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jeremybenn |
/**
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* @file
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* DNS - host name to IP address resolver.
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*
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*/
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/**
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* This file implements a DNS host name to IP address resolver.
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* Port to lwIP from uIP
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* by Jim Pettinato April 2007
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* uIP version Copyright (c) 2002-2003, Adam Dunkels.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote
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* products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
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* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
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* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*
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* DNS.C
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*
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* The lwIP DNS resolver functions are used to lookup a host name and
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* map it to a numerical IP address. It maintains a list of resolved
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* hostnames that can be queried with the dns_lookup() function.
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* New hostnames can be resolved using the dns_query() function.
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*
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* The lwIP version of the resolver also adds a non-blocking version of
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* gethostbyname() that will work with a raw API application. This function
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* checks for an IP address string first and converts it if it is valid.
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* gethostbyname() then does a dns_lookup() to see if the name is
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* already in the table. If so, the IP is returned. If not, a query is
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* issued and the function returns with a ERR_INPROGRESS status. The app
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* using the dns client must then go into a waiting state.
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*
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* Once a hostname has been resolved (or found to be non-existent),
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* the resolver code calls a specified callback function (which
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* must be implemented by the module that uses the resolver).
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*/
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/*-----------------------------------------------------------------------------
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* RFC 1035 - Domain names - implementation and specification
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* RFC 2181 - Clarifications to the DNS Specification
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*----------------------------------------------------------------------------*/
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/** @todo: define good default values (rfc compliance) */
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/** @todo: improve answer parsing, more checkings... */
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/** @todo: check RFC1035 - 7.3. Processing responses */
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/*-----------------------------------------------------------------------------
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* Includes
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*----------------------------------------------------------------------------*/
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#include "lwip/opt.h"
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#if LWIP_DNS /* don't build if not configured for use in lwipopts.h */
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#include "lwip/udp.h"
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#include "lwip/mem.h"
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#include "lwip/dns.h"
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#include <string.h>
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/** DNS server IP address */
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#ifndef DNS_SERVER_ADDRESS
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#define DNS_SERVER_ADDRESS inet_addr("208.67.222.222") /* resolver1.opendns.com */
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#endif
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/** DNS server port address */
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#ifndef DNS_SERVER_PORT
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#define DNS_SERVER_PORT 53
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#endif
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/** DNS maximum number of retries when asking for a name, before "timeout". */
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#ifndef DNS_MAX_RETRIES
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#define DNS_MAX_RETRIES 4
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#endif
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/** DNS resource record max. TTL (one week as default) */
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#ifndef DNS_MAX_TTL
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#define DNS_MAX_TTL 604800
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#endif
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/* DNS protocol flags */
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#define DNS_FLAG1_RESPONSE 0x80
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#define DNS_FLAG1_OPCODE_STATUS 0x10
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#define DNS_FLAG1_OPCODE_INVERSE 0x08
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#define DNS_FLAG1_OPCODE_STANDARD 0x00
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#define DNS_FLAG1_AUTHORATIVE 0x04
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#define DNS_FLAG1_TRUNC 0x02
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#define DNS_FLAG1_RD 0x01
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#define DNS_FLAG2_RA 0x80
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#define DNS_FLAG2_ERR_MASK 0x0f
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#define DNS_FLAG2_ERR_NONE 0x00
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#define DNS_FLAG2_ERR_NAME 0x03
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/* DNS protocol states */
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#define DNS_STATE_UNUSED 0
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#define DNS_STATE_NEW 1
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#define DNS_STATE_ASKING 2
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#define DNS_STATE_DONE 3
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#ifdef PACK_STRUCT_USE_INCLUDES
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# include "arch/bpstruct.h"
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#endif
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PACK_STRUCT_BEGIN
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/** DNS message header */
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struct dns_hdr {
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PACK_STRUCT_FIELD(u16_t id);
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PACK_STRUCT_FIELD(u8_t flags1);
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PACK_STRUCT_FIELD(u8_t flags2);
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PACK_STRUCT_FIELD(u16_t numquestions);
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PACK_STRUCT_FIELD(u16_t numanswers);
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PACK_STRUCT_FIELD(u16_t numauthrr);
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PACK_STRUCT_FIELD(u16_t numextrarr);
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} PACK_STRUCT_STRUCT;
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PACK_STRUCT_END
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#ifdef PACK_STRUCT_USE_INCLUDES
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# include "arch/epstruct.h"
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#endif
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#define SIZEOF_DNS_HDR 12
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#ifdef PACK_STRUCT_USE_INCLUDES
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# include "arch/bpstruct.h"
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#endif
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PACK_STRUCT_BEGIN
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/** DNS query message structure */
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struct dns_query {
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/* DNS query record starts with either a domain name or a pointer
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to a name already present somewhere in the packet. */
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PACK_STRUCT_FIELD(u16_t type);
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PACK_STRUCT_FIELD(u16_t class);
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} PACK_STRUCT_STRUCT;
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PACK_STRUCT_END
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#ifdef PACK_STRUCT_USE_INCLUDES
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# include "arch/epstruct.h"
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#endif
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#define SIZEOF_DNS_QUERY 4
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#ifdef PACK_STRUCT_USE_INCLUDES
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# include "arch/bpstruct.h"
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#endif
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PACK_STRUCT_BEGIN
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/** DNS answer message structure */
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struct dns_answer {
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/* DNS answer record starts with either a domain name or a pointer
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to a name already present somewhere in the packet. */
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PACK_STRUCT_FIELD(u16_t type);
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PACK_STRUCT_FIELD(u16_t class);
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PACK_STRUCT_FIELD(u32_t ttl);
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PACK_STRUCT_FIELD(u16_t len);
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} PACK_STRUCT_STRUCT;
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PACK_STRUCT_END
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#ifdef PACK_STRUCT_USE_INCLUDES
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# include "arch/epstruct.h"
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#endif
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#define SIZEOF_DNS_ANSWER 10
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/** DNS table entry */
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struct dns_table_entry {
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u8_t state;
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u8_t numdns;
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u8_t tmr;
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u8_t retries;
