Adding upstream version 2.7.6.upstream/2.7.6upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

22 files changed, 4009 insertions, 0 deletions

diff --git a/src/utils/common/cert.c b/src/utils/common/cert.c
new file mode 100644
index 0000000..b9cf2c4
--- /dev/null
+++ b/src/utils/common/cert.c
@@ -0,0 +1,61 @@
+/*  Copyright (C) 2016 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <gnutls/abstract.h>
+#include <gnutls/crypto.h>
+
+#include "utils/common/cert.h"
+#include "libknot/error.h"
+
+static int spki_hash(gnutls_x509_crt_t cert, gnutls_digest_algorithm_t alg,
+                     uint8_t *hash, size_t size)
+{
+	if (!cert || !hash || gnutls_hash_get_len(alg) != size) {
+		return KNOT_EINVAL;
+	}
+
+	gnutls_pubkey_t key = { 0 };
+	if (gnutls_pubkey_init(&key) != GNUTLS_E_SUCCESS) {
+		return KNOT_ENOMEM;
+	}
+
+	if (gnutls_pubkey_import_x509(key, cert, 0) != GNUTLS_E_SUCCESS) {
+		gnutls_pubkey_deinit(key);
+		return KNOT_ERROR;
+	}
+
+	gnutls_datum_t der = { 0 };
+	if (gnutls_pubkey_export2(key, GNUTLS_X509_FMT_DER, &der) != GNUTLS_E_SUCCESS) {
+		gnutls_pubkey_deinit(key);
+		return KNOT_ERROR;
+	}
+
+	int ret = gnutls_hash_fast(alg, der.data, der.size, hash);
+
+	gnutls_free(der.data);
+	gnutls_pubkey_deinit(key);
+
+	if (ret != GNUTLS_E_SUCCESS) {
+		return KNOT_ERROR;
+	}
+
+	return KNOT_EOK;
+}
+
+int cert_get_pin(gnutls_x509_crt_t cert, uint8_t *pin, size_t size)
+{
+	return spki_hash(cert, GNUTLS_DIG_SHA256, pin, size);
+}
diff --git a/src/utils/common/cert.h b/src/utils/common/cert.h
new file mode 100644
index 0000000..ad4901b
--- /dev/null
+++ b/src/utils/common/cert.h
@@ -0,0 +1,36 @@
+/*  Copyright (C) 2016 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <gnutls/x509.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#define CERT_PIN_LEN 32
+
+/*!
+ * \brief Get certificate pin value.
+ *
+ * The pin is a SHA-256 hash of the X.509 SubjectPublicKeyInfo.
+ *
+ * \param[in]  crt   Certificate.
+ * \param[out] pin   Pin.
+ * \param[in]  size  Length of the pin, must be CERT_PIN_LEN.
+ *
+ * \return Error code, KNOT_EOK if successful.
+ */
+int cert_get_pin(gnutls_x509_crt_t crt, uint8_t *pin, size_t size);
diff --git a/src/utils/common/exec.c b/src/utils/common/exec.c
new file mode 100644
index 0000000..1d97600
--- /dev/null
+++ b/src/utils/common/exec.c
@@ -0,0 +1,692 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <arpa/inet.h>
+#include <stdlib.h>
+#include <time.h>
+
+#include "libdnssec/random.h"
+#include "utils/common/exec.h"
+#include "utils/common/msg.h"
+#include "utils/common/netio.h"
+#include "utils/common/params.h"
+#include "libknot/libknot.h"
+#include "contrib/ctype.h"
+#include "contrib/sockaddr.h"
+#include "contrib/openbsd/strlcat.h"
+#include "contrib/ucw/lists.h"
+#include "contrib/wire_ctx.h"
+
+static knot_lookup_t rtypes[] = {
+	{ KNOT_RRTYPE_A,      "has IPv4 address" },
+	{ KNOT_RRTYPE_NS,     "nameserver is" },
+	{ KNOT_RRTYPE_CNAME,  "is an alias for" },
+	{ KNOT_RRTYPE_SOA,    "start of authority is" },
+	{ KNOT_RRTYPE_PTR,    "points to" },
+	{ KNOT_RRTYPE_MX,     "mail is handled by" },
+	{ KNOT_RRTYPE_TXT,    "description is" },
+	{ KNOT_RRTYPE_AAAA,   "has IPv6 address" },
+	{ KNOT_RRTYPE_LOC,    "location is" },
+	{ KNOT_RRTYPE_DS,     "delegation signature is" },
+	{ KNOT_RRTYPE_SSHFP,  "SSH fingerprint is" },
+	{ KNOT_RRTYPE_RRSIG,  "RR set signature is" },
+	{ KNOT_RRTYPE_DNSKEY, "DNSSEC key is" },
+	{ KNOT_RRTYPE_TLSA,   "has TLS certificate" },
+	{ 0, NULL }
+};
+
+static void print_header(const knot_pkt_t *packet, const style_t *style)
+{
+	char flags[64] = "";
+	char unknown_rcode[64] = "";
+	char unknown_opcode[64] = "";
+
+	const char *rcode_str = NULL;
+	const char *opcode_str = NULL;
+
+	// Get extended RCODE.
+	const char *code_name = knot_pkt_ext_rcode_name(packet);
+	if (code_name[0] != '\0') {
+		rcode_str = code_name;
+	} else {
+		uint16_t code = knot_pkt_ext_rcode(packet);
+		(void)snprintf(unknown_rcode, sizeof(unknown_rcode), "RCODE %d", code);
+		rcode_str = unknown_rcode;
+	}
+
+	// Get OPCODE.
+	uint8_t code = knot_wire_get_opcode(packet->wire);
+	const knot_lookup_t *opcode = knot_lookup_by_id(knot_opcode_names, code);
+	if (opcode != NULL) {
+		opcode_str = opcode->name;
+	} else {
+		(void)snprintf(unknown_opcode, sizeof(unknown_opcode), "OPCODE %d", code);
+		opcode_str = unknown_opcode;
+	}
+
+	// Get flags.
+	size_t flags_rest = sizeof(flags);
+	const size_t flag_len = 4;
+	if (knot_wire_get_qr(packet->wire) != 0 && flags_rest > flag_len) {
+		flags_rest -= strlcat(flags, " qr", flags_rest);
+	}
+	if (knot_wire_get_aa(packet->wire) != 0 && flags_rest > flag_len) {
+		flags_rest -= strlcat(flags, " aa", flags_rest);
+	}
+	if (knot_wire_get_tc(packet->wire) != 0 && flags_rest > flag_len) {
+		flags_rest -= strlcat(flags, " tc", flags_rest);
+	}
+	if (knot_wire_get_rd(packet->wire) != 0 && flags_rest > flag_len) {
+		flags_rest -= strlcat(flags, " rd", flags_rest);
+	}
+	if (knot_wire_get_ra(packet->wire) != 0 && flags_rest > flag_len) {
+		flags_rest -= strlcat(flags, " ra", flags_rest);
+	}
+	if (knot_wire_get_z(packet->wire) != 0 && flags_rest > flag_len) {
+		flags_rest -= strlcat(flags, " z", flags_rest);
+	}
+	if (knot_wire_get_ad(packet->wire) != 0 && flags_rest > flag_len) {
+		flags_rest -= strlcat(flags, " ad", flags_rest);
+	}
+	if (knot_wire_get_cd(packet->wire) != 0 && flags_rest > flag_len) {
+		strlcat(flags, " cd", flags_rest);
+	}
+
+	uint16_t id = knot_wire_get_id(packet->wire);
+	uint16_t qdcount = knot_wire_get_qdcount(packet->wire);
+	uint16_t ancount = knot_wire_get_ancount(packet->wire);
+	uint16_t nscount = knot_wire_get_nscount(packet->wire);
+	uint16_t arcount = knot_wire_get_arcount(packet->wire);
+
+	if (knot_pkt_has_tsig(packet)) {
+		arcount++;
+	}
+
+	// Print formatted info.
+	switch (style->format) {
+	case FORMAT_NSUPDATE:
+		printf(";; ->>HEADER<<- opcode: %s; status: %s; id: %u\n"
+		       ";; Flags:%1s; "
+		       "ZONE: %u; PREREQ: %u; UPDATE: %u; ADDITIONAL: %u\n",
+		       opcode_str, rcode_str, id, flags, qdcount, ancount,
+		       nscount, arcount);
+		break;
+	default:
+		printf(";; ->>HEADER<<- opcode: %s; status: %s; id: %u\n"
+		       ";; Flags:%1s; "
+		       "QUERY: %u; ANSWER: %u; AUTHORITY: %u; ADDITIONAL: %u\n",
+		       opcode_str, rcode_str, id, flags, qdcount, ancount,
+		       nscount, arcount);
+		break;
+	}
+}
+
+static void print_footer(const size_t total_len,
+                         const size_t msg_count,
+                         const size_t rr_count,
+                         const net_t  *net,
+                         const float  elapsed,
+                         time_t       exec_time,
+                         const bool   incoming)
+{
+	struct tm tm;
+	char date[64];
+
+	// Get current timestamp.
+	if (exec_time == 0) {
+		exec_time = time(NULL);
+	}
+
+	// Create formatted date-time string.
+	localtime_r(&exec_time, &tm);
+	strftime(date, sizeof(date), "%Y-%m-%d %H:%M:%S %Z", &tm);
+
+	// Print messages statistics.
+	if (incoming) {
+		printf(";; Received %zu B", total_len);
+	} else {
+		printf(";; Sent %zu B", total_len);
+	}
+
+	// If multimessage (XFR) print additional statistics.
+	if (msg_count > 0) {
+		printf(" (%zu messages, %zu records)\n", msg_count, rr_count);
+	} else {
+		printf("\n");
+	}
+	// Print date.
+	printf(";; Time %s\n", date);
+
+	// Print connection statistics.
+	if (net != NULL) {
+		if (incoming) {
+			printf(";; From %s", net->remote_str);
+		} else {
+			printf(";; To %s", net->remote_str);
+		}
+
+		if (elapsed >= 0) {
+			printf(" in %.1f ms\n", elapsed);
+		} else {
+			printf("\n");
+		}
+	}
+}
+
+static void print_hex(const uint8_t *data, uint16_t len)
+{
+	for (int i = 0; i < len; i++) {
+		printf("%02X", data[i]);
+	}
+}
+
+static void print_nsid(const uint8_t *data, uint16_t len)
+{
+	if (len == 0) {
+		return;
+	}
+
+	print_hex(data, len);
+
+	// Check if printable string.
+	for (int i = 0; i < len; i++) {
+		if (!is_print(data[i])) {
+			return;
+		}
+	}
+	printf(" \"%.*s\"", len, data);
+}
+
+static void print_edns_client_subnet(const uint8_t *data, uint16_t len)
+{
+	knot_edns_client_subnet_t ecs = { 0 };
+	int ret = knot_edns_client_subnet_parse(&ecs, data, len);
+	if (ret != KNOT_EOK) {
+		return;
+	}
+
+	struct sockaddr_storage addr = { 0 };
+	ret = knot_edns_client_subnet_get_addr(&addr, &ecs);
+	assert(ret == KNOT_EOK);
+
+	char addr_str[SOCKADDR_STRLEN] = { 0 };
+	sockaddr_tostr(addr_str, sizeof(addr_str), (struct sockaddr *)&addr);
+
+	printf("%s/%u/%u", addr_str, ecs.source_len, ecs.scope_len);
+}
+
+static void print_section_opt(const knot_pkt_t *packet)
+{
+	char unknown_ercode[64] = "";
+	const char *ercode_str = NULL;
+
+	uint16_t ercode = knot_edns_get_ext_rcode(packet->opt_rr);
+	if (ercode > 0) {
+		ercode = knot_edns_whole_rcode(ercode,
+		                               knot_wire_get_rcode(packet->wire));
+	}
+
+	const knot_lookup_t *item = knot_lookup_by_id(knot_rcode_names, ercode);
+	if (item != NULL) {
+		ercode_str = item->name;
+	} else {
+		(void)snprintf(unknown_ercode, sizeof(unknown_ercode), "RCODE %d", ercode);
+		ercode_str = unknown_ercode;
+	}
+
+	printf("Version: %u; flags: %s; UDP size: %u B; ext-rcode: %s\n",
+	       knot_edns_get_version(packet->opt_rr),
+	       (knot_edns_do(packet->opt_rr) != 0) ? "do" : "",
+	       knot_edns_get_payload(packet->opt_rr),
+	       ercode_str);
+
+	assert(packet->opt_rr->rrs.count > 0);
+	knot_rdata_t *rdata = packet->opt_rr->rrs.rdata;
+	wire_ctx_t wire = wire_ctx_init_const(rdata->data, rdata->len);
+
+	while (wire_ctx_available(&wire) >= KNOT_EDNS_OPTION_HDRLEN) {
+		uint16_t opt_code = wire_ctx_read_u16(&wire);
+		uint16_t opt_len = wire_ctx_read_u16(&wire);
+		uint8_t *opt_data = wire.position;
+
+		if (wire.error != KNOT_EOK) {
+			WARN("invalid OPT record data\n");
+			return;
+		}
+
+		switch (opt_code) {
+		case KNOT_EDNS_OPTION_NSID:
+			printf(";; NSID: ");
+			print_nsid(opt_data, opt_len);
+			break;
+		case KNOT_EDNS_OPTION_CLIENT_SUBNET:
+			printf(";; CLIENT-SUBNET: ");
+			print_edns_client_subnet(opt_data, opt_len);
+			break;
+		case KNOT_EDNS_OPTION_PADDING:
+			printf(";; PADDING: %u B", opt_len);
+			break;
+		case KNOT_EDNS_OPTION_COOKIE:
+			printf(";; COOKIE: ");
+			print_hex(opt_data, opt_len);
+			break;
+		default:
+			printf(";; Option (%u): ", opt_code);
+			print_hex(opt_data, opt_len);
+		}
+		printf("\n");
+
+		wire_ctx_skip(&wire, opt_len);
+	}
+
+	if (wire_ctx_available(&wire) > 0) {
+		WARN("invalid OPT record data\n");
+	}
+}
+
+static void print_section_question(const knot_dname_t *owner,
+                                   const uint16_t     qclass,
+                                   const uint16_t     qtype,
+                                   const style_t      *style)
+{
+	size_t buflen = 8192;
+	char *buf = calloc(buflen, 1);
+
+	// Don't print zero TTL.
