--- /dev/null
+/**
+ * @file
+ * DNS - host name to IP address resolver.
+ *
+ */
+
+/**
+
+ * This file implements a DNS host name to IP address resolver.
+
+ * Port to lwIP from uIP
+ * by Jim Pettinato April 2007
+
+ * uIP version Copyright (c) 2002-2003, Adam Dunkels.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ * products derived from this software without specific prior
+ * written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
+ * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
+ * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ *
+ * DNS.C
+ *
+ * The lwIP DNS resolver functions are used to lookup a host name and
+ * map it to a numerical IP address. It maintains a list of resolved
+ * hostnames that can be queried with the dns_lookup() function.
+ * New hostnames can be resolved using the dns_query() function.
+ *
+ * The lwIP version of the resolver also adds a non-blocking version of
+ * gethostbyname() that will work with a raw API application. This function
+ * checks for an IP address string first and converts it if it is valid.
+ * gethostbyname() then does a dns_lookup() to see if the name is
+ * already in the table. If so, the IP is returned. If not, a query is
+ * issued and the function returns with a ERR_INPROGRESS status. The app
+ * using the dns client must then go into a waiting state.
+ *
+ * Once a hostname has been resolved (or found to be non-existent),
+ * the resolver code calls a specified callback function (which
+ * must be implemented by the module that uses the resolver).
+ */
+
+/*-----------------------------------------------------------------------------
+ * RFC 1035 - Domain names - implementation and specification
+ * RFC 2181 - Clarifications to the DNS Specification
+ *----------------------------------------------------------------------------*/
+
+/** @todo: define good default values (rfc compliance) */
+/** @todo: improve answer parsing, more checkings... */
+/** @todo: check RFC1035 - 7.3. Processing responses */
+
+/*-----------------------------------------------------------------------------
+ * Includes
+ *----------------------------------------------------------------------------*/
+
+#include "lwip/opt.h"
+
+#if LWIP_DNS /* don't build if not configured for use in lwipopts.h */
+
+#include "lwip/udp.h"
+#include "lwip/mem.h"
+#include "lwip/dns.h"
+
+#include <string.h>
+
+/** DNS server IP address */
+#ifndef DNS_SERVER_ADDRESS
+#define DNS_SERVER_ADDRESS inet_addr("208.67.222.222") /* resolver1.opendns.com */
+#endif
+
+/** DNS server port address */
+#ifndef DNS_SERVER_PORT
+#define DNS_SERVER_PORT 53
+#endif
+
+/** DNS maximum number of retries when asking for a name, before "timeout". */
+#ifndef DNS_MAX_RETRIES
+#define DNS_MAX_RETRIES 4
+#endif
+
+/** DNS resource record max. TTL (one week as default) */
+#ifndef DNS_MAX_TTL
+#define DNS_MAX_TTL 604800
+#endif
+
+/* DNS protocol flags */
+#define DNS_FLAG1_RESPONSE 0x80
+#define DNS_FLAG1_OPCODE_STATUS 0x10
+#define DNS_FLAG1_OPCODE_INVERSE 0x08
+#define DNS_FLAG1_OPCODE_STANDARD 0x00
+#define DNS_FLAG1_AUTHORATIVE 0x04
+#define DNS_FLAG1_TRUNC 0x02
+#define DNS_FLAG1_RD 0x01
+#define DNS_FLAG2_RA 0x80
+#define DNS_FLAG2_ERR_MASK 0x0f
