/*
 * nsd-xfer.c -- nsd-xfer(8).
 *
 * Copyright (c) 2001-2011, NLnet Labs. All rights reserved.
 *
 * See LICENSE for the license.
 *
 */

#include <config.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <limits.h>
#include <assert.h>
#include <errno.h>
#include <netdb.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>

#include "dname.h"
#include "dns.h"
#include "packet.h"
#include "query.h"
#include "region-allocator.h"
#include "tsig.h"
#include "tsig-openssl.h"
#include "util.h"


/*
 * Number of seconds to wait when recieving no data from the remote
 * server.
 */
#define MAX_WAITING_TIME TCP_TIMEOUT

/*
 * Exit codes are based on named-xfer for now.  See ns_defs.h in
 * bind8.
 */
#define XFER_UPTODATE	0
#define XFER_SUCCESS	1
#define XFER_FAIL		3

struct axfr_state
{
	int verbose;
	size_t packets_received;
	size_t bytes_received;

	int s;			/* AXFR socket.  */
	query_type *q;		/* Query buffer.  */
	uint16_t query_id;	/* AXFR query ID.  */
	tsig_record_type *tsig;	/* TSIG data.  */

	int first_transfer;	 /* First transfer of this zone.  */
	uint32_t last_serial;    /* Otherwise the last serial.  */
	uint32_t zone_serial;	 /* And the new zone serial.  */
	const dname_type *zone;	 /* Zone name.  */

	int    done;		/* AXFR is complete.  */
	size_t rr_count;	/* Number of RRs received so far.  */

	/*
	 * Region used to allocate data needed to process a single RR.
	 */
	region_type *rr_region;

	/*
	 * Region used to store owner and origin of previous RR (used
	 * for pretty printing of zone data).
	 */
	struct state_pretty_rr *pretty_rr;
};
typedef struct axfr_state axfr_state_type;

static sig_atomic_t timeout_flag = 0;
static void to_alarm(int sig);		/* our alarm() signal handler */

extern char *optarg;
extern int optind;

static uint16_t init_query(query_type *q,
			   const dname_type *dname,
			   uint16_t type,
			   uint16_t klass,
			   tsig_record_type *tsig);


/*
 * Check if two getaddrinfo result lists have records with matching
 * ai_family fields.
 */
int check_matching_address_family(struct addrinfo *a, struct addrinfo *b);

/*
 * Returns the first record with ai_family == FAMILY, or NULL if no
 * such record is found.
 */
struct addrinfo *find_by_address_family(struct addrinfo *addrs, int family);

/*
 * Assigns pointers to hostname and port and wipes out the optional delimiter.
 */
void get_hostname_port_frm_str(char* arg, const char** hostname,
	const char** port);

/*
 * Log an error message and exit.
 */
static void error(const char *format, ...) ATTR_FORMAT(printf, 1, 2);
static void
error(const char *format, ...)
{
	va_list args;
	va_start(args, format);
	log_vmsg(LOG_ERR, format, args);
	va_end(args);
	exit(XFER_FAIL);
}


/*
 * Log a warning message.
 */
static void warning(const char *format, ...) ATTR_FORMAT(printf, 1, 2);
static void
warning(const char *format, ...)
{
	va_list args;
	va_start(args, format);
	log_vmsg(LOG_WARNING, format, args);
	va_end(args);
}


/*
 * Display usage information and exit.
 */
static void
usage (void)
{
	fprintf(stderr,
		"Usage: nsd-xfer [OPTION]... -z zone -f file server...\n"
		"NSD AXFR client.\n\nSupported options:\n"
		"  -4            Only use IPv4 connections.\n"
		"  -6            Only use IPv6 connections.\n"
		"  -a src[@port] Local hostname/ip-address for the \
connection, including optional source port.\n"
		"  -f file       Output zone file name.\n"
		"  -p port       The port to connect to.\n"
		"  -s serial     The current zone serial.\n"
		"  -T tsiginfo   The TSIG key file name.  The file is removed "
		"after reading the\n               key.\n"
		"  -v           Verbose output.\n");
	fprintf(stderr,
		"  -z zone      Specify the name of the zone to transfer.\n"
		"  server       The name or IP address of the master server.\n"
		"\nVersion %s. Report bugs to <%s>.\n", PACKAGE_VERSION, PACKAGE_BUGREPORT);
	exit(XFER_FAIL);
}


