1 | /**
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2 | * @file
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3 | * DNS - host name to IP address resolver.
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4 | *
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5 | */
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6 |
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7 | /**
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8 |
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9 | * This file implements a DNS host name to IP address resolver.
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10 |
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11 | * Port to lwIP from uIP
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12 | * by Jim Pettinato April 2007
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13 |
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14 | * uIP version Copyright (c) 2002-2003, Adam Dunkels.
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15 | * All rights reserved.
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16 | *
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17 | * Redistribution and use in source and binary forms, with or without
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18 | * modification, are permitted provided that the following conditions
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19 | * are met:
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20 | * 1. Redistributions of source code must retain the above copyright
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21 | * notice, this list of conditions and the following disclaimer.
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22 | * 2. Redistributions in binary form must reproduce the above copyright
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23 | * notice, this list of conditions and the following disclaimer in the
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24 | * documentation and/or other materials provided with the distribution.
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25 | * 3. The name of the author may not be used to endorse or promote
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26 | * products derived from this software without specific prior
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27 | * written permission.
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28 | *
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29 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
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30 | * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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31 | * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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32 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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33 | * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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34 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
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35 | * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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36 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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37 | * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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38 | * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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39 | * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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40 | *
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41 | *
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42 | * DNS.C
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43 | *
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44 | * The lwIP DNS resolver functions are used to lookup a host name and
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45 | * map it to a numerical IP address. It maintains a list of resolved
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46 | * hostnames that can be queried with the dns_lookup() function.
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47 | * New hostnames can be resolved using the dns_query() function.
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48 | *
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49 | * The lwIP version of the resolver also adds a non-blocking version of
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50 | * gethostbyname() that will work with a raw API application. This function
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51 | * checks for an IP address string first and converts it if it is valid.
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52 | * gethostbyname() then does a dns_lookup() to see if the name is
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53 | * already in the table. If so, the IP is returned. If not, a query is
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54 | * issued and the function returns with a ERR_INPROGRESS status. The app
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55 | * using the dns client must then go into a waiting state.
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56 | *
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57 | * Once a hostname has been resolved (or found to be non-existent),
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58 | * the resolver code calls a specified callback function (which
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59 | * must be implemented by the module that uses the resolver).
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60 | */
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61 |
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62 | /*-----------------------------------------------------------------------------
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63 | * RFC 1035 - Domain names - implementation and specification
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64 | * RFC 2181 - Clarifications to the DNS Specification
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65 | *----------------------------------------------------------------------------*/
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66 |
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67 | /** @todo: define good default values (rfc compliance) */
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68 | /** @todo: improve answer parsing, more checkings... */
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69 | /** @todo: check RFC1035 - 7.3. Processing responses */
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70 |
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71 | /*-----------------------------------------------------------------------------
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72 | * Includes
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73 | *----------------------------------------------------------------------------*/
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74 |
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75 | #include "lwip/opt.h"
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76 |
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77 | #if LWIP_DNS /* don't build if not configured for use in lwipopts.h */
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78 |
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79 | #include "lwip/udp.h"
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80 | #include "lwip/mem.h"
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81 | #include "lwip/memp.h"
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82 | #include "lwip/dns.h"
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83 |
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84 | #include <string.h>
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85 |
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86 | /** DNS server IP address */
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87 | #ifndef DNS_SERVER_ADDRESS
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88 | #define DNS_SERVER_ADDRESS(ipaddr) (ip4_addr_set_u32(ipaddr, ipaddr_addr("208.67.222.222"))) /* resolver1.opendns.com */
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89 | #endif
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90 |
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91 | /** DNS server port address */
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92 | #ifndef DNS_SERVER_PORT
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93 | #define DNS_SERVER_PORT 53
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94 | #endif
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95 |
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96 | /** DNS maximum number of retries when asking for a name, before "timeout". */
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97 | #ifndef DNS_MAX_RETRIES
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98 | #define DNS_MAX_RETRIES 4
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99 | #endif
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100 |
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101 | /** DNS resource record max. TTL (one week as default) */
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102 | #ifndef DNS_MAX_TTL
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103 | #define DNS_MAX_TTL 604800
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104 | #endif
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105 |
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106 | /* DNS protocol flags */
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107 | #define DNS_FLAG1_RESPONSE 0x80
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108 | #define DNS_FLAG1_OPCODE_STATUS 0x10
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109 | #define DNS_FLAG1_OPCODE_INVERSE 0x08
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110 | #define DNS_FLAG1_OPCODE_STANDARD 0x00
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111 | #define DNS_FLAG1_AUTHORATIVE 0x04
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112 | #define DNS_FLAG1_TRUNC 0x02
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113 | #define DNS_FLAG1_RD 0x01
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114 | #define DNS_FLAG2_RA 0x80
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115 | #define DNS_FLAG2_ERR_MASK 0x0f
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116 | #define DNS_FLAG2_ERR_NONE 0x00
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117 | #define DNS_FLAG2_ERR_NAME 0x03
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118 |
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119 | /* DNS protocol states */
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120 | #define DNS_STATE_UNUSED 0
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121 | #define DNS_STATE_NEW 1
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122 | #define DNS_STATE_ASKING 2
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123 | #define DNS_STATE_DONE 3
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124 |
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125 | #ifdef PACK_STRUCT_USE_INCLUDES
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126 | # include "arch/bpstruct.h"
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127 | #endif
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128 | PACK_STRUCT_BEGIN
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129 | /** DNS message header */
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130 | struct dns_hdr {
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131 | PACK_STRUCT_FIELD(u16_t id);
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132 | PACK_STRUCT_FIELD(u8_t flags1);
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133 | PACK_STRUCT_FIELD(u8_t flags2);
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134 | PACK_STRUCT_FIELD(u16_t numquestions);
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135 | PACK_STRUCT_FIELD(u16_t numanswers);
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136 | PACK_STRUCT_FIELD(u16_t numauthrr);
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137 | PACK_STRUCT_FIELD(u16_t numextrarr);
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138 | } PACK_STRUCT_STRUCT;
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139 | PACK_STRUCT_END
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140 | #ifdef PACK_STRUCT_USE_INCLUDES
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141 | # include "arch/epstruct.h"
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142 | #endif
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143 | #define SIZEOF_DNS_HDR 12
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144 |
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145 | /** DNS query message structure.
