| |
| /* 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_SYS_SOCKET_H |
| # include <sys/socket.h> |
| #endif |
| #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 <stdlib.h> |
| #include <string.h> |
| #include "ares.h" |
| #include "ares_dns.h" |
| #include "ares_private.h" |
| |
| /* 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_mkquery(const char *name, int dnsclass, int type, unsigned short id, |
| int rd, unsigned char **buf, int *buflen) |
| { |
| int len; |
| unsigned char *q; |
| const char *p; |
| |
| /* Set our results early, in case we bail out early with an error. */ |
| *buflen = 0; |
| *buf = NULL; |
| |
| /* Compute the length of the encoded name so we can check buflen. |
| * Start counting at 1 for the zero-length label at the end. */ |
| len = 1; |
| for (p = name; *p; p++) |
| { |
| if (*p == '\\' && *(p + 1) != 0) |
| p++; |
| len++; |
| } |
| /* If there are n periods in the name, there are n + 1 labels, and |
| * thus n + 1 length fields, unless the name is empty or ends with a |
| * period. So add 1 unless name is empty or ends with a period. |
| */ |
| if (*name && *(p - 1) != '.') |
| len++; |
| |
| /* Immediately 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."). We aren't |
| * doing this just to be a stickler about RFCs. For names that are |
| * too long, 'dnscache' closes its TCP connection to us immediately |
| * (when using TCP) and ignores the request when using UDP, and |
| * BIND's named returns ServFail (TCP or UDP). Sending a request |
| * that we know will cause 'dnscache' to close the TCP connection is |
| * painful, since that makes any other outstanding requests on that |
| * connection fail. And sending a UDP request that we know |
| * 'dnscache' will ignore is bad because resources will be tied up |
| * until we time-out the request. |
| */ |
| if (len > MAXCDNAME) |
| return ARES_EBADNAME; |
| |
| *buflen = len + HFIXEDSZ + QFIXEDSZ; |
| *buf = malloc(*buflen); |
| 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); |
| |
| /* 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 == '.') |
| 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) |
| 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); |
| |
| return ARES_SUCCESS; |
| } |