+	knot_dump_style_t qstyle = style->style;
+	qstyle.empty_ttl = true;
+
+	knot_rrset_t *question = knot_rrset_new(owner, qtype, qclass, 0, NULL);
+
+	if (knot_rrset_txt_dump_header(question, 0, buf, buflen, &qstyle) < 0) {
+		WARN("can't print whole question section\n");
+	}
+
+	printf("%s\n", buf);
+
+	knot_rrset_free(question, NULL);
+	free(buf);
+}
+
+static void print_section_full(const knot_rrset_t *rrsets,
+                               const uint16_t     count,
+                               const style_t      *style,
+                               const bool         no_tsig)
+{
+	size_t buflen = 8192;
+	char *buf = calloc(buflen, 1);
+
+	for (size_t i = 0; i < count; i++) {
+		// Ignore OPT records.
+		if (rrsets[i].type == KNOT_RRTYPE_OPT) {
+			continue;
+		}
+
+		// Exclude TSIG record.
+		if (no_tsig && rrsets[i].type == KNOT_RRTYPE_TSIG) {
+			continue;
+		}
+
+		if (knot_rrset_txt_dump(&rrsets[i], &buf, &buflen,
+		                        &(style->style)) < 0) {
+				WARN("can't print whole section\n");
+				break;
+		}
+		printf("%s", buf);
+	}
+
+	free(buf);
+}
+
+static void print_section_dig(const knot_rrset_t *rrsets,
+                              const uint16_t     count,
+                              const style_t      *style)
+{
+	size_t buflen = 8192;
+	char *buf = calloc(buflen, 1);
+
+	for (size_t i = 0; i < count; i++) {
+		const knot_rrset_t *rrset = &rrsets[i];
+		uint16_t rrset_rdata_count = rrset->rrs.count;
+		for (uint16_t j = 0; j < rrset_rdata_count; j++) {
+			while (knot_rrset_txt_dump_data(rrset, j, buf, buflen,
+			                                &(style->style)) < 0) {
+				buflen += 4096;
+				// Oversize protection.
+				if (buflen > 100000) {
+					WARN("can't print whole section\n");
+					break;
+				}
+
+				char *newbuf = realloc(buf, buflen);
+				if (newbuf == NULL) {
+					WARN("can't print whole section\n");
+					break;
+				}
+				buf = newbuf;
+			}
+			printf("%s\n", buf);
+		}
+	}
+
+	free(buf);
+}
+
+static void print_section_host(const knot_rrset_t *rrsets,
+                               const uint16_t     count,
+                               const style_t      *style)
+{
+	size_t buflen = 8192;
+	char *buf = calloc(buflen, 1);
+
+	for (size_t i = 0; i < count; i++) {
+		const knot_rrset_t *rrset = &rrsets[i];
+		const knot_lookup_t *descr;
+		char type[32] = "NULL";
+		char *owner;
+
+		owner = knot_dname_to_str_alloc(rrset->owner);
+		if (style->style.ascii_to_idn != NULL) {
+			style->style.ascii_to_idn(&owner);
+		}
+		descr = knot_lookup_by_id(rtypes, rrset->type);
+
+		uint16_t rrset_rdata_count = rrset->rrs.count;
+		for (uint16_t j = 0; j < rrset_rdata_count; j++) {
+			if (rrset->type == KNOT_RRTYPE_CNAME &&
+			    style->hide_cname) {
+				continue;
+			}
+
+			while (knot_rrset_txt_dump_data(rrset, j, buf, buflen,
+			                                &(style->style)) < 0) {
+				buflen += 4096;
+				// Oversize protection.
+				if (buflen > 100000) {
+					WARN("can't print whole section\n");
+					break;
+				}
+
+				char *newbuf = realloc(buf, buflen);
+				if (newbuf == NULL) {
+					WARN("can't print whole section\n");
+					break;
+				}
+				buf = newbuf;
+			}
+
+			if (descr != NULL) {
+				printf("%s %s %s\n", owner, descr->name, buf);
+			} else {
+				knot_rrtype_to_string(rrset->type, type,
+						      sizeof(type));
+				printf("%s has %s record %s\n",
+				       owner, type, buf);
+			}
+		}
+
+		free(owner);
+	}
+
+	free(buf);
+}
+
+static void print_error_host(const knot_pkt_t *packet, const style_t *style)
+{
+	char type[32] = "Unknown";
+	const char *rcode_str = "Unknown";
+
+	knot_rrtype_to_string(knot_pkt_qtype(packet), type, sizeof(type));
+
+	// Get extended RCODE.
+	const char *code_name = knot_pkt_ext_rcode_name(packet);
+	if (code_name[0] != '\0') {
+		rcode_str = code_name;
+	}
+
+	// Get record owner.
+	char *owner = knot_dname_to_str_alloc(knot_pkt_qname(packet));
+	if (style->style.ascii_to_idn != NULL) {
+		style->style.ascii_to_idn(&owner);
+	}
+
+	if (knot_pkt_ext_rcode(packet) == KNOT_RCODE_NOERROR) {
+		printf("Host %s has no %s record\n", owner, type);
+	} else {
+		printf("Host %s type %s error: %s\n", owner, type, rcode_str);
+	}
+
+	free(owner);
+}
+
+knot_pkt_t *create_empty_packet(const uint16_t max_size)
+{
+	// Create packet skeleton.
+	knot_pkt_t *packet = knot_pkt_new(NULL, max_size, NULL);
+	if (packet == NULL) {
+		DBG_NULL;
+		return NULL;
+	}
+
+	// Set random sequence id.
+	knot_wire_set_id(packet->wire, dnssec_random_uint16_t());
+
+	return packet;
+}
+
+void print_header_xfr(const knot_pkt_t *packet, const style_t *style)
+{
+	if (style == NULL) {
+		DBG_NULL;
+		return;
+	}
+
+	char xfr[16] = "AXFR";
+
+	switch (knot_pkt_qtype(packet)) {
+	case KNOT_RRTYPE_AXFR:
+		break;
+	case KNOT_RRTYPE_IXFR:
+		xfr[0] = 'I';
+		break;
+	default:
+		return;
+	}
+
+	if (style->show_header) {
+		char *owner = knot_dname_to_str_alloc(knot_pkt_qname(packet));
+		if (style->style.ascii_to_idn != NULL) {
+			style->style.ascii_to_idn(&owner);
+		}
+		if (owner != NULL) {
+			printf(";; %s for %s\n", xfr, owner);
+			free(owner);
+		}
+	}
+}
+
+void print_data_xfr(const knot_pkt_t *packet,
+                    const style_t    *style)
+{
+	if (packet == NULL || style == NULL) {
+		DBG_NULL;
+		return;
+	}
+
+	const knot_pktsection_t *answers = knot_pkt_section(packet, KNOT_ANSWER);
+
+	switch (style->format) {
+	case FORMAT_DIG:
+		print_section_dig(knot_pkt_rr(answers, 0), answers->count, style);
+		break;
+	case FORMAT_HOST:
+		print_section_host(knot_pkt_rr(answers, 0), answers->count, style);
+		break;
+	case FORMAT_FULL:
+		print_section_full(knot_pkt_rr(answers, 0), answers->count, style, true);
+
+		// Print TSIG record.
+		if (style->show_tsig && knot_pkt_has_tsig(packet)) {
+			print_section_full(packet->tsig_rr, 1, style, false);
+		}
+		break;
+	default:
+		break;
+	}
+}
+
+void print_footer_xfr(const size_t  total_len,
+                      const size_t  msg_count,
+                      const size_t  rr_count,
+                      const net_t   *net,
+                      const float   elapsed,
+                      const time_t  exec_time,
+                      const style_t *style)
+{
+	if (style == NULL) {
+		DBG_NULL;
+		return;
+	}
+
+	if (style->show_footer) {
+		print_footer(total_len, msg_count, rr_count, net, elapsed,
+		             exec_time, true);
+	}
+}
+
+void print_packet(const knot_pkt_t *packet,
+                  const net_t      *net,
+                  const size_t     size,
+                  const float      elapsed,
+                  const time_t     exec_time,
+                  const bool       incoming,
+                  const style_t    *style)
+{
+	if (packet == NULL || style == NULL) {
+		DBG_NULL;
+		return;
+	}
+
+	const knot_pktsection_t *answers = knot_pkt_section(packet,
+	                                                    KNOT_ANSWER);
+	const knot_pktsection_t *authority = knot_pkt_section(packet,
+	                                                      KNOT_AUTHORITY);
+	const knot_pktsection_t *additional = knot_pkt_section(packet,
+	                                                       KNOT_ADDITIONAL);
+
+	uint16_t qdcount = knot_wire_get_qdcount(packet->wire);
+	uint16_t ancount = knot_wire_get_ancount(packet->wire);
+	uint16_t nscount = knot_wire_get_nscount(packet->wire);
+	uint16_t arcount = knot_wire_get_arcount(packet->wire);
+
+	// Disable additionals printing if there are no other records.
+	// OPT record may be placed anywhere within additionals!
+	if (knot_pkt_has_edns(packet) && arcount == 1) {
+		arcount = 0;
+	}
+
+	// Print packet information header.
+	if (style->show_header) {
+		if (net != NULL) {
+			print_tls(&net->tls);
+		}
+		print_header(packet, style);
+	}
+
+	// Print EDNS section.
+	if (style->show_edns && knot_pkt_has_edns(packet)) {
+		printf("%s", style->show_section ? "\n;; EDNS PSEUDOSECTION:\n;; " : ";;");
+		print_section_opt(packet);
+	}
+
+	// Print DNS sections.
+	switch (style->format) {
+	case FORMAT_DIG:
+		if (ancount > 0) {
+			print_section_dig(knot_pkt_rr(answers, 0), ancount, style);
+		}
+		break;
+	case FORMAT_HOST:
+		if (ancount > 0) {
+			print_section_host(knot_pkt_rr(answers, 0), ancount, style);
+		} else {
+			print_error_host(packet, style);
+		}
+		break;
+	case FORMAT_NSUPDATE:
+		if (style->show_question && qdcount > 0) {
+			printf("%s", style->show_section ? "\n;; ZONE SECTION:\n;; " : ";;");
+			print_section_question(knot_pkt_qname(packet),
+			                       knot_pkt_qclass(packet),
+			                       knot_pkt_qtype(packet),
+			                       style);
+		}
+
+		if (style->show_answer && ancount > 0) {
+			printf("%s", style->show_section ? "\n;; PREREQUISITE SECTION:\n" : "");
+			print_section_full(knot_pkt_rr(answers, 0), ancount, style, true);
+		}
+
+		if (style->show_authority && nscount > 0) {
+			printf("%s", style->show_section ? "\n;; UPDATE SECTION:\n" : "");
+			print_section_full(knot_pkt_rr(authority, 0), nscount, style, true);
+		}
+
+		if (style->show_additional && arcount > 0) {
+			printf("%s", style->show_section ? "\n;; ADDITIONAL DATA:\n" : "");
+			print_section_full(knot_pkt_rr(additional, 0), arcount, style, true);
+		}
+		break;
+	case FORMAT_FULL:
+		if (style->show_question && qdcount > 0) {
+			printf("%s", style->show_section ? "\n;; QUESTION SECTION:\n;; " : ";;");
+			print_section_question(knot_pkt_qname(packet),
+			                       knot_pkt_qclass(packet),
+			                       knot_pkt_qtype(packet),
+			                       style);
+		}
+
+		if (style->show_answer && ancount > 0) {
+			printf("%s", style->show_section ? "\n;; ANSWER SECTION:\n" : "");
+			print_section_full(knot_pkt_rr(answers, 0), ancount, style, true);
+		}
+
+		if (style->show_authority && nscount > 0) {
+			printf("%s", style->show_section ? "\n;; AUTHORITY SECTION:\n" : "");
+			print_section_full(knot_pkt_rr(authority, 0), nscount, style, true);
+		}
+
+		if (style->show_additional && arcount > 0) {
+			printf("%s", style->show_section ? "\n;; ADDITIONAL SECTION:\n" : "");
+			print_section_full(knot_pkt_rr(additional, 0), arcount, style, true);
+		}
+		break;
+	default:
+		break;
+	}
+
+	// Print TSIG section.