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146 | No packing needed: only used locally on the stack. */
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147 | struct dns_query {
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148 | /* DNS query record starts with either a domain name or a pointer
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149 | to a name already present somewhere in the packet. */
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150 | u16_t type;
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151 | u16_t cls;
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152 | };
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153 | #define SIZEOF_DNS_QUERY 4
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154 |
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155 | /** DNS answer message structure.
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156 | No packing needed: only used locally on the stack. */
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157 | struct dns_answer {
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158 | /* DNS answer record starts with either a domain name or a pointer
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159 | to a name already present somewhere in the packet. */
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160 | u16_t type;
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161 | u16_t cls;
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162 | u32_t ttl;
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163 | u16_t len;
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164 | };
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165 | #define SIZEOF_DNS_ANSWER 10
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166 |
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167 | /** DNS table entry */
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168 | struct dns_table_entry {
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169 | u8_t state;
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170 | u8_t numdns;
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171 | u8_t tmr;
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172 | u8_t retries;
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173 | u8_t seqno;
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174 | u8_t err;
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175 | u32_t ttl;
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176 | char name[DNS_MAX_NAME_LENGTH];
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177 | ip_addr_t ipaddr;
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178 | /* pointer to callback on DNS query done */
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179 | dns_found_callback found;
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180 | void *arg;
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181 | };
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182 |
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183 | #if DNS_LOCAL_HOSTLIST
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184 |
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185 | #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
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186 | /** Local host-list. For hostnames in this list, no
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187 | * external name resolution is performed */
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188 | static struct local_hostlist_entry *local_hostlist_dynamic;
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189 | #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
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190 |
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191 | /** Defining this allows the local_hostlist_static to be placed in a different
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192 | * linker section (e.g. FLASH) */
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193 | #ifndef DNS_LOCAL_HOSTLIST_STORAGE_PRE
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194 | #define DNS_LOCAL_HOSTLIST_STORAGE_PRE static
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195 | #endif /* DNS_LOCAL_HOSTLIST_STORAGE_PRE */
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196 | /** Defining this allows the local_hostlist_static to be placed in a different
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197 | * linker section (e.g. FLASH) */
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198 | #ifndef DNS_LOCAL_HOSTLIST_STORAGE_POST
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199 | #define DNS_LOCAL_HOSTLIST_STORAGE_POST
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200 | #endif /* DNS_LOCAL_HOSTLIST_STORAGE_POST */
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201 | DNS_LOCAL_HOSTLIST_STORAGE_PRE struct local_hostlist_entry local_hostlist_static[]
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202 | DNS_LOCAL_HOSTLIST_STORAGE_POST = DNS_LOCAL_HOSTLIST_INIT;
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203 |
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204 | #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
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205 |
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206 | static void dns_init_local();
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207 | #endif /* DNS_LOCAL_HOSTLIST */
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208 |
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209 |
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210 | /* forward declarations */
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211 | static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port);
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212 | static void dns_check_entries(void);
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213 |
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214 | /*-----------------------------------------------------------------------------
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215 | * Globales
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216 | *----------------------------------------------------------------------------*/
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217 |
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218 | /* DNS variables */
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219 | static struct udp_pcb *dns_pcb;
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220 | static u8_t dns_seqno;
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221 | static struct dns_table_entry dns_table[DNS_TABLE_SIZE];
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222 | static ip_addr_t dns_servers[DNS_MAX_SERVERS];
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223 | /** Contiguous buffer for processing responses */
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224 | static u8_t dns_payload_buffer[LWIP_MEM_ALIGN_BUFFER(DNS_MSG_SIZE)];
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225 | static u8_t* dns_payload;
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226 |
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227 | /**
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228 | * Initialize the resolver: set up the UDP pcb and configure the default server
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229 | * (DNS_SERVER_ADDRESS).
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230 | */
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231 | void
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232 | dns_init()
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233 | {
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234 | ip_addr_t dnsserver;
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235 |
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236 | dns_payload = (u8_t *)LWIP_MEM_ALIGN(dns_payload_buffer);
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237 |
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238 | /* initialize default DNS server address */
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239 | DNS_SERVER_ADDRESS(&dnsserver);
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240 |
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241 | LWIP_DEBUGF(DNS_DEBUG, ("dns_init: initializing\n"));
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242 |
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243 | /* if dns client not yet initialized... */
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244 | if (dns_pcb == NULL) {
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245 | dns_pcb = udp_new();
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246 |
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247 | if (dns_pcb != NULL) {
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248 | /* initialize DNS table not needed (initialized to zero since it is a
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249 | * global variable) */
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250 | LWIP_ASSERT("For implicit initialization to work, DNS_STATE_UNUSED needs to be 0",
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251 | DNS_STATE_UNUSED == 0);
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252 |
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253 | /* initialize DNS client */
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254 | udp_bind(dns_pcb, IP_ADDR_ANY, 0);
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255 | udp_recv(dns_pcb, dns_recv, NULL);
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256 |
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257 | /* initialize default DNS primary server */
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258 | dns_setserver(0, &dnsserver);
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259 | }
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260 | }
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261 | #if DNS_LOCAL_HOSTLIST
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262 | dns_init_local();
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263 | #endif
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264 | }
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265 |
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266 | /**
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267 | * Initialize one of the DNS servers.