+#define DNS_FLAG2_ERR_NONE 0x00
+#define DNS_FLAG2_ERR_NAME 0x03
+
+/* DNS protocol states */
+#define DNS_STATE_UNUSED 0
+#define DNS_STATE_NEW 1
+#define DNS_STATE_ASKING 2
+#define DNS_STATE_DONE 3
+
+#ifdef PACK_STRUCT_USE_INCLUDES
+# include "arch/bpstruct.h"
+#endif
+PACK_STRUCT_BEGIN
+/** DNS message header */
+struct dns_hdr {
+ u16_t id;
+ u8_t flags1;
+ u8_t flags2;
+ u16_t numquestions;
+ u16_t numanswers;
+ u16_t numauthrr;
+ u16_t numextrarr;
+} PACK_STRUCT_STRUCT;
+PACK_STRUCT_END
+#ifdef PACK_STRUCT_USE_INCLUDES
+# include "arch/epstruct.h"
+#endif
+
+#ifdef PACK_STRUCT_USE_INCLUDES
+# include "arch/bpstruct.h"
+#endif
+PACK_STRUCT_BEGIN
+/** DNS query message structure */
+struct dns_query {
+ /* DNS query record starts with either a domain name or a pointer
+ to a name already present somewhere in the packet. */
+ u16_t type;
+ u16_t class;
+} PACK_STRUCT_STRUCT;
+PACK_STRUCT_END
+#ifdef PACK_STRUCT_USE_INCLUDES
+# include "arch/epstruct.h"
+#endif
+
+#ifdef PACK_STRUCT_USE_INCLUDES
+# include "arch/bpstruct.h"
+#endif
+PACK_STRUCT_BEGIN
+/** DNS answer message structure */
+struct dns_answer {
+ /* DNS answer record starts with either a domain name or a pointer
+ to a name already present somewhere in the packet. */
+ u16_t type;
+ u16_t class;
+ u32_t ttl;
+ u16_t len;
+} PACK_STRUCT_STRUCT;
+PACK_STRUCT_END
+#ifdef PACK_STRUCT_USE_INCLUDES
+# include "arch/epstruct.h"
+#endif
+
+/** DNS table entry */
+struct dns_table_entry {
+ u8_t state;
+ u8_t numdns;
+ u8_t tmr;
+ u8_t retries;
+ u8_t seqno;
+ u8_t err;
+ u32_t ttl;
+ char name[DNS_MAX_NAME_LENGTH];
+ struct ip_addr ipaddr;
+ /* pointer to callback on DNS query done */
+ dns_found_callback found;
+ void *arg;
+};
+
+
+/* forward declarations */
+static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port);
+static void dns_check_entries(void);
+
+/*-----------------------------------------------------------------------------
+ * Globales
+ *----------------------------------------------------------------------------*/
+
+/* DNS variables */
+static struct udp_pcb *dns_pcb;
+static u8_t dns_seqno;
+static struct dns_table_entry dns_table[DNS_TABLE_SIZE];
+static struct ip_addr dns_servers[DNS_MAX_SERVERS];
+
+#if (DNS_USES_STATIC_BUF == 1)
+static u8_t dns_payload[DNS_MSG_SIZE];
+#endif /* (DNS_USES_STATIC_BUF == 1) */
+
+/**
+ * Initialize the resolver: set up the UDP pcb and configure the default server
+ * (DNS_SERVER_ADDRESS).
+ */
+void
+dns_init()
+{
+ struct ip_addr dnsserver;
+
+ /* initialize default DNS server address */
+ dnsserver.addr = DNS_SERVER_ADDRESS;
+
+ LWIP_DEBUGF(DNS_DEBUG, ("dns_init: initializing\n"));
+
+ /* if dns client not yet initialized... */
+ if (dns_pcb == NULL) {
+ dns_pcb = udp_new();
+
+ if (dns_pcb != NULL) {
+ /* initialize DNS table not needed (initialized to zero since it is a
+ * global variable) */
+ LWIP_ASSERT("For implicit initialization to work, DNS_STATE_UNUSED needs to be 0",
+ DNS_STATE_UNUSED == 0);
+
+ /* initialize DNS client */
+ udp_bind(dns_pcb, IP_ADDR_ANY, 0);
+ udp_recv(dns_pcb, dns_recv, NULL);
+
+ /* initialize default DNS primary server */
+ dns_setserver(0, &dnsserver);
+ }
+ }
+}
+
+/**
+ * Initialize one of the DNS servers.
