diff options
Diffstat (limited to 'core/lwip/src/core/dns.c')
| -rw-r--r-- | core/lwip/src/core/dns.c | 975 |
1 files changed, 975 insertions, 0 deletions
diff --git a/core/lwip/src/core/dns.c b/core/lwip/src/core/dns.c new file mode 100644 index 0000000..ca807c1 --- /dev/null +++ b/core/lwip/src/core/dns.c @@ -0,0 +1,975 @@ +/** + * @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/memp.h" +#include "lwip/dns.h" + +#include <string.h> + +/** DNS server IP address */ +#ifndef DNS_SERVER_ADDRESS +#define DNS_SERVER_ADDRESS(ipaddr) (ip4_addr_set_u32(ipaddr, ipaddr_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 { + PACK_STRUCT_FIELD(u16_t id); + PACK_STRUCT_FIELD(u8_t flags1); + PACK_STRUCT_FIELD(u8_t flags2); + PACK_STRUCT_FIELD(u16_t numquestions); + PACK_STRUCT_FIELD(u16_t numanswers); + PACK_STRUCT_FIELD(u16_t numauthrr); + PACK_STRUCT_FIELD(u16_t numextrarr); +} PACK_STRUCT_STRUCT; +PACK_STRUCT_END +#ifdef PACK_STRUCT_USE_INCLUDES +# include "arch/epstruct.h" +#endif +#define SIZEOF_DNS_HDR 12 + +/** DNS query message structure. + No packing needed: only used locally on the stack. */ +struct dns_query { + /* DNS query record starts with either a domain name or a pointer + to a name already present somewhere in the packet. */ + u16_t type; + u16_t cls; +}; +#define SIZEOF_DNS_QUERY 4 + +/** DNS answer message structure. + No packing needed: only used locally on the stack. */ +struct dns_answer { + /* DNS answer record starts with either a domain name or a pointer + to a name already present somewhere in the packet. */ + u16_t type; + u16_t cls; + u32_t ttl; + u16_t len; +}; +#define SIZEOF_DNS_ANSWER 10 + +/** 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]; + ip_addr_t ipaddr; + /* pointer to callback on DNS query done */ + dns_found_callback found; + void *arg; +}; + +#if DNS_LOCAL_HOSTLIST + +#if DNS_LOCAL_HOSTLIST_IS_DYNAMIC +/** Local host-list. For hostnames in this list, no + * external name resolution is performed */ +static struct local_hostlist_entry *local_hostlist_dynamic; +#else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ + +/** Defining this allows the local_hostlist_static to be placed in a different + * linker section (e.g. FLASH) */ +#ifndef DNS_LOCAL_HOSTLIST_STORAGE_PRE +#define DNS_LOCAL_HOSTLIST_STORAGE_PRE static +#endif /* DNS_LOCAL_HOSTLIST_STORAGE_PRE */ +/** Defining this allows the local_hostlist_static to be placed in a different + * linker section (e.g. FLASH) */ +#ifndef DNS_LOCAL_HOSTLIST_STORAGE_POST +#define DNS_LOCAL_HOSTLIST_STORAGE_POST +#endif /* DNS_LOCAL_HOSTLIST_STORAGE_POST */ +DNS_LOCAL_HOSTLIST_STORAGE_PRE struct local_hostlist_entry local_hostlist_static[] + DNS_LOCAL_HOSTLIST_STORAGE_POST = DNS_LOCAL_HOSTLIST_INIT; + +#endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ + +static void dns_init_local(); +#endif /* DNS_LOCAL_HOSTLIST */ + + +/* forward declarations */ +static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *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 ip_addr_t dns_servers[DNS_MAX_SERVERS]; +/** Contiguous buffer for processing responses */ +static u8_t dns_payload_buffer[LWIP_MEM_ALIGN_BUFFER(DNS_MSG_SIZE)]; +static u8_t* dns_payload; + +/** + * Initialize the resolver: set up the UDP pcb and configure the default server + * (DNS_SERVER_ADDRESS). + */ +void +dns_init() +{ + ip_addr_t dnsserver; + + dns_payload = (u8_t *)LWIP_MEM_ALIGN(dns_payload_buffer); + + /* initialize default DNS server address */ + DNS_SERVER_ADDRESS(&dnsserver); + + 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); + } + } +#if DNS_LOCAL_HOSTLIST + dns_init_local(); +#endif +} + +/** + * Initialize one of the DNS servers. + * + * @param numdns the index of the DNS server to set must be < DNS_MAX_SERVERS + * @param dnsserver IP address of the DNS server to set + */ +void +dns_setserver(u8_t