+	if (style->show_tsig && knot_pkt_has_tsig(packet)) {
+		printf("%s", style->show_section ? "\n;; TSIG PSEUDOSECTION:\n" : "");
+		print_section_full(packet->tsig_rr, 1, style, false);
+	}
+
+	// Print packet statistics.
+	if (style->show_footer) {
+		printf("\n");
+		print_footer(size, 0, 0, net, elapsed, exec_time, incoming);
+	}
+}
diff --git a/src/utils/common/exec.h b/src/utils/common/exec.h
new file mode 100644
index 0000000..0c5ad5d
--- /dev/null
+++ b/src/utils/common/exec.h
@@ -0,0 +1,97 @@
+/*  Copyright (C) 2016 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \file
+ *
+ * \brief Common executives for utils.
+ *
+ * \addtogroup knot_utils
+ * @{
+ */
+
+#pragma once
+
+#include <time.h>
+
+#include "utils/common/netio.h"
+#include "utils/common/params.h"
+#include "libknot/libknot.h"
+
+/*!
+ * \brief Allocates empty packet and sets packet size and random id.
+ *
+ * \param max_size	Maximal packet size.
+ *
+ * \retval packet	if success.
+ * \retval NULL		if error.
+ */
+knot_pkt_t *create_empty_packet(const uint16_t max_size);
+
+/*!
+ * \brief Prints information header for transfer.
+ *
+ * \param packet	Parsed packet.
+ * \param style		Style of the output.
+ */
+void print_header_xfr(const knot_pkt_t *packet, const style_t *style);
+
+/*!
+ * \brief Prints answer section for 1 transfer message.
+ *
+ * \param packet	Response packet.
+ * \param style		Style of the output.
+ */
+void print_data_xfr(const knot_pkt_t *packet, const style_t *style);
+
+/*!
+ * \brief Prints trailing statistics for transfer.
+ *
+ * \param total_len	Total reply size (all messages).
+ * \param msg_count	Number of messages.
+ * \param rr_count	Total number of answer records.
+ * \param net		Connection information.
+ * \param elapsed	Total elapsed time.
+ * \param exec_time	Time of the packet creation.
+ * \param style		Style of the otput.
+ */
+void print_footer_xfr(const size_t  total_len,
+                      const size_t  msg_count,
+                      const size_t  rr_count,
+                      const net_t   *net,
+                      const float   elapsed,
+                      const time_t  exec_time,
+                      const style_t *style);
+
+/*!
+ * \brief Prints one response packet.
+ *
+ * \param packet	Response packet.
+ * \param net		Connection information.
+ * \param size		Original packet wire size.
+ * \param elapsed	Total elapsed time.
+ * \param exec_time	Time of the packet creation.
+ * \param incoming	Indicates if the packet is input.
+ * \param style		Style of the otput.
+ */
+void print_packet(const knot_pkt_t *packet,
+                  const net_t      *net,
+                  const size_t     size,
+                  const float      elapsed,
+                  const time_t     exec_time,
+                  const bool       incoming,
+                  const style_t    *style);
+
+/*! @} */
diff --git a/src/utils/common/hex.c b/src/utils/common/hex.c
new file mode 100644
index 0000000..2ffa9f2
--- /dev/null
+++ b/src/utils/common/hex.c
@@ -0,0 +1,82 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include "libknot/libknot.h"
+#include "contrib/ctype.h"
+#include "contrib/tolower.h"
+
+/*!
+ * \brief Convert HEX char to byte.
+ * \note Expects valid lowercase letters.
+ */
+static uint8_t hex_to_num(int c)
+{
+	if (c >= '0' && c <= '9') {
+		return c - '0';
+	} else {
+		return c - 'a' + 10;
+	}
+}
+
+/*!
+ * \brief Convert string encoded in hex to bytes.
+ */
+int hex_decode(const char *input, uint8_t **output, size_t *output_size)
+{
+	if (!input || input[0] == '\0' || !output || !output_size) {
+		return KNOT_EINVAL;
+	}
+
+	// input validation (length and content)
+
+	size_t input_size = strlen(input);
+	if (input_size % 2 != 0) {
+		return KNOT_EMALF;
+	}
+
+	for (size_t i = 0; i < input_size; i++) {
+		if (!is_xdigit(input[i])) {
+			return KNOT_EMALF;
+		}
+	}
+
+	// output allocation
+
+	size_t result_size = input_size / 2;
+	assert(result_size > 0);
+	uint8_t *result = malloc(result_size);
+	if (!result) {
+		return KNOT_ENOMEM;
+	}
+
+	// conversion
+
+	for (size_t i = 0; i < result_size; i++) {
+		int high_nib = knot_tolower(input[2 * i]);
+		int low_nib  = knot_tolower(input[2 * i + 1]);
+
+		result[i] = hex_to_num(high_nib) << 4 | hex_to_num(low_nib);
+	}
+
+	*output = result;
+	*output_size = result_size;
+
+	return KNOT_EOK;
+}
diff --git a/src/utils/common/hex.h b/src/utils/common/hex.h
new file mode 100644
index 0000000..8f9f445
--- /dev/null
+++ b/src/utils/common/hex.h
@@ -0,0 +1,42 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+/*!
+ * \file
+ *
+ * \brief Coversion between HEX strings and bytes.
+ *
+ * \addtogroup knot_utils
+ * @{
+ */
+
+#pragma once
+
+#include <stdint.h>
+#include <stdlib.h>
+
+/*!
+ * \brief Convert string encoded in hex to bytes.
+ *
+ * \param input        Hex encoded input string.
+ * \param output       Decoded bytes.
+ * \param output_size  Size of the output.
+ *
+ * \return Error code, KNOT_EOK if successful.
+ */
+int hex_decode(const char *input, uint8_t **output, size_t *output_size);
+
+/*! @} */
diff --git a/src/utils/common/lookup.c b/src/utils/common/lookup.c
new file mode 100644
index 0000000..168d649
--- /dev/null
+++ b/src/utils/common/lookup.c
@@ -0,0 +1,279 @@
+/*  Copyright (C) 2016 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <string.h>
+
+#include "utils/common/lookup.h"
+#include "contrib/mempattern.h"
+#include "contrib/ucw/mempool.h"
+#include "libknot/error.h"
+
+int lookup_init(lookup_t *lookup)
+{
+	if (lookup == NULL) {
+		return KNOT_EINVAL;
+	}
+	memset(lookup, 0, sizeof(*lookup));
+
+	mm_ctx_mempool(&lookup->mm, MM_DEFAULT_BLKSIZE);
+	lookup->trie = trie_create(&lookup->mm);
+	if (lookup->trie == NULL) {
+		mp_delete(lookup->mm.ctx);
+		return KNOT_ENOMEM;
+	}
+
+	return KNOT_EOK;
+}
+
+static void reset_output(lookup_t *lookup)
+{
+	if (lookup == NULL) {
+		return;
+	}
+
+	mm_free(&lookup->mm, lookup->found.key);
+	lookup->found.key = NULL;
+	lookup->found.data = NULL;
+
+	lookup->iter.count = 0;
+
+	mm_free(&lookup->mm, lookup->iter.first_key);
+	lookup->iter.first_key = NULL;
+
+	trie_it_free(lookup->iter.it);
+	lookup->iter.it = NULL;
+}
+
+void lookup_deinit(lookup_t *lookup)
+{
+	if (lookup == NULL) {
+		return;
+	}
+
+	reset_output(lookup);
+
+	trie_free(lookup->trie);
+	mp_delete(lookup->mm.ctx);
+}
+
+int lookup_insert(lookup_t *lookup, const char *str, void *data)
+{
+	if (lookup == NULL || str == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	size_t str_len = strlen(str);
+	if (str_len == 0) {
+		return KNOT_EINVAL;
+	}
+
+	trie_val_t *val = trie_get_ins(lookup->trie, str, str_len);
+	if (val == NULL) {
+		return KNOT_ENOMEM;
+	}
+	*val = data;
+
+	return KNOT_EOK;
+}
+
+static int set_key(lookup_t *lookup, char **dst, const char *key, size_t key_len)
+{
+	if (*dst != NULL) {
+		mm_free(&lookup->mm, *dst);
+	}
+	*dst = mm_alloc(&lookup->mm, key_len + 1);
+	if (*dst == NULL) {
+		return KNOT_ENOMEM;
+	}
+	memcpy(*dst, key, key_len);
+	(*dst)[key_len] = '\0';
+
+	return KNOT_EOK;
+}
+
+int lookup_search(lookup_t *lookup, const char *str, size_t str_len)
+{
+	if (lookup == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	// Change NULL string to the empty one.
+	if (str == NULL) {
+		str = "";
+	}
+
+	reset_output(lookup);
+
+	size_t new_len = 0;
+	trie_it_t *it = trie_it_begin(lookup->trie);
+	for (; !trie_it_finished(it); trie_it_next(it)) {
+		size_t len;
+		const char *key = trie_it_key(it, &len);
+
+		// Compare with a shorter key.
+		if (len < str_len) {
+			int ret = memcmp(str, key, len);
+			if (ret >= 0) {
+				continue;
+			} else {
+				break;
+			}
+		}
+
+		// Compare with an equal length or longer key.
+		int ret = memcmp(str, key, str_len);
+		if (ret == 0) {
+			lookup->iter.count++;
+
+			// First candidate.
+			if (lookup->iter.count == 1) {
+				ret = set_key(lookup, &lookup->found.key, key, len);
+				if (ret != KNOT_EOK) {
+					break;
+				}
+				lookup->found.data = *trie_it_val(it);
+				new_len = len;
+			// Another candidate.
+			} else if (new_len > str_len) {
+				if (new_len > len) {
+					new_len = len;
+				}
+				while (memcmp(lookup->found.key, key, new_len) != 0) {
+					new_len--;
+				}
+			}
+		// Stop if greater than the key, and also than all the following keys.
+		} else if (ret < 0) {
+			break;
+		}
+	}
+	trie_it_free(it);
+
+	switch (lookup->iter.count) {
+	case 0:
+		return KNOT_ENOENT;
+	case 1:
+		return KNOT_EOK;
+	default:
+		// Store full name of the first candidate.
+		if (set_key(lookup, &lookup->iter.first_key, lookup->found.key,
+		            strlen(lookup->found.key)) != KNOT_EOK) {
+			return KNOT_ENOMEM;
+		}
+		lookup->found.key[new_len] = '\0';
+		lookup->found.data = NULL;
+
+		return KNOT_EFEWDATA;
+	}
+}
+
+void lookup_list(lookup_t *lookup)
+{
+	if (lookup == NULL || lookup->iter.first_key == NULL) {
+		return;
+	}
+
+	if (lookup->iter.it != NULL) {
+		if (trie_it_finished(lookup->iter.it)) {
+			trie_it_free(lookup->iter.it);
+			lookup->iter.it = NULL;
+			return;
+		}
+
+		trie_it_next(lookup->iter.it);
+
+		size_t len;
+		const char *key = trie_it_key(lookup->iter.it, &len);
+
+		int ret = set_key(lookup, &lookup->found.key, key, len);
+		if (ret == KNOT_EOK) {
+			lookup->found.data = *trie_it_val(lookup->iter.it);
+		}
+		return;
+	}
+
+	lookup->iter.it = trie_it_begin(lookup->trie);
+	while (!trie_it_finished(lookup->iter.it)) {
+		size_t len;
+		const char *key = trie_it_key(lookup->iter.it, &len);
+
+		if (strncmp(key, lookup->iter.first_key, len) == 0) {
+			int ret = set_key(lookup, &lookup->found.key, key, len);
+			if (ret == KNOT_EOK) {
+				lookup->found.data = *trie_it_val(lookup->iter.it);
+			}
+			break;
+		}
+		trie_it_next(lookup->iter.it);
+	}
+}
+
+static void print_options(lookup_t *lookup, EditLine *el)
+{
+	// Get terminal lines.