+ *
+ * @param numdns the index of the DNS server to set must be < DNS_MAX_SERVERS
+ * @param dnsserver IP address of the DNS server to set
+ */
+void
+dns_setserver(u8_t numdns, struct ip_addr *dnsserver)
+{
+ if ((numdns < DNS_MAX_SERVERS) && (dns_pcb != NULL) &&
+ (dnsserver != NULL) && (dnsserver->addr !=0 )) {
+ dns_servers[numdns] = (*dnsserver);
+ }
+}
+
+/**
+ * Obtain one of the currently configured DNS server.
+ *
+ * @param numdns the index of the DNS server
+ * @return IP address of the indexed DNS server or "ip_addr_any" if the DNS
+ * server has not been configured.
+ */
+struct ip_addr
+dns_getserver(u8_t numdns)
+{
+ if (numdns < DNS_MAX_SERVERS) {
+ return dns_servers[numdns];
+ } else {
+ return *IP_ADDR_ANY;
+ }
+}
+
+/**
+ * The DNS resolver client timer - handle retries and timeouts and should
+ * be called every DNS_TMR_INTERVAL milliseconds (every second by default).
+ */
+void
+dns_tmr(void)
+{
+ if (dns_pcb != NULL) {
+ LWIP_DEBUGF(DNS_DEBUG, ("dns_tmr: dns_check_entries\n"));
+ dns_check_entries();
+ }
+}
+
+/**
+ * Look up a hostname in the array of known hostnames.
+ *
+ * @note This function only looks in the internal array of known
+ * hostnames, it does not send out a query for the hostname if none
+ * was found. The function dns_enqueue() can be used to send a query
+ * for a hostname.
+ *
+ * @param name the hostname to look up
+ * @return the hostname's IP address, as u32_t (instead of struct ip_addr to
+ * better check for failure: != 0) or 0 if the hostname was not found
+ * in the cached dns_table.
+ */
+static u32_t
+dns_lookup(const char *name)
+{
+ u8_t i;
+
+ /* Walk through name list, return entry if found. If not, return NULL. */
+ for (i = 0; i < DNS_TABLE_SIZE; ++i) {
+ if ((dns_table[i].state == DNS_STATE_DONE) &&
+ (strcmp(name, dns_table[i].name) == 0)) {
+ LWIP_DEBUGF(DNS_DEBUG, ("dns_lookup: \"%s\": found = ", name));
+ ip_addr_debug_print(DNS_DEBUG, &(dns_table[i].ipaddr));
+ LWIP_DEBUGF(DNS_DEBUG, ("\n"));
+ return dns_table[i].ipaddr.addr;
+ }
+ }
+
+ return 0;
+}
+
+#if DNS_DOES_NAME_CHECK
+/**
+ * Compare the "dotted" name "query" with the encoded name "response"
+ * to make sure an answer from the DNS server matches the current dns_table
+ * entry (otherwise, answers might arrive late for hostname not on the list
+ * any more).
+ *
+ * @param query hostname (not encoded) from the dns_table
+ * @param response encoded hostname in the DNS response
+ * @return 0: names equal; 1: names differ
+ */
+static u8_t
+dns_compare_name(unsigned char *query, unsigned char *response)
+{
+ unsigned char n;
+
+ do {
+ n = *response++;
+ /** @see RFC 1035 - 4.1.4. Message compression */
+ if ((n & 0xc0) == 0xc0) {
+ /* Compressed name */
+ break;
+ } else {
+ /* Not compressed name */
+ while (n > 0) {
+ if ((*query) != (*response)) {
+ return 1;
+ }
+ ++response;
+ ++query;
+ --n;
+ };
+ ++query;
+ }
+ } while (*response != 0);
+
+ return 0;
+}
+#endif /* DNS_DOES_NAME_CHECK */
+
+/**
+ * Walk through a compact encoded DNS name and return the end of the name.
+ *
+ * @param query encoded DNS name in the DNS server response
+ * @return end of the name
+ */
+static unsigned char *
+dns_parse_name(unsigned char *query)
+{
+ unsigned char n;
+
+ do {
+ n = *query++;
+ /** @see RFC 1035 - 4.1.4. Message compression */
+ if ((n & 0xc0) == 0xc0) {
+ /* Compressed name */
+ break;
+ } else {
+ /* Not compressed name */
+ while (n > 0) {
+ ++query;
+ --n;
+ };
+ }
+ } while (*query != 0);
+
+ return query + 1;
+}
+
+/**
+ * Send a DNS query packet.
