libresolv_query.c

/*
 * Copyright (c) 2013 by Wil Tan <[email protected]>
 *
 * Based on dump_dns.c from the dnscap <https://www.dns-oarc.net/tools/dnscap>
 * originally written by Paul Vixie.
 *
 * Copyright (c) 2007 by Internet Systems Consortium, Inc. ("ISC")
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <resolv.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>


extern const char *_res_opcodes[];

#define MY_GET16(s, cp) do { \
        register const u_char *t_cp = (const u_char *)(cp); \
        (s) = ((u_int16_t)t_cp[0] << 8) \
            | ((u_int16_t)t_cp[1]) \
            ; \
        (cp) += NS_INT16SZ; \
} while (0)

#define MY_GET32(l, cp) do { \
        register const u_char *t_cp = (const u_char *)(cp); \
        (l) = ((u_int32_t)t_cp[0] << 24) \
            | ((u_int32_t)t_cp[1] << 16) \
            | ((u_int32_t)t_cp[2] << 8) \
            | ((u_int32_t)t_cp[3]) \
            ; \
        (cp) += NS_INT32SZ; \
} while (0)

static void
dump_dns_rr(ns_msg *msg, ns_rr *rr, ns_sect sect, FILE *trace) {
	char buf[NS_MAXDNAME];
	u_int class, type;
	const u_char *rd;
	u_int32_t soa[5];
	u_int16_t mx;
	int n;

	class = ns_rr_class(*rr);
	type = ns_rr_type(*rr);
	fprintf(trace, "%s,%s,%s",
		ns_rr_name(*rr),
		p_class(class),
		p_type(type));
	if (sect == ns_s_qd)
		return;
	fprintf(trace, ",%lu", (u_long)ns_rr_ttl(*rr));
	rd = ns_rr_rdata(*rr);
	switch (type) {
	case ns_t_soa:
		n = ns_name_uncompress(ns_msg_base(*msg), ns_msg_end(*msg),
				       rd, buf, sizeof buf);
		if (n < 0)
			goto error;
		putc(',', trace);
		fputs(buf, trace);
		rd += n;
		n = ns_name_uncompress(ns_msg_base(*msg), ns_msg_end(*msg),
				       rd, buf, sizeof buf);
		if (n < 0)
			goto error;
		putc(',', trace);
		fputs(buf, trace);
		rd += n;
		if (ns_msg_end(*msg) - rd < 5*NS_INT32SZ)
			goto error;
		for (n = 0; n < 5; n++)
			MY_GET32(soa[n], rd);
		sprintf(buf, "%u,%u,%u,%u,%u",
			soa[0], soa[1], soa[2], soa[3], soa[4]);
		break;
	case ns_t_a:
		inet_ntop(AF_INET, rd, buf, sizeof buf);
		break;
	case ns_t_aaaa:
		inet_ntop(AF_INET6, rd, buf, sizeof buf);
		break;
	case ns_t_mx:
		MY_GET16(mx, rd);
		fprintf(trace, ",%u", mx);
		/* FALLTHROUGH */
	case ns_t_ns:
	case ns_t_ptr:
	case ns_t_cname:
		n = ns_name_uncompress(ns_msg_base(*msg), ns_msg_end(*msg),
				       rd, buf, sizeof buf);
		if (n < 0)
			goto error;
		break;
	case ns_t_txt:
		snprintf(buf, (size_t)rd[0]+1, "%s", rd+1);
		break;
	default:
 error:
		sprintf(buf, "[%u]", ns_rr_rdlen(*rr));
	}
	if (buf[0] != '\0') {
		putc(',', trace);
		fputs(buf, trace);
	}
}


static void
dump_dns_sect(ns_msg *msg, ns_sect sect, FILE *trace, const char *endline) {
        int rrnum, rrmax;
        const char *sep;
        ns_rr rr;

        rrmax = ns_msg_count(*msg, sect);
        if (rrmax == 0) {
                fputs(" 0", trace);
                return;
        }
        fprintf(trace, " %s%d", endline, rrmax);
        sep = "";
        for (rrnum = 0; rrnum < rrmax; rrnum++) {
                if (ns_parserr(msg, sect, rrnum, &rr)) {
                        fputs(strerror(errno), trace);
                        return;
                }
                fprintf(trace, " %s", sep);
                dump_dns_rr(msg, &rr, sect, trace);
                sep = endline;
        }
}

void
dump_dns(const u_char *payload, size_t paylen,
	  FILE *trace, const char *endline)
{
	u_int opcode, rcode, id;
	const char *sep;
	ns_msg msg;

	fprintf(trace, " %sdns ", endline);
	if (ns_initparse(payload, paylen, &msg) < 0) {
		fputs(strerror(errno), trace);
		return;
	}
	opcode = ns_msg_getflag(msg, ns_f_opcode);
	rcode = ns_msg_getflag(msg, ns_f_rcode);
	id = ns_msg_id(msg);
	fprintf(trace, "%s,%s,%u", _res_opcodes[opcode], p_rcode(rcode), id);
	sep = ",";
#define FLAG(t,f) if (ns_msg_getflag(msg, f)) { \
			fprintf(trace, "%s%s", sep, t); \
			sep = "|"; \
		  }
	FLAG("qr", ns_f_qr);
	FLAG("aa", ns_f_aa);
	FLAG("tc", ns_f_tc);
	FLAG("rd", ns_f_rd);
	FLAG("ra", ns_f_ra);
	FLAG("z", ns_f_z);
	FLAG("ad", ns_f_ad);
	FLAG("cd", ns_f_cd);
#undef FLAG

	dump_dns_sect(&msg, ns_s_an, trace, endline);
}


int main() {
	u_char answer[1024] = "";
	res_init();
	int rv = res_query("google.com", ns_c_in, ns_t_txt, answer, sizeof(answer));
	printf("rv=%d\n", rv);
	dump_dns(answer, rv, stdout, "\n");
	printf("\n");

}