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u8_t seqno;
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u8_t err;
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u32_t ttl;
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char name[DNS_MAX_NAME_LENGTH];
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struct ip_addr ipaddr;
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/* pointer to callback on DNS query done */
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dns_found_callback found;
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void *arg;
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};
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#if DNS_LOCAL_HOSTLIST
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/** struct used for local host-list */
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struct local_hostlist_entry {
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/** static hostname */
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const char *name;
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/** static host address in network byteorder */
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u32_t addr;
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struct local_hostlist_entry *next;
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};
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#if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
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/** Local host-list. For hostnames in this list, no
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* external name resolution is performed */
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static struct local_hostlist_entry *local_hostlist_dynamic;
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#else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
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/** Defining this allows the local_hostlist_static to be placed in a different
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* linker section (e.g. FLASH) */
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#ifndef DNS_LOCAL_HOSTLIST_STORAGE_PRE
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#define DNS_LOCAL_HOSTLIST_STORAGE_PRE static
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#endif /* DNS_LOCAL_HOSTLIST_STORAGE_PRE */
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/** Defining this allows the local_hostlist_static to be placed in a different
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* linker section (e.g. FLASH) */
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#ifndef DNS_LOCAL_HOSTLIST_STORAGE_POST
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#define DNS_LOCAL_HOSTLIST_STORAGE_POST
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#endif /* DNS_LOCAL_HOSTLIST_STORAGE_POST */
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DNS_LOCAL_HOSTLIST_STORAGE_PRE struct local_hostlist_entry local_hostlist_static[]
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DNS_LOCAL_HOSTLIST_STORAGE_POST = DNS_LOCAL_HOSTLIST_INIT;
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#endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
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static void dns_init_local();
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#endif /* DNS_LOCAL_HOSTLIST */
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/* forward declarations */
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static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port);
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static void dns_check_entries(void);
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/*-----------------------------------------------------------------------------
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* Globales
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*----------------------------------------------------------------------------*/
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/* DNS variables */
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static struct udp_pcb *dns_pcb;
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static u8_t dns_seqno;
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static struct dns_table_entry dns_table[DNS_TABLE_SIZE];
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static struct ip_addr dns_servers[DNS_MAX_SERVERS];
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#if (DNS_USES_STATIC_BUF == 1)
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static u8_t dns_payload[DNS_MSG_SIZE];
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#endif /* (DNS_USES_STATIC_BUF == 1) */
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/**
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* Initialize the resolver: set up the UDP pcb and configure the default server
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* (DNS_SERVER_ADDRESS).
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*/
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void
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dns_init()
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{
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struct ip_addr dnsserver;
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/* initialize default DNS server address */
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dnsserver.addr = DNS_SERVER_ADDRESS;
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LWIP_DEBUGF(DNS_DEBUG, ("dns_init: initializing\n"));
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/* if dns client not yet initialized... */
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if (dns_pcb == NULL) {
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dns_pcb = udp_new();
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if (dns_pcb != NULL) {
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/* initialize DNS table not needed (initialized to zero since it is a
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* global variable) */
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LWIP_ASSERT("For implicit initialization to work, DNS_STATE_UNUSED needs to be 0",
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DNS_STATE_UNUSED == 0);
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/* initialize DNS client */
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udp_bind(dns_pcb, IP_ADDR_ANY, 0);
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udp_recv(dns_pcb, dns_recv, NULL);
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/* initialize default DNS primary server */
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dns_setserver(0, &dnsserver);
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}
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}
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#if DNS_LOCAL_HOSTLIST
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dns_init_local();
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#endif
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}
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/**
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* Initialize one of the DNS servers.
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*
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* @param numdns the index of the DNS server to set must be < DNS_MAX_SERVERS
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* @param dnsserver IP address of the DNS server to set
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*/
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void
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dns_setserver(u8_t numdns, struct ip_addr *dnsserver)
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{
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if ((numdns < DNS_MAX_SERVERS) && (dns_pcb != NULL) &&
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(dnsserver != NULL) && (dnsserver->addr !=0 )) {
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dns_servers[numdns] = (*dnsserver);
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}
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}
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/**
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* Obtain one of the currently configured DNS server.
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*
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* @param numdns the index of the DNS server
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* @return IP address of the indexed DNS server or "ip_addr_any" if the DNS
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* server has not been configured.
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*/
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struct ip_addr
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dns_getserver(u8_t numdns)
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{
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if (numdns < DNS_MAX_SERVERS) {
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return dns_servers[numdns];
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} else {
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return *IP_ADDR_ANY;
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}
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}
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/**
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* The DNS resolver client timer - handle retries and timeouts and should
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* be called every DNS_TMR_INTERVAL milliseconds (every second by default).
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*/
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void
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dns_tmr(void)
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{
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if (dns_pcb != NULL) {
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LWIP_DEBUGF(DNS_DEBUG, ("dns_tmr: dns_check_entries\n"));
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dns_check_entries();
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}
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}
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#if DNS_LOCAL_HOSTLIST
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static void
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dns_init_local()
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{
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#if DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT)
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int i;
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struct local_hostlist_entry *entry;
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/* Dynamic: copy entries from DNS_LOCAL_HOSTLIST_INIT to list */
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struct local_hostlist_entry local_hostlist_init[] = DNS_LOCAL_HOSTLIST_INIT;
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for (i = 0; i < sizeof(local_hostlist_init) / sizeof(struct local_hostlist_entry); i++) {
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entry = mem_malloc(sizeof(struct local_hostlist_entry));
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LWIP_ASSERT("mem-error in dns_init_local", entry != NULL);
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if (entry != NULL) {
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struct local_hostlist_entry *init_entry = &local_hostlist_init[i];
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entry->name = init_entry->name;
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entry->addr = init_entry->addr;
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347 |
|
|
entry->next = local_hostlist_dynamic;
|
348 |
|
|
local_hostlist_dynamic = entry;
|
349 |
|
|
}
|
350 |
|
|
}
|
351 |
|
|
#endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT) */
|
352 |
|
|
}
|
353 |
|
|
|
354 |
|
|
/**
|
355 |
|
|
* Scans the local host-list for a hostname.