+ *
+ * @param numdns index of the DNS server in the dns_servers table
+ * @param name hostname to query
+ * @param id index of the hostname in dns_table, used as transaction ID in the
+ * DNS query packet
+ * @return ERR_OK if packet is sent; an err_t indicating the problem otherwise
+ */
+static err_t
+dns_send(u8_t numdns, const char* name, u8_t id)
+{
+ err_t err;
+ struct dns_hdr *hdr;
+ struct dns_query qry;
+ struct pbuf *p;
+ char *query, *nptr;
+ const char *pHostname;
+ u8_t n;
+
+ LWIP_DEBUGF(DNS_DEBUG, ("dns_send: dns_servers[%"U16_F"] \"%s\": request\n",
+ (u16_t)(numdns), name));
+ LWIP_ASSERT("dns server out of array", numdns < DNS_MAX_SERVERS);
+ LWIP_ASSERT("dns server has no IP address set", dns_servers[numdns].addr != 0);
+
+ /* if here, we have either a new query or a retry on a previous query to process */
+ p = pbuf_alloc(PBUF_TRANSPORT, sizeof(struct dns_hdr) + DNS_MAX_NAME_LENGTH +
+ sizeof(struct dns_query), PBUF_RAM);
+ if (p != NULL) {
+ LWIP_ASSERT("pbuf must be in one piece", p->next == NULL);
+ /* fill dns header */
+ hdr = (struct dns_hdr*)p->payload;
+ memset(hdr, 0, sizeof(struct dns_hdr));
+ hdr->id = htons(id);
+ hdr->flags1 = DNS_FLAG1_RD;
+ hdr->numquestions = htons(1);
+ query = (char*)hdr + sizeof(struct dns_hdr);
+ pHostname = name;
+ --pHostname;
+
+ /* convert hostname into suitable query format. */
+ do {
+ ++pHostname;
+ nptr = query;
+ ++query;
+ for(n = 0; *pHostname != '.' && *pHostname != 0; ++pHostname) {
+ *query = *pHostname;
+ ++query;
+ ++n;
+ }
+ *nptr = n;
+ } while(*pHostname != 0);
+ *query++='\0';
+
+ /* fill dns query */
+ qry.type = htons(DNS_RRTYPE_A);
+ qry.class = htons(DNS_RRCLASS_IN);
+ MEMCPY( query, &qry, sizeof(struct dns_query));
+
+ /* resize pbuf to the exact dns query */
+ pbuf_realloc(p, (query + sizeof(struct dns_query)) - ((char*)(p->payload)));
+
+ /* connect to the server for faster receiving */
+ udp_connect(dns_pcb, &dns_servers[numdns], DNS_SERVER_PORT);
+ /* send dns packet */
+ err = udp_sendto(dns_pcb, p, &dns_servers[numdns], DNS_SERVER_PORT);
+
+ /* free pbuf */
+ pbuf_free(p);
+ } else {
+ err = ERR_MEM;
+ }
+
+ return err;
+}
+
+/**
+ * dns_check_entry() - see if pEntry has not yet been queried and, if so, sends out a query.
