/* uip-resolv.c * DNS host name to IP address resolver. * Author: Adam Dunkels * * The uIP DNS resolver functions are used to lookup a hostname and * map it to a numerical IP address. It maintains a list of resolved * hostnames that can be queried with the resolv_lookup() * function. New hostnames can be resolved using the resolv_query() * function. * * When a hostname has been resolved (or found to be non-existant), * the resolver code calls a callback function called resolv_found() * that must be implemented by the module that uses the resolver. * * 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. * * This file is part of the uIP TCP/IP stack. * * $Id: resolv.c,v 1.1.1.1 2007-08-26 23:07:05 patacongo Exp $ * */ #include #include #include #include #ifndef NULL #define NULL (void *)0 #endif /* NULL */ /** \internal The maximum number of retries when asking for a name. */ #define MAX_RETRIES 8 /** \internal The DNS message header. */ struct dns_hdr { uint16 id; uint8 flags1, flags2; #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 uint16 numquestions; uint16 numanswers; uint16 numauthrr; uint16 numextrarr; }; /** \internal The 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. */ uint16 type; uint16 class; uint16 ttl[2]; uint16 len; uip_ipaddr_t ipaddr; }; struct namemap { #define STATE_UNUSED 0 #define STATE_NEW 1 #define STATE_ASKING 2 #define STATE_DONE 3 #define STATE_ERROR 4 uint8 state; uint8 tmr; uint8 retries; uint8 seqno; uint8 err; char name[32]; uip_ipaddr_t ipaddr; }; #ifndef CONFIG_UIP_RESOLV_ENTRIES #define RESOLV_ENTRIES 4 #else /* CONFIG_UIP_RESOLV_ENTRIES */ #define RESOLV_ENTRIES CONFIG_UIP_RESOLV_ENTRIES #endif /* CONFIG_UIP_RESOLV_ENTRIES */ static struct namemap names[RESOLV_ENTRIES]; static uint8 seqno; static struct uip_udp_conn *resolv_conn = NULL; /*---------------------------------------------------------------------------*/ /** \internal * Walk through a compact encoded DNS name and return the end of it. * * \return The end of the name. */ /*---------------------------------------------------------------------------*/ static unsigned char *parse_name(unsigned char *query) { unsigned char n; do { n = *query++; while(n > 0) { ++query; --n; }; } while(*query != 0); return query + 1; } /*---------------------------------------------------------------------------*/ /** \internal * Runs through the list of names to see if there are any that have * not yet been queried and, if so, sends out a query. */ /*---------------------------------------------------------------------------*/ static void check_entries(void) { register struct dns_hdr *hdr; char *query, *nptr, *nameptr; static uint8 i; static uint8 n; register struct namemap *namemapptr; for(i = 0; i < RESOLV_ENTRIES; ++i) { namemapptr = &names[i]; if(namemapptr->state == STATE_NEW || namemapptr->state == STATE_ASKING) { if(namemapptr->state == STATE_ASKING) { if(--namemapptr->tmr == 0) { if(++namemapptr->retries == MAX_RETRIES) { namemapptr->state = STATE_ERROR; resolv_found(namemapptr->name, NULL); continue; } namemapptr->tmr = namemapptr->retries; } else { /* printf("Timer %d\n", namemapptr->tmr);*/ /* Its timer has not run out, so we move on to next entry. */ continue; } } else { namemapptr->state = STATE_ASKING; namemapptr->tmr = 1; namemapptr->retries = 0; } hdr = (struct dns_hdr *)uip_appdata; memset(hdr, 0, sizeof(struct dns_hdr)); hdr->id = htons(i); hdr->flags1 = DNS_FLAG1_RD; hdr->numquestions = HTONS(1); query = (char *)uip_appdata + 12; nameptr = namemapptr->name; --nameptr; /* Convert hostname into suitable query format. */ do { ++nameptr; nptr = query; ++query; for(n = 0; *nameptr != '.' && *nameptr != 0; ++nameptr) { *query = *nameptr; ++query; ++n; } *nptr = n; } while(*nameptr != 0); { static unsigned char endquery[] = {0,0,1,0,1}; memcpy(query, endquery, 5); } uip_udp_send((unsigned char)(query + 5 - (char *)uip_appdata)); break; } } } /*---------------------------------------------------------------------------*/ /** \internal * Called when new UDP data arrives. */ /*---------------------------------------------------------------------------*/ static void newdata(void) { unsigned char *nameptr; struct dns_answer *ans; struct dns_hdr *hdr; static uint8 nquestions, nanswers; static uint8 i; register struct namemap *namemapptr; hdr = (struct dns_hdr *)uip_appdata; /* printf("ID %d\n", htons(hdr->id)); printf("Query %d\n", hdr->flags1 & DNS_FLAG1_RESPONSE); printf("Error %d\n", hdr->flags2 & DNS_FLAG2_ERR_MASK); printf("Num questions %d, answers %d, authrr %d, extrarr %d\n", htons(hdr->numquestions), htons(hdr->numanswers), htons(hdr->numauthrr), htons(hdr->numextrarr)); */ /* The ID in the DNS header should be our entry into the name table. */ i = htons(hdr->id); namemapptr = &names[i]; if(i < RESOLV_ENTRIES && namemapptr->state == STATE_ASKING) { /* This entry is now finished. */ namemapptr->state = STATE_DONE; namemapptr->err = hdr->flags2 & DNS_FLAG2_ERR_MASK; /* Check for error. If so, call callback to inform. */ if(namemapptr->err != 0) { namemapptr->state = STATE_ERROR; resolv_found(namemapptr->name, NULL); return; } /* 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); /* Skip the name in the question. XXX: This should really be checked agains the name in the question, to be sure that they match. */ nameptr = parse_name((unsigned char *)uip_appdata + 12) + 4; while(nanswers > 0) { /* The first byte in the answer resource record determines if it is a compressed record or a normal one. */ if(*nameptr & 0xc0) { /* Compressed name. */ nameptr +=2; /* printf("Compressed anwser\n");*/ } else { /* Not compressed name. */ nameptr = parse_name(nameptr); } ans = (struct dns_answer *)nameptr; /* printf("Answer: type %x, class %x, ttl %x, length %x\n", htons(ans->type), htons(ans->class), (htons(ans->ttl[0]) << 16) | htons(ans->ttl[1]), htons(ans->len));*/ /* Check for IP address type and Internet class. Others are discarded. */ if(ans->type == HTONS(1) && ans->class == HTONS(1) && ans->len == HTONS(4)) { /* printf("IP address %d.%d.%d.%d\n", htons(ans->ipaddr[0]) >> 8, htons(ans->ipaddr[0]) & 0xff, htons(ans->ipaddr[1]) >> 8, htons(ans->ipaddr[1]) & 0xff);*/ /* XXX: we should really check that this IP address is the one we want. */ namemapptr->ipaddr[0] = ans->ipaddr[0]; namemapptr->ipaddr[1] = ans->ipaddr[1]; resolv_found(namemapptr->name, namemapptr->ipaddr); return; } else { nameptr = nameptr + 10 + htons(ans->len); } --nanswers; } } } /* This function is called by the UIP interrupt handling logic whenevent an * event of interest occurs. */ void uip_interrupt_udp_event(void) { if(uip_udp_conn->rport == HTONS(53)) { if(uip_poll()) { check_entries(); } if(uip_newdata()) { newdata(); } } } /** * Queues a name so that a question for the name will be sent out. * * \param name The hostname that is to be queried. */ /*---------------------------------------------------------------------------*/ void resolv_query(char *name) { static uint8 i; static uint8 lseq, lseqi; register struct namemap *nameptr; lseq = lseqi = 0; for(i = 0; i < RESOLV_ENTRIES; ++i) { nameptr = &names[i]; if(nameptr->state == STATE_UNUSED) { break; } if(seqno - nameptr->seqno > lseq) { lseq = seqno - nameptr->seqno; lseqi = i; } } if(i == RESOLV_ENTRIES) { i = lseqi; nameptr = &names[i]; } /* printf("Using entry %d\n", i);*/ strcpy(nameptr->name, name); nameptr->state = STATE_NEW; nameptr->seqno = seqno; ++seqno; } /*---------------------------------------------------------------------------*/ /** * 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 resolv_query() can be used to send a query * for a hostname. * * \return A pointer to a 4-byte representation of the hostname's IP * address, or NULL if the hostname was not found in the array of * hostnames. */ /*---------------------------------------------------------------------------*/ uint16 * resolv_lookup(char *name) { static uint8 i; struct namemap *nameptr; /* Walk through the list to see if the name is in there. If it is not, we return NULL. */ for(i = 0; i < RESOLV_ENTRIES; ++i) { nameptr = &names[i]; if(nameptr->state == STATE_DONE && strcmp(name, nameptr->name) == 0) { return nameptr->ipaddr; } } return NULL; } /*---------------------------------------------------------------------------*/ /** * Obtain the currently configured DNS server. * * \return A pointer to a 4-byte representation of the IP address of * the currently configured DNS server or NULL if no DNS server has * been configured. */ /*---------------------------------------------------------------------------*/ uint16 * resolv_getserver(void) { if(resolv_conn == NULL) { return NULL; } return resolv_conn->ripaddr; } /*---------------------------------------------------------------------------*/ /** * Configure which DNS server to use for queries. * * \param dnsserver A pointer to a 4-byte representation of the IP * address of the DNS server to be configured. */ /*---------------------------------------------------------------------------*/ void resolv_conf(uint16 *dnsserver) { if(resolv_conn != NULL) { uip_udp_remove(resolv_conn); } resolv_conn = uip_udp_new(dnsserver, HTONS(53)); } /*---------------------------------------------------------------------------*/ /** * Initalize the resolver. */ /*---------------------------------------------------------------------------*/ void resolv_init(void) { static uint8 i; for(i = 0; i < RESOLV_ENTRIES; ++i) { names[i].state = STATE_DONE; } } /*---------------------------------------------------------------------------*/ /** @} */ /** @} */