|
356 |
|
|
*
|
357 |
|
|
* @param hostname Hostname to look for in the local host-list
|
358 |
|
|
* @return The first IP address for the hostname in the local host-list or
|
359 |
|
|
* INADDR_NONE if not found.
|
360 |
|
|
*/
|
361 |
|
|
static u32_t
|
362 |
|
|
dns_lookup_local(const char *hostname)
|
363 |
|
|
{
|
364 |
|
|
#if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
|
365 |
|
|
struct local_hostlist_entry *entry = local_hostlist_dynamic;
|
366 |
|
|
while(entry != NULL) {
|
367 |
|
|
if(strcmp(entry->name, hostname) == 0) {
|
368 |
|
|
return entry->addr;
|
369 |
|
|
}
|
370 |
|
|
entry = entry->next;
|
371 |
|
|
}
|
372 |
|
|
#else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
|
373 |
|
|
int i;
|
374 |
|
|
for (i = 0; i < sizeof(local_hostlist_static) / sizeof(struct local_hostlist_entry); i++) {
|
375 |
|
|
if(strcmp(local_hostlist_static[i].name, hostname) == 0) {
|
376 |
|
|
return local_hostlist_static[i].addr;
|
377 |
|
|
}
|
378 |
|
|
}
|
379 |
|
|
#endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
|
380 |
|
|
return INADDR_NONE;
|
381 |
|
|
}
|
382 |
|
|
|
383 |
|
|
#if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
|
384 |
|
|
/** Remove all entries from the local host-list for a specific hostname
|
385 |
|
|
* and/or IP addess
|
386 |
|
|
*
|
387 |
|
|
* @param hostname hostname for which entries shall be removed from the local
|
388 |
|
|
* host-list
|
389 |
|
|
* @param addr address for which entries shall be removed from the local host-list
|
390 |
|
|
* @return the number of removed entries
|
391 |
|
|
*/
|
392 |
|
|
int
|
393 |
|
|
dns_local_removehost(const char *hostname, const struct ip_addr *addr)
|
394 |
|
|
{
|
395 |
|
|
int removed = 0;
|
396 |
|
|
struct local_hostlist_entry *entry = local_hostlist_dynamic;
|
397 |
|
|
struct local_hostlist_entry *last_entry = NULL;
|
398 |
|
|
while (entry != NULL) {
|
399 |
|
|
if (((hostname == NULL) || !strcmp(entry->name, hostname)) &&
|
400 |
|
|
((addr == NULL) || (entry->addr == addr->addr))) {
|
401 |
|
|
struct local_hostlist_entry *free_entry;
|
402 |
|
|
if (last_entry != NULL) {
|
403 |
|
|
last_entry->next = entry->next;
|
404 |
|
|
} else {
|
405 |
|
|
local_hostlist_dynamic = entry->next;
|
406 |
|
|
}
|
407 |
|
|
free_entry = entry;
|
408 |
|
|
entry = entry->next;
|
409 |
|
|
mem_free(free_entry);
|
410 |
|
|
removed++;
|
411 |
|
|
} else {
|
412 |
|
|
last_entry = entry;
|
413 |
|
|
entry = entry->next;
|
414 |
|
|
}
|
415 |
|
|
}
|
416 |
|
|
return removed;
|
417 |
|
|
}
|
418 |
|
|
|
419 |
|
|
/**
|
420 |
|
|
* Add a hostname/IP address pair to the local host-list.
|
421 |
|
|
* Duplicates are not checked.
|
422 |
|
|
*
|
423 |
|
|
* @param hostname hostname of the new entry
|
424 |
|
|
* @param addr IP address of the new entry
|
425 |
|
|
* @return ERR_OK if succeeded or ERR_MEM on memory error
|
426 |
|
|
*/
|
427 |
|
|
err_t
|
428 |
|
|
dns_local_addhost(const char *hostname, const struct ip_addr *addr)
|
429 |
|
|
{
|
430 |
|
|
struct local_hostlist_entry *entry;
|
431 |
|
|
entry = mem_malloc(sizeof(struct local_hostlist_entry));
|
432 |
|
|
if (entry == NULL) {
|
433 |
|
|
return ERR_MEM;
|
434 |
|
|
}
|
435 |
|
|
entry->name = hostname;
|
436 |
|
|
entry->addr = addr->addr;
|
437 |
|
|
entry->next = local_hostlist_dynamic;
|
438 |
|
|
local_hostlist_dynamic = entry;
|
439 |
|
|
return ERR_OK;
|
440 |
|
|
}
|
441 |
|
|
#endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC*/
|
442 |
|
|
#endif /* DNS_LOCAL_HOSTLIST */
|
443 |
|
|
|
444 |
|
|
/**
|
445 |
|
|
* Look up a hostname in the array of known hostnames.
|
446 |
|
|
*
|
447 |
|
|
* @note This function only looks in the internal array of known
|
448 |
|
|
* hostnames, it does not send out a query for the hostname if none
|
449 |
|
|
* was found. The function dns_enqueue() can be used to send a query
|
450 |
|
|
* for a hostname.
|
451 |
|
|
*
|
452 |
|
|
* @param name the hostname to look up
|
453 |
|
|
* @return the hostname's IP address, as u32_t (instead of struct ip_addr to
|
454 |
|
|
* better check for failure: != INADDR_NONE) or INADDR_NONE if the hostname
|
455 |
|
|
* was not found in the cached dns_table.