/*
 * Find an HMAC algorithm based on its id.
 */
static tsig_algorithm_type *
tsig_get_algorithm_by_id(uint8_t alg)
{
	if (alg == TSIG_HMAC_MD5)
		return tsig_get_algorithm_by_name("hmac-md5");
#ifdef HAVE_EVP_SHA1
	if (alg == TSIG_HMAC_SHA1)
		return tsig_get_algorithm_by_name("hmac-sha1");
#endif /* HAVE_EVP_SHA1 */
#ifdef HAVE_EVP_SHA256
	if (alg == TSIG_HMAC_SHA256)
		return tsig_get_algorithm_by_name("hmac-sha256");
#endif /* HAVE_EVP_SHA256 */

        return NULL;
}


/*
 * Signal handler for timeouts (SIGALRM). This function is called when
 * the alarm() value that was set counts down to zero.  This indicates
 * that we haven't received a response from the server.
 *
 * All we do is set a flag and return from the signal handler. The
 * occurrence of the signal interrupts the read() system call (errno
 * == EINTR) above, and we then check the timeout_flag flag.
 */
static void
to_alarm(int ATTR_UNUSED(sig))
{
	timeout_flag = 1;
}

/*
 * Read a line from IN.  If successful, the line is stripped of
 * leading and trailing whitespace and non-zero is returned.
 */
static int
tsig_read_line(FILE *in, char *line, size_t size)
{
	if (!fgets(line, size, in)) {
		return 0;
	} else {
		strip_string(line);
		return 1;
	}
}

static tsig_key_type *
read_tsig_key_data(region_type *region, FILE *in,
	int ATTR_UNUSED(default_family), tsig_algorithm_type** tsig_algo)
{
	char line[4000];
	tsig_key_type *key = (tsig_key_type *) region_alloc(
		region, sizeof(tsig_key_type));
	int size;
	uint8_t algo = 0;
	uint8_t data[4000];

	/* server address */
	if (!tsig_read_line(in, line, sizeof(line))) {
		error("failed to read TSIG key server address: '%s'",
		      strerror(errno));
		return NULL;
	}
	/* server address unused */

	/* tsig keyname */
	if (!tsig_read_line(in, line, sizeof(line))) {
		error("failed to read TSIG key name: '%s'", strerror(errno));
		return NULL;
	}

	key->name = dname_parse(region, line);
	if (!key->name) {
		error("failed to parse TSIG key name '%s'", line);
		return NULL;
	}

	/* tsig algorithm */
	if (!tsig_read_line(in, line, sizeof(line))) {
		error("failed to read TSIG key algorithm: '%s'", strerror(errno));
		return NULL;
	}
	algo = (uint8_t) atoi((const char*) line);
	*tsig_algo = tsig_get_algorithm_by_id(algo);
	if (*tsig_algo == NULL) {
		error("failed to parse TSIG key algorithm %i: '%s'\n", algo, strerror(errno));
		return NULL;
	}

	/* tsig secret */
	if (!tsig_read_line(in, line, sizeof(line))) {
		error("failed to read TSIG key data: '%s'\n", strerror(errno));
		return NULL;
	}

	size = b64_pton(line, data, sizeof(data));
	if (size == -1) {
		error("failed to parse TSIG key data");
		return NULL;
	}

	key->size = size;
	key->data = (uint8_t *) region_alloc_init(region, data, key->size);

	return key;
}

/*
 * Read the TSIG key from a .tsiginfo file and remove the file.
 */
static tsig_key_type *
read_tsig_key(region_type *region,
	      const char *tsiginfo_filename,
	      int default_family, tsig_algorithm_type** algo)
{
	FILE *in;
	tsig_key_type *key;

	in = fopen(tsiginfo_filename, "r");
	if (!in) {
		error("failed to open %s: %s",
		      tsiginfo_filename,
		      strerror(errno));
		return NULL;
	}

	key = read_tsig_key_data(region, in, default_family, algo);