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268 | *
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269 | * @param numdns the index of the DNS server to set must be < DNS_MAX_SERVERS
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270 | * @param dnsserver IP address of the DNS server to set
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271 | */
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272 | void
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273 | dns_setserver(u8_t numdns, ip_addr_t *dnsserver)
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274 | {
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275 | if ((numdns < DNS_MAX_SERVERS) && (dns_pcb != NULL) &&
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276 | (dnsserver != NULL) && !ip_addr_isany(dnsserver)) {
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277 | dns_servers[numdns] = (*dnsserver);
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278 | }
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279 | }
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280 |
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281 | /**
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282 | * Obtain one of the currently configured DNS server.
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283 | *
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284 | * @param numdns the index of the DNS server
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285 | * @return IP address of the indexed DNS server or "ip_addr_any" if the DNS
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286 | * server has not been configured.
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287 | */
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288 | ip_addr_t
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289 | dns_getserver(u8_t numdns)
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290 | {
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291 | if (numdns < DNS_MAX_SERVERS) {
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292 | return dns_servers[numdns];
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293 | } else {
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294 | return *IP_ADDR_ANY;
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295 | }
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296 | }
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297 |
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298 | /**
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299 | * The DNS resolver client timer - handle retries and timeouts and should
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300 | * be called every DNS_TMR_INTERVAL milliseconds (every second by default).
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301 | */
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302 | void
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303 | dns_tmr(void)
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304 | {
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305 | if (dns_pcb != NULL) {
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306 | LWIP_DEBUGF(DNS_DEBUG, ("dns_tmr: dns_check_entries\n"));
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307 | dns_check_entries();
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308 | }
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309 | }
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310 |
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311 | #if DNS_LOCAL_HOSTLIST
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312 | static void
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313 | dns_init_local()
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314 | {
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315 | #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT)
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316 | int i;
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317 | struct local_hostlist_entry *entry;
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318 | /* Dynamic: copy entries from DNS_LOCAL_HOSTLIST_INIT to list */
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319 | struct local_hostlist_entry local_hostlist_init[] = DNS_LOCAL_HOSTLIST_INIT;
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320 | size_t namelen;
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321 | for (i = 0; i < sizeof(local_hostlist_init) / sizeof(struct local_hostlist_entry); i++) {
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322 | struct local_hostlist_entry *init_entry = &local_hostlist_init[i];
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323 | LWIP_ASSERT("invalid host name (NULL)", init_entry->name != NULL);
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324 | namelen = strlen(init_entry->name);
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325 | LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN);
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326 | entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST);
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327 | LWIP_ASSERT("mem-error in dns_init_local", entry != NULL);
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328 | if (entry != NULL) {
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329 | entry->name = (char*)entry + sizeof(struct local_hostlist_entry);
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330 | MEMCPY((char*)entry->name, init_entry->name, namelen);
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331 | ((char*)entry->name)[namelen] = 0;
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332 | entry->addr = init_entry->addr;
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333 | entry->next = local_hostlist_dynamic;
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334 | local_hostlist_dynamic = entry;
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335 | }
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336 | }
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337 | #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT) */
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338 | }
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339 |
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340 | /**
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341 | * Scans the local host-list for a hostname.
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342 | *
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343 | * @param hostname Hostname to look for in the local host-list
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344 | * @return The first IP address for the hostname in the local host-list or
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345 | * IPADDR_NONE if not found.
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346 | */
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347 | static u32_t
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348 | dns_lookup_local(const char *hostname)
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349 | {
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350 | #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
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351 | struct local_hostlist_entry *entry = local_hostlist_dynamic;
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352 | while(entry != NULL) {
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353 | if(strcmp(entry->name, hostname) == 0) {
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354 | return ip4_addr_get_u32(&entry->addr);
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355 | }
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356 | entry = entry->next;
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357 | }
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358 | #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
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359 | int i;
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360 | for (i = 0; i < sizeof(local_hostlist_static) / sizeof(struct local_hostlist_entry); i++) {
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361 | if(strcmp(local_hostlist_static[i].name, hostname) == 0) {
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362 | return ip4_addr_get_u32(&local_hostlist_static[i].addr);
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363 | }
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364 | }
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365 | #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
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366 | return IPADDR_NONE;
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367 | }
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368 |
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369 | #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
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370 | /** Remove all entries from the local host-list for a specific hostname
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371 | * and/or IP addess
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372 | *
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373 | * @param hostname hostname for which entries shall be removed from the local
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374 | * host-list
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375 | * @param addr address for which entries shall be removed from the local host-list
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376 | * @return the number of removed entries
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377 | */
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378 | int
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379 | dns_local_removehost(const char *hostname, const ip_addr_t *addr)
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380 | {
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381 | int removed = 0;
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382 | struct local_hostlist_entry *entry = local_hostlist_dynamic;
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383 | struct local_hostlist_entry *last_entry = NULL;
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384 | while (entry != NULL) {
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385 | if (((hostname == NULL) || !strcmp(entry->name, hostname)) &&
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386 | ((addr == NULL) || ip_addr_cmp(&entry->addr, addr))) {
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387 | struct local_hostlist_entry *free_entry;
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388 | if (last_entry != NULL) {
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389 | last_entry->next = entry->next;
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390 | } else {
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391 | local_hostlist_dynamic = entry->next;
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392 | }
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393 | free_entry = entry;
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394 | entry = entry->next;
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395 | memp_free(MEMP_LOCALHOSTLIST, free_entry);
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396 | removed++;
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397 | } else {
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398 | last_entry = entry;
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399 | entry = entry->next;
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400 | }
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401 | }
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402 | return removed;
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403 | }
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404 |
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405 | /**
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406 | * Add a hostname/IP address pair to the local host-list.
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407 | * Duplicates are not checked.