|
456 |
|
|
*/
|
457 |
|
|
static u32_t
|
458 |
|
|
dns_lookup(const char *name)
|
459 |
|
|
{
|
460 |
|
|
u8_t i;
|
461 |
|
|
#if DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN)
|
462 |
|
|
u32_t addr;
|
463 |
|
|
#endif /* DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN) */
|
464 |
|
|
#if DNS_LOCAL_HOSTLIST
|
465 |
|
|
if ((addr = dns_lookup_local(name)) != INADDR_NONE) {
|
466 |
|
|
return addr;
|
467 |
|
|
}
|
468 |
|
|
#endif /* DNS_LOCAL_HOSTLIST */
|
469 |
|
|
#ifdef DNS_LOOKUP_LOCAL_EXTERN
|
470 |
|
|
if((addr = DNS_LOOKUP_LOCAL_EXTERN(name)) != INADDR_NONE) {
|
471 |
|
|
return addr;
|
472 |
|
|
}
|
473 |
|
|
#endif /* DNS_LOOKUP_LOCAL_EXTERN */
|
474 |
|
|
|
475 |
|
|
/* Walk through name list, return entry if found. If not, return NULL. */
|
476 |
|
|
for (i = 0; i < DNS_TABLE_SIZE; ++i) {
|
477 |
|
|
if ((dns_table[i].state == DNS_STATE_DONE) &&
|
478 |
|
|
(strcmp(name, dns_table[i].name) == 0)) {
|
479 |
|
|
LWIP_DEBUGF(DNS_DEBUG, ("dns_lookup: \"%s\": found = ", name));
|
480 |
|
|
ip_addr_debug_print(DNS_DEBUG, &(dns_table[i].ipaddr));
|
481 |
|
|
LWIP_DEBUGF(DNS_DEBUG, ("\n"));
|
482 |
|
|
return dns_table[i].ipaddr.addr;
|
483 |
|
|
}
|
484 |
|
|
}
|
485 |
|
|
|
486 |
|
|
return INADDR_NONE;
|
487 |
|
|
}
|
488 |
|
|
|
489 |
|
|
#if DNS_DOES_NAME_CHECK
|
490 |
|
|
/**
|
491 |
|
|
* Compare the "dotted" name "query" with the encoded name "response"
|
492 |
|
|
* to make sure an answer from the DNS server matches the current dns_table
|
493 |
|
|
* entry (otherwise, answers might arrive late for hostname not on the list
|
494 |
|
|
* any more).
|
495 |
|
|
*
|
496 |
|
|
* @param query hostname (not encoded) from the dns_table
|
497 |
|
|
* @param response encoded hostname in the DNS response
|
498 |
|
|
* @return 0: names equal; 1: names differ
|
499 |
|
|
*/
|
500 |
|
|
static u8_t
|
501 |
|
|
dns_compare_name(unsigned char *query, unsigned char *response)
|
502 |
|
|
{
|
503 |
|
|
unsigned char n;
|
504 |
|
|
|
505 |
|
|
do {
|
506 |
|
|
n = *response++;
|
507 |
|
|
/** @see RFC 1035 - 4.1.4. Message compression */
|
508 |
|
|
if ((n & 0xc0) == 0xc0) {
|
509 |
|
|
/* Compressed name */
|
510 |
|
|
break;
|
511 |
|
|
} else {
|
512 |
|
|
/* Not compressed name */
|
513 |
|
|
while (n > 0) {
|
514 |
|
|
if ((*query) != (*response)) {
|
515 |
|
|
return 1;
|
516 |
|
|
}
|
517 |
|
|
++response;
|
518 |
|
|
++query;
|
519 |
|
|
--n;
|
520 |
|
|
};
|
521 |
|
|
++query;
|
522 |
|
|
}
|
523 |
|
|
} while (*response != 0);
|
524 |
|
|
|
525 |
|
|
return 0;
|
526 |
|
|
}
|
527 |
|
|
#endif /* DNS_DOES_NAME_CHECK */
|
528 |
|
|
|
529 |
|
|
/**
|
530 |
|
|
* Walk through a compact encoded DNS name and return the end of the name.
|
531 |
|
|
*
|
532 |
|
|
* @param query encoded DNS name in the DNS server response
|
533 |
|
|
* @return end of the name
|
534 |
|
|
*/
|
535 |
|
|
static unsigned char *
|
536 |
|
|
dns_parse_name(unsigned char *query)
|
537 |
|
|
{
|
538 |
|
|
unsigned char n;
|
539 |
|
|
|
540 |
|
|
do {
|
541 |
|
|
n = *query++;
|
542 |
|
|
/** @see RFC 1035 - 4.1.4. Message compression */
|
543 |
|
|
if ((n & 0xc0) == 0xc0) {
|
544 |
|
|
/* Compressed name */
|
545 |
|
|
break;
|
546 |
|
|
} else {
|
547 |
|
|
/* Not compressed name */
|
548 |
|
|
while (n > 0) {
|
549 |
|
|
++query;
|
550 |
|
|
--n;
|
551 |
|
|
};
|
552 |
|
|
}
|
553 |
|
|
} while (*query != 0);
|
554 |
|
|
|
555 |
|
|
return query + 1;
|
556 |
|
|
}
|
557 |
|
|
|
558 |
|
|
/**
|
559 |
|
|
* Send a DNS query packet.