+	unsigned lines = 0;
+	if (el_get(el, EL_GETTC, "li", &lines) != 0 || lines < 3) {
+		return;
+	}
+
+	for (size_t i = 1; i <= lookup->iter.count; i++) {
+		lookup_list(lookup);
+		printf("\n%s", lookup->found.key);
+
+		if (i > 1 && i % (lines - 1) == 0 && i < lookup->iter.count) {
+			printf("\n Display next from %zu possibilities? (y or n)",
+			       lookup->iter.count);
+			char next;
+			el_getc(el, &next);
+			if (next != 'y') {
+				break;
+			}
+		}
+	}
+
+	printf("\n");
+	fflush(stdout);
+}
+
+void lookup_complete(lookup_t *lookup, const char *str, size_t str_len,
+                     EditLine *el, bool add_space)
+{
+	if (lookup == NULL || el == NULL) {
+		return;
+	}
+
+	// Try to complete the command name.
+	int ret = lookup_search(lookup, str, str_len);
+	switch (ret) {
+	case KNOT_EOK:
+		el_deletestr(el, str_len);
+		el_insertstr(el, lookup->found.key);
+		if (add_space) {
+			el_insertstr(el, " ");
+		}
+		break;
+	case KNOT_EFEWDATA:
+		if (strlen(lookup->found.key) > str_len) {
+			el_deletestr(el, str_len);
+			el_insertstr(el, lookup->found.key);
+		} else {
+			print_options(lookup, el);
+		}
+		break;
+	default:
+		break;
+	}
+}
diff --git a/src/utils/common/lookup.h b/src/utils/common/lookup.h
new file mode 100644
index 0000000..a8eb065
--- /dev/null
+++ b/src/utils/common/lookup.h
@@ -0,0 +1,122 @@
+/*  Copyright (C) 2016 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \file
+ *
+ * \brief Lookup container for textual strings.
+ *
+ * \addtogroup knot_utils
+ * @{
+ */
+
+#pragma once
+
+#include <histedit.h>
+
+#include "libknot/mm_ctx.h"
+#include "contrib/qp-trie/trie.h"
+
+/*! Lookup context. */
+typedef struct {
+	/*! Memory pool context. */
+	knot_mm_t mm;
+	/*! Main trie storage. */
+	trie_t *trie;
+
+	/*! Current (iteration) data context. */
+	struct {
+		/*! Stored key. */
+		char *key;
+		/*! Corresponding key data. */
+		void *data;
+	} found;
+
+	/*! Iteration context. */
+	struct {
+		/*! Total number of possibilies. */
+		size_t count;
+		/*! The first possibility. */
+		char *first_key;
+		/*! Hat-trie iterator. */
+		trie_it_t *it;
+	} iter;
+} lookup_t;
+
+/*!
+ * Initializes the lookup context.
+ *
+ * \param[in] lookup  Lookup context.
+ *
+ * \return Error code, KNOT_EOK if successful.
+ */
+int lookup_init(lookup_t *lookup);
+
+/*!
+ * Deinitializes the lookup context.
+ *
+ * \param[in] lookup  Lookup context.
+ */
+void lookup_deinit(lookup_t *lookup);
+
+/*!
+ * Inserts given key and data into the lookup.
+ *
+ * \param[in] lookup  Lookup context.
+ * \param[in] str     Textual key.
+ * \param[in] data    Key textual data.
+ *
+ * \return Error code, KNOT_EOK if successful.
+ */
+int lookup_insert(lookup_t *lookup, const char *str, void *data);
+
+/*!
+ * Searches the lookup container for the given key.
+ *
+ * \note If one candidate, lookup.found contains the key/data,
+ *       if more candidates, lookup.found contains the common key prefix and
+ *       lookup.iter.first_key is the first candidate key.
+ *
+ * \param[in] lookup   Lookup context.
+ * \param[in] str      Textual key.
+ * \param[in] str_len  Textual key length.
+ *
+ * \return Error code, KNOT_EOK if 1 candidate, KNOT_ENOENT if no candidate,
+ *         and KNOT_EFEWDATA if more candidates are possible.
+ */
+int lookup_search(lookup_t *lookup, const char *str, size_t str_len);
+
+/*!
+ * Moves the lookup iterator to the next key candidate.
+ *
+ * \note lookup.found is updated.
+ *
+ * \param[in] lookup   Lookup context.
+ */
+void lookup_list(lookup_t *lookup);
+
+/*!
+ * Completes the string based on the lookup content or prints all candidates.
+ *
+ * \param[in] lookup     Lookup context.
+ * \param[in] str        Textual key.
+ * \param[in] str_len    Textual key length.
+ * \param[in] el         Editline context.
+ * \param[in] add_space  Add one space after completed string flag.
+ */
+void lookup_complete(lookup_t *lookup, const char *str, size_t str_len,
+                     EditLine *el, bool add_space);
+
+/*! @} */
diff --git a/src/utils/common/msg.c b/src/utils/common/msg.c
new file mode 100644
index 0000000..c3375d3
--- /dev/null
+++ b/src/utils/common/msg.c
@@ -0,0 +1,40 @@
+/*  Copyright (C) 2011 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "utils/common/msg.h"
+
+static volatile int MSG_DBG_STATE = 0; /* True if debugging is enabled. */
+
+int msg_enable_debug(int val)
+{
+	return MSG_DBG_STATE = val;
+}
+
+int msg_debug(const char *fmt, ...)
+{
+	int n = 0;
+	if (MSG_DBG_STATE) {
+		va_list ap;
+		va_start(ap, fmt);
+		n = vprintf(fmt, ap);
+		va_end(ap);
+	}
+	return n;
+}
diff --git a/src/utils/common/msg.h b/src/utils/common/msg.h
new file mode 100644
index 0000000..a300afe
--- /dev/null
+++ b/src/utils/common/msg.h
@@ -0,0 +1,50 @@
+/*  Copyright (C) 2011 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \file msg.h
+ *
+ * \author Daniel Salzman <daniel.salzman@nic.cz>
+ *
+ * \brief Simple output formatting framework.
+ *
+ * \addtogroup knot_utils
+ * @{
+ */
+
+#pragma once
+
+#include <stdio.h>
+
+#define ERROR_		";; ERROR: "
+#define INFO_		";; INFO: "
+#define WARNING_	";; WARNING: "
+#define DEBUG_		";; DEBUG: "
+
+#define ERR(msg, ...)	{ fprintf(stderr, ERROR_ msg, ##__VA_ARGS__); fflush(stderr); }
+#define INFO(msg, ...)	{ fprintf(stdout, INFO_ msg, ##__VA_ARGS__); fflush(stdout); }
+#define WARN(msg, ...)	{ fprintf(stderr, WARNING_ msg, ##__VA_ARGS__); fflush(stderr); }
+#define DBG(msg, ...)	msg_debug(DEBUG_ msg, ##__VA_ARGS__)
+
+/*! \brief Enable/disable debugging. */
+int msg_enable_debug(int val);
+
+/*! \brief Print debug message. */
+int msg_debug(const char *fmt, ...);
+
+/*! \brief Debug message for null input. */
+#define DBG_NULL	DBG("%s: null parameter\n", __func__)
+
+/*! @} */
diff --git a/src/utils/common/netio.c b/src/utils/common/netio.c
new file mode 100644
index 0000000..9a27d33
--- /dev/null
+++ b/src/utils/common/netio.c
@@ -0,0 +1,593 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <arpa/inet.h>
+#include <fcntl.h>
+#include <netdb.h>
+#include <poll.h>
+#include <stdlib.h>
+#include <netinet/in.h>
+#include <sys/socket.h>
+
+#ifdef HAVE_SYS_UIO_H
+#include <sys/uio.h>
+#endif
+
+#include "utils/common/netio.h"
+#include "utils/common/msg.h"
+#include "utils/common/tls.h"
+#include "libknot/libknot.h"
+#include "contrib/sockaddr.h"
+
+srv_info_t *srv_info_create(const char *name, const char *service)
+{
+	if (name == NULL || service == NULL) {
+		DBG_NULL;
+		return NULL;
+	}
+
+	// Create output structure.
+	srv_info_t *server = calloc(1, sizeof(srv_info_t));
+
+	// Check output.
+	if (server == NULL) {
+		return NULL;
+	}
+
+	// Fill output.
+	server->name = strdup(name);
+	server->service = strdup(service);
+
+	if (server->name == NULL || server->service == NULL) {
+		srv_info_free(server);
+		return NULL;
+	}
+
+	// Return result.
+	return server;
+}
+
+void srv_info_free(srv_info_t *server)
+{
+	if (server == NULL) {
+		DBG_NULL;
+		return;
+	}
+
+	free(server->name);
+	free(server->service);
+	free(server);
+}
+
+int get_iptype(const ip_t ip)
+{
+	switch (ip) {
+	case IP_4:
+		return AF_INET;
+	case IP_6:
+		return AF_INET6;
+	default:
+		return AF_UNSPEC;
+	}
+}
+
+int get_socktype(const protocol_t proto, const uint16_t type)
+{
+	switch (proto) {
+	case PROTO_TCP:
+		return SOCK_STREAM;
+	case PROTO_UDP:
+		return SOCK_DGRAM;
+	default:
+		if (type == KNOT_RRTYPE_AXFR || type == KNOT_RRTYPE_IXFR) {
+			return SOCK_STREAM;
+		} else {
+			return SOCK_DGRAM;
+		}
+	}
+}
+
+const char *get_sockname(const int socktype)
+{
+	switch (socktype) {
+	case SOCK_STREAM:
+		return "TCP";
+	case SOCK_DGRAM:
+		return "UDP";
+	default:
+		return "UNKNOWN";
+	}
+}
+
+static int get_addr(const srv_info_t *server,
+                    const int        iptype,
+                    const int        socktype,
+                    struct addrinfo  **info)
+{
+	struct addrinfo hints;
+
+	// Set connection hints.
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = iptype;
+	hints.ai_socktype = socktype;
+
+	// Get connection parameters.
+	if (getaddrinfo(server->name, server->service, &hints, info) != 0) {
+		ERR("can't resolve address %s@%s\n",
+		    server->name, server->service);
+		return -1;
+	}
+
+	return 0;
+}
+
+void get_addr_str(const struct sockaddr_storage *ss,
+                  const int                     socktype,
+                  char                          **dst)
+{
+	char addr_str[SOCKADDR_STRLEN] = {0};
+
+	// Get network address string and port number.
+	sockaddr_tostr(addr_str, sizeof(addr_str), (struct sockaddr *)ss);
+
+	// Calculate needed buffer size
+	const char *sock_name = get_sockname(socktype);
+	size_t buflen = strlen(addr_str) + strlen(sock_name) + 3 /* () */;
+
+	// Free previous string if any and write result
+	free(*dst);
+	*dst = malloc(buflen);
+	if (*dst != NULL) {
+		int ret = snprintf(*dst, buflen, "%s(%s)", addr_str, sock_name);
+		if (ret <= 0 || ret >= buflen) {
+			**dst = '\0';
+		}
+	}
+}
+
+int net_init(const srv_info_t    *local,
+             const srv_info_t    *remote,
+             const int           iptype,
+             const int           socktype,
+             const int           wait,
+             const net_flags_t   flags,
+             const tls_params_t  *tls_params,
+             net_t               *net)
+{
+	if (remote == NULL || net == NULL) {
+		DBG_NULL;
+		return KNOT_EINVAL;
+	}
+
+	// Clean network structure.
+	memset(net, 0, sizeof(*net));
+
+	// Get remote address list.
+	if (get_addr(remote, iptype, socktype, &net->remote_info) != 0) {
+		net_clean(net);
+		return KNOT_NET_EADDR;
+	}
+
+	// Set current remote address.
+	net->srv = net->remote_info;
+
+	// Get local address if specified.
+	if (local != NULL) {
+		if (get_addr(local, iptype, socktype, &net->local_info) != 0) {
+			net_clean(net);
+			return KNOT_NET_EADDR;
+		}
+	}
+
+	// Store network parameters.
+	net->iptype = iptype;
+	net->socktype = socktype;
+	net->wait = wait;
+	net->local = local;
+	net->remote = remote;
+	net->flags = flags;
+
+	// Prepare for TLS.
+	if (tls_params != NULL && tls_params->enable) {
+		int ret = tls_ctx_init(&net->tls, tls_params, net->wait);
+		if (ret != KNOT_EOK) {
+			net_clean(net);
+			return ret;
+		}
+	}
+
+	return KNOT_EOK;
+}
+
+/**
+ * Connect with TCP Fast Open.