	fclose(in);

	if (unlink(tsiginfo_filename) == -1) {
		warning("failed to remove %s: %s",
			tsiginfo_filename,
			strerror(errno));
	}

	return key;
}

/*
 * Read SIZE bytes from the socket into BUF.  Keep reading unless an
 * error occurs (except for EAGAIN) or EOF is reached.
 */
static int
read_socket(int s, void *buf, size_t size)
{
	char *data = (char *) buf;
	size_t total_count = 0;

	while (total_count < size) {
		ssize_t count = read(s, data + total_count, size - total_count);
		if (count == -1) {
			/* Error or interrupt.  */
			if (errno != EAGAIN) {
				error("network read failed: %s",
				      strerror(errno));
				return 0;
			} else {
				continue;
			}
		} else if (count == 0) {
			/* End of file (connection closed?)  */
			error("network read failed: Connection closed by peer");
			return 0;
		}
		total_count += count;
	}

	return 1;
}

static int
parse_response(FILE *out, axfr_state_type *state)
{
	size_t rr_count;
	size_t qdcount = QDCOUNT(state->q->packet);
	size_t ancount = ANCOUNT(state->q->packet);

	/* Skip question section.  */
	for (rr_count = 0; rr_count < qdcount; ++rr_count) {
		if (!packet_skip_rr(state->q->packet, 1)) {
			error("bad RR in question section");
			return 0;
		}
	}

	/* Read RRs from answer section and print them.  */
	for (rr_count = 0; rr_count < ancount; ++rr_count) {
		domain_table_type *owners
			= domain_table_create(state->rr_region);
		rr_type *record = packet_read_rr(
			state->rr_region, owners, state->q->packet, 0);
		if (!record) {
			error("bad RR in answer section");
			return 0;
		}

		if (state->rr_count == 0
		    && (record->type != TYPE_SOA || record->klass != CLASS_IN))
		{
			error("First RR must be the SOA record, but is a %s record",
			      rrtype_to_string(record->type));
			return 0;
		} else if (state->rr_count > 0
			   && record->type == TYPE_SOA
			   && record->klass == CLASS_IN)
		{
			state->done = 1;
			return 1;
		}

		++state->rr_count;

		if (!print_rr(out, state->pretty_rr, record)) {
			return 0;
		}

		region_free_all(state->rr_region);
	}

	return 1;
}

static int
send_query(int s, query_type *q)
{
	uint16_t size = htons(buffer_remaining(q->packet));

	if (!write_socket(s, &size, sizeof(size))) {
		error("network write failed: %s", strerror(errno));
		return 0;
	}
	if (!write_socket(s, buffer_begin(q->packet), buffer_limit(q->packet)))
	{
		error("network write failed: %s", strerror(errno));
		return 0;
	}
	return 1;
}

static int
receive_response_no_timeout(axfr_state_type *state)
{
	uint16_t size;

	buffer_clear(state->q->packet);
	if (!read_socket(state->s, &size, sizeof(size))) {
		return 0;
	}
	size = ntohs(size);
	if (size > state->q->maxlen) {
		error("response size (%d) exceeds maximum (%d)",
		      (int) size, (int) state->q->maxlen);
		return 0;
	}
	if (!read_socket(state->s, buffer_begin(state->q->packet), size)) {
		return 0;
	}

	buffer_set_position(state->q->packet, size);

	++state->packets_received;
	state->bytes_received += sizeof(size) + size;

	return 1;
}

static int
receive_response(axfr_state_type *state)
{
	int result;

	timeout_flag = 0;
	alarm(MAX_WAITING_TIME);
	result = receive_response_no_timeout(state);
	alarm(0);
	if (!result && timeout_flag) {
		error("timeout reading response, server unreachable?");
	}

	return result;
}

static int
check_response_tsig(query_type *q, tsig_record_type *tsig)
{
	if (!tsig)
		return 1;

	if (!tsig_find_rr(tsig, q->packet)) {
		error("error parsing response");
		return 0;
	}
	if (tsig->status == TSIG_NOT_PRESENT) {
		if (tsig->response_count == 0) {
			error("required TSIG not present");
			return 0;
		}
		if (tsig->updates_since_last_prepare > 100) {
			error("too many response packets without TSIG");
			return 0;
		}
		tsig_update(tsig, q->packet, buffer_limit(q->packet));
		return 1;
	}