|
560 |
|
|
*
|
561 |
|
|
* @param numdns index of the DNS server in the dns_servers table
|
562 |
|
|
* @param name hostname to query
|
563 |
|
|
* @param id index of the hostname in dns_table, used as transaction ID in the
|
564 |
|
|
* DNS query packet
|
565 |
|
|
* @return ERR_OK if packet is sent; an err_t indicating the problem otherwise
|
566 |
|
|
*/
|
567 |
|
|
static err_t
|
568 |
|
|
dns_send(u8_t numdns, const char* name, u8_t id)
|
569 |
|
|
{
|
570 |
|
|
err_t err;
|
571 |
|
|
struct dns_hdr *hdr;
|
572 |
|
|
struct dns_query qry;
|
573 |
|
|
struct pbuf *p;
|
574 |
|
|
char *query, *nptr;
|
575 |
|
|
const char *pHostname;
|
576 |
|
|
u8_t n;
|
577 |
|
|
|
578 |
|
|
LWIP_DEBUGF(DNS_DEBUG, ("dns_send: dns_servers[%"U16_F"] \"%s\": request\n",
|
579 |
|
|
(u16_t)(numdns), name));
|
580 |
|
|
LWIP_ASSERT("dns server out of array", numdns < DNS_MAX_SERVERS);
|
581 |
|
|
LWIP_ASSERT("dns server has no IP address set", dns_servers[numdns].addr != 0);
|
582 |
|
|
|
583 |
|
|
/* if here, we have either a new query or a retry on a previous query to process */
|
584 |
|
|
p = pbuf_alloc(PBUF_TRANSPORT, SIZEOF_DNS_HDR + DNS_MAX_NAME_LENGTH +
|
585 |
|
|
SIZEOF_DNS_QUERY, PBUF_RAM);
|
586 |
|
|
if (p != NULL) {
|
587 |
|
|
LWIP_ASSERT("pbuf must be in one piece", p->next == NULL);
|
588 |
|
|
/* fill dns header */
|
589 |
|
|
hdr = (struct dns_hdr*)p->payload;
|
590 |
|
|
memset(hdr, 0, SIZEOF_DNS_HDR);
|
591 |
|
|
hdr->id = htons(id);
|
592 |
|
|
hdr->flags1 = DNS_FLAG1_RD;
|
593 |
|
|
hdr->numquestions = htons(1);
|
594 |
|
|
query = (char*)hdr + SIZEOF_DNS_HDR;
|
595 |
|
|
pHostname = name;
|
596 |
|
|
--pHostname;
|
597 |
|
|
|
598 |
|
|
/* convert hostname into suitable query format. */
|
599 |
|
|
do {
|
600 |
|
|
++pHostname;
|
601 |
|
|
nptr = query;
|
602 |
|
|
++query;
|
603 |
|
|
for(n = 0; *pHostname != '.' && *pHostname != 0; ++pHostname) {
|
604 |
|
|
*query = *pHostname;
|
605 |
|
|
++query;
|
606 |
|
|
++n;
|
607 |
|
|
}
|
608 |
|
|
*nptr = n;
|
609 |
|
|
} while(*pHostname != 0);
|
610 |
|
|
*query++='\0';
|
611 |
|
|
|
612 |
|
|
/* fill dns query */
|
613 |
|
|
qry.type = htons(DNS_RRTYPE_A);
|
614 |
|
|
qry.class = htons(DNS_RRCLASS_IN);
|
615 |
|
|
MEMCPY( query, &qry, SIZEOF_DNS_QUERY);
|
616 |
|
|
|
617 |
|
|
/* resize pbuf to the exact dns query */
|
618 |
|
|
pbuf_realloc(p, (query + SIZEOF_DNS_QUERY) - ((char*)(p->payload)));
|
619 |
|
|
|
620 |
|
|
/* connect to the server for faster receiving */
|
621 |
|
|
udp_connect(dns_pcb, &dns_servers[numdns], DNS_SERVER_PORT);
|
622 |
|
|
/* send dns packet */
|
623 |
|
|
err = udp_sendto(dns_pcb, p, &dns_servers[numdns], DNS_SERVER_PORT);
|
624 |
|
|
|
625 |
|
|
/* free pbuf */
|
626 |
|
|
pbuf_free(p);
|
627 |
|
|
} else {
|
628 |
|
|
err = ERR_MEM;
|
629 |
|
|
}
|
630 |
|
|
|
631 |
|
|
return err;
|
632 |
|
|
}
|
633 |
|
|
|
634 |
|
|
/**
|
635 |
|
|
* dns_check_entry() - see if pEntry has not yet been queried and, if so, sends out a query.
|
636 |
|
|
* Check an entry in the dns_table:
|
637 |
|
|
* - send out query for new entries
|
638 |
|
|
* - retry old pending entries on timeout (also with different servers)
|
639 |
|
|
* - remove completed entries from the table if their TTL has expired
|
640 |
|
|
*
|
641 |
|
|
* @param i index of the dns_table entry to check
|
642 |
|
|
*/
|
643 |
|
|
static void
|
644 |
|
|
dns_check_entry(u8_t i)
|
645 |
|
|
{
|
646 |
|
|
struct dns_table_entry *pEntry = &dns_table[i];
|
647 |
|
|
|
648 |
|
|
LWIP_ASSERT("array index out of bounds", i < DNS_TABLE_SIZE);
|
649 |
|
|
|
650 |
|
|
switch(pEntry->state) {
|
651 |
|
|
|
652 |
|
|
case DNS_STATE_NEW: {
|
653 |
|
|
/* initialize new entry */
|
654 |
|
|
pEntry->state = DNS_STATE_ASKING;
|
655 |
|
|
pEntry->numdns = 0;
|
656 |
|
|
pEntry->tmr = 1;
|
657 |
|
|
pEntry->retries = 0;
|
658 |
|
|
|
659 |
|
|
/* send DNS packet for this entry */
|
660 |
|
|
dns_send(pEntry->numdns, pEntry->name, i);
|
661 |
|
|
break;
|
662 |
|
|
}
|
663 |
|
|
|
664 |
|
|
case DNS_STATE_ASKING: {
|
665 |
|
|
if (--pEntry->tmr == 0) {
|
666 |
|
|
if (++pEntry->retries == DNS_MAX_RETRIES) {
|
667 |
|
|
if ((pEntry->numdns+1<DNS_MAX_SERVERS) && (dns_servers[pEntry->numdns+1].addr!=0)) {
|
668 |
|
|
