From 90364defb038d5d6b97acf9df9ed152d2393a863 Mon Sep 17 00:00:00 2001 From: "hpopescu@ixiacom.com" Date: Fri, 10 Aug 2012 12:06:09 +0300 Subject: Added new feature (rfc2671) --- ares_create_query.c | 209 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 209 insertions(+) create mode 100644 ares_create_query.c (limited to 'ares_create_query.c') diff --git a/ares_create_query.c b/ares_create_query.c new file mode 100644 index 0000000..ef48ad8 --- /dev/null +++ b/ares_create_query.c @@ -0,0 +1,209 @@ + +/* 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 +#endif +#ifdef HAVE_NETINET_IN_H +# include +#endif +#ifdef HAVE_ARPA_NAMESER_H +# include +#else +# include "nameser.h" +#endif +#ifdef HAVE_ARPA_NAMESER_COMPAT_H +# include +#endif + +#include +#include +#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_create_query(const char *name, int dnsclass, int type, + unsigned short id, int rd, unsigned char **buf, + int *buflen, int max_udp_size) +{ + 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 + (max_udp_size ? EDNSFIXEDSZ : 0); + *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); + + 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 == '.') + 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); + + if (max_udp_size) + { + q += QFIXEDSZ; + memset(q, 0, EDNSFIXEDSZ); + q++; + DNS_RR_SET_TYPE(q, ns_t_opt); + DNS_RR_SET_CLASS(q, max_udp_size); + } + + return ARES_SUCCESS; +} -- cgit v1.2.3