*
* @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(const char *query, struct pbuf *p, u16_t start_offset)
{
int n;
u16_t response_offset = start_offset;
do {
n = pbuf_try_get_at(p, response_offset);
if ((n < 0) || (response_offset == 0xFFFF)) {
/* error or overflow */
return 0xFFFF;
}
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) {
int c = pbuf_try_get_at(p, response_offset);
if (c < 0) {
return 0xFFFF;
}
if (lwip_tolower((*query)) != lwip_tolower((u8_t)c)) {
return 0xFFFF;
}
if (response_offset == 0xFFFF) {
/* would overflow */
return 0xFFFF;
}
response_offset++;
++query;
--n;
}
++query;
}
n = pbuf_try_get_at(p, response_offset);
if (n < 0) {
return 0xFFFF;
}
} while (n != 0);
if (response_offset == 0xFFFF) {
/* would overflow */
return 0xFFFF;
}
return (u16_t)(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_skip_name(struct pbuf *p, u16_t query_idx)
{
int n;
u16_t offset = query_idx;
do {
n = pbuf_try_get_at(p, offset++);
if ((n < 0) || (offset == 0)) {
return 0xFFFF;
}
/** @see RFC 1035 - 4.1.4. Message compression */
if ((n & 0xc0) == 0xc0) {
/* Compressed name: since we only want to skip it (not check it), stop here */
break;
} else {
/* Not compressed name */
if (offset + n >= p->tot_len) {
return 0xFFFF;
}
offset = (u16_t)(offset + n);
}
n = pbuf_try_get_at(p, offset);
if (n < 0) {
return 0xFFFF;
}
} while (n != 0);
if (offset == 0xFFFF) {
return 0xFFFF;
}
return (u16_t)(offset + 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])
#if LWIP_DNS_SUPPORT_MDNS_QUERIES
&& !entry->is_mdns
#endif
) {
/* 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) {
const ip_addr_t *dst;
u16_t dst_port;
/* fill dns header */
memset(&hdr, 0, SIZEOF_DNS_HDR);
hdr.id = lwip_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);
if (query_idx + n + 1 > 0xFFFF) {
/* u16_t overflow */
goto overflow_return;
}
pbuf_put_at(p, query_idx, n);
pbuf_take_at(p, hostname_part, copy_len, (u16_t)(query_idx + 1));
query_idx = (u16_t)(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));
#if LWIP_DNS_SUPPORT_MDNS_QUERIES
if (entry->is_mdns) {
dst_port = DNS_MQUERY_PORT;
#if LWIP_IPV6
if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype)) {
dst = &dns_mquery_v6group;
}
#endif
#if LWIP_IPV4 && LWIP_IPV6
else
#endif
#if LWIP_IPV4
{
dst = &dns_mquery_v4group;
}
#endif
} else
#endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
{
dst_port = DNS_SERVER_PORT;
dst = &dns_servers[entry->server_idx];
}
err = udp_sendto(dns_pcbs[pcb_idx], p, dst, dst_port);
/* free pbuf */
pbuf_free(p);
} else {
err = ERR_MEM;
}
return err;
overflow_return:
pbuf_free(p);
return ERR_VAL;
}
#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 *pcb;
pcb = udp_new_ip_type(IPADDR_TYPE_ANY);
if (pcb == 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)) {
err = udp_bind(pcb, IP_ANY_TYPE, port);
} else {
/* this port is not allowed, try again */
err = ERR_USE;
}
} while (err == ERR_USE);
if (err != ERR_OK) {
udp_remove(pcb);
return NULL;
}
udp_recv(pcb, dns_recv, NULL);
return pcb;
}
/**
* 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 (so overflow is no issue) */
for (i = 0, idx = (u8_t)(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;
}
/**
* Check whether there are other backup DNS servers available to try
*/
static u8_t
dns_backupserver_available(struct dns_table_entry *pentry)
{
u8_t ret = 0;
if (pentry) {
if ((pentry->server_idx + 1 < DNS_MAX_SERVERS) && !ip_addr_isany_val(dns_servers[pentry->server_idx + 1])) {
ret = 1;
}
}
return ret;
}
/**
* 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:
/* initialize new entry */
entry->txid = dns_create_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 (dns_backupserver_available(entry)
#if LWIP_DNS_SUPPORT_MDNS_QUERIES
&& !entry->is_mdns
#endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
) {
/* 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);
}
}
/**
* Save TTL and call dns_call_found for correct response.