/* change of server */
|
669 |
|
|
pEntry->numdns++;
|
670 |
|
|
pEntry->tmr = 1;
|
671 |
|
|
pEntry->retries = 0;
|
672 |
|
|
break;
|
673 |
|
|
} else {
|
674 |
|
|
LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": timeout\n", pEntry->name));
|
675 |
|
|
/* call specified callback function if provided */
|
676 |
|
|
if (pEntry->found)
|
677 |
|
|
(*pEntry->found)(pEntry->name, NULL, pEntry->arg);
|
678 |
|
|
/* flush this entry */
|
679 |
|
|
pEntry->state = DNS_STATE_UNUSED;
|
680 |
|
|
pEntry->found = NULL;
|
681 |
|
|
break;
|
682 |
|
|
}
|
683 |
|
|
}
|
684 |
|
|
|
685 |
|
|
/* wait longer for the next retry */
|
686 |
|
|
pEntry->tmr = pEntry->retries;
|
687 |
|
|
|
688 |
|
|
/* send DNS packet for this entry */
|
689 |
|
|
dns_send(pEntry->numdns, pEntry->name, i);
|
690 |
|
|
}
|
691 |
|
|
break;
|
692 |
|
|
}
|
693 |
|
|
|
694 |
|
|
case DNS_STATE_DONE: {
|
695 |
|
|
/* if the time to live is nul */
|
696 |
|
|
if (--pEntry->ttl == 0) {
|
697 |
|
|
LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": flush\n", pEntry->name));
|
698 |
|
|
/* flush this entry */
|
699 |
|
|
pEntry->state = DNS_STATE_UNUSED;
|
700 |
|
|
pEntry->found = NULL;
|
701 |
|
|
}
|
702 |
|
|
break;
|
703 |
|
|
}
|
704 |
|
|
case DNS_STATE_UNUSED:
|
705 |
|
|
/* nothing to do */
|
706 |
|
|
break;
|
707 |
|
|
default:
|
708 |
|
|
LWIP_ASSERT("unknown dns_table entry state:", 0);
|
709 |
|
|
break;
|
710 |
|
|
}
|
711 |
|
|
}
|
712 |
|
|
|
713 |
|
|
/**
|
714 |
|
|
* Call dns_check_entry for each entry in dns_table - check all entries.
|
715 |
|
|
*/
|
716 |
|
|
static void
|
717 |
|
|
dns_check_entries(void)
|
718 |
|
|
{
|
719 |
|
|
u8_t i;
|
720 |
|
|
|
721 |
|
|
for (i = 0; i < DNS_TABLE_SIZE; ++i) {
|
722 |
|
|
dns_check_entry(i);
|
723 |
|
|
}
|
724 |
|
|
}
|
725 |
|
|
|
726 |
|
|
/**
|
727 |
|
|
* Receive input function for DNS response packets arriving for the dns UDP pcb.
|
728 |
|
|
*
|
729 |
|
|
* @params see udp.h
|
730 |
|
|
*/
|
731 |
|
|
static void
|
732 |
|
|
dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port)
|
733 |
|
|
{
|
734 |
|
|
u8_t i;
|
735 |
|
|
char *pHostname;
|
736 |
|
|
struct dns_hdr *hdr;
|
737 |
|
|
struct dns_answer ans;
|
738 |
|
|
struct dns_table_entry *pEntry;
|
739 |
|
|
u8_t nquestions, nanswers;
|
740 |
|
|
#if (DNS_USES_STATIC_BUF == 0)
|
741 |
|
|
u8_t dns_payload[DNS_MSG_SIZE];
|
742 |
|
|
#endif /* (DNS_USES_STATIC_BUF == 0) */
|
743 |
|
|
#if (DNS_USES_STATIC_BUF == 2)
|
744 |
|
|
u8_t* dns_payload;
|
745 |
|
|
#endif /* (DNS_USES_STATIC_BUF == 2) */
|
746 |
|
|
|
747 |
|
|
LWIP_UNUSED_ARG(arg);
|
748 |
|
|
LWIP_UNUSED_ARG(pcb);
|
749 |
|
|
LWIP_UNUSED_ARG(addr);
|
750 |
|
|
LWIP_UNUSED_ARG(port);
|
751 |
|
|
|
752 |
|
|
/* is the dns message too big ? */
|
753 |
|
|
if (p->tot_len > DNS_MSG_SIZE) {
|
754 |
|
|
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too big\n"));
|
755 |
|
|
/* free pbuf and return */
|
756 |
|
|
goto memerr1;
|
757 |
|
|
}
|
758 |
|
|
|
759 |
|
|
/* is the dns message big enough ? */
|
760 |
|
|
if (p->tot_len < (SIZEOF_DNS_HDR + SIZEOF_DNS_QUERY + SIZEOF_DNS_ANSWER)) {
|
761 |
|
|
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too small\n"));
|
762 |
|
|
/* free pbuf and return */
|
763 |
|
|
goto memerr1;
|
764 |
|
|
}
|
765 |
|
|
|
766 |
|
|
#if (DNS_USES_STATIC_BUF == 2)
|
767 |
|
|
dns_payload = mem_malloc(p->tot_len);
|
768 |
|
|
if (dns_payload == NULL) {
|
769 |
|
|
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: mem_malloc error\n"));
|
770 |
|
|
/* free pbuf and return */
|
771 |
|
|
goto memerr1;
|
772 |
|
|
}
|
773 |
|
|
#endif /* (DNS_USES_STATIC_BUF == 2) */
|
774 |
|
|
|
775 |
|
|
/* copy dns payload inside static buffer for processing */
|
776 |
|
|
if (pbuf_copy_partial(p, dns_payload, p->tot_len, 0) == p->tot_len) {
|
777 |
|
|
/* The ID in the DNS header should be our entry into the name table. */
|
778 |
|
|
hdr = (struct dns_hdr*)dns_payload;
|
779 |
|
|
i = htons(hdr->id);
|
780 |
|
|
if (i < DNS_TABLE_SIZE) {
|
781 |
|
|
pEntry = &dns_table[i];
|
782 |
|
|
if(pEntry->state == DNS_STATE_ASKING) {
|
783 |
|
|
/* This entry is now completed. */
|
784 |
|
|
pEntry->state = DNS_STATE_DONE;
|
785 |
|
|
pEntry->err = hdr->flags2 & DNS_FLAG2_ERR_MASK;