+ * Check an entry in the dns_table:
+ * - send out query for new entries
+ * - retry old pending entries on timeout (also with different servers)
+ * - remove completed entries from the table if their TTL has expired
+ *
+ * @param i index of the dns_table entry to check
+ */
+static void
+dns_check_entry(u8_t i)
+{
+ struct dns_table_entry *pEntry = &dns_table[i];
+
+ LWIP_ASSERT("array index out of bounds", i < DNS_TABLE_SIZE);
+
+ switch(pEntry->state) {
+
+ case DNS_STATE_NEW: {
+ /* initialize new entry */
+ pEntry->state = DNS_STATE_ASKING;
+ pEntry->numdns = 0;
+ pEntry->tmr = 1;
+ pEntry->retries = 0;
+
+ /* send DNS packet for this entry */
+ dns_send(pEntry->numdns, pEntry->name, i);
+ break;
+ }
+
+ case DNS_STATE_ASKING: {
+ if (--pEntry->tmr == 0) {
+ if (++pEntry->retries == DNS_MAX_RETRIES) {
+ if ((pEntry->numdns+1<DNS_MAX_SERVERS) && (dns_servers[pEntry->numdns+1].addr!=0)) {
+ /* change of server */
+ pEntry->numdns++;
+ pEntry->tmr = 1;
+ pEntry->retries = 0;
+ break;
+ } else {
+ LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": timeout\n", pEntry->name));
+ /* call specified callback function if provided */
+ if (pEntry->found)
+ (*pEntry->found)(pEntry->name, NULL, pEntry->arg);
+ /* flush this entry */
+ pEntry->state = DNS_STATE_UNUSED;
+ pEntry->found = NULL;
+ break;
+ }
+ }
+
+ /* wait longer for the next retry */
+ pEntry->tmr = pEntry->retries;
+
+ /* send DNS packet for this entry */
+ dns_send(pEntry->numdns, pEntry->name, i);
+ }
+ break;
+ }
+
+ case DNS_STATE_DONE: {
+ /* if the time to live is nul */
+ if (--pEntry->ttl == 0) {
+ LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": flush\n", pEntry->name));
+ /* flush this entry */
+ pEntry->state = DNS_STATE_UNUSED;
+ pEntry->found = NULL;
+ }
+ break;
+ }
+ case DNS_STATE_UNUSED:
+ /* nothing to do */
+ break;
+ default:
+ LWIP_ASSERT("unknown dns_table entry state:", 0);
+ break;
+ }
+}
+
+/**
+ * Call dns_check_entry for each entry in dns_table - check all entries.
+ */
+static void
+dns_check_entries(void)
+{
+ u8_t i;
+
+ for (i = 0; i < DNS_TABLE_SIZE; ++i) {
+ dns_check_entry(i);
+ }
+}
+
+/**
+ * Receive input function for DNS response packets arriving for the dns UDP pcb.
+ *
+ * @params see udp.h
+ */
+static void
+dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port)
+{
+ u8_t i;
+ char *pHostname;
+ struct dns_hdr *hdr;
+ struct dns_answer ans;
+ struct dns_table_entry *pEntry;
+ u8_t nquestions, nanswers;
+#if (DNS_USES_STATIC_BUF == 0)
+ u8_t dns_payload[DNS_MSG_SIZE];
+#endif /* (DNS_USES_STATIC_BUF == 0) */
+#if (DNS_USES_STATIC_BUF == 2)
+ u8_t* dns_payload;
+#endif /* (DNS_USES_STATIC_BUF == 2) */
+
+ LWIP_UNUSED_ARG(arg);
+ LWIP_UNUSED_ARG(pcb);
+ LWIP_UNUSED_ARG(addr);
+ LWIP_UNUSED_ARG(port);
+
+ /* is the dns message too big ? */
+ if (p->tot_len > DNS_MSG_SIZE) {
+ LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too big\n"));
+ /* free pbuf and return */
+ goto memerr1;
+ }
+
+ /* is the dns message big enough ? */
+ if (p->tot_len < (sizeof(struct dns_hdr) + sizeof(struct dns_query) + sizeof(struct dns_answer))) {
+ LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too small\n"));
+ /* free pbuf and return */
+ goto memerr1;
+ }
+
+#if (DNS_USES_STATIC_BUF == 2)
+ dns_payload = mem_malloc(p->tot_len);
+ if (dns_payload == NULL) {
+ LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: mem_malloc error\n"));
+ /* free pbuf and return */
+ goto memerr1;
+ }
+#endif /* (DNS_USES_STATIC_BUF == 2) */
+
+ /* copy dns payload inside static buffer for processing */
+ if (pbuf_copy_partial(p, dns_payload, p->tot_len, 0) == p->tot_len) {
