/**************************************************************************** * libs/libc/netdb/lib_dnsquery.c * DNS host name to IP address resolver. * * The DNS resolver functions are used to lookup a hostname and map it to a * numerical IP address. * * Copyright (C) 2007, 2009, 2012, 2014-2018 Gregory Nutt. All rights * reserved. * Author: Gregory Nutt * * Based heavily on portions of uIP: * * Author: Adam Dunkels * 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. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include #include #include #include #include #include #include #include #include "netdb/lib_dns.h" /**************************************************************************** * Pre-processor Definitions ****************************************************************************/ /* Buffer sizes * * The SEND_BUFFER_SIZE depends the configured DNS name size: * * sizeof(DNS query0 = Header (12 bytes) + DNS Name (Variable) + * Query type (2 bytes) + Query Class (2 bytes) * * sizeof(DNS Name) = Encoded length (1 byte) + Maximum length of name + * NUL-terminator (1 byte) */ #define SEND_BUFFER_SIZE (16 + CONFIG_NETDB_DNSCLIENT_NAMESIZE + 2) #define RECV_BUFFER_SIZE CONFIG_NETDB_DNSCLIENT_MAXRESPONSE /**************************************************************************** * Private Types ****************************************************************************/ struct dns_query_s { int sd; /* DNS server socket */ int result; /* Explanation of the failure */ FAR const char *hostname; /* Hostname to lookup */ FAR union dns_addr_u *addr; /* Location to return host address */ FAR int *naddr; /* Number of returned addresses */ }; /* Query info to check response against. */ struct dns_query_info_s { uint16_t id; /* Query ID */ uint16_t rectype; /* Queried record type */ uint16_t qnamelen; /* Queried hostname length */ char qname[CONFIG_NETDB_DNSCLIENT_NAMESIZE + 2]; /* Queried hostname in * encoded format + NUL */ }; /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Name: dns_parse_name * * Description: * Walk through a compact encoded DNS name and return the end of it. * * Input Parameters: * * query - A pointer to the starting byte of the name entry in the DNS * response. * queryend - A pointer to the byte after the last byte of the response. * * Returned Value: * Pointer to the first byte after the parsed name, or the value of * `queryend` if the name did not fit into provided DNS response. * ****************************************************************************/ static FAR uint8_t *dns_parse_name(FAR uint8_t *query, FAR uint8_t *queryend) { uint8_t n; while (query < queryend) { n = *query++; /* Check for a leading or trailing pointer */ if ((n & 0xc0) != 0) { /* Eat second pointer byte and terminate search */ ninfo("Compressed answer\n"); query++; break; } /* Check for final label with zero-length */ if (!n) { break; } /* Eat non-empty label */ query += n; } if (query >= queryend) { /* Always return `queryend` in case of errors */ nerr("ERROR: DNS response is too short\n"); query = queryend; } return query; } /**************************************************************************** * Name: dns_alloc_id * * Description: * Gets a new ID for query. Function manufactures a reasonably unique ID, * but we accept rare collisions, since they are harmless when resolver * clients retry failed DNS few times. * ****************************************************************************/ static inline uint16_t dns_alloc_id(void) { struct timespec ts; clock_gettime(CLOCK_REALTIME, &ts); return (uint32_t)ts.tv_nsec + ((uint32_t)ts.tv_nsec >> 16); } /**************************************************************************** * Name: dns_send_query * * Description: * 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 int dns_send_query(int sd, FAR const char *name, FAR union dns_addr_u *uaddr, uint16_t rectype, FAR struct dns_query_info_s *qinfo) { FAR struct dns_header_s *hdr; FAR uint8_t *dest; FAR uint8_t *nptr; FAR char *qname; FAR char *qptr; FAR const char *src; uint8_t buffer[SEND_BUFFER_SIZE]; uint16_t id; socklen_t addrlen; int ret; int len; int n; /* Get a new ID for query */ id = dns_alloc_id(); /* Initialize the request header */ hdr = (FAR struct dns_header_s *)buffer; memset(hdr, 0, sizeof(*hdr)); hdr->id = htons(id); hdr->flags1 = DNS_FLAG1_RD; hdr->numquestions = HTONS(1); /* Convert hostname into suitable query format. * * There is space for CONFIG_NETDB_DNSCLIENT_NAMESIZE * plus one pre-pended name length and NUL-terminator * (other pre-pended name lengths replace dots). */ src = name - 1; dest = buffer + sizeof(*hdr); qname = qinfo->qname; len = 0; do { /* Copy the name string to both query and saved info. */ src++; nptr = dest++; qptr = qname++; len++; for (n = 0; *src != '.' && *src != '\0' && len <= CONFIG_NETDB_DNSCLIENT_NAMESIZE; src++) { *dest++ = *(FAR uint8_t *)src; *qname++ = *(FAR uint8_t *)src; n++; len++; } /* Pre-pend the name length */ *nptr = n; *qptr = n; } while (*src != '\0' && len <= CONFIG_NETDB_DNSCLIENT_NAMESIZE); /* Add NUL termination */ *dest++ = '\0'; *qname++ = '\0'; /* Store name length to saved info */ DEBUGASSERT(len <= CONFIG_NETDB_DNSCLIENT_NAMESIZE + 1); DEBUGASSERT(qname - qinfo->qname == len + 1); qinfo->qnamelen = len; /* Add DNS record type, and DNS class */ *dest++ = (rectype >> 8); /* DNS record type (big endian) */ *dest++ = (rectype & 0xff); *dest++ = (DNS_CLASS_IN >> 8); /* DNS record class (big endian) */ *dest++ = (DNS_CLASS_IN & 0xff); qinfo->rectype = htons(rectype); qinfo->id = hdr->id; /* Send the request */ if (uaddr->addr.sa_family == AF_INET) { addrlen = sizeof(struct sockaddr_in); } else { addrlen = sizeof(struct sockaddr_in6); } ret = connect(sd, &uaddr->addr, addrlen); if (ret < 0) { ret = -get_errno(); nerr("ERROR: connect failed: %d\n", ret); return ret; } ret = send(sd, buffer, dest - buffer, 0); if (ret < 0) { ret = -get_errno(); nerr("ERROR: sendto failed: %d\n", ret); return ret; } return OK; } /**************************************************************************** * Name: dns_recv_response * * Description: * Called when new UDP data arrives * * Returned Value: * Returns number of valid IP address responses. Negated errno value is * returned in all other cases. * ****************************************************************************/ static int dns_recv_response(int sd, FAR union dns_addr_u *addr, int naddr, FAR struct dns_query_info_s *qinfo) { FAR uint8_t *nameptr; FAR uint8_t *namestart; FAR uint8_t *endofbuffer; char buffer[RECV_BUFFER_SIZE]; FAR struct dns_answer_s *ans; FAR struct dns_header_s *hdr; FAR struct dns_question_s *que; uint16_t nquestions; uint16_t nanswers; int naddr_read; int ret; if (naddr <= 0) { return -ERANGE; } /* Receive the response */ ret = recv(sd, buffer, RECV_BUFFER_SIZE, 0); if (ret < 0) { ret = -get_errno(); nerr("ERROR: recv failed: %d\n", ret); return ret; } if (ret < sizeof(*hdr)) { /* DNS header can't fit in received data */ nerr("ERROR: DNS response is too short\n"); return -EILSEQ; } hdr = (FAR struct dns_header_s *)buffer; endofbuffer = (FAR uint8_t *)buffer + ret; ninfo("ID %d\n", ntohs(hdr->id)); ninfo("Query %d\n", hdr->flags1 & DNS_FLAG1_RESPONSE); ninfo("Error %d\n", hdr->flags2 & DNS_FLAG2_ERR_MASK); ninfo("Num questions %d, answers %d, authrr %d, extrarr %d\n", ntohs(hdr->numquestions), ntohs(hdr->numanswers), ntohs(hdr->numauthrr), ntohs(hdr->numextrarr)); /* Check