|
786 |
|
|
|
787 |
|
|
/* We only care about the question(s) and the answers. The authrr
|
788 |
|
|
and the extrarr are simply discarded. */
|
789 |
|
|
nquestions = htons(hdr->numquestions);
|
790 |
|
|
nanswers = htons(hdr->numanswers);
|
791 |
|
|
|
792 |
|
|
/* Check for error. If so, call callback to inform. */
|
793 |
|
|
if (((hdr->flags1 & DNS_FLAG1_RESPONSE) == 0) || (pEntry->err != 0) || (nquestions != 1)) {
|
794 |
|
|
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", pEntry->name));
|
795 |
|
|
/* call callback to indicate error, clean up memory and return */
|
796 |
|
|
goto responseerr;
|
797 |
|
|
}
|
798 |
|
|
|
799 |
|
|
#if DNS_DOES_NAME_CHECK
|
800 |
|
|
/* Check if the name in the "question" part match with the name in the entry. */
|
801 |
|
|
if (dns_compare_name((unsigned char *)(pEntry->name), (unsigned char *)dns_payload + SIZEOF_DNS_HDR) != 0) {
|
802 |
|
|
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", pEntry->name));
|
803 |
|
|
/* call callback to indicate error, clean up memory and return */
|
804 |
|
|
goto responseerr;
|
805 |
|
|
}
|
806 |
|
|
#endif /* DNS_DOES_NAME_CHECK */
|
807 |
|
|
|
808 |
|
|
/* Skip the name in the "question" part */
|
809 |
|
|
pHostname = (char *) dns_parse_name((unsigned char *)dns_payload + SIZEOF_DNS_HDR) + SIZEOF_DNS_QUERY;
|
810 |
|
|
|
811 |
|
|
while(nanswers > 0) {
|
812 |
|
|
/* skip answer resource record's host name */
|
813 |
|
|
pHostname = (char *) dns_parse_name((unsigned char *)pHostname);
|
814 |
|
|
|
815 |
|
|
/* Check for IP address type and Internet class. Others are discarded. */
|
816 |
|
|
MEMCPY(&ans, pHostname, SIZEOF_DNS_ANSWER);
|
817 |
|
|
if((ntohs(ans.type) == DNS_RRTYPE_A) && (ntohs(ans.class) == DNS_RRCLASS_IN) && (ntohs(ans.len) == sizeof(struct ip_addr)) ) {
|
818 |
|
|
/* read the answer resource record's TTL, and maximize it if needed */
|
819 |
|
|
pEntry->ttl = ntohl(ans.ttl);
|
820 |
|
|
if (pEntry->ttl > DNS_MAX_TTL) {
|
821 |
|
|
pEntry->ttl = DNS_MAX_TTL;
|
822 |
|
|
}
|
823 |
|
|
/* read the IP address after answer resource record's header */
|
824 |
|
|
MEMCPY( &(pEntry->ipaddr), (pHostname+SIZEOF_DNS_ANSWER), sizeof(struct ip_addr));
|
825 |
|
|
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", pEntry->name));
|
826 |
|
|
ip_addr_debug_print(DNS_DEBUG, (&(pEntry->ipaddr)));
|
827 |
|
|
LWIP_DEBUGF(DNS_DEBUG, ("\n"));
|
828 |
|
|
/* call specified callback function if provided */
|
829 |
|
|
if (pEntry->found) {
|
830 |
|
|
(*pEntry->found)(pEntry->name, &pEntry->ipaddr, pEntry->arg);
|
831 |
|
|
}
|
832 |
|
|
/* deallocate memory and return */
|
833 |
|
|
goto memerr2;
|
834 |
|
|
} else {
|
835 |
|
|
pHostname = pHostname + SIZEOF_DNS_ANSWER + htons(ans.len);
|
836 |
|
|
}
|
837 |
|
|
--nanswers;
|
838 |
|
|
}
|
839 |
|
|
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in response\n", pEntry->name));
|
840 |
|
|
/* call callback to indicate error, clean up memory and return */
|
841 |
|
|
goto responseerr;
|
842 |
|
|
}
|
843 |
|
|
}
|
844 |
|
|
}
|
845 |
|
|
|
846 |
|
|
/* deallocate memory and return */
|
847 |
|
|
goto memerr2;
|
848 |
|
|
|
849 |
|
|
responseerr:
|
850 |
|
|
/* ERROR: call specified callback function with NULL as name to indicate an error */
|
851 |
|
|
if (pEntry->found) {
|
852 |
|
|
(*pEntry->found)(pEntry->name, NULL, pEntry->arg);
|
853 |
|
|
}
|
854 |
|
|
/* flush this entry */
|
855 |
|
|
pEntry->state = DNS_STATE_UNUSED;
|
856 |
|
|
pEntry->found = NULL;
|
857 |
|
|
|
858 |
|
|
memerr2:
|
859 |
|
|
#if (DNS_USES_STATIC_BUF == 2)
|
860 |
|
|
/* free dns buffer */
|
861 |
|
|
mem_free(dns_payload);
|
862 |
|
|
#endif /* (DNS_USES_STATIC_BUF == 2) */
|
863 |
|
|
|
864 |
|
|
memerr1:
|
865 |
|
|
/* free pbuf */
|
866 |
|
|
pbuf_free(p);
|
867 |
|
|
return;
|
868 |
|
|
}
|
869 |
|
|
|
870 |
|
|
/**
|
871 |
|
|
* Queues a new hostname to resolve and sends out a DNS query for that hostname
|
872 |
|
|
*
|
873 |
|
|
* @param name the hostname that is to be queried
|
874 |
|
|
* @param found a callback founction to be called on success, failure or timeout
|
875 |
|
|
* @param callback_arg argument to pass to the callback function
|
876 |
|
|
* @return @return a err_t return code.