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408 | *
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409 | * @param hostname hostname of the new entry
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410 | * @param addr IP address of the new entry
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411 | * @return ERR_OK if succeeded or ERR_MEM on memory error
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412 | */
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413 | err_t
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414 | dns_local_addhost(const char *hostname, const ip_addr_t *addr)
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415 | {
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416 | struct local_hostlist_entry *entry;
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417 | size_t namelen;
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418 | LWIP_ASSERT("invalid host name (NULL)", hostname != NULL);
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419 | namelen = strlen(hostname);
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420 | LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN);
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421 | entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST);
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422 | if (entry == NULL) {
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423 | return ERR_MEM;
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424 | }
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425 | entry->name = (char*)entry + sizeof(struct local_hostlist_entry);
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426 | MEMCPY((char*)entry->name, hostname, namelen);
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427 | ((char*)entry->name)[namelen] = 0;
|
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428 | ip_addr_copy(entry->addr, *addr);
|
---|
429 | entry->next = local_hostlist_dynamic;
|
---|
430 | local_hostlist_dynamic = entry;
|
---|
431 | return ERR_OK;
|
---|
432 | }
|
---|
433 | #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC*/
|
---|
434 | #endif /* DNS_LOCAL_HOSTLIST */
|
---|
435 |
|
---|
436 | /**
|
---|
437 | * Look up a hostname in the array of known hostnames.
|
---|
438 | *
|
---|
439 | * @note This function only looks in the internal array of known
|
---|
440 | * hostnames, it does not send out a query for the hostname if none
|
---|
441 | * was found. The function dns_enqueue() can be used to send a query
|
---|
442 | * for a hostname.
|
---|
443 | *
|
---|
444 | * @param name the hostname to look up
|
---|
445 | * @return the hostname's IP address, as u32_t (instead of ip_addr_t to
|
---|
446 | * better check for failure: != IPADDR_NONE) or IPADDR_NONE if the hostname
|
---|
447 | * was not found in the cached dns_table.
|
---|
448 | */
|
---|
449 | static u32_t
|
---|
450 | dns_lookup(const char *name)
|
---|
451 | {
|
---|
452 | u8_t i;
|
---|
453 | #if DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN)
|
---|
454 | u32_t addr;
|
---|
455 | #endif /* DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN) */
|
---|
456 | #if DNS_LOCAL_HOSTLIST
|
---|
457 | if ((addr = dns_lookup_local(name)) != IPADDR_NONE) {
|
---|
458 | return addr;
|
---|
459 | }
|
---|
460 | #endif /* DNS_LOCAL_HOSTLIST */
|
---|
461 | #ifdef DNS_LOOKUP_LOCAL_EXTERN
|
---|
462 | if((addr = DNS_LOOKUP_LOCAL_EXTERN(name)) != IPADDR_NONE) {
|
---|
463 | return addr;
|
---|
464 | }
|
---|
465 | #endif /* DNS_LOOKUP_LOCAL_EXTERN */
|
---|
466 |
|
---|
467 | /* Walk through name list, return entry if found. If not, return NULL. */
|
---|
468 | for (i = 0; i < DNS_TABLE_SIZE; ++i) {
|
---|
469 | if ((dns_table[i].state == DNS_STATE_DONE) &&
|
---|
470 | (strcmp(name, dns_table[i].name) == 0)) {
|
---|
471 | LWIP_DEBUGF(DNS_DEBUG, ("dns_lookup: \"%s\": found = ", name));
|
---|
472 | ip_addr_debug_print(DNS_DEBUG, &(dns_table[i].ipaddr));
|
---|
473 | LWIP_DEBUGF(DNS_DEBUG, ("\n"));
|
---|
474 | return ip4_addr_get_u32(&dns_table[i].ipaddr);
|
---|
475 | }
|
---|
476 | }
|
---|
477 |
|
---|
478 | return IPADDR_NONE;
|
---|
479 | }
|
---|
480 |
|
---|
481 | #if DNS_DOES_NAME_CHECK
|
---|
482 | /**
|
---|
483 | * Compare the "dotted" name "query" with the encoded name "response"
|
---|
484 | * to make sure an answer from the DNS server matches the current dns_table
|
---|
485 | * entry (otherwise, answers might arrive late for hostname not on the list
|
---|
486 | * any more).
|
---|
487 | *
|
---|
488 | * @param query hostname (not encoded) from the dns_table
|
---|
489 | * @param response encoded hostname in the DNS response
|
---|
490 | * @return 0: names equal; 1: names differ
|
---|
491 | */
|
---|
492 | static u8_t
|
---|
493 | dns_compare_name(unsigned char *query, unsigned char *response)
|
---|
494 | {
|
---|
495 | unsigned char n;
|
---|
496 |
|
---|
497 | do {
|
---|
498 | n = *response++;
|
---|
499 | /** @see RFC 1035 - 4.1.4. Message compression */
|
---|
500 | if ((n & 0xc0) == 0xc0) {
|
---|
501 | /* Compressed name */
|
---|
502 | break;
|
---|
503 | } else {
|
---|
504 | /* Not compressed name */
|
---|
505 | while (n > 0) {
|
---|
506 | if ((*query) != (*response)) {
|
---|
507 | return 1;
|
---|
508 | }
|
---|
509 | ++response;
|
---|
510 | ++query;
|
---|
511 | --n;
|
---|
512 | };
|
---|
513 | ++query;
|
---|
514 | }
|
---|
515 | } while (*response != 0);
|
---|
516 |
|
---|
517 | return 0;
|
---|
518 | }
|
---|
519 | #endif /* DNS_DOES_NAME_CHECK */
|
---|
520 |
|
---|
521 | /**
|
---|
522 | * Walk through a compact encoded DNS name and return the end of the name.