for error */ if ((hdr->flags2 & DNS_FLAG2_ERR_MASK) != 0) { nerr("ERROR: DNS reported error: flags2=%02x\n", hdr->flags2); return -EPROTO; } /* Check for matching ID. */ if (hdr->id != qinfo->id) { nerr("ERROR: DNS wrong response ID (expected %d, got %d)\n", ntohs(qinfo->id), ntohs(hdr->id)); return -EBADMSG; } /* We only care about the question(s) and the answers. The authrr * and the extrarr are simply discarded. */ nquestions = ntohs(hdr->numquestions); nanswers = ntohs(hdr->numanswers); /* We only ever send queries with one question. */ if (nquestions != 1) { nerr("ERROR: DNS wrong number of questions %d\n", nquestions); return -EBADMSG; } /* Skip the name in the answer, but do check that it * matches against the name in the question. */ namestart = (uint8_t *)buffer + sizeof(*hdr); nameptr = dns_parse_name(namestart, endofbuffer); if (nameptr == endofbuffer) { return -EILSEQ; } /* Since dns_parse_name() skips any pointer bytes, * we cannot compare for equality here. */ if (nameptr - namestart < qinfo->qnamelen) { nerr("ERROR: DNS response name wrong length\n"); return -EBADMSG; } /* qname is NUL-terminated and we must include NUL to the comparison. */ if (memcmp(namestart, qinfo->qname, qinfo->qnamelen + 1) != 0) { nerr("ERROR: DNS response with wrong name\n"); return -EBADMSG; } /* Validate query type and class */ que = (FAR struct dns_question_s *)nameptr; ninfo("Question: type=%04x, class=%04x\n", ntohs(que->type), ntohs(que->class)); if (que->type != qinfo->rectype || que->class != HTONS(DNS_CLASS_IN)) { nerr("ERROR: DNS response with wrong question\n"); return -EBADMSG; } /* Skip over question */ nameptr += sizeof(struct dns_question_s); ret = OK; naddr_read = 0; for (; nanswers > 0; nanswers--) { /* Each answer starts with a name */ nameptr = dns_parse_name(nameptr, endofbuffer); if (nameptr == endofbuffer) { ret = -EILSEQ; nwarn("Further parse returned %d\n", ret); break; } ans = (FAR struct dns_answer_s *)nameptr; ninfo("Answer: type=%04x, class=%04x, ttl=%06x, length=%04x \n", ntohs(ans->type), ntohs(ans->class), (ntohs(ans->ttl[0]) << 16) | ntohs(ans->ttl[1]), ntohs(ans->len)); /* Check for IPv4/6 address type and Internet class. Others are * discarded. */ #ifdef CONFIG_NET_IPv4 if (ans->type == HTONS(DNS_RECTYPE_A) && ans->class == HTONS(DNS_CLASS_IN) && ans->len == HTONS(4) && nameptr + 10 + 4 <= endofbuffer) { FAR struct sockaddr_in *inaddr; nameptr += 10 + 4; ninfo("IPv4 address: %d.%d.%d.%d\n", (int)((ans->u.ipv4.s_addr) & 0xff), (int)((ans->u.ipv4.s_addr >> 8) & 0xff), (int)((ans->u.ipv4.s_addr >> 16) & 0xff), (int)((ans->u.ipv4.s_addr >> 24) & 0xff)); inaddr = &addr[naddr_read].ipv4; inaddr->sin_family = AF_INET; inaddr->sin_port = 0; inaddr->sin_addr.s_addr = ans->u.ipv4.s_addr; if (++naddr_read >= naddr) { ret = -ERANGE; break; } } else #endif #ifdef CONFIG_NET_IPv6 if (ans->type == HTONS(DNS_RECTYPE_AAAA) && ans->class == HTONS(DNS_CLASS_IN) && ans->len == HTONS(16) && nameptr + 10 + 16 <= endofbuffer) { FAR struct sockaddr_in6 *inaddr; nameptr += 10 + 16; ninfo("IPv6 address: %04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x\n", ntohs(ans->u.ipv6.s6_addr[7]), ntohs(ans->u.ipv6.s6_addr[6]), ntohs(ans->u.ipv6.s6_addr[5]), ntohs(ans->u.ipv6.s6_addr[4]), ntohs(ans->u.ipv6.s6_addr[3]), ntohs(ans->u.ipv6.s6_addr[2]), ntohs(ans->u.ipv6.s6_addr[1]), ntohs(*ans->u.ipv6.s6_addr)); inaddr = &addr[naddr_read].ipv6; inaddr->sin6_family = AF_INET6; inaddr->sin6_port = 0; memcpy(inaddr->sin6_addr.s6_addr, ans->u.ipv6.s6_addr, 16); if (++naddr_read >= naddr) { ret = -ERANGE; break; } } else #endif { nameptr = nameptr + 10 + ntohs(ans->len); } } if (naddr_read == 0 && ret == OK) { ret = -EADDRNOTAVAIL; } return naddr_read > 0 ? naddr_read : ret; } /**************************************************************************** * Name: dns_query_callback * * Description: * Using the DNS information and this DNS server address, look up the * hostname. * * Input Parameters: * arg - Query arguments * addr - DNS name server address * addrlen - Length of the DNS name server address. * * Returned Value: * Returns one (1) if the query was successful. Zero is returned in all * other cases. The result field of the query structure is set to a * negated errno value indicate the reason for the last failure (only). * ****************************************************************************/ static int dns_query_callback(FAR void *arg, FAR struct sockaddr *addr, FAR socklen_t addrlen) { FAR struct dns_query_s *query = (FAR struct dns_query_s *)arg; FAR struct dns_query_info_s qinfo; int next = 0; int retries; int ret; /* Loop while receive timeout errors occur and there are remaining * retries. */ for (retries = 0; retries < CONFIG_NETDB_DNSCLIENT_RETRIES; retries++) { #ifdef CONFIG_NET_IPv6 /* Send the IPv6 query */ ret = dns_send_query(query->sd, query->hostname, (FAR union dns_addr_u *)addr, DNS_RECTYPE_AAAA, &qinfo); if (ret < 0) { nerr("ERROR: IPv6 dns_send_query failed: %d\n", ret); query->result = ret; } else { /* Obtain the IPv6 response */ ret = dns_recv_response(query->sd, &query->addr[next], *query->naddr - next, &qinfo); if (ret >= 0) { next += ret; } else { nerr("ERROR: IPv6 dns_recv_response failed: %d\n", ret); query->result = ret; } } #endif #ifdef CONFIG_NET_IPv4 /* Send the IPv4 query */ ret = dns_send_query(query->sd, query->hostname, (FAR union dns_addr_u *)addr, DNS_RECTYPE_A, &qinfo); if (ret < 0) { nerr("ERROR: IPv4 dns_send_query failed: %d\n", ret); query->result = ret; } else { /* Obtain the IPv4 response */ ret = dns_recv_response(query->sd, &query->addr[next], *query->naddr - next, &qinfo); if (ret >= 0) { next += ret; } else { nerr("ERROR: IPv4 dns_recv_response failed: %d\n", ret); query->result = ret; } } #endif /* CONFIG_NET_IPv4 */ if (next > 0) { #if CONFIG_NETDB_DNSCLIENT_ENTRIES > 0 /* Save the answer in the DNS cache */ dns_save_answer(query->hostname, query->addr, next); #endif /* Return 1 to indicate to (1) stop the traversal, and (2) * indicate that the address was found. */ *query->naddr = next; return 1; } else if (query->result != -EAGAIN) { break; } } return 0; } /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: dns_query * * Description: * Using the DNS resolver socket (sd), look up the 'hostname', and * return its IP address in 'ipaddr' * * Input Parameters: * sd - The socket descriptor previously initialized by dsn_bind(). * hostname - The hostname string to be resolved. * addr - The location to return the IP addresses associated with the * hostname. * naddr - On entry, the count of addresses backing up the 'addr' * pointer. On return, this location will hold the actual count of * the returned addresses. * * Returned Value: * Returns zero (OK) if the query was successful. * ****************************************************************************/ int dns_query(int sd, FAR const char *hostname, FAR union dns_addr_u *addr, FAR int *naddr) { FAR struct dns_query_s query; int ret; /* Set up the query info structure */ query.sd = sd; query.result = -EADDRNOTAVAIL; query.hostname = hostname; query.addr = addr; query.naddr = naddr; /* Perform the query. dns_foreach_nameserver() will return: * * 1 - The query was successful. * 0 - Look up failed * <0 - Some other failure (?, shouldn't happen) */ ret = dns_foreach_nameserver(dns_query_callback, &query); if (ret > 0) { /* The lookup was successful */ ret = OK; } else if (ret == 0) { ret = query.result; } return ret; }