*/
static void
dns_correct_response(u8_t idx, u32_t ttl)
{
struct dns_table_entry *entry = &dns_table[idx];
entry->state = DNS_STATE_DONE;
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", entry->name));
ip_addr_debug_print_val(DNS_DEBUG, entry->ipaddr);
LWIP_DEBUGF(DNS_DEBUG, ("\n"));
/* read the answer resource record's TTL, and maximize it if needed */
entry->ttl = ttl;
if (entry->ttl > DNS_MAX_TTL) {
entry->ttl = DNS_MAX_TTL;
}
dns_call_found(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 */
/* entry reused during callback? */
if (entry->state == DNS_STATE_DONE) {
entry->state = DNS_STATE_UNUSED;
}
}
}
/**
* Receive input function for DNS response packets arriving for the dns UDP pcb.
*/
static void
dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port)
{
u8_t i;
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 ignore_packet;
}
/* 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 = lwip_htons(hdr.id);
for (i = 0; i < DNS_TABLE_SIZE; i++) {
struct dns_table_entry *entry = &dns_table[i];
if ((entry->state == DNS_STATE_ASKING) &&
(entry->txid == txid)) {
/* We only care about the question(s) and the answers. The authrr
and the extrarr are simply discarded. */
nquestions = lwip_htons(hdr.numquestions);
nanswers = lwip_htons(hdr.numanswers);
/* Check for correct response. */
if ((hdr.flags1 & DNS_FLAG1_RESPONSE) == 0) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": not a response\n", entry->name));
goto ignore_packet; /* ignore this packet */
}
if (nquestions != 1) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
goto ignore_packet; /* ignore this packet */
}
#if LWIP_DNS_SUPPORT_MDNS_QUERIES
if (!entry->is_mdns)
#endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
{
/* 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])) {
goto ignore_packet; /* ignore this packet */
}
}
/* 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));
goto ignore_packet; /* ignore this packet */
}
/* check if "question" part matches the request */
if (pbuf_copy_partial(p, &qry, SIZEOF_DNS_QUERY, res_idx) != SIZEOF_DNS_QUERY) {
goto ignore_packet; /* ignore this packet */
}
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));
goto ignore_packet; /* ignore this packet */
}
/* skip the rest of the "question" part */
if (res_idx + SIZEOF_DNS_QUERY > 0xFFFF) {
goto ignore_packet;
}
res_idx = (u16_t)(res_idx + SIZEOF_DNS_QUERY);
/* Check for error. If so, call callback to inform. */
if (hdr.flags2 & DNS_FLAG2_ERR_MASK) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", entry->name));
/* if there is another backup DNS server to try
* then don't stop the DNS request
*/
if (dns_backupserver_available(entry)) {
/* avoid retrying the same server */
entry->retries = DNS_MAX_RETRIES-1;
entry->tmr = 1;
/* contact next available server for this entry */
dns_check_entry(i);
goto ignore_packet;
}
} else {
while ((nanswers > 0) && (res_idx < p->tot_len)) {
/* skip answer resource record's host name */
res_idx = dns_skip_name(p, res_idx);
if (res_idx == 0xFFFF) {
goto ignore_packet; /* ignore this packet */
}
/* Check for IP address type and Internet class. Others are discarded. */
if (pbuf_copy_partial(p, &ans, SIZEOF_DNS_ANSWER, res_idx) != SIZEOF_DNS_ANSWER) {
goto ignore_packet; /* ignore this packet */
}
if (res_idx + SIZEOF_DNS_ANSWER > 0xFFFF) {
goto ignore_packet;
}
res_idx = (u16_t)(res_idx + SIZEOF_DNS_ANSWER);
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;
/* read the IP address after answer resource record's header */
if (pbuf_copy_partial(p, &ip4addr, sizeof(ip4_addr_t), res_idx) != sizeof(ip4_addr_t)) {