+ */
+static int fastopen_connect(int sockfd, const struct addrinfo *srv)
+{
+#if __APPLE__
+	// connection is performed lazily when first data are sent
+	struct sa_endpoints ep = {0};
+	ep.sae_dstaddr = srv->ai_addr;
+	ep.sae_dstaddrlen = srv->ai_addrlen;
+	int flags =  CONNECT_DATA_IDEMPOTENT|CONNECT_RESUME_ON_READ_WRITE;
+
+	return connectx(sockfd, &ep, SAE_ASSOCID_ANY, flags, NULL, 0, NULL, NULL);
+#elif defined(MSG_FASTOPEN) // Linux with RFC 7413
+	// connect() will be called implicitly with sendto(), sendmsg()
+	return 0;
+#else
+	errno = ENOTSUP;
+	return -1;
+#endif
+}
+
+/**
+ * Sends data with TCP Fast Open.
+ */
+static int fastopen_send(int sockfd, const struct msghdr *msg, int timeout)
+{
+#if __APPLE__
+	return sendmsg(sockfd, msg, 0);
+#elif defined(MSG_FASTOPEN)
+	int ret = sendmsg(sockfd, msg, MSG_FASTOPEN);
+	if (ret == -1 && errno == EINPROGRESS) {
+		struct pollfd pfd = {
+			.fd = sockfd,
+			.events = POLLOUT,
+			.revents = 0,
+		};
+		if (poll(&pfd, 1, 1000 * timeout) != 1) {
+			errno = ETIMEDOUT;
+			return -1;
+		}
+		ret = sendmsg(sockfd, msg, 0);
+	}
+	return ret;
+#else
+	errno = ENOTSUP;
+	return -1;
+#endif
+}
+
+int net_connect(net_t *net)
+{
+	if (net == NULL || net->srv == NULL) {
+		DBG_NULL;
+		return KNOT_EINVAL;
+	}
+
+	// Set remote information string.
+	get_addr_str((struct sockaddr_storage *)net->srv->ai_addr,
+	             net->socktype, &net->remote_str);
+
+	// Create socket.
+	int sockfd = socket(net->srv->ai_family, net->socktype, 0);
+	if (sockfd == -1) {
+		WARN("can't create socket for %s\n", net->remote_str);
+		return KNOT_NET_ESOCKET;
+	}
+
+	// Initialize poll descriptor structure.
+	struct pollfd pfd = {
+		.fd = sockfd,
+		.events = POLLOUT,
+		.revents = 0,
+	};
+
+	// Set non-blocking socket.
+	if (fcntl(sockfd, F_SETFL, O_NONBLOCK) == -1) {
+		WARN("can't set non-blocking socket for %s\n", net->remote_str);
+		return KNOT_NET_ESOCKET;
+	}
+
+	// Bind address to socket if specified.
+	if (net->local_info != NULL) {
+		if (bind(sockfd, net->local_info->ai_addr,
+		         net->local_info->ai_addrlen) == -1) {
+			WARN("can't assign address %s\n", net->local->name);
+			return KNOT_NET_ESOCKET;
+		}
+	}
+
+	if (net->socktype == SOCK_STREAM) {
+		int  cs, err, ret = 0;
+		socklen_t err_len = sizeof(err);
+		bool     fastopen = net->flags & NET_FLAGS_FASTOPEN;
+
+		// Connect using socket.
+		if (fastopen) {
+			ret = fastopen_connect(sockfd, net->srv);
+		} else {
+			ret = connect(sockfd, net->srv->ai_addr, net->srv->ai_addrlen);
+		}
+		if (ret != 0 && errno != EINPROGRESS) {
+			WARN("can't connect to %s\n", net->remote_str);
+			close(sockfd);
+			return KNOT_NET_ECONNECT;
+		}
+
+		// Check for connection timeout.
+		if (!fastopen && poll(&pfd, 1, 1000 * net->wait) != 1) {
+			WARN("connection timeout for %s\n", net->remote_str);
+			close(sockfd);
+			return KNOT_NET_ECONNECT;
+		}
+
+		// Check if NB socket is writeable.
+		cs = getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &err, &err_len);
+		if (cs < 0 || err != 0) {
+			WARN("can't connect to %s\n", net->remote_str);
+			close(sockfd);
+			return KNOT_NET_ECONNECT;
+		}
+
+		// Establish TLS connection.
+		if (net->tls.params != NULL) {
+			int ret = tls_ctx_connect(&net->tls, sockfd, net->tls.params->sni);
+			if (ret != KNOT_EOK) {
+				close(sockfd);
+				return ret;
+			}
+		}
+	}
+
+	// Store socket descriptor.
+	net->sockfd = sockfd;
+
+	return KNOT_EOK;
+}
+
+int net_set_local_info(net_t *net)
+{
+	if (net == NULL) {
+		DBG_NULL;
+		return KNOT_EINVAL;
+	}
+
+	if (net->local_info != NULL) {
+		free(net->local_info->ai_addr);
+		freeaddrinfo(net->local_info);
+	}
+
+	socklen_t local_addr_len = sizeof(struct sockaddr_storage);
+	struct sockaddr_storage *local_addr = calloc(1, local_addr_len);
+
+	if (getsockname(net->sockfd, (struct sockaddr *)local_addr,
+	                &local_addr_len) == -1) {
+		WARN("can't get local address\n");
+		free(local_addr);
+		return KNOT_NET_ESOCKET;
+	}
+
+	net->local_info = calloc(1, sizeof(struct addrinfo));
+	net->local_info->ai_family = net->srv->ai_family;
+	net->local_info->ai_socktype = net->srv->ai_socktype;
+	net->local_info->ai_protocol = net->srv->ai_protocol;
+	net->local_info->ai_addrlen = local_addr_len;
+	net->local_info->ai_addr = (struct sockaddr *)local_addr;
+
+	get_addr_str((struct sockaddr_storage *)net->local_info->ai_addr,
+	             net->socktype, &net->local_str);
+
+	return KNOT_EOK;
+}
+
+int net_send(const net_t *net, const uint8_t *buf, const size_t buf_len)
+{
+	if (net == NULL || buf == NULL) {
+		DBG_NULL;
+		return KNOT_EINVAL;
+	}
+
+	// Send data over UDP.
+	if (net->socktype == SOCK_DGRAM) {
+		if (sendto(net->sockfd, buf, buf_len, 0, net->srv->ai_addr,
+		           net->srv->ai_addrlen) != (ssize_t)buf_len) {
+			WARN("can't send query to %s\n", net->remote_str);
+			return KNOT_NET_ESEND;
+		}
+	// Send data over TLS.
+	} else if (net->tls.params != NULL) {
+		int ret = tls_ctx_send((tls_ctx_t *)&net->tls, buf, buf_len);
+		if (ret != KNOT_EOK) {
+			WARN("can't send query to %s\n", net->remote_str);
+			return KNOT_NET_ESEND;
+		}
+	// Send data over TCP.
+	} else {
+		bool fastopen = net->flags & NET_FLAGS_FASTOPEN;
+
+		// Leading packet length bytes.
+		uint16_t pktsize = htons(buf_len);
+
+		struct iovec iov[2];
+		iov[0].iov_base = &pktsize;
+		iov[0].iov_len = sizeof(pktsize);
+		iov[1].iov_base = (uint8_t *)buf;
+		iov[1].iov_len = buf_len;
+
+		// Compute packet total length.
+		ssize_t total = iov[0].iov_len + iov[1].iov_len;
+
+		struct msghdr msg = {0};
+		msg.msg_iov = iov;
+		msg.msg_iovlen = sizeof(iov) / sizeof(*iov);
+		msg.msg_name = net->srv->ai_addr;
+		msg.msg_namelen = net->srv->ai_addrlen;
+
+		int ret = 0;
+		if (fastopen) {
+			ret = fastopen_send(net->sockfd, &msg, net->wait);
+		} else {
+			ret = sendmsg(net->sockfd, &msg, 0);
+		}
+		if (ret != total) {
+			WARN("can't send query to %s\n", net->remote_str);
+			return KNOT_NET_ESEND;
+		}
+	}
+
+	return KNOT_EOK;
+}
+
+int net_receive(const net_t *net, uint8_t *buf, const size_t buf_len)
+{
+	if (net == NULL || buf == NULL) {
+		DBG_NULL;
+		return KNOT_EINVAL;
+	}
+
+	// Initialize poll descriptor structure.
+	struct pollfd pfd = {
+		.fd = net->sockfd,
+		.events = POLLIN,
+		.revents = 0,
+	};
+
+	// Receive data over UDP.
+	if (net->socktype == SOCK_DGRAM) {
+		struct sockaddr_storage from;
+		memset(&from, '\0', sizeof(from));
+
+		// Receive replies unless correct reply or timeout.
+		while (true) {
+			socklen_t from_len = sizeof(from);
+
+			// Wait for datagram data.
+			if (poll(&pfd, 1, 1000 * net->wait) != 1) {
+				WARN("response timeout for %s\n",
+				     net->remote_str);
+				return KNOT_NET_ETIMEOUT;
+			}
+
+			// Receive whole UDP datagram.
+			ssize_t ret = recvfrom(net->sockfd, buf, buf_len, 0,
+			                       (struct sockaddr *)&from, &from_len);
+			if (ret <= 0) {
+				WARN("can't receive reply from %s\n",
+				     net->remote_str);
+				return KNOT_NET_ERECV;
+			}
+
+			// Compare reply address with the remote one.
+			if (from_len > sizeof(from) ||
+			    memcmp(&from, net->srv->ai_addr, from_len) != 0) {
+				char *src = NULL;
+				get_addr_str(&from, net->socktype, &src);
+				WARN("unexpected reply source %s\n", src);
+				free(src);
+				continue;
+			}
+
+			return ret;
+		}
+	// Receive data over TLS.
+	} else if (net->tls.params != NULL) {
+		int ret = tls_ctx_receive((tls_ctx_t *)&net->tls, buf, buf_len);
+		if (ret < 0) {
+			WARN("can't receive reply from %s\n", net->remote_str);
+			return KNOT_NET_ERECV;
+		}
+
+		return ret;
+	// Receive data over TCP.
+	} else {
+		uint32_t total = 0;
+
+		uint16_t msg_len = 0;
+		// Receive TCP message header.
+		while (total < sizeof(msg_len)) {
+			if (poll(&pfd, 1, 1000 * net->wait) != 1) {
+				WARN("response timeout for %s\n",
+				     net->remote_str);
+				return KNOT_NET_ETIMEOUT;
+			}
+
+			// Receive piece of message.
+			ssize_t ret = recv(net->sockfd, (uint8_t *)&msg_len + total,
+				           sizeof(msg_len) - total, 0);
+			if (ret <= 0) {
+				WARN("can't receive reply from %s\n",
+				     net->remote_str);
+				return KNOT_NET_ERECV;
+			}
+			total += ret;
+		}
+
+		// Convert number to host format.
+		msg_len = ntohs(msg_len);
+		if (msg_len > buf_len) {
+			return KNOT_ESPACE;
+		}
+
+		total = 0;
+
+		// Receive whole answer message by parts.
+		while (total < msg_len) {
+			if (poll(&pfd, 1, 1000 * net->wait) != 1) {
+				WARN("response timeout for %s\n",
+				     net->remote_str);
+				return KNOT_NET_ETIMEOUT;
+			}
+
+			// Receive piece of message.
+			ssize_t ret = recv(net->sockfd, buf + total, msg_len - total, 0);
+			if (ret <= 0) {
+				WARN("can't receive reply from %s\n",
+				     net->remote_str);
+				return KNOT_NET_ERECV;
+			}
+			total += ret;
+		}
+
+		return total;
+	}
+
+	return KNOT_NET_ERECV;
+}
+
+void net_close(net_t *net)
+{
+	if (net == NULL) {
+		DBG_NULL;
+		return;
+	}
+
+	tls_ctx_close(&net->tls);
+	close(net->sockfd);
+	net->sockfd = -1;
+}
+
+void net_clean(net_t *net)
+{
+	if (net == NULL) {
+		DBG_NULL;
+		return;
+	}
+
+	free(net->local_str);
+	free(net->remote_str);
+
+	if (net->local_info != NULL) {
+		freeaddrinfo(net->local_info);
+	}
+
+	if (net->remote_info != NULL) {
+		freeaddrinfo(net->remote_info);
+	}
+
+	tls_ctx_deinit(&net->tls);
+}
diff --git a/src/utils/common/netio.h b/src/utils/common/netio.h
new file mode 100644
index 0000000..d861149
--- /dev/null
+++ b/src/utils/common/netio.h
@@ -0,0 +1,229 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \file
+ *
+ * \brief Networking abstraction for utilities.