|
---|
523 | *
|
---|
524 | * @param query encoded DNS name in the DNS server response
|
---|
525 | * @return end of the name
|
---|
526 | */
|
---|
527 | static unsigned char *
|
---|
528 | dns_parse_name(unsigned char *query)
|
---|
529 | {
|
---|
530 | unsigned char n;
|
---|
531 |
|
---|
532 | do {
|
---|
533 | n = *query++;
|
---|
534 | /** @see RFC 1035 - 4.1.4. Message compression */
|
---|
535 | if ((n & 0xc0) == 0xc0) {
|
---|
536 | /* Compressed name */
|
---|
537 | break;
|
---|
538 | } else {
|
---|
539 | /* Not compressed name */
|
---|
540 | while (n > 0) {
|
---|
541 | ++query;
|
---|
542 | --n;
|
---|
543 | };
|
---|
544 | }
|
---|
545 | } while (*query != 0);
|
---|
546 |
|
---|
547 | return query + 1;
|
---|
548 | }
|
---|
549 |
|
---|
550 | /**
|
---|
551 | * Send a DNS query packet.
|
---|
552 | *
|
---|
553 | * @param numdns index of the DNS server in the dns_servers table
|
---|
554 | * @param name hostname to query
|
---|
555 | * @param id index of the hostname in dns_table, used as transaction ID in the
|
---|
556 | * DNS query packet
|
---|
557 | * @return ERR_OK if packet is sent; an err_t indicating the problem otherwise
|
---|
558 | */
|
---|
559 | static err_t
|
---|
560 | dns_send(u8_t numdns, const char* name, u8_t id)
|
---|
561 | {
|
---|
562 | err_t err;
|
---|
563 | struct dns_hdr *hdr;
|
---|
564 | struct dns_query qry;
|
---|
565 | struct pbuf *p;
|
---|
566 | char *query, *nptr;
|
---|
567 | const char *pHostname;
|
---|
568 | u8_t n;
|
---|
569 |
|
---|
570 | LWIP_DEBUGF(DNS_DEBUG, ("dns_send: dns_servers[%"U16_F"] \"%s\": request\n",
|
---|
571 | (u16_t)(numdns), name));
|
---|
572 | LWIP_ASSERT("dns server out of array", numdns < DNS_MAX_SERVERS);
|
---|
573 | LWIP_ASSERT("dns server has no IP address set", !ip_addr_isany(&dns_servers[numdns]));
|
---|
574 |
|
---|
575 | /* if here, we have either a new query or a retry on a previous query to process */
|
---|
576 | p = pbuf_alloc(PBUF_TRANSPORT, SIZEOF_DNS_HDR + DNS_MAX_NAME_LENGTH +
|
---|
577 | SIZEOF_DNS_QUERY, PBUF_RAM);
|
---|
578 | if (p != NULL) {
|
---|
579 | LWIP_ASSERT("pbuf must be in one piece", p->next == NULL);
|
---|
580 | /* fill dns header */
|
---|
581 | hdr = (struct dns_hdr*)p->payload;
|
---|
582 | memset(hdr, 0, SIZEOF_DNS_HDR);
|
---|
583 | hdr->id = htons(id);
|
---|
584 | hdr->flags1 = DNS_FLAG1_RD;
|
---|
585 | hdr->numquestions = PP_HTONS(1);
|
---|
586 | query = (char*)hdr + SIZEOF_DNS_HDR;
|
---|
587 | pHostname = name;
|
---|
588 | --pHostname;
|
---|
589 |
|
---|
590 | /* convert hostname into suitable query format. */
|
---|
591 | do {
|
---|
592 | ++pHostname;
|
---|
593 | nptr = query;
|
---|
594 | ++query;
|
---|
595 | for(n = 0; *pHostname != '.' && *pHostname != 0; ++pHostname) {
|
---|
596 | *query = *pHostname;
|
---|
597 | ++query;
|
---|
598 | ++n;
|
---|
599 | }
|
---|
600 | *nptr = n;
|
---|
601 | } while(*pHostname != 0);
|
---|
602 | *query++='\0';
|
---|
603 |
|
---|
604 | /* fill dns query */
|
---|
605 | qry.type = PP_HTONS(DNS_RRTYPE_A);
|
---|
606 | qry.cls = PP_HTONS(DNS_RRCLASS_IN);
|
---|
607 | SMEMCPY(query, &qry, SIZEOF_DNS_QUERY);
|
---|
608 |
|
---|
609 | /* resize pbuf to the exact dns query */
|
---|
610 | pbuf_realloc(p, (u16_t)((query + SIZEOF_DNS_QUERY) - ((char*)(p->payload))));
|
---|
611 |
|
---|
612 | /* connect to the server for faster receiving */
|
---|
613 | udp_connect(dns_pcb, &dns_servers[numdns], DNS_SERVER_PORT);
|
---|
614 | /* send dns packet */
|
---|
615 | err = udp_sendto(dns_pcb, p, &dns_servers[numdns], DNS_SERVER_PORT);
|
---|
616 |
|
---|
617 | /* free pbuf */
|
---|
618 | pbuf_free(p);
|
---|
619 | } else {
|
---|
620 | err = ERR_MEM;
|
---|
621 | }
|
---|
622 |
|
---|
623 | return err;
|
---|
624 | }
|
---|
625 |
|
---|
626 | /**
|
---|
627 | * dns_check_entry() - see if pEntry has not yet been queried and, if so, sends out a query.