numdns, ip_addr_t *dnsserver) +{ + /* + * hpa: the lwip code has the dnsserver->addr != 0 test, but that would + * seem to indicate that there is no way to cancel a previously given + * DNS server... + */ + if ((numdns < DNS_MAX_SERVERS) && (dns_pcb != NULL) && + (dnsserver != NULL) /* && !ip_addr_isany(dnsserver) */) { + 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. + */ +ip_addr_t +dns_getserver(u8_t numdns) +{ + if (numdns < DNS_MAX_SERVERS) { + return dns_servers[numdns]; + } else { + return *IP_ADDR_ANY; + } +} + +/** + * The DNS resolver client timer - handle retries and timeouts and should + * be called every DNS_TMR_INTERVAL milliseconds (every second by default). + */ +void +dns_tmr(void) +{ + if (dns_pcb != NULL) { + LWIP_DEBUGF(DNS_DEBUG, ("dns_tmr: dns_check_entries\n")); + dns_check_entries(); + } +} + +#if DNS_LOCAL_HOSTLIST +static void +dns_init_local() +{ +#if DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT) + int i; + struct local_hostlist_entry *entry; + /* Dynamic: copy entries from DNS_LOCAL_HOSTLIST_INIT to list */ + struct local_hostlist_entry local_hostlist_init[] = DNS_LOCAL_HOSTLIST_INIT; + size_t namelen; + for (i = 0; i < sizeof(local_hostlist_init) / sizeof(struct local_hostlist_entry); i++) { + struct local_hostlist_entry *init_entry = &local_hostlist_init[i]; + LWIP_ASSERT("invalid host name (NULL)", init_entry->name != NULL); + namelen = strlen(init_entry->name); + LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN); + entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST); + LWIP_ASSERT("mem-error in dns_init_local", entry != NULL); + if (entry != NULL) { + entry->name = (char*)entry + sizeof(struct local_hostlist_entry); + MEMCPY((char*)entry->name, init_entry->name, namelen); + ((char*)entry->name)[namelen] = 0; + entry->addr = init_entry->addr; + entry->next = local_hostlist_dynamic; + local_hostlist_dynamic = entry; + } + } +#endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT) */ +} + +/** + * Scans the local host-list for a hostname. + * + * @param hostname Hostname to look for in the local host-list + * @return The first IP address for the hostname in the local host-list or + * IPADDR_NONE if not found. + */ +static u32_t +dns_lookup_local(const char *hostname) +{ +#if DNS_LOCAL_HOSTLIST_IS_DYNAMIC + struct local_hostlist_entry *entry = local_hostlist_dynamic; + while(entry != NULL) { + if(strcmp(entry->name, hostname) == 0) { + return ip4_addr_get_u32(&entry->addr); + } + entry = entry->next; + } +#else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ + int i; + for (i = 0; i < sizeof(local_hostlist_static) / sizeof(struct local_hostlist_entry); i++) { + if(strcmp(local_hostlist_static[i].name, hostname) == 0) { + return ip4_addr_get_u32(&local_hostlist_static[i].addr); + } + } +#endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ + return IPADDR_NONE; +} + +#if DNS_LOCAL_HOSTLIST_IS_DYNAMIC +/** Remove all entries from the local host-list for a specific hostname + * and/or IP addess + * + * @param hostname hostname for which entries shall be removed from the local + * host-list + * @param addr address for which entries shall be removed from the local host-list + * @return the number of removed entries + */ +int +dns_local_removehost(const char *hostname, const ip_addr_t *addr) +{ + int removed = 0; + struct local_hostlist_entry *entry = local_hostlist_dynamic; + struct local_hostlist_entry *last_entry = NULL; + while (entry != NULL) { + if (((hostname == NULL) || !strcmp(entry->name, hostname)) && + ((addr == NULL) || ip_addr_cmp(&entry->addr, addr))) { + struct local_hostlist_entry *free_entry; + if (last_entry != NULL) { + last_entry->next = entry->next; + } else { + local_hostlist_dynamic = entry->next; + } + free_entry = entry; + entry = entry->next; + memp_free(MEMP_LOCALHOSTLIST, free_entry); + removed++; + } else { + last_entry = entry; + entry = entry->next; + } + } + return removed; +} + +/** + * Add a hostname/IP address pair to the local host-list. + * Duplicates are not checked. + * + * @param hostname hostname of the new entry + * @param addr IP address of the new entry + * @return ERR_OK if succeeded or ERR_MEM on memory error + */ +err_t +dns_local_addhost(const char *hostname, const ip_addr_t *addr) +{ + struct local_hostlist_entry *entry; + size_t namelen; + LWIP_ASSERT("invalid host name (NULL)", hostname != NULL); + namelen = strlen(hostname); + LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN); + entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST); + if (entry == NULL) { + return ERR_MEM; + } + entry->name = (char*)entry + sizeof(struct local_hostlist_entry); + MEMCPY((char*)entry->name, hostname, namelen); + ((char*)entry->name)[namelen] = 0; + ip_addr_copy(entry->addr, *addr); + entry->next = local_hostlist_dynamic; + local_hostlist_dynamic = entry; + return ERR_OK; +} +#endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC*/ +#endif /* DNS_LOCAL_HOSTLIST */ + +/** + * Look up a hostname in the array of known hostnames. + * + * @note This function only looks in the internal array of known + * hostnames, it does not send out a query for the hostname if none + * was found. The function dns_enqueue() can be used to send a query + * for a hostname. + * + * @param name the hostname to look up + * @return the hostname's IP address, as u32_t (instead of ip_addr_t to + * better check for failure: != IPADDR_NONE) or IPADDR_NONE if the hostname + * was not found in the cached dns_table. + */ +static u32_t +dns_lookup(const char *name) +{ + u8_t i; +#if DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN) + u32_t addr; +#endif /* DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN) */ +#if DNS_LOCAL_HOSTLIST + if ((addr = dns_lookup_local(name)) != IPADDR_NONE) { + return addr; + } +#endif /* DNS_LOCAL_HOSTLIST */ +#ifdef DNS_LOOKUP_LOCAL_EXTERN + if((addr = DNS_LOOKUP_LOCAL_EXTERN(name)) != IPADDR_NONE) { + return addr; + } +#endif /* DNS_LOOKUP_LOCAL_EXTERN */ + + /* Walk through name list, return entry if found. If not, return NULL. */ + for (i = 0; i < DNS_TABLE_SIZE; ++i) { + if ((dns_table[i].state == DNS_STATE_DONE) && + (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 ip4_addr_get_u32(&dns_table[i].ipaddr); + } + } + + return IPADDR_NONE; +} + +#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", !ip_addr_isany(&dns_servers[numdns])); + + /* if here, we have either a new query or a retry on a previous query to process */ + p = pbuf_alloc(PBUF_TRANSPORT, SIZEOF_DNS_HDR + DNS_MAX_NAME_LENGTH + + SIZEOF_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_DNS_HDR); + hdr->id = htons(id); + hdr->flags1 = DNS_FLAG1_RD; + hdr->numquestions = PP_HTONS(1); + query = (char*)hdr + SIZEOF_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 = PP_HTONS(DNS_RRTYPE_A); + qry.cls = PP_HTONS(DNS_RRCLASS_IN); + SMEMCPY(query, &qry, SIZEOF_DNS_QUERY); + + /* resize pbuf to the exact dns query */ + pbuf_realloc(p, (u16_t)((query + SIZEOF_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) +{ + err_t err; + 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 */ + err = dns_send(pEntry->numdns, pEntry->name, i); + if (err != ERR_OK) { + LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING, + ("dns_send returned error: %s\n", lwip_strerr(err))); + } + break; + } + + case DNS_STATE_ASKING: { + if (--pEntry->tmr == 0) { + if (++pEntry->retries == DNS_MAX_RETRIES) { + if ((pEntry->numdns+1<DNS_MAX_SERVERS) && !ip_addr_isany(&dns_servers[pEntry->numdns+1])) { + /* 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 */ + err = dns_send(pEntry->numdns, pEntry->name, i); + if (err != ERR_OK) { + LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING, + ("dns_send returned error: %s\n", lwip_strerr(err))); + } + } + break; + } + + case DNS_STATE_DONE: { + /* if the time to live is nul */ + if (--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, ip_addr_t *addr, u16_t port) +{ + u16_t i; + char *pHostname; + struct dns_hdr *hdr; + struct dns_answer ans; + struct dns_table_entry *pEntry; + u16_t nquestions, nanswers; + + 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 memerr; + } + + /* is the dns message big enough ? */ + if (p->tot_len < (SIZEOF_DNS_HDR + SIZEOF_DNS_QUERY + SIZEOF_DNS_ANSWER)) { + LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too small\n")); + /* free pbuf and return */ + goto memerr; + } + + /* copy dns payload inside static buffer for processing */ + if (pbuf_copy_partial(p, 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_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_DNS_HDR) + SIZEOF_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. */ + SMEMCPY(&ans, pHostname, SIZEOF_DNS_ANSWER); + if((ans.type == PP_HTONS(DNS_RRTYPE_A)) && (ans.cls == PP_HTONS(DNS_RRCLASS_IN)) && + (ans.len == PP_HTONS(sizeof(ip_addr_t))) ) { + /* 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 */ + SMEMCPY(&(pEntry->ipaddr), (pHostname+SIZEOF_DNS_ANSWER), sizeof(ip_addr_t)); + 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 memerr; + } else { + pHostname = pHostname + SIZEOF_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 memerr; + +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; + +memerr: + /* free pbuf */ + pbuf_free(p); + return; +} + +/** + * Queues a new hostname to resolve and sends out a DNS query for that hostname + * + * @param name the hostname that is to be queried + * @param 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; + size_t namelen; + + /* 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; + namelen = LWIP_MIN(strlen(name), DNS_MAX_NAME_LENGTH-1); + MEMCPY(pEntry->name, name, namelen); + pEntry->name[namelen] = 0; + + /* force to send query without waiting timer */ + dns_check_entry(i); + + /* dns query is enqueued */ + return ERR_INPROGRESS; +} + +/** + * Resolve a hostname (string) into an IP address. + * NON-BLOCKING callback version for use with raw API!!! + * + * Returns immediately with one of err_t return codes: + * - ERR_OK if hostname is a valid IP address string or the host + * name is already in the local names table. + * - ERR_INPROGRESS enqueue a request to be sent to the DNS server + * for resolution if no errors are present. + * - ERR_ARG: dns client not initialized or invalid hostname + * + * @param hostname the hostname that is to be queried + * @param addr pointer to a ip_addr_t where to store the address if it is already + * cached in the dns_table (only valid if ERR_OK is returned!) + * @param found a callback function to be called on success, failure or timeout (only if + * ERR_INPROGRESS is returned!) + * @param callback_arg argument to pass to the callback function + * @return a err_t return code. + */ +err_t +dns_gethostbyname(const char *hostname, ip_addr_t *addr, dns_found_callback found, + void *callback_arg) +{ + u32_t ipaddr; + /* 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_ARG; + } + +#if LWIP_HAVE_LOOPIF + if (strcmp(hostname, "localhost")==0) { + ip_addr_set_loopback(addr); + return ERR_OK; + } +#endif /* LWIP_HAVE_LOOPIF */ + + /* host name already in octet notation? set ip addr and return ERR_OK */ + ipaddr = ipaddr_addr(hostname); + if (ipaddr == IPADDR_NONE) { + /* already have this address cached? */ + ipaddr = dns_lookup(hostname); + } + if (ipaddr != IPADDR_NONE) { + ip4_addr_set_u32(addr, ipaddr); + return ERR_OK; + } + + /* queue query with specified callback */ + return dns_enqueue(hostname, found, callback_arg); +} + +#endif /* LWIP_DNS */ |