	ARCOUNT_SET(q->packet, ARCOUNT(q->packet) - 1);

	if (tsig->status == TSIG_ERROR) {
		error("TSIG record is not correct");
		return 0;
	} else if (tsig->error_code != TSIG_ERROR_NOERROR) {
		error("TSIG error code: %s",
		      tsig_error(tsig->error_code));
		return 0;
	} else {
		tsig_update(tsig, q->packet, tsig->position);
		if (!tsig_verify(tsig)) {
			error("TSIG record did not authenticate");
			return 0;
		}
		tsig_prepare(tsig);
	}

	return 1;
}


/*
 * Query the server for the zone serial. Return 1 if the zone serial
 * is higher than the current serial, 0 if the zone serial is lower or
 * equal to the current serial, and -1 on error.
 *
 * On success, the zone serial is returned in ZONE_SERIAL.
 */
static int
check_serial(axfr_state_type *state)
{
	region_type *local;
	uint16_t query_id;
	uint16_t i;
	domain_table_type *owners;

	query_id = init_query(
		state->q, state->zone, TYPE_SOA, CLASS_IN, state->tsig);

	if (!send_query(state->s, state->q)) {
		return -1;
	}

	if (state->tsig) {
		/* Prepare for checking responses. */
		tsig_prepare(state->tsig);
	}

	if (!receive_response(state)) {
		return -1;
	}
	buffer_flip(state->q->packet);

	if (buffer_limit(state->q->packet) <= QHEADERSZ) {
		error("response size (%d) is too small",
		      (int) buffer_limit(state->q->packet));
		return -1;
	}

	if (!QR(state->q->packet)) {
		error("response is not a response");
		return -1;
	}

	if (TC(state->q->packet)) {
		error("response is truncated");
		return -1;
	}

	if (ID(state->q->packet) != query_id) {
		error("bad response id (%d), expected (%d)",
		      (int) ID(state->q->packet), (int) query_id);
		return -1;
	}

	if (RCODE(state->q->packet) != RCODE_OK) {
		error("error response %d (%s)", (int) RCODE(state->q->packet),
				rcode2str((int) RCODE(state->q->packet)));
		return -1;
	}

	if (QDCOUNT(state->q->packet) != 1) {
		error("question section count not equal to 1");
		return -1;
	}

	if (ANCOUNT(state->q->packet) == 0) {
		error("answer section is empty");
		return -1;
	}

	if (!check_response_tsig(state->q, state->tsig)) {
		return -1;
	}

	buffer_set_position(state->q->packet, QHEADERSZ);

	local = region_create(xalloc, free);
	owners = domain_table_create(local);

	/* Skip question records. */
	for (i = 0; i < QDCOUNT(state->q->packet); ++i) {
		rr_type *record
			= packet_read_rr(local, owners, state->q->packet, 1);
		if (!record) {
			error("bad RR in question section");
			region_destroy(local);
			return -1;
		}

		if (dname_compare(state->zone, domain_dname(record->owner)) != 0
		    || record->type != TYPE_SOA
		    || record->klass != CLASS_IN)
		{
			error("response does not match query");
			region_destroy(local);
			return -1;
		}
	}

	/* Find the SOA record in the response.  */
	for (i = 0; i < ANCOUNT(state->q->packet); ++i) {
		rr_type *record
			= packet_read_rr(local, owners, state->q->packet, 0);
		if (!record) {
			error("bad RR in answer section");
			region_destroy(local);
			return -1;
		}

		if (dname_compare(state->zone, domain_dname(record->owner)) == 0
		    && record->type == TYPE_SOA
		    && record->klass == CLASS_IN)
		{
			assert(record->rdata_count == 7);
			assert(rdata_atom_size(record->rdatas[2]) == 4);
			state->zone_serial = read_uint32(
				rdata_atom_data(record->rdatas[2]));
			region_destroy(local);
			return (state->first_transfer
				|| compare_serial(state->zone_serial,
						  state->last_serial) > 0);
		}
	}