|
---|
628 | * Check an entry in the dns_table:
|
---|
629 | * - send out query for new entries
|
---|
630 | * - retry old pending entries on timeout (also with different servers)
|
---|
631 | * - remove completed entries from the table if their TTL has expired
|
---|
632 | *
|
---|
633 | * @param i index of the dns_table entry to check
|
---|
634 | */
|
---|
635 | static void
|
---|
636 | dns_check_entry(u8_t i)
|
---|
637 | {
|
---|
638 | err_t err;
|
---|
639 | struct dns_table_entry *pEntry = &dns_table[i];
|
---|
640 |
|
---|
641 | LWIP_ASSERT("array index out of bounds", i < DNS_TABLE_SIZE);
|
---|
642 |
|
---|
643 | switch(pEntry->state) {
|
---|
644 |
|
---|
645 | case DNS_STATE_NEW: {
|
---|
646 | /* initialize new entry */
|
---|
647 | pEntry->state = DNS_STATE_ASKING;
|
---|
648 | pEntry->numdns = 0;
|
---|
649 | pEntry->tmr = 1;
|
---|
650 | pEntry->retries = 0;
|
---|
651 |
|
---|
652 | /* send DNS packet for this entry */
|
---|
653 | err = dns_send(pEntry->numdns, pEntry->name, i);
|
---|
654 | if (err != ERR_OK) {
|
---|
655 | LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING,
|
---|
656 | ("dns_send returned error: %s\n", lwip_strerr(err)));
|
---|
657 | }
|
---|
658 | break;
|
---|
659 | }
|
---|
660 |
|
---|
661 | case DNS_STATE_ASKING: {
|
---|
662 | if (--pEntry->tmr == 0) {
|
---|
663 | if (++pEntry->retries == DNS_MAX_RETRIES) {
|
---|
664 | if ((pEntry->numdns+1<DNS_MAX_SERVERS) && !ip_addr_isany(&dns_servers[pEntry->numdns+1])) {
|
---|
665 | /* change of server */
|
---|
666 | pEntry->numdns++;
|
---|
667 | pEntry->tmr = 1;
|
---|
668 | pEntry->retries = 0;
|
---|
669 | break;
|
---|
670 | } else {
|
---|
671 | LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": timeout\n", pEntry->name));
|
---|
672 | /* call specified callback function if provided */
|
---|
673 | if (pEntry->found)
|
---|
674 | (*pEntry->found)(pEntry->name, NULL, pEntry->arg);
|
---|
675 | /* flush this entry */
|
---|
676 | pEntry->state = DNS_STATE_UNUSED;
|
---|
677 | pEntry->found = NULL;
|
---|
678 | break;
|
---|
679 | }
|
---|
680 | }
|
---|
681 |
|
---|
682 | /* wait longer for the next retry */
|
---|
683 | pEntry->tmr = pEntry->retries;
|
---|
684 |
|
---|
685 | /* send DNS packet for this entry */
|
---|
686 | err = dns_send(pEntry->numdns, pEntry->name, i);
|
---|
687 | if (err != ERR_OK) {
|
---|
688 | LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING,
|
---|
689 | ("dns_send returned error: %s\n", lwip_strerr(err)));
|
---|
690 | }
|
---|
691 | }
|
---|
692 | break;
|
---|
693 | }
|
---|
694 |
|
---|
695 | case DNS_STATE_DONE: {
|
---|
696 | /* if the time to live is nul */
|
---|
697 | if (--pEntry->ttl == 0) {
|
---|
698 | LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": flush\n", pEntry->name));
|
---|
699 | /* flush this entry */
|
---|
700 | pEntry->state = DNS_STATE_UNUSED;
|
---|
701 | pEntry->found = NULL;
|
---|
702 | }
|
---|
703 | break;
|
---|
704 | }
|
---|
705 | case DNS_STATE_UNUSED:
|
---|
706 | /* nothing to do */
|
---|
707 | break;
|
---|
708 | default:
|
---|
709 | LWIP_ASSERT("unknown dns_table entry state:", 0);
|
---|
710 | break;
|
---|
711 | }
|
---|
712 | }
|
---|
713 |
|
---|
714 | /**
|
---|
715 | * Call dns_check_entry for each entry in dns_table - check all entries.
|
---|
716 | */
|
---|
717 | static void
|
---|
718 | dns_check_entries(void)
|
---|
719 | {
|
---|
720 | u8_t i;
|
---|
721 |
|
---|
722 | for (i = 0; i < DNS_TABLE_SIZE; ++i) {
|
---|
723 | dns_check_entry(i);
|
---|
724 | }
|
---|
725 | }
|
---|
726 |
|
---|
727 | /**
|
---|
728 | * Receive input function for DNS response packets arriving for the dns UDP pcb.
|
---|
729 | *
|
---|
730 | * @params see udp.h
|
---|
731 | */
|
---|
732 | static void
|
---|
733 | dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port)
|
---|
734 | {
|
---|
735 | u16_t i;
|
---|
736 | char *pHostname;
|
---|
737 | struct dns_hdr *hdr;
|
---|
738 | struct dns_answer ans;
|
---|
739 | struct dns_table_entry *pEntry;
|
---|
740 | u16_t nquestions, nanswers;
|
---|
741 |
|
---|
742 | LWIP_UNUSED_ARG(arg);
|
---|
743 | LWIP_UNUSED_ARG(pcb);
|
---|
744 | LWIP_UNUSED_ARG(addr);
|
---|
745 | LWIP_UNUSED_ARG(port);
|
---|
746 |
|
---|
747 | /* is the dns message too big ? */
|
---|
748 | if (p->tot_len > DNS_MSG_SIZE) {
|
---|
749 | LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too big\n"));
|
---|
750 | /* free pbuf and return */
|
---|
751 | goto memerr;
|
---|
752 | }
|
---|
753 |
|
---|
754 | /* is the dns message big enough ? */
|
---|
755 | if (p->tot_len < (SIZEOF_DNS_HDR + SIZEOF_DNS_QUERY + SIZEOF_DNS_ANSWER)) {
|
---|
756 | LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too small\n"));
|
---|
757 | /* free pbuf and return */
|
---|
