| |
| /* Copyright 1998 by the Massachusetts Institute of Technology. |
| * |
| * Permission to use, copy, modify, and distribute this |
| * software and its documentation for any purpose and without |
| * fee is hereby granted, provided that the above copyright |
| * notice appear in all copies and that both that copyright |
| * notice and this permission notice appear in supporting |
| * documentation, and that the name of M.I.T. not be used in |
| * advertising or publicity pertaining to distribution of the |
| * software without specific, written prior permission. |
| * M.I.T. makes no representations about the suitability of |
| * this software for any purpose. It is provided "as is" |
| * without express or implied warranty. |
| */ |
| |
| #include "ares_setup.h" |
| |
| #ifdef HAVE_NETINET_IN_H |
| # include <netinet/in.h> |
| #endif |
| #ifdef HAVE_ARPA_NAMESER_H |
| # include <arpa/nameser.h> |
| #else |
| # include "nameser.h" |
| #endif |
| #ifdef HAVE_ARPA_NAMESER_COMPAT_H |
| # include <arpa/nameser_compat.h> |
| #endif |
| |
| #include "ares.h" |
| #include "ares_dns.h" |
| #include "ares_private.h" |
| |
| #ifndef T_OPT |
| # define T_OPT 41 /* EDNS0 option (meta-RR) */ |
| #endif |
| |
| /* Header format, from RFC 1035: |
| * 1 1 1 1 1 1 |
| * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 |
| * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| * | ID | |
| * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| * |QR| Opcode |AA|TC|RD|RA| Z | RCODE | |
| * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| * | QDCOUNT | |
| * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| * | ANCOUNT | |
| * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| * | NSCOUNT | |
| * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| * | ARCOUNT | |
| * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| * |
| * AA, TC, RA, and RCODE are only set in responses. Brief description |
| * of the remaining fields: |
| * ID Identifier to match responses with queries |
| * QR Query (0) or response (1) |
| * Opcode For our purposes, always QUERY |
| * RD Recursion desired |
| * Z Reserved (zero) |
| * QDCOUNT Number of queries |
| * ANCOUNT Number of answers |
| * NSCOUNT Number of name server records |
| * ARCOUNT Number of additional records |
| * |
| * Question format, from RFC 1035: |
| * 1 1 1 1 1 1 |
| * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 |
| * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| * | | |
| * / QNAME / |
| * / / |
| * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| * | QTYPE | |
| * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| * | QCLASS | |
| * +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ |
| * |
| * The query name is encoded as a series of labels, each represented |
| * as a one-byte length (maximum 63) followed by the text of the |
| * label. The list is terminated by a label of length zero (which can |
| * be thought of as the root domain). |
| */ |
| |
| int ares_create_query(const char *name, int dnsclass, int type, |
| unsigned short id, int rd, unsigned char **bufp, |
| int *buflenp, int max_udp_size) |
| { |
| size_t len; |
| unsigned char *q; |
| const char *p; |
| size_t buflen; |
| unsigned char *buf; |
| |
| /* Set our results early, in case we bail out early with an error. */ |
| *buflenp = 0; |
| *bufp = NULL; |
| |
| /* Allocate a memory area for the maximum size this packet might need. +2 |
| * is for the length byte and zero termination if no dots or ecscaping is |
| * used. |
| */ |
| len = strlen(name) + 2 + HFIXEDSZ + QFIXEDSZ + |
| (max_udp_size ? EDNSFIXEDSZ : 0); |
| buf = ares_malloc(len); |
| if (!buf) |
| return ARES_ENOMEM; |
| |
| /* Set up the header. */ |
| q = buf; |
| memset(q, 0, HFIXEDSZ); |
| DNS_HEADER_SET_QID(q, id); |
| DNS_HEADER_SET_OPCODE(q, QUERY); |
| if (rd) { |
| DNS_HEADER_SET_RD(q, 1); |
| } |
| else { |
| DNS_HEADER_SET_RD(q, 0); |
| } |
| DNS_HEADER_SET_QDCOUNT(q, 1); |
| |
| if (max_udp_size) { |
| DNS_HEADER_SET_ARCOUNT(q, 1); |
| } |
| |
| /* A name of "." is a screw case for the loop below, so adjust it. */ |
| if (strcmp(name, ".") == 0) |
| name++; |
| |
| /* Start writing out the name after the header. */ |
| q += HFIXEDSZ; |
| while (*name) |
| { |
| if (*name == '.') { |
| free (buf); |
| return ARES_EBADNAME; |
| } |
| |
| /* Count the number of bytes in this label. */ |
| len = 0; |
| for (p = name; *p && *p != '.'; p++) |
| { |
| if (*p == '\\' && *(p + 1) != 0) |
| p++; |
| len++; |
| } |
| if (len > MAXLABEL) { |
| free (buf); |
| return ARES_EBADNAME; |
| } |
| |
| /* Encode the length and copy the data. */ |
| *q++ = (unsigned char)len; |
| for (p = name; *p && *p != '.'; p++) |
| { |
| if (*p == '\\' && *(p + 1) != 0) |
| p++; |
| *q++ = *p; |
| } |
| |
| /* Go to the next label and repeat, unless we hit the end. */ |
| if (!*p) |
| break; |
| name = p + 1; |
| } |
| |
| /* Add the zero-length label at the end. */ |
| *q++ = 0; |
| |
| /* Finish off the question with the type and class. */ |
| DNS_QUESTION_SET_TYPE(q, type); |
| DNS_QUESTION_SET_CLASS(q, dnsclass); |
| |
| q += QFIXEDSZ; |
| if (max_udp_size) |
| { |
| memset(q, 0, EDNSFIXEDSZ); |
| q++; |
| DNS_RR_SET_TYPE(q, T_OPT); |
| DNS_RR_SET_CLASS(q, max_udp_size); |
| q += (EDNSFIXEDSZ-1); |
| } |
| buflen = (q - buf); |
| |
| /* Reject names that are longer than the maximum of 255 bytes that's |
| * specified in RFC 1035 ("To simplify implementations, the total length of |
| * a domain name (i.e., label octets and label length octets) is restricted |
| * to 255 octets or less."). */ |
| if (buflen > (MAXCDNAME + HFIXEDSZ + QFIXEDSZ + |
| (max_udp_size ? EDNSFIXEDSZ : 0))) { |
| free (buf); |
| return ARES_EBADNAME; |
| } |
| |
| /* we know this fits in an int at this point */ |
| *buflenp = (int) buflen; |
| *bufp = buf; |
| |
| return ARES_SUCCESS; |
| } |