	error("SOA not found in answer");
	region_destroy(local);
	return -1;
}

/*
 * Receive and parse the AXFR response packets.
 */
static int
handle_axfr_response(FILE *out, axfr_state_type *axfr)
{
	while (!axfr->done) {
		if (!receive_response(axfr)) {
			return 0;
		}

		buffer_flip(axfr->q->packet);

		if (buffer_limit(axfr->q->packet) <= QHEADERSZ) {
			error("response size (%d) is too small",
			      (int) buffer_limit(axfr->q->packet));
			return 0;
		}

		if (!QR(axfr->q->packet)) {
			error("response is not a response");
			return 0;
		}

		if (ID(axfr->q->packet) != axfr->query_id) {
			error("bad response id (%d), expected (%d)",
			      (int) ID(axfr->q->packet),
			      (int) axfr->query_id);
			return 0;
		}

		if (RCODE(axfr->q->packet) != RCODE_OK) {
			error("error response %d (%s)", (int) RCODE(axfr->q->packet),
					rcode2str((int) RCODE(axfr->q->packet)));
			return 0;
		}

		if (QDCOUNT(axfr->q->packet) > 1) {
			error("query section count greater than 1");
			return 0;
		}

		if (ANCOUNT(axfr->q->packet) == 0) {
			error("answer section is empty");
			return 0;
		}

		if (!check_response_tsig(axfr->q, axfr->tsig)) {
			return 0;
		}

		buffer_set_position(axfr->q->packet, QHEADERSZ);

		if (!parse_response(out, axfr)) {
			return 0;
		}
	}
	return 1;
}

static int
axfr(FILE *out, axfr_state_type *state, const char *server)
{
	state->query_id = init_query(
		state->q, state->zone, TYPE_AXFR, CLASS_IN, state->tsig);

	log_msg(LOG_INFO,
		"send AXFR query to %s for %s",
		server,
		dname_to_string(state->zone, NULL));

	if (!send_query(state->s, state->q)) {
		return 0;
	}

	if (state->tsig) {
		/* Prepare for checking responses.  */
		tsig_prepare(state->tsig);
	}

	return handle_axfr_response(out, state);
}

static uint16_t
init_query(query_type *q,
	   const dname_type *dname,
	   uint16_t type,
	   uint16_t klass,
	   tsig_record_type *tsig)
{
	uint16_t query_id = qid_generate();

	buffer_clear(q->packet);

	/* Set up the header */
	ID_SET(q->packet, query_id);
	FLAGS_SET(q->packet, 0);
	OPCODE_SET(q->packet, OPCODE_QUERY);
	AA_SET(q->packet);
	QDCOUNT_SET(q->packet, 1);
	ANCOUNT_SET(q->packet, 0);
	NSCOUNT_SET(q->packet, 0);
	ARCOUNT_SET(q->packet, 0);
	buffer_skip(q->packet, QHEADERSZ);

	/* The question record.  */
	buffer_write(q->packet, dname_name(dname), dname->name_size);
	buffer_write_u16(q->packet, type);
	buffer_write_u16(q->packet, klass);

	if (tsig) {
		tsig_init_query(tsig, query_id);
		tsig_prepare(tsig);
		tsig_update(tsig, q->packet, buffer_position(q->packet));
		tsig_sign(tsig);
		tsig_append_rr(tsig, q->packet);
		ARCOUNT_SET(q->packet, 1);
	}

	buffer_flip(q->packet);

	return ID(q->packet);
}

static void
print_zone_header(FILE *out, axfr_state_type *state, const char *server)
{
	time_t now = time(NULL);
	fprintf(out, "; NSD version %s\n", PACKAGE_VERSION);
	fprintf(out, "; zone '%s'", dname_to_string(state->zone, NULL));
	if (state->first_transfer) {
		fprintf(out, "   first transfer\n");
	} else {
		fprintf(out,
			"   last serial %lu\n",
			(unsigned long) state->last_serial);
	}
	fprintf(out, "; from %s using AXFR at %s", server, ctime(&now));
	if (state->tsig) {
		fprintf(out, "; TSIG verified with key '%s'\n",
			dname_to_string(state->tsig->key->name, NULL));
	} else {
		fprintf(out, "; NOT TSIG verified\n");
	}
}