758 | goto memerr;
|
---|
759 | }
|
---|
760 |
|
---|
761 | /* copy dns payload inside static buffer for processing */
|
---|
762 | if (pbuf_copy_partial(p, dns_payload, p->tot_len, 0) == p->tot_len) {
|
---|
763 | /* The ID in the DNS header should be our entry into the name table. */
|
---|
764 | hdr = (struct dns_hdr*)dns_payload;
|
---|
765 | i = htons(hdr->id);
|
---|
766 | if (i < DNS_TABLE_SIZE) {
|
---|
767 | pEntry = &dns_table[i];
|
---|
768 | if(pEntry->state == DNS_STATE_ASKING) {
|
---|
769 | /* This entry is now completed. */
|
---|
770 | pEntry->state = DNS_STATE_DONE;
|
---|
771 | pEntry->err = hdr->flags2 & DNS_FLAG2_ERR_MASK;
|
---|
772 |
|
---|
773 | /* We only care about the question(s) and the answers. The authrr
|
---|
774 | and the extrarr are simply discarded. */
|
---|
775 | nquestions = htons(hdr->numquestions);
|
---|
776 | nanswers = htons(hdr->numanswers);
|
---|
777 |
|
---|
778 | /* Check for error. If so, call callback to inform. */
|
---|
779 | if (((hdr->flags1 & DNS_FLAG1_RESPONSE) == 0) || (pEntry->err != 0) || (nquestions != 1)) {
|
---|
780 | LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", pEntry->name));
|
---|
781 | /* call callback to indicate error, clean up memory and return */
|
---|
782 | goto responseerr;
|
---|
783 | }
|
---|
784 |
|
---|
785 | #if DNS_DOES_NAME_CHECK
|
---|
786 | /* Check if the name in the "question" part match with the name in the entry. */
|
---|
787 | if (dns_compare_name((unsigned char *)(pEntry->name), (unsigned char *)dns_payload + SIZEOF_DNS_HDR) != 0) {
|
---|
788 | LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", pEntry->name));
|
---|
789 | /* call callback to indicate error, clean up memory and return */
|
---|
790 | goto responseerr;
|
---|
791 | }
|
---|
792 | #endif /* DNS_DOES_NAME_CHECK */
|
---|
793 |
|
---|
794 | /* Skip the name in the "question" part */
|
---|
795 | pHostname = (char *) dns_parse_name((unsigned char *)dns_payload + SIZEOF_DNS_HDR) + SIZEOF_DNS_QUERY;
|
---|
796 |
|
---|
797 | while (nanswers > 0) {
|
---|
798 | /* skip answer resource record's host name */
|
---|
799 | pHostname = (char *) dns_parse_name((unsigned char *)pHostname);
|
---|
800 |
|
---|
801 | /* Check for IP address type and Internet class. Others are discarded. */
|
---|
802 | SMEMCPY(&ans, pHostname, SIZEOF_DNS_ANSWER);
|
---|
803 | if((ans.type == PP_HTONS(DNS_RRTYPE_A)) && (ans.cls == PP_HTONS(DNS_RRCLASS_IN)) &&
|
---|
804 | (ans.len == PP_HTONS(sizeof(ip_addr_t))) ) {
|
---|
805 | /* read the answer resource record's TTL, and maximize it if needed */
|
---|
806 | pEntry->ttl = ntohl(ans.ttl);
|
---|
807 | if (pEntry->ttl > DNS_MAX_TTL) {
|
---|
808 | pEntry->ttl = DNS_MAX_TTL;
|
---|
809 | }
|
---|
810 | /* read the IP address after answer resource record's header */
|
---|
811 | SMEMCPY(&(pEntry->ipaddr), (pHostname+SIZEOF_DNS_ANSWER), sizeof(ip_addr_t));
|
---|
812 | LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", pEntry->name));
|
---|
813 | ip_addr_debug_print(DNS_DEBUG, (&(pEntry->ipaddr)));
|
---|
814 | LWIP_DEBUGF(DNS_DEBUG, ("\n"));
|
---|
815 | /* call specified callback function if provided */
|
---|
816 | if (pEntry->found) {
|
---|
817 | (*pEntry->found)(pEntry->name, &pEntry->ipaddr, pEntry->arg);
|
---|
818 | }
|
---|
819 | /* deallocate memory and return */
|
---|
820 | goto memerr;
|
---|
821 | } else {
|
---|
822 | pHostname = pHostname + SIZEOF_DNS_ANSWER + htons(ans.len);
|
---|
823 | }
|
---|
824 | --nanswers;
|
---|
825 | }
|
---|
826 | LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in response\n", pEntry->name));
|
---|
827 | /* call callback to indicate error, clean up memory and return */
|
---|
828 | goto responseerr;
|
---|
829 | }
|
---|
830 | }
|
---|
831 | }
|
---|
832 |
|
---|
833 | /* deallocate memory and return */
|
---|
834 | goto memerr;
|
---|
835 |
|
---|
836 | responseerr:
|
---|
837 | /* ERROR: call specified callback function with NULL as name to indicate an error */
|
---|
838 | if (pEntry->found) {
|
---|
839 | (*pEntry->found)(pEntry->name, NULL, pEntry->arg);
|
---|
840 | }
|
---|
841 | /* flush this entry */
|
---|
842 | pEntry->state = DNS_STATE_UNUSED;
|
---|
843 | pEntry->found = NULL;
|
---|
844 |
|
---|
845 | memerr:
|
---|
846 | /* free pbuf */
|
---|
847 | pbuf_free(p);
|
---|
848 | return;
|
---|
849 | }
|
---|
850 |
|
---|
851 | /**
|
---|
852 | * Queues a new hostname to resolve and sends out a DNS query for that hostname
|
---|
853 | *
|
---|
854 | * @param name the hostname that is to be queried
|
---|
855 | * @param found a callback founction to be called on success, failure or timeout
|
---|
856 | * @param callback_arg argument to pass to the callback function
|
---|
857 | * @return @return a err_t return code.