goto ignore_packet; /* ignore this packet */
}
ip_addr_copy_from_ip4(dns_table[i].ipaddr, ip4addr);
pbuf_free(p);
/* handle correct response */
dns_correct_response(i, lwip_ntohl(ans.ttl));
return;
}
}
#endif /* LWIP_IPV4 */
#if LWIP_IPV6
if ((ans.type == PP_HTONS(DNS_RRTYPE_AAAA)) && (ans.len == PP_HTONS(sizeof(ip6_addr_p_t)))) {
#if LWIP_IPV4 && LWIP_IPV6
if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype))
#endif /* LWIP_IPV4 && LWIP_IPV6 */
{
ip6_addr_p_t ip6addr;
/* read the IP address after answer resource record's header */
if (pbuf_copy_partial(p, &ip6addr, sizeof(ip6_addr_p_t), res_idx) != sizeof(ip6_addr_p_t)) {
goto ignore_packet; /* ignore this packet */
}
/* @todo: scope ip6addr? Might be required for link-local addresses at least? */
ip_addr_copy_from_ip6_packed(dns_table[i].ipaddr, ip6addr);
pbuf_free(p);
/* handle correct response */
dns_correct_response(i, lwip_ntohl(ans.ttl));
return;
}
}
#endif /* LWIP_IPV6 */
}
/* skip this answer */
if ((int)(res_idx + lwip_htons(ans.len)) > 0xFFFF) {
goto ignore_packet; /* ignore this packet */
}
res_idx = (u16_t)(res_idx + lwip_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 */
dns_table[i].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV6;
} else {
/* IPv6 failed, try IPv4 */
dns_table[i].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV4;
}
pbuf_free(p);
dns_table[i].state = DNS_STATE_NEW;
dns_check_entry(i);
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 */
pbuf_free(p);
dns_call_found(i, NULL);
dns_table[i].state = DNS_STATE_UNUSED;
return;
}
}
}
ignore_packet:
/* deallocate memory and return */
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 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) LWIP_DNS_ISMDNS_ARG(u8_t is_mdns))
{
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_strnicmp(name, dns_table[i].name, sizeof(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) {
u8_t age = (u8_t)(dns_seqno - entry->seqno);
if (age > lseq) {
lseq = age;
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
#if LWIP_DNS_SUPPORT_MDNS_QUERIES
entry->is_mdns = is_mdns;
#endif
dns_seqno++;
/* force to send query without waiting timer */
dns_check_entry(i);
/* dns query is enqueued */
return ERR_INPROGRESS;
}
/**
* @ingroup dns
* 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)
{
return dns_gethostbyname_addrtype(hostname, addr, found, callback_arg, LWIP_DNS_ADDRTYPE_DEFAULT);
}
/**
* @ingroup dns
* Like dns_gethostbyname, but returned address type can be controlled:
* @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
* @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)
{
size_t hostnamelen;
#if LWIP_DNS_SUPPORT_MDNS_QUERIES
u8_t is_mdns;
#endif
/* 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_V4(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;
}
}
#else /* LWIP_IPV4 && LWIP_IPV6 */
LWIP_UNUSED_ARG(dns_addrtype);
#endif /* LWIP_IPV4 && LWIP_IPV6 */
#if LWIP_DNS_SUPPORT_MDNS_QUERIES
if (strstr(hostname, ".local") == &hostname[hostnamelen] - 6) {
is_mdns = 1;
} else {
is_mdns = 0;
}
if (!is_mdns)
#endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
{
/* prevent calling found callback if no server is set, return error instead */
if (ip_addr_isany_val(dns_servers[0])) {
return ERR_VAL;
}
}
/* queue query with specified callback */
return dns_enqueue(hostname, hostnamelen, found, callback_arg LWIP_DNS_ADDRTYPE_ARG(dns_addrtype)
LWIP_DNS_ISMDNS_ARG(is_mdns));
}
#endif /* LWIP_DNS */
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