static void
print_stats(axfr_state_type *state)
{
	log_msg(LOG_INFO,
		"received %lu RRs in %lu bytes (using %lu response packets)",
		(unsigned long) state->rr_count,
		(unsigned long) state->bytes_received,
		(unsigned long) state->packets_received);
}

int
main(int argc, char *argv[])
{
	region_type *region = region_create(xalloc, free);
	int c;
	query_type q;
	struct addrinfo hints, *res0, *res;
	const char *zone_filename = NULL;
	const char *local_hostname = NULL;
	struct addrinfo *local_address, *local_addresses = NULL;
	const char *port = TCP_PORT;
	const char *local_port = NULL;
	int default_family = DEFAULT_AI_FAMILY;
	struct sigaction mysigaction;
	FILE *zone_file;
	const char *tsig_key_filename = NULL;
	tsig_key_type *tsig_key = NULL;
	axfr_state_type state;

	log_init("nsd-xfer");

	/* Initialize the query.  */
	memset(&q, 0, sizeof(query_type));
	q.region = region;
	q.addrlen = sizeof(q.addr);
	q.packet = buffer_create(region, QIOBUFSZ);
	q.maxlen = TCP_MAX_MESSAGE_LEN;

	/* Initialize the state.  */
	state.verbose = 0;
	state.packets_received = 0;
	state.bytes_received = 0;
	state.q = &q;
	state.tsig = NULL;
	state.zone = NULL;
	state.first_transfer = 1;
	state.done = 0;
	state.rr_count = 0;
	state.rr_region = region_create(xalloc, free);
	state.pretty_rr = create_pretty_rr(region);

	region_add_cleanup(region, cleanup_region, state.rr_region);

	srandom((unsigned long) getpid() * (unsigned long) time(NULL));

	if (!tsig_init(region)) {
		error("TSIG initialization failed");
	}

	/* Parse the command line... */
	while ((c = getopt(argc, argv, "46a:f:hp:s:T:vz:")) != -1) {
		switch (c) {
		case '4':
			default_family = AF_INET;
			break;
		case '6':
#ifdef INET6
			default_family = AF_INET6;
#else /* !INET6 */
			error("IPv6 support not enabled.");
#endif /* !INET6 */
			break;
		case 'a':
			get_hostname_port_frm_str((char *) optarg,
				&local_hostname, &local_port);
			break;
		case 'f':
			zone_filename = optarg;
			break;
		case 'h':
			usage();
			break;
		case 'p':
			port = optarg;
			break;
		case 's': {
			uint32_t v;
			const char *t;
 			state.first_transfer = 0;
			v = strtoserial(optarg, &t);
			if (optarg[0] == '\0' || *t != '\0')
			{
				error("bad serial '%s'", optarg);
				exit(XFER_FAIL);
			}
			state.last_serial = v;
			break;
		}
		case 'T':
			tsig_key_filename = optarg;
			break;
		case 'v':
			++state.verbose;
			break;
		case 'z':
			state.zone = dname_parse(region, optarg);
			if (!state.zone) {
				error("incorrect domain name '%s'", optarg);
			}
			break;
		case '?':
		default:
			usage();
		}
	}
	argc -= optind;
	argv += optind;

	if (argc == 0 || !zone_filename || !state.zone)
		usage();

	if (tsig_key_filename) {
		tsig_algorithm_type *tsig_algo = NULL;
		tsig_key = read_tsig_key(
			region, tsig_key_filename, default_family, &tsig_algo);
		if (!tsig_key) {
			error("cannot initialize TSIG: error in tsiginfo file");
			exit(XFER_FAIL);
		}

		tsig_add_key(tsig_key);

		state.tsig = (tsig_record_type *) region_alloc(
			region, sizeof(tsig_record_type));
		tsig_create_record(state.tsig, region);
		tsig_init_record(state.tsig, tsig_algo, tsig_key);
	}

	mysigaction.sa_handler = to_alarm;
	sigfillset(&mysigaction.sa_mask);
	mysigaction.sa_flags = 0;
	if (sigaction(SIGALRM, &mysigaction, NULL) < 0) {
		error("cannot set signal handler");
	}