|
---|
858 | */
|
---|
859 | static err_t
|
---|
860 | dns_enqueue(const char *name, dns_found_callback found, void *callback_arg)
|
---|
861 | {
|
---|
862 | u8_t i;
|
---|
863 | u8_t lseq, lseqi;
|
---|
864 | struct dns_table_entry *pEntry = NULL;
|
---|
865 | size_t namelen;
|
---|
866 |
|
---|
867 | /* search an unused entry, or the oldest one */
|
---|
868 | lseq = lseqi = 0;
|
---|
869 | for (i = 0; i < DNS_TABLE_SIZE; ++i) {
|
---|
870 | pEntry = &dns_table[i];
|
---|
871 | /* is it an unused entry ? */
|
---|
872 | if (pEntry->state == DNS_STATE_UNUSED)
|
---|
873 | break;
|
---|
874 |
|
---|
875 | /* check if this is the oldest completed entry */
|
---|
876 | if (pEntry->state == DNS_STATE_DONE) {
|
---|
877 | if ((dns_seqno - pEntry->seqno) > lseq) {
|
---|
878 | lseq = dns_seqno - pEntry->seqno;
|
---|
879 | lseqi = i;
|
---|
880 | }
|
---|
881 | }
|
---|
882 | }
|
---|
883 |
|
---|
884 | /* if we don't have found an unused entry, use the oldest completed one */
|
---|
885 | if (i == DNS_TABLE_SIZE) {
|
---|
886 | if ((lseqi >= DNS_TABLE_SIZE) || (dns_table[lseqi].state != DNS_STATE_DONE)) {
|
---|
887 | /* no entry can't be used now, table is full */
|
---|
888 | LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS entries table is full\n", name));
|
---|
889 | return ERR_MEM;
|
---|
890 | } else {
|
---|
891 | /* use the oldest completed one */
|
---|
892 | i = lseqi;
|
---|
893 | pEntry = &dns_table[i];
|
---|
894 | }
|
---|
895 | }
|
---|
896 |
|
---|
897 | /* use this entry */
|
---|
898 | LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS entry %"U16_F"\n", name, (u16_t)(i)));
|
---|
899 |
|
---|
900 | /* fill the entry */
|
---|
901 | pEntry->state = DNS_STATE_NEW;
|
---|
902 | pEntry->seqno = dns_seqno++;
|
---|
903 | pEntry->found = found;
|
---|
904 | pEntry->arg = callback_arg;
|
---|
905 | namelen = LWIP_MIN(strlen(name), DNS_MAX_NAME_LENGTH-1);
|
---|
906 | MEMCPY(pEntry->name, name, namelen);
|
---|
907 | pEntry->name[namelen] = 0;
|
---|
908 |
|
---|
909 | /* force to send query without waiting timer */
|
---|
910 | dns_check_entry(i);
|
---|
911 |
|
---|
912 | /* dns query is enqueued */
|
---|
913 | return ERR_INPROGRESS;
|
---|
914 | }
|
---|
915 |
|
---|
916 | /**
|
---|
917 | * Resolve a hostname (string) into an IP address.
|
---|
918 | * NON-BLOCKING callback version for use with raw API!!!
|
---|
919 | *
|
---|
920 | * Returns immediately with one of err_t return codes:
|
---|
921 | * - ERR_OK if hostname is a valid IP address string or the host
|
---|
922 | * name is already in the local names table.
|
---|
923 | * - ERR_INPROGRESS enqueue a request to be sent to the DNS server
|
---|
924 | * for resolution if no errors are present.
|
---|
925 | * - ERR_ARG: dns client not initialized or invalid hostname
|
---|
926 | *
|
---|
927 | * @param hostname the hostname that is to be queried
|
---|
928 | * @param addr pointer to a ip_addr_t where to store the address if it is already
|
---|
929 | * cached in the dns_table (only valid if ERR_OK is returned!)
|
---|
930 | * @param found a callback function to be called on success, failure or timeout (only if
|
---|
931 | * ERR_INPROGRESS is returned!)
|
---|
932 | * @param callback_arg argument to pass to the callback function
|
---|
933 | * @return a err_t return code.
|
---|
934 | */
|
---|
935 | err_t
|
---|
936 | dns_gethostbyname(const char *hostname, ip_addr_t *addr, dns_found_callback found,
|
---|
937 | void *callback_arg)
|
---|
938 | {
|
---|
939 | u32_t ipaddr;
|
---|
940 | /* not initialized or no valid server yet, or invalid addr pointer
|
---|
941 | * or invalid hostname or invalid hostname length */
|
---|
942 | if ((dns_pcb == NULL) || (addr == NULL) ||
|
---|
943 | (!hostname) || (!hostname[0]) ||
|
---|
944 | (strlen(hostname) >= DNS_MAX_NAME_LENGTH)) {
|
---|
945 | return ERR_ARG;
|
---|
946 | }
|
---|
947 |
|
---|
948 | #if LWIP_HAVE_LOOPIF
|
---|
949 | if (strcmp(hostname, "localhost")==0) {
|
---|
950 | ip_addr_set_loopback(addr);
|
---|
951 | return ERR_OK;
|
---|
952 | }
|
---|
953 | #endif /* LWIP_HAVE_LOOPIF */
|
---|
954 |
|
---|
955 | /* host name already in octet notation? set ip addr and return ERR_OK */
|
---|
956 | ipaddr = ipaddr_addr(hostname);
|
---|
957 | if (ipaddr == IPADDR_NONE) {
|
---|
958 | /* already have this address cached? */
|
---|
959 | ipaddr = dns_lookup(hostname);
|
---|
960 | }
|
---|
961 | if (ipaddr != IPADDR_NONE) {
|
---|
962 | ip4_addr_set_u32(addr, ipaddr);
|
---|
963 | return ERR_OK;
|
---|
964 | }
|
---|
965 |
|
---|
966 | /* queue query with specified callback */
|
---|
967 | return dns_enqueue(hostname, found, callback_arg);
|
---|
968 | }
|
---|
969 |
|
---|
970 | #endif /* LWIP_DNS */
|
---|