+ /* The ID in the DNS header should be our entry into the name table. */
+ hdr = (struct dns_hdr*)dns_payload;
+ i = htons(hdr->id);
+ if (i < DNS_TABLE_SIZE) {
+ pEntry = &dns_table[i];
+ if(pEntry->state == DNS_STATE_ASKING) {
+ /* This entry is now completed. */
+ pEntry->state = DNS_STATE_DONE;
+ pEntry->err = hdr->flags2 & DNS_FLAG2_ERR_MASK;
+
+ /* We only care about the question(s) and the answers. The authrr
+ and the extrarr are simply discarded. */
+ nquestions = htons(hdr->numquestions);
+ nanswers = htons(hdr->numanswers);
+
+ /* Check for error. If so, call callback to inform. */
+ if (((hdr->flags1 & DNS_FLAG1_RESPONSE) == 0) || (pEntry->err != 0) || (nquestions != 1)) {
+ LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", pEntry->name));
+ /* call callback to indicate error, clean up memory and return */
+ goto responseerr;
+ }
+
+#if DNS_DOES_NAME_CHECK
+ /* Check if the name in the "question" part match with the name in the entry. */
+ if (dns_compare_name((unsigned char *)(pEntry->name), (unsigned char *)dns_payload + sizeof(struct dns_hdr)) != 0) {
+ LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", pEntry->name));
+ /* call callback to indicate error, clean up memory and return */
+ goto responseerr;
+ }
+#endif /* DNS_DOES_NAME_CHECK */
+
+ /* Skip the name in the "question" part */
+ pHostname = (char *) dns_parse_name((unsigned char *)dns_payload + sizeof(struct dns_hdr)) + sizeof(struct dns_query);
+
+ while(nanswers > 0) {
+ /* skip answer resource record's host name */
+ pHostname = (char *) dns_parse_name((unsigned char *)pHostname);
+
+ /* Check for IP address type and Internet class. Others are discarded. */
+ MEMCPY(&ans, pHostname, sizeof(struct dns_answer));
+ if((ntohs(ans.type) == DNS_RRTYPE_A) && (ntohs(ans.class) == DNS_RRCLASS_IN) && (ntohs(ans.len) == sizeof(struct ip_addr)) ) {
+ /* read the answer resource record's TTL, and maximize it if needed */
+ pEntry->ttl = ntohl(ans.ttl);
+ if (pEntry->ttl > DNS_MAX_TTL) {
+ pEntry->ttl = DNS_MAX_TTL;
+ }
+ /* read the IP address after answer resource record's header */
+ MEMCPY( &(pEntry->ipaddr), (pHostname+sizeof(struct dns_answer)), sizeof(struct ip_addr));
+ LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", pEntry->name));
+ ip_addr_debug_print(DNS_DEBUG, (&(pEntry->ipaddr)));
+ LWIP_DEBUGF(DNS_DEBUG, ("\n"));
+ /* call specified callback function if provided */
+ if (pEntry->found) {
+ (*pEntry->found)(pEntry->name, &pEntry->ipaddr, pEntry->arg);
+ }
+ /* deallocate memory and return */
+ goto memerr2;
+ } else {
+ pHostname = pHostname + sizeof(struct dns_answer) + htons(ans.len);
+ }
+ --nanswers;
+ }
+ LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in response\n", pEntry->name));
+ /* call callback to indicate error, clean up memory and return */
+ goto responseerr;
+ }
+ }
+ }
+
+ /* deallocate memory and return */
+ goto memerr2;
+
+responseerr:
+ /* ERROR: call specified callback function with NULL as name to indicate an error */
+ if (pEntry->found) {
+ (*pEntry->found)(pEntry->name, NULL, pEntry->arg);
+ }
+ /* flush this entry */
+ pEntry->state = DNS_STATE_UNUSED;
+ pEntry->found = NULL;
+
+memerr2:
+#if (DNS_USES_STATIC_BUF == 2)
+ /* free dns buffer */
+ mem_free(dns_payload);
+#endif /* (DNS_USES_STATIC_BUF == 2) */
+
+memerr1:
+ /* free pbuf */
+ pbuf_free(p);
+ return;
+}
+
+/**
+ * Queues a new hostname to resolve and sends out a DNS query for that hostname
+ *
+ * @param name the hostname that is to be queried
+ * @param found a callback founction to be called on success, failure or timeout
+ * @param callback_arg argument to pass to the callback function
+ * @return @return a err_t return code.