	memset(&hints, 0, sizeof(hints));
	hints.ai_family = default_family;
	hints.ai_socktype = SOCK_STREAM;
	hints.ai_protocol = IPPROTO_TCP;

	if (local_hostname) {
		int rc = getaddrinfo(local_hostname, local_port,
				     &hints, &local_addresses);
		if (rc) {
			error("local hostname '%s' not found: %s",
				local_hostname, gai_strerror(rc));
		}
	}

	for (/*empty*/; *argv; ++argv) {
		/* Try each server separately until one succeeds.  */
		int rc;

		rc = getaddrinfo(*argv, port, &hints, &res0);
		if (rc) {
			warning("skipping bad address %s: %s\n", *argv,
				gai_strerror(rc));
			continue;
		}

		if (local_addresses
		    && !check_matching_address_family(res0, local_addresses))
		{
			warning("no local address family matches remote "
				"address family, skipping server '%s'",
				*argv);
			continue;
		}

		for (res = res0; res; res = res->ai_next) {
			if (res->ai_addrlen > (socklen_t)sizeof(q.addr))
				continue;

			/*
			 * If a local address is specified, use an
			 * address with the same family as the remote
			 * address.
			 */
			local_address = find_by_address_family(local_addresses,
				res->ai_family);
			if (local_addresses && !local_address) {
				/* Continue with next remote address.  */
				continue;
			}

			state.s = socket(res->ai_family, res->ai_socktype,
					 res->ai_protocol);
			if (state.s == -1) {
				warning("cannot create socket: %s\n",
					strerror(errno));
				continue;
			}

			/* Bind socket to local address, if required.  */
			if (local_address && bind(state.s,
				local_address->ai_addr,
				local_address->ai_addrlen) < 0)
			{
				warning("cannot bind to %s: %s\n",
					local_hostname, strerror(errno));
			}

			if (connect(state.s, res->ai_addr, res->ai_addrlen) < 0)
			{
				warning("cannot connect to %s: %s\n",
					*argv,
					strerror(errno));
				close(state.s);
				continue;
			}

			memcpy(&q.addr, res->ai_addr, res->ai_addrlen);

			rc = check_serial(&state);
			if (rc == -1) {
				close(state.s);
				continue;
			}
			if (rc == 0) {
				/* Zone is up-to-date.  */
				close(state.s);
				exit(XFER_UPTODATE);
			} else if (rc > 0) {
				zone_file = fopen(zone_filename, "w");
				if (!zone_file) {
					error("cannot open or create zone file '%s' for writing: %s",
					      zone_filename, strerror(errno));
					close(state.s);
					exit(XFER_FAIL);
				}

				print_zone_header(zone_file, &state, *argv);

				if (axfr(zone_file, &state, *argv)) {
					/* AXFR succeeded, done.  */
					fclose(zone_file);
					close(state.s);

					if (state.verbose > 0) {
						print_stats(&state);
					}

					exit(XFER_SUCCESS);
				}

				fclose(zone_file);
			}

			close(state.s);
		}

		freeaddrinfo(res0);
	}

	log_msg(LOG_ERR,
		"cannot contact an authoritative server, zone NOT transferred");
	exit(XFER_FAIL);
}

void
get_hostname_port_frm_str(char* arg, const char** hostname,
	const char** port)
{
	/* parse -a src[@port] option */
	char* delim = strchr(arg, '@');

	if (delim) {
		*delim = '\0';
		*port = delim+1;
	}
	*hostname = arg;
}


int
check_matching_address_family(struct addrinfo *a0, struct addrinfo *b0)
{
	struct addrinfo *a;
	struct addrinfo *b;

	for (a = a0; a; a = a->ai_next) {
		for (b = b0; b; b = b->ai_next) {
			if (a->ai_family == b->ai_family) {
				return 1;
			}
		}
	}
	return 0;
}

struct addrinfo *
find_by_address_family(struct addrinfo *addrs, int family)
{
	for (; addrs; addrs = addrs->ai_next) {
		if (addrs->ai_family == family) {
			return addrs;
		}
	}
	return NULL;
}