|
877 |
|
|
*/
|
878 |
|
|
static err_t
|
879 |
|
|
dns_enqueue(const char *name, dns_found_callback found, void *callback_arg)
|
880 |
|
|
{
|
881 |
|
|
u8_t i;
|
882 |
|
|
u8_t lseq, lseqi;
|
883 |
|
|
struct dns_table_entry *pEntry = NULL;
|
884 |
|
|
|
885 |
|
|
/* search an unused entry, or the oldest one */
|
886 |
|
|
lseq = lseqi = 0;
|
887 |
|
|
for (i = 0; i < DNS_TABLE_SIZE; ++i) {
|
888 |
|
|
pEntry = &dns_table[i];
|
889 |
|
|
/* is it an unused entry ? */
|
890 |
|
|
if (pEntry->state == DNS_STATE_UNUSED)
|
891 |
|
|
break;
|
892 |
|
|
|
893 |
|
|
/* check if this is the oldest completed entry */
|
894 |
|
|
if (pEntry->state == DNS_STATE_DONE) {
|
895 |
|
|
if ((dns_seqno - pEntry->seqno) > lseq) {
|
896 |
|
|
lseq = dns_seqno - pEntry->seqno;
|
897 |
|
|
lseqi = i;
|
898 |
|
|
}
|
899 |
|
|
}
|
900 |
|
|
}
|
901 |
|
|
|
902 |
|
|
/* if we don't have found an unused entry, use the oldest completed one */
|
903 |
|
|
if (i == DNS_TABLE_SIZE) {
|
904 |
|
|
if ((lseqi >= DNS_TABLE_SIZE) || (dns_table[lseqi].state != DNS_STATE_DONE)) {
|
905 |
|
|
/* no entry can't be used now, table is full */
|
906 |
|
|
LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS entries table is full\n", name));
|
907 |
|
|
return ERR_MEM;
|
908 |
|
|
} else {
|
909 |
|
|
/* use the oldest completed one */
|
910 |
|
|
i = lseqi;
|
911 |
|
|
pEntry = &dns_table[i];
|
912 |
|
|
}
|
913 |
|
|
}
|
914 |
|
|
|
915 |
|
|
/* use this entry */
|
916 |
|
|
LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS entry %"U16_F"\n", name, (u16_t)(i)));
|
917 |
|
|
|
918 |
|
|
/* fill the entry */
|
919 |
|
|
pEntry->state = DNS_STATE_NEW;
|
920 |
|
|
pEntry->seqno = dns_seqno++;
|
921 |
|
|
pEntry->found = found;
|
922 |
|
|
pEntry->arg = callback_arg;
|
923 |
|
|
strcpy(pEntry->name, name);
|
924 |
|
|
|
925 |
|
|
/* force to send query without waiting timer */
|
926 |
|
|
dns_check_entry(i);
|
927 |
|
|
|
928 |
|
|
/* dns query is enqueued */
|
929 |
|
|
return ERR_INPROGRESS;
|
930 |
|
|
}
|
931 |
|
|
|
932 |
|
|
/**
|
933 |
|
|
* Resolve a hostname (string) into an IP address.
|
934 |
|
|
* NON-BLOCKING callback version for use with raw API!!!
|
935 |
|
|
*
|
936 |
|
|
* Returns immediately with one of err_t return codes:
|
937 |
|
|
* - ERR_OK if hostname is a valid IP address string or the host
|
938 |
|
|
* name is already in the local names table.
|
939 |
|
|
* - ERR_INPROGRESS enqueue a request to be sent to the DNS server
|
940 |
|
|
* for resolution if no errors are present.
|
941 |
|
|
*
|
942 |
|
|
* @param hostname the hostname that is to be queried
|
943 |
|
|
* @param addr pointer to a struct ip_addr where to store the address if it is already
|
944 |
|
|
* cached in the dns_table (only valid if ERR_OK is returned!)
|
945 |
|
|
* @param found a callback function to be called on success, failure or timeout (only if
|
946 |
|
|
* ERR_INPROGRESS is returned!)
|
947 |
|
|
* @param callback_arg argument to pass to the callback function
|
948 |
|
|
* @return a err_t return code.
|
949 |
|
|
*/
|
950 |
|
|
err_t
|
951 |
|
|
dns_gethostbyname(const char *hostname, struct ip_addr *addr, dns_found_callback found,
|
952 |
|
|
void *callback_arg)
|
953 |
|
|
{
|
954 |
|
|
/* not initialized or no valid server yet, or invalid addr pointer
|
955 |
|
|
* or invalid hostname or invalid hostname length */
|
956 |
|
|
if ((dns_pcb == NULL) || (addr == NULL) ||
|
957 |
|
|
(!hostname) || (!hostname[0]) ||
|
958 |
|
|
(strlen(hostname) >= DNS_MAX_NAME_LENGTH)) {
|
959 |
|
|
return ERR_VAL;
|
960 |
|
|
}
|
961 |
|
|
|
962 |
|
|
#if LWIP_HAVE_LOOPIF
|
963 |
|
|
if (strcmp(hostname,"localhost")==0) {
|
964 |
|
|
addr->addr = htonl(INADDR_LOOPBACK);
|
965 |
|
|
return ERR_OK;
|
966 |
|
|
}
|
967 |
|
|
#endif /* LWIP_HAVE_LOOPIF */
|
968 |
|
|
|
969 |
|
|
/* host name already in octet notation? set ip addr and return ERR_OK
|
970 |
|
|
* already have this address cached? */
|
971 |
|
|
if (((addr->addr = inet_addr(hostname)) != INADDR_NONE) ||
|
972 |
|
|
((addr->addr = dns_lookup(hostname)) != INADDR_NONE)) {
|
973 |
|
|
return ERR_OK;
|
974 |
|
|
}
|
975 |
|
|
|
976 |
|
|
/* queue query with specified callback */
|
977 |
|
|
return dns_enqueue(hostname, found, callback_arg);
|
978 |
|
|
}
|
979 |
|
|
|
980 |
|
|
#endif /* LWIP_DNS */
|