+ *
+ * \addtogroup knot_utils
+ * @{
+ */
+
+#pragma once
+
+#include <netdb.h>
+#include <stdint.h>
+#include <sys/socket.h>
+
+#include "utils/common/params.h"
+#include "utils/common/tls.h"
+
+/*! \brief Structure containing server information. */
+typedef struct {
+	/*! List node (for list container). */
+	node_t	n;
+	/*! Name or address of the server. */
+	char	*name;
+	/*! Name or number of the service. */
+	char	*service;
+} srv_info_t;
+
+typedef enum {
+	NET_FLAGS_NONE = 0,
+	NET_FLAGS_FASTOPEN = 1 << 0,
+} net_flags_t;
+
+typedef struct {
+	/*! Socket descriptor. */
+	int sockfd;
+
+	/*! IP protocol type. */
+	int iptype;
+	/*! Socket type. */
+	int socktype;
+	/*! Timeout for all network operations. */
+	int wait;
+	/*! Connection flags. */
+	net_flags_t flags;
+
+	/*! Local interface parameters. */
+	const srv_info_t *local;
+	/*! Remote server parameters. */
+	const srv_info_t *remote;
+
+	/*! Local description string (used for logging). */
+	char *local_str;
+	/*! Remote description string (used for logging). */
+	char *remote_str;
+
+	/*! Output from getaddrinfo for remote server. If the server is
+	 *  specified using domain name, this structure may contain more
+	 *  results.
+	 */
+	struct addrinfo *remote_info;
+	/*! Currently used result from remote_info. */
+	struct addrinfo *srv;
+	/*! Output from getaddrinfo for local address. Only first result is
+	 *  used.
+	 */
+	struct addrinfo *local_info;
+
+	/*! TLS context. */
+	tls_ctx_t tls;
+} net_t;
+
+/*!
+ * \brief Creates and fills server structure.
+ *
+ * \param name		Address or host name.
+ * \param service	Port number or service name.
+ *
+ * \retval server	if success.
+ * \retval NULL		if error.
+ */
+srv_info_t *srv_info_create(const char *name, const char *service);
+
+/*!
+ * \brief Destroys server structure.
+ *
+ * \param server	Server structure to destroy.
+ */
+void srv_info_free(srv_info_t *server);
+
+/*!
+ * \brief Translates enum IP version type to int version.
+ *
+ * \param ip		IP version to convert.
+ *
+ * \retval AF_INET, AF_INET6 or AF_UNSPEC.
+ */
+int get_iptype(const ip_t ip);
+
+/*!
+ * \brief Translates enum IP protocol type to int version in context to the
+ *        current DNS query type.
+ *
+ * \param proto		IP protocol type to convert.
+ * \param type		DNS query type number.
+ *
+ * \retval SOCK_STREAM or SOCK_DGRAM.
+ */
+int get_socktype(const protocol_t proto, const uint16_t type);
+
+/*!
+ * \brief Translates int socket type to the common string one.
+ *
+ * \param socktype	Socket type (SOCK_STREAM or SOCK_DGRAM).
+ *
+ * \retval "TCP" or "UDP".
+ */
+const char *get_sockname(const int socktype);
+
+/*!
+ * \brief Translates int socket type to the common string one.
+ *
+ * \param ss		Socket address storage.
+ * \param socktype	Socket type (SOCK_STREAM or SOCK_DGRAM).
+ * \param dst		Output string.
+ */
+void get_addr_str(const struct sockaddr_storage *ss,
+                  const int                     socktype,
+                  char                          **dst);
+
+/*!
+ * \brief Initializes network structure and resolves local and remote addresses.
+ *
+ * \param local		Local address and service description.
+ * \param remote	Remote address and service description.
+ * \param iptype	IP version.
+ * \param socktype	Socket type.
+ * \param wait		Network timeout interval.
+ * \param tls_params	TLS parameters.
+ * \param flags		Connection flags.
+ * \param net		Network structure to initialize.
+ *
+ * \retval KNOT_EOK	if success.
+ * \retval errcode	if error.
+ */
+int net_init(const srv_info_t    *local,
+             const srv_info_t    *remote,
+             const int           iptype,
+             const int           socktype,
+             const int           wait,
+             const net_flags_t   flags,
+             const tls_params_t  *tls_params,
+             net_t               *net);
+
+/*!
+ * \brief Creates socket and connects (if TCP) to remote address specified
+ *        by net->srv.
+ *
+ * \param net		Connection parameters.
+ *
+ * \retval KNOT_EOK	if success.
+ * \retval errcode	if error.
+ */
+int net_connect(net_t *net);
+
+/*!
+ * \brief Fills in local address information.
+ *
+ * \param net		Connection parameters.
+ *
+ * \retval KNOT_EOK	if success.
+ * \retval errcode	if error.
+ */
+int net_set_local_info(net_t *net);
+
+/*!
+ * \brief Sends data to connected remote server.
+ *
+ * \param net		Connection parameters.
+ * \param buf		Data to send.
+ * \param buf_len	Length of the data to send.
+ *
+ * \retval KNOT_EOK	if success.
+ * \retval errcode	if error.
+ */
+int net_send(const net_t *net, const uint8_t *buf, const size_t buf_len);
+
+/*!
+ * \brief Receives data from connected remote server.
+ *
+ * \param net		Connection parameters.
+ * \param buf		Buffer for incoming data.
+ * \param buf_len	Length of the buffer.
+ *
+ * \retval >=0		length of successfully received data.
+ * \retval errcode	if error.
+ */
+int net_receive(const net_t *net, uint8_t *buf, const size_t buf_len);
+
+/*!
+ * \brief Closes current network connection.
+ *
+ * \param net		Connection parameters.
+ */
+void net_close(net_t *net);
+
+/*!
+ * \brief Cleans up network structure.
+ *
+ * \param net		Connection parameters.
+ */
+void net_clean(net_t *net);
+
+/*! @} */
diff --git a/src/utils/common/params.c b/src/utils/common/params.c
new file mode 100644
index 0000000..e374314
--- /dev/null
+++ b/src/utils/common/params.c
@@ -0,0 +1,347 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <arpa/inet.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <netinet/in.h>
+#include <sys/socket.h>
+
+#ifdef LIBIDN
+#include LIBIDN_HEADER
+#endif
+
+#include "utils/common/params.h"
+#include "utils/common/msg.h"
+#include "utils/common/resolv.h"
+#include "utils/common/token.h"
+#include "libknot/libknot.h"
+#include "contrib/macros.h"
+#include "contrib/mempattern.h"
+#include "contrib/openbsd/strlcpy.h"
+#include "contrib/strtonum.h"
+
+#define IPV4_REVERSE_DOMAIN	"in-addr.arpa."
+#define IPV6_REVERSE_DOMAIN	"ip6.arpa."
+
+char *name_from_idn(const char *idn_name) {
+#ifdef LIBIDN
+	char *name = NULL;
+
+	int rc = idna_to_ascii_lz(idn_name, &name, 0);
+	if (rc != IDNA_SUCCESS) {
+		ERR("IDNA (%s)\n", idna_strerror(rc));
+		return NULL;
+	}
+
+	return name;
+#endif
+	return strdup(idn_name);
+}
+
+void name_to_idn(char **name) {
+#ifdef LIBIDN
+	char *idn_name = NULL;
+
+	int rc = idna_to_unicode_8zlz(*name, &idn_name, 0);
+	if (rc != IDNA_SUCCESS) {
+		return;
+	}
+
+	free(*name);
+	*name = idn_name;
+#endif
+	return;
+}
+
+/*!
+ * \brief Checks if string is a prefix of reference string.
+ *
+ * \param pref		Prefix string.
+ * \param pref_len	Prefix length.
+ * \param str		Reference string (must have trailing zero).
+ *
+ * \retval -1		\a pref is not a prefix of \a str.
+ * \retval  0<=		number of chars after prefix \a pref in \a str.
+ */
+static int cmp_prefix(const char *pref, const size_t pref_len,
+                      const char *str)
+{
+	size_t i = 0;
+	while (1) {
+		// Different characters => NOT prefix.
+		if (pref[i] != str[i]) {
+			return -1;
+		}
+
+		i++;
+
+		// Pref IS a prefix of pref.
+		if (i == pref_len) {
+			size_t rest = 0;
+			while (str[i + rest] != '\0') {
+				rest++;
+			}
+			return rest;
+		// Pref is longer then ref => NOT prefix.
+		} else if (str[i] == '\0') {
+			return -1;
+		}
+	}
+}
+
+int best_param(const char *str, const size_t str_len, const param_t *tbl,
+               bool *unique)
+{
+	if (str == NULL || str_len == 0 || tbl == NULL) {
+		DBG_NULL;
+		return KNOT_EINVAL;
+	}
+
+	int best_pos = -1;
+	int best_match = INT_MAX;
+	size_t matches = 0;
+	for (int i = 0; tbl[i].name != NULL; i++) {
+		int ret = cmp_prefix(str, str_len, tbl[i].name);
+		switch (ret) {
+		case -1:
+			continue;
+		case 0:
+			*unique = true;
+			return i;
+		default:
+			if (ret < best_match) {
+				best_pos = i;
+				best_match = ret;
+			}
+			matches++;
+		}
+	}
+
+	switch (matches) {
+	case 0:
+		return KNOT_ENOTSUP;
+	case 1:
+		*unique = true;
+		return best_pos;
+	default:
+		*unique = false;
+		return best_pos;
+	}
+}
+
+char *get_reverse_name(const char *name)
+{
+	struct in_addr	addr4;
+	struct in6_addr	addr6;
+	int		ret;
+	char		buf[128] = "\0";
+
+	if (name == NULL) {
+		DBG_NULL;
+		return NULL;
+	}
+
+	// Check name for IPv4 address, IPv6 address or other.
+	if (inet_pton(AF_INET, name, &addr4) == 1) {
+		uint32_t num = ntohl(addr4.s_addr);
+
+		// Create IPv4 reverse FQD name.
+		ret = snprintf(buf, sizeof(buf), "%u.%u.%u.%u.%s",
+		               (num >>  0) & 0xFF, (num >>  8) & 0xFF,
+		               (num >> 16) & 0xFF, (num >> 24) & 0xFF,
+		               IPV4_REVERSE_DOMAIN);
+		if (ret < 0 || (size_t)ret >= sizeof(buf)) {
+			return NULL;
+		}
+
+		return strdup(buf);
+	} else if (inet_pton(AF_INET6, name, &addr6) == 1) {
+		char	*pos = buf;
+		size_t  len = sizeof(buf);
+		uint8_t left, right;
+
+		// Create IPv6 reverse name.
+		for (int i = 15; i >= 0; i--) {
+			left = ((addr6.s6_addr)[i] & 0xF0) >> 4;
+			right = (addr6.s6_addr)[i] & 0x0F;
+
+			ret = snprintf(pos, len, "%x.%x.", right, left);
+			if (ret < 0 || (size_t)ret >= len) {
+				return NULL;
+			}
+
+			pos += ret;
+			len -= ret;
+		}
+
+		// Add IPv6 reverse domain.
+		ret = snprintf(pos, len, "%s", IPV6_REVERSE_DOMAIN);
+		if (ret < 0 || (size_t)ret >= len) {
+			return NULL;
+		}
+
+		return strdup(buf);
+	} else {
+		return NULL;
+	}
+}
+
+char *get_fqd_name(const char *name)
+{
+	char *fqd_name = NULL;
+
+	if (name == NULL) {
+		DBG_NULL;
+		return NULL;
+	}
+
+	size_t name_len = strlen(name);
+
+	// If the name is FQDN, make a copy.
+	if (name[name_len - 1] == '.') {
+		fqd_name = strdup(name);
+	// Else make a copy and append a trailing dot.
+	} else {
+		size_t fqd_name_size = name_len + 2;
+		fqd_name = malloc(fqd_name_size);
+		if (fqd_name != NULL) {
+			strlcpy(fqd_name, name, fqd_name_size);
+			fqd_name[name_len] = '.';
+			fqd_name[name_len + 1] = 0;
+		}
+	}
+
+	return fqd_name;
+}
+
+int params_parse_class(const char *value, uint16_t *rclass)
+{
+	if (value == NULL || rclass == NULL) {
+		DBG_NULL;
+		return KNOT_EINVAL;
+	}
+
+	if (knot_rrclass_from_string(value, rclass) == 0) {
+		return KNOT_EOK;
+	} else {
+		return KNOT_EINVAL;
+	}
+}
+
+int params_parse_type(const char *value, uint16_t *rtype, int64_t *serial,
+                      bool *notify)
+{
+	if (value == NULL || rtype == NULL || serial == NULL) {
+		DBG_NULL;
+		return KNOT_EINVAL;
+	}
+
+	// Find and parse type name.