+ */
+static err_t
+dns_enqueue(const char *name, dns_found_callback found, void *callback_arg)
+{
+ u8_t i;
+ u8_t lseq, lseqi;
+ struct dns_table_entry *pEntry = NULL;
+
+ /* search an unused entry, or the oldest one */
+ lseq = lseqi = 0;
+ for (i = 0; i < DNS_TABLE_SIZE; ++i) {
+ pEntry = &dns_table[i];
+ /* is it an unused entry ? */
+ if (pEntry->state == DNS_STATE_UNUSED)
+ break;
+
+ /* check if this is the oldest completed entry */
+ if (pEntry->state == DNS_STATE_DONE) {
+ if ((dns_seqno - pEntry->seqno) > lseq) {
+ lseq = dns_seqno - pEntry->seqno;
+ lseqi = i;
+ }
+ }
+ }
+
+ /* if we don't have found an unused entry, use the oldest completed one */
+ if (i == DNS_TABLE_SIZE) {
+ if ((lseqi >= DNS_TABLE_SIZE) || (dns_table[lseqi].state != DNS_STATE_DONE)) {
+ /* no entry can't be used now, table is full */
+ LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS entries table is full\n", name));
+ return ERR_MEM;
+ } else {
+ /* use the oldest completed one */
+ i = lseqi;
+ pEntry = &dns_table[i];
+ }
+ }
+
+ /* use this entry */
+ LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS entry %"U16_F"\n", name, (u16_t)(i)));
+
+ /* fill the entry */
+ pEntry->state = DNS_STATE_NEW;
+ pEntry->seqno = dns_seqno++;
+ pEntry->found = found;
+ pEntry->arg = callback_arg;
+ strcpy(pEntry->name, name);
+
+ /* force to send query without waiting timer */
+ dns_check_entry(i);
+
+ /* dns query is enqueued */
+ return ERR_INPROGRESS;
+}
+
+/**
+ * Resolve a hostname (string) into an IP address.
+ * NON-BLOCKING callback version for use with raw API!!!
+ *
+ * Returns immediately with one of err_t return codes:
+ * - ERR_OK if hostname is a valid IP address string or the host
+ * name is already in the local names table.
+ * - ERR_INPROGRESS enqueue a request to be sent to the DNS server
+ * for resolution if no errors are present.
+ *
+ * @param hostname the hostname that is to be queried
+ * @param addr pointer to a struct ip_addr where to store the address if it is already
+ * cached in the dns_table (only valid if ERR_OK is returned!)
+ * @param found a callback function to be called on success, failure or timeout (only if
+ * ERR_INPROGRESS is returned!)
+ * @param callback_arg argument to pass to the callback function
+ * @return a err_t return code.
+ */
+err_t
+dns_gethostbyname(const char *hostname, struct ip_addr *addr, dns_found_callback found,
+ void *callback_arg)
+{
+ /* not initialized or no valid server yet, or invalid addr pointer
+ * or invalid hostname or invalid hostname length */
+ if ((dns_pcb == NULL) || (addr == NULL) ||
+ (!hostname) || (!hostname[0]) ||
+ (strlen(hostname) >= DNS_MAX_NAME_LENGTH)) {
+ return ERR_VAL;
+ }
+
+#if LWIP_HAVE_LOOPIF
+ if (strcmp(hostname,"localhost")==0) {
+ addr->addr = INADDR_LOOPBACK;
+ return ERR_OK;
+ }
+#endif /* LWIP_HAVE_LOOPIF */
+
+ /* host name already in octet notation? set ip addr and return ERR_OK
+ * already have this address cached? */
+ if (((addr->addr = inet_addr(hostname)) != INADDR_NONE) ||
+ ((addr->addr = dns_lookup(hostname)) != 0)) {
+ return ERR_OK;
+ }
+
+ /* queue query with specified callback */
+ return dns_enqueue(hostname, found, callback_arg);
+}
+
+#endif /* LWIP_DNS */