+	size_t param_pos = strcspn(value, "=");
+	char *type_char = strndup(value, param_pos);
+
+	if (knot_rrtype_from_string(type_char, rtype) != 0) {
+		size_t cmp_len = MAX(strlen("NOTIFY"), param_pos);
+		if (strncasecmp(type_char, "NOTIFY", cmp_len) == 0) {
+			*rtype = KNOT_RRTYPE_SOA;
+			*notify = true;
+		} else {
+			free(type_char);
+			return KNOT_EINVAL;
+		}
+	} else {
+		*notify = false;
+	}
+
+	free(type_char);
+
+	// Parse additional parameter.
+	if (param_pos == strlen(value)) {
+		// IXFR requires serial parameter.
+		if (*rtype == KNOT_RRTYPE_IXFR) {
+			DBG("SOA serial is required for IXFR query\n");
+			return KNOT_EINVAL;
+		} else {
+			*serial = -1;
+		}
+	} else {
+		// Additional parameter is accepted for IXFR or NOTIFY.
+		if (*rtype == KNOT_RRTYPE_IXFR || *notify) {
+			const char *param_str = value + 1 + param_pos;
+			char *end;
+
+			// Convert string to serial.
+			unsigned long long num = strtoull(param_str, &end, 10);
+
+			// Check for bad serial string.
+			if (end == param_str || *end != '\0' || num > UINT32_MAX) {
+				DBG("bad SOA serial '%s'\n", param_str);
+				return KNOT_EINVAL;
+			}
+
+			*serial = num;
+		} else {
+			DBG("unsupported parameter '%s'\n", value);
+			return KNOT_EINVAL;
+		}
+	}
+
+	return KNOT_EOK;
+}
+
+int params_parse_server(const char *value, list_t *servers, const char *def_port)
+{
+	if (value == NULL || servers == NULL) {
+		DBG_NULL;
+		return KNOT_EINVAL;
+	}
+
+	// Add specified nameserver.
+	srv_info_t *server = parse_nameserver(value, def_port);
+	if (server == NULL) {
+		return KNOT_EINVAL;
+	}
+	add_tail(servers, (node_t *)server);
+
+	return KNOT_EOK;
+}
+
+int params_parse_wait(const char *value, int32_t *dst)
+{
+	if (value == NULL || dst == NULL) {
+		DBG_NULL;
+		return KNOT_EINVAL;
+	}
+
+	uint32_t num;
+	int ret = str_to_u32(value, &num);
+	if (ret != KNOT_EOK) {
+		return ret;
+	}
+
+	// Check for minimal value.
+	if (num < 1) {
+		num = 1;
+	// Reduce maximal value. Poll takes signed int in milliseconds.
+	} else if (num > INT32_MAX / 1000) {
+		num = INT32_MAX / 1000;
+	}
+
+	*dst = num;
+
+	return KNOT_EOK;
+}
diff --git a/src/utils/common/params.h b/src/utils/common/params.h
new file mode 100644
index 0000000..4059446
--- /dev/null
+++ b/src/utils/common/params.h
@@ -0,0 +1,172 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \file
+ *
+ * \brief Common utils parameters processing.
+ *
+ * \addtogroup knot_utils
+ * @{
+ */
+
+#pragma once
+
+#include <limits.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdio.h>
+
+#include "libknot/libknot.h"
+#include "contrib/ucw/lists.h"
+
+#define DEFAULT_IPV4_NAME	"127.0.0.1"
+#define DEFAULT_IPV6_NAME	"::1"
+#define DEFAULT_DNS_PORT	"53"
+#define DEFAULT_DNS_TLS_PORT	"853"
+#define DEFAULT_UDP_SIZE	512
+#define DEFAULT_EDNS_SIZE	4096
+#define MAX_PACKET_SIZE		65535
+
+#define SEP_CHARS		"\n\t "
+
+/*! \brief Variants of IP protocol. */
+typedef enum {
+	IP_ALL,
+	IP_4,
+	IP_6
+} ip_t;
+
+/*! \brief Variants of transport protocol. */
+typedef enum {
+	PROTO_ALL,
+	PROTO_TCP,
+	PROTO_UDP
+} protocol_t;
+
+/*! \brief Variants of output type. */
+typedef enum {
+	/*!< Verbose output (same for host and dig). */
+	FORMAT_FULL,
+	/*!< Short dig output. */
+	FORMAT_DIG,
+	/*!< Brief host output. */
+	FORMAT_HOST,
+	/*!< Brief nsupdate output. */
+	FORMAT_NSUPDATE
+} format_t;
+
+/*! \brief Text output settings. */
+typedef struct {
+	/*!< Output format. */
+	format_t	format;
+
+	/*!< Style of rrset dump. */
+	knot_dump_style_t	style;
+
+	/*!< Show query packet. */
+	bool	show_query;
+	/*!< Show header info. */
+	bool	show_header;
+	/*!< Show section name. */
+	bool	show_section;
+	/*!< Show EDNS pseudosection. */
+	bool	show_edns;
+	/*!< Show QUERY/ZONE section. */
+	bool	show_question;
+	/*!< Show ANSWER/PREREQ section. */
+	bool	show_answer;
+	/*!< Show UPDATE/AUTHORITY section. */
+	bool	show_authority;
+	/*!< Show ADDITIONAL section. */
+	bool	show_additional;
+	/*!< Show TSIG pseudosection. */
+	bool	show_tsig;
+	/*!< Show footer info. */
+	bool	show_footer;
+
+	/*!< KHOST - Hide CNAME record in answer (duplicity reduction). */
+	bool	hide_cname;
+} style_t;
+
+/*! \brief Parameter handler. */
+typedef int (*param_handle_f)(const char *arg, void *params);
+
+/*! \brief Parameter argument type. */
+typedef enum {
+	ARG_NONE,
+	ARG_REQUIRED,
+	ARG_OPTIONAL
+} arg_t;
+
+/*! \brief Parameter specification. */
+typedef struct {
+	const char     *name;
+	arg_t          arg;
+	param_handle_f handler;
+} param_t;
+
+inline static void print_version(const char *program_name)
+{
+	printf("%s (Knot DNS), version %s\n", program_name, PACKAGE_VERSION);
+}
+
+/*!
+ * \brief Transforms localized IDN string to ASCII punycode.
+ *
+ * \param idn_name	IDN name to transform.
+ *
+ * \retval NULL		if transformation fails.
+ * \retval string	if ok.
+ */
+char *name_from_idn(const char *idn_name);
+
+/*!
+ * \brief Transforms ASCII punycode to localized IDN string.
+ *
+ * If an error occurs or IDN support is missing, this function does nothing.
+ *
+ * \param name	ASCII name to transform and replace with IDN name.
+ */
+void name_to_idn(char **name);
+
+/*!
+ * \brief Find the best parameter match in table based on prefix equality.
+ *
+ * \param str		Parameter name to look up.
+ * \param str_len	Parameter name length.
+ * \param tbl		Parameter table.
+ * \param unique	Indication if output is unique result.
+ *
+ * \retval >=0		looked up parameter position in \a tbl.
+ * \retval err		if error.
+ */
+int best_param(const char *str, const size_t str_len, const param_t *tbl,
+               bool *unique);
+
+char *get_reverse_name(const char *name);
+
+char *get_fqd_name(const char *name);
+
+int params_parse_class(const char *value, uint16_t *rclass);
+
+int params_parse_type(const char *value, uint16_t *rtype, int64_t *serial,
+                      bool *notify);
+
+int params_parse_server(const char *value, list_t *servers, const char *def_port);
+
+int params_parse_wait(const char *value, int32_t *dst);
+
+/*! @} */
diff --git a/src/utils/common/resolv.c b/src/utils/common/resolv.c
new file mode 100644
index 0000000..b5f84c5
--- /dev/null
+++ b/src/utils/common/resolv.c
@@ -0,0 +1,208 @@
+/*  Copyright (C) 2016 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include "utils/common/resolv.h"
+#include "utils/common/msg.h"
+#include "utils/common/params.h"
+#include "libknot/libknot.h"
+#include "contrib/ucw/lists.h"
+
+#define RESOLV_FILE	"/etc/resolv.conf"
+
+srv_info_t* parse_nameserver(const char *str, const char *def_port)
+{
+	char *host = NULL, *port = NULL;
+	const char *addr = NULL, *sep = NULL;
+	size_t addr_len = 0;
+	char separator = ':';
+
+	if (str == NULL || def_port == NULL) {
+		DBG_NULL;
+		return NULL;
+	}
+
+	const size_t str_len = strlen(str);
+	const char *str_end = str + str_len;
+
+	// [address]:port notation.
+	if (*str == '[') {
+		addr = str + 1;
+		const char *addr_end = strchr(addr, ']');
+		// Missing closing bracket -> stop processing.
+		if (addr_end == NULL) {
+			return NULL;
+		}
+		addr_len = addr_end - addr;
+		str += 1 + addr_len + 1;
+	// Address@port notation.
+	} else if ((sep = strchr(str, '@')) != NULL) {
+		addr = str;
+		addr_len = sep - addr;
+		str += addr_len;
+		separator = '@';
+	// Address#port notation.
+	} else if ((sep = strchr(str, '#')) != NULL) {
+		addr = str;
+		addr_len = sep - addr;
+		str += addr_len;
+		separator = '#';
+	// IPv4:port notation.
+	} else if ((sep = strchr(str, ':')) != NULL) {
+		addr = str;
+		// Not IPv4 address -> no port.
+		if (strchr(sep + 1, ':') != NULL) {
+			addr_len = str_len;
+			str = str_end;
+		} else {
+			addr_len = sep - addr;
+			str += addr_len;
+		}
+	// No port specified.
+	} else {
+		addr = str;
+		addr_len = str_len;
+		str = str_end;
+	}
+
+	// Process port.
+	if (str < str_end) {
+		// Check port separator.
+		if (*str != separator) {
+			return NULL;
+		}
+		str++;
+
+		// Check for missing port.
+		if (str >= str_end) {
+			return NULL;
+		}
+
+		port = strdup(str);
+	} else {
+		port = strdup(def_port);
+	}
+
+	host = strndup(addr, addr_len);
+
+	// Create server structure.
+	srv_info_t *server = srv_info_create(host, port);
+
+	free(host);
+	free(port);
+
+	return server;
+}
+
+static size_t get_resolv_nameservers(list_t *servers, const char *def_port)
+{
+	char	line[512];
+
+	// Open config file.
+	FILE *f = fopen(RESOLV_FILE, "r");
+	if (f == NULL) {
+		return 0;
+	}
+
+	// Read lines from config file.
+	while (fgets(line, sizeof(line), f) != NULL) {
+		size_t len;
+		char   *pos = line;
+		char   *option, *value;
+
+		// Find leading white characters.
+		len = strspn(pos, SEP_CHARS);
+		pos += len;
+
+		// Start of the first token.
+		option = pos;
+
+		// Find length of the token.
+		len = strcspn(pos, SEP_CHARS);
+		pos += len;
+
+		// Check if the token is not empty.
+		if (len == 0) {
+			continue;
+		}
+
+		// Find separating white characters.
+		len = strspn(pos, SEP_CHARS);
+		pos += len;
+
+		// Check if there is a separation between tokens.
+		if (len == 0) {
+			continue;
+		}
+
+		// Copy of the second token.
+		value = strndup(pos, strcspn(pos, SEP_CHARS));
+
+		// Process value with respect to option name.
+		if (strncmp(option, "nameserver", strlen("nameserver")) == 0) {
+			srv_info_t *server;
+
+			server = parse_nameserver(value, def_port);
+
+			// If value is correct, add nameserver to the list.
+			if (server != NULL) {
+				add_tail(servers, (node_t *)server);
+			}
+		}
+
+		// Drop value string.
+		free(value);
+	}
+
+	// Close config file.
+	fclose(f);
+
+	// Return number of servers.
+	return list_size(servers);
+}
+
+void get_nameservers(list_t *servers, const char *def_port)
+{
+	if (servers == NULL || def_port == NULL) {
+		DBG_NULL;
+		return;
+	}
+
+	// Initialize list of servers.
+	init_list(servers);
+
+	// Read nameservers from resolv file or use the default ones.
+	if (get_resolv_nameservers(servers, def_port) == 0) {
+		srv_info_t *server;
+
+		// Add default ipv6 nameservers.
+		server = srv_info_create(DEFAULT_IPV6_NAME, def_port);
+
+		if (server != NULL) {
+			add_tail(servers, (node_t *)server);
+		}
+
+		// Add default ipv4 nameservers.
+		server = srv_info_create(DEFAULT_IPV4_NAME, def_port);
+
+		if (server != NULL) {
+			add_tail(servers, (node_t *)server);
+		}
+	}
+}
diff --git a/src/utils/common/resolv.h b/src/utils/common/resolv.h
new file mode 100644
index 0000000..bcf1a0f
--- /dev/null
+++ b/src/utils/common/resolv.h
@@ -0,0 +1,36 @@
+/*  Copyright (C) 2011 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \file resolv.h
+ *
+ * \author Daniel Salzman <daniel.salzman@nic.cz>
+ *
+ * \brief resolv.conf processing.
+ *
+ * \addtogroup knot_utils
+ * @{
+ */
+
+#pragma once
+
+#include "utils/common/netio.h"
+#include "contrib/ucw/lists.h"
+
+srv_info_t* parse_nameserver(const char *str, const char *def_port);
+
+void get_nameservers(list_t *servers, const char *def_port);
+
+/*! @} */
diff --git a/src/utils/common/sign.c b/src/utils/common/sign.c
new file mode 100644
index 0000000..f8e9f29
--- /dev/null
+++ b/src/utils/common/sign.c
@@ -0,0 +1,109 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <string.h>
+
+#include "utils/common/sign.h"
+#include "libknot/errcode.h"
+#include "libknot/tsig-op.h"
+
+int sign_context_init_tsig(sign_context_t *ctx, const knot_tsig_key_t *key)
+{
+	if (!ctx || !key) {
+		return KNOT_EINVAL;
+	}
+
+	size_t digest_size = dnssec_tsig_algorithm_size(key->algorithm);
+	if (digest_size == 0) {
+		return KNOT_EINVAL;
+	}
+
+	uint8_t *digest = calloc(1, digest_size);
+	if (!digest) {
+		return KNOT_ENOMEM;
+	}
+
+	ctx->digest_size = digest_size;
+	ctx->digest = digest;
+	ctx->tsig_key = key;
+
+	return KNOT_EOK;
+}
+
+void sign_context_deinit(sign_context_t *ctx)
+{
+	if (!ctx) {
+		return;
+	}
+
+	free(ctx->digest);
+
+	memset(ctx, 0, sizeof(*ctx));
+}
+
+int sign_packet(knot_pkt_t *pkt, sign_context_t *sign_ctx)
+{
+	if (pkt == NULL || sign_ctx == NULL || sign_ctx->digest == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	uint8_t *wire = pkt->wire;
+	size_t  *wire_size = &pkt->size;
+	size_t  max_size = pkt->max_size;
+
+	int ret = knot_pkt_reserve(pkt, knot_tsig_wire_size(sign_ctx->tsig_key));
+	if (ret != KNOT_EOK) {
+		return ret;
+	}
+
+	return knot_tsig_sign(wire, wire_size, max_size, NULL, 0,
+	                      sign_ctx->digest, &sign_ctx->digest_size,
+	                      sign_ctx->tsig_key, 0, 0);
+}
+
+int verify_packet(const knot_pkt_t *pkt, const sign_context_t *sign_ctx)
+{
+	if (pkt == NULL || sign_ctx == NULL || sign_ctx->digest == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	const uint8_t *wire = pkt->wire;
+	const size_t  *wire_size = &pkt->size;
+
+	if (pkt->tsig_rr == NULL) {
+		return KNOT_ENOTSIG;
+	}
+
+	int ret = knot_tsig_client_check(pkt->tsig_rr, wire, *wire_size,
+	                                 sign_ctx->digest, sign_ctx->digest_size,
+	                                 sign_ctx->tsig_key, 0);
+	if (ret != KNOT_EOK) {
+		return ret;
+	}
+
+	switch (knot_tsig_rdata_error(pkt->tsig_rr)) {
+	case KNOT_RCODE_BADSIG:
+		return KNOT_TSIG_EBADSIG;
+	case KNOT_RCODE_BADKEY:
+		return KNOT_TSIG_EBADKEY;
+	case KNOT_RCODE_BADTIME:
+		return KNOT_TSIG_EBADTIME;
+	case KNOT_RCODE_BADTRUNC:
+		return KNOT_TSIG_EBADTRUNC;
+	default:
+		return KNOT_EOK;
+	}
+}
diff --git a/src/utils/common/sign.h b/src/utils/common/sign.h
new file mode 100644
index 0000000..d1912a0
--- /dev/null
+++ b/src/utils/common/sign.h
@@ -0,0 +1,63 @@
+/*  Copyright (C) 2015 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+#include "libknot/packet/pkt.h"
+#include "libknot/tsig.h"
+
+/*!
+ * \brief Holds data required between signing and signature verification.
+ */
+struct sign_context {
+	size_t digest_size;
+	uint8_t *digest;
+	const knot_tsig_key_t *tsig_key;
+};
+
+typedef struct sign_context sign_context_t;
+
+/*!
+ * \brief Initialize signing context for TSIG.
+ */
+int sign_context_init_tsig(sign_context_t *ctx, const knot_tsig_key_t *key);
+
+/*!
+ * \brief Clean up signing context.
+ *
+ * \param ctx  Sign context.
+ */
+void sign_context_deinit(sign_context_t *ctx);
+
+/*!
+ * \brief Signs outgoing DNS packet.
+ *
+ * \param pkt       Packet to sign.
+ * \param sign_ctx  Signing context.
+ *
+ * \return Error code, KNOT_EOK if successful.
+ */
+int sign_packet(knot_pkt_t *pkt, sign_context_t *sign_ctx);
+
+/*!
+ * \brief Verifies signature for incoming DNS packet.
+ *
+ * \param pkt       Packet verify sign.
+ * \param sign_ctx  Signing context.
+ *
+ * \return Error code, KNOT_EOK if successful.
+ */
+int verify_packet(const knot_pkt_t *pkt, const sign_context_t *sign_ctx);
diff --git a/src/utils/common/tls.c b/src/utils/common/tls.c
new file mode 100644
index 0000000..91b747f
--- /dev/null
+++ b/src/utils/common/tls.c
@@ -0,0 +1,495 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <arpa/inet.h>
+#include <stdbool.h>
+#include <string.h>
+#include <gnutls/gnutls.h>
+#include <gnutls/x509.h>
+#include <poll.h>
+
+#include "utils/common/tls.h"
+#include "utils/common/cert.h"
+#include "utils/common/msg.h"
+#include "contrib/base64.h"
+#include "libknot/errcode.h"
+
+void tls_params_init(tls_params_t *params)
+{
+	if (params == NULL) {
+		return;
+	}
+
+	memset(params, 0, sizeof(*params));
+
+	init_list(&params->ca_files);
+	init_list(&params->pins);
+}
+
+int tls_params_copy(tls_params_t *dst, const tls_params_t *src)
+{
+	if (dst == NULL || src == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	tls_params_init(dst);
+
+	dst->enable = src->enable;
+	dst->system_ca = src->system_ca;
+	if (src->hostname != NULL) {
+		dst->hostname = strdup(src->hostname);
+		if (dst->hostname == NULL) {
+			tls_params_clean(dst);
+			return KNOT_ENOMEM;
+		}
+	}
+
+	if (src->sni != NULL) {
+		dst->sni = strdup(src->sni);
+		if (dst->sni == NULL) {
+			tls_params_clean(dst);
+			return KNOT_ENOMEM;
+		}
+	}
+
+	ptrnode_t *n = NULL;
+	WALK_LIST(n, src->ca_files) {
+		char *src_file = (char *)n->d;
+		char *file = strdup(src_file);
+		if (file == NULL || ptrlist_add(&dst->ca_files, file, NULL) == NULL) {
+			tls_params_clean(dst);
+			return KNOT_ENOMEM;
+		}
+	}
+	WALK_LIST(n, src->pins) {
+		uint8_t *src_pin = (uint8_t *)n->d;
+		uint8_t *pin = malloc(1 + src_pin[0]);
+		if (pin == NULL || ptrlist_add(&dst->pins, pin, NULL) == NULL) {
+			tls_params_clean(dst);
+			return KNOT_ENOMEM;
+		}
+		memcpy(pin, src_pin, 1 + src_pin[0]);
+	}
+
+	return KNOT_EOK;
+}
+
+void tls_params_clean(tls_params_t *params)
+{
+	if (params == NULL) {
+		return;
+	}
+
+	ptrnode_t *node = NULL, *nxt = NULL;
+	WALK_LIST_DELSAFE(node, nxt, params->ca_files) {
+		free(node->d);
+	}
+	ptrlist_free(&params->ca_files, NULL);
+
+	WALK_LIST_DELSAFE(node, nxt, params->pins) {
+		free(node->d);
+	}
+	ptrlist_free(&params->pins, NULL);
+
+	free(params->hostname);
+	free(params->sni);
+
+	memset(params, 0, sizeof(*params));
+}
+
+static bool check_pin(const uint8_t *cert_pin, size_t cert_pin_len, const list_t *pins)
+{
+	if (EMPTY_LIST(*pins)) {
+		return false;
+	}
+
+	ptrnode_t *n = NULL;
+	WALK_LIST(n, *pins) {
+		uint8_t *pin = (uint8_t *)n->d;
+		if (pin[0] == cert_pin_len &&
+		    memcmp(cert_pin, &pin[1], cert_pin_len) == 0) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+static int check_certificates(gnutls_session_t session, const list_t *pins)
+{
+	if (gnutls_certificate_type_get(session) != GNUTLS_CRT_X509) {
+		DBG("TLS, invalid certificate type\n");
+		return GNUTLS_E_CERTIFICATE_ERROR;
+	}
+
+	unsigned cert_list_size;
+	const gnutls_datum_t *cert_list =
+		gnutls_certificate_get_peers(session, &cert_list_size);
+	if (cert_list == NULL || cert_list_size == 0) {
+		DBG("TLS, empty certificate list\n");
+		return GNUTLS_E_CERTIFICATE_ERROR;
+	}
+
+	size_t matches = 0;
+
+	DBG("TLS, received certificate hierarchy:\n");
+	for (int i = 0; i < cert_list_size; i++) {
+		gnutls_x509_crt_t cert;
+		int ret = gnutls_x509_crt_init(&cert);
+		if (ret != GNUTLS_E_SUCCESS) {
+			return ret;
+		}
+
+		ret = gnutls_x509_crt_import(cert, &cert_list[i], GNUTLS_X509_FMT_DER);
+		if (ret != GNUTLS_E_SUCCESS) {
+			gnutls_x509_crt_deinit(cert);
+			return ret;
+		}
+
+		gnutls_datum_t cert_name = { 0 };
+		ret = gnutls_x509_crt_get_dn2(cert, &cert_name);
+		if (ret != GNUTLS_E_SUCCESS) {
+			gnutls_x509_crt_deinit(cert);
+			return ret;
+		}
+		DBG(" #%i, %s\n", i + 1, cert_name.data);
+		gnutls_free(cert_name.data);
+
+		uint8_t cert_pin[CERT_PIN_LEN] = { 0 };
+		ret = cert_get_pin(cert, cert_pin, sizeof(cert_pin));
+		if (ret != KNOT_EOK) {
+			gnutls_x509_crt_deinit(cert);
+			return GNUTLS_E_CERTIFICATE_ERROR;
+		}
+
+		// Check if correspond to a specified PIN.
+		bool match = check_pin(cert_pin, sizeof(cert_pin), pins);
+		if (match) {
+			matches++;
+		}
+
+		uint8_t *txt_pin;
+		ret = base64_encode_alloc(cert_pin, sizeof(cert_pin), &txt_pin);
+		if (ret < 0) {
+			gnutls_x509_crt_deinit(cert);
+			return ret;
+		}
+		DBG("     SHA-256 PIN: %.*s%s\n", ret, txt_pin, match ? ", MATCH" : "");
+		free(txt_pin);
+
+		gnutls_x509_crt_deinit(cert);
+	}
+
+	if (matches > 0) {
+		return GNUTLS_E_SUCCESS;
+	} else if (EMPTY_LIST(*pins)) {
+		DBG("TLS, skipping certificate PIN check\n");
+		return GNUTLS_E_SUCCESS;
+	} else {
+		DBG("TLS, no certificate PIN match\n");
+		return GNUTLS_E_CERTIFICATE_ERROR;
+	}
+}
+
+static bool do_verification(const tls_params_t *params)
+{
+	return params->hostname != NULL || params->system_ca ||
+	       !EMPTY_LIST(params->ca_files);
+}
+
+static int verify_certificate(gnutls_session_t session)
+{
+	tls_ctx_t *ctx = gnutls_session_get_ptr(session);
+
+	// Check for pinned certificates and print certificate hierarchy.
+	int ret = check_certificates(session, &ctx->params->pins);
+	if (ret != GNUTLS_E_SUCCESS) {
+		return ret;
+	}
+
+	if (!do_verification(ctx->params)) {
+		DBG("TLS, skipping certificate verification\n");
+		return GNUTLS_E_SUCCESS;
+	}
+
+	// Set server certificate check.
+	gnutls_typed_vdata_st data[2] = {
+		{ .type = GNUTLS_DT_KEY_PURPOSE_OID,
+		  .data = (void *)GNUTLS_KP_TLS_WWW_SERVER },
+		{ .type = GNUTLS_DT_DNS_HOSTNAME,
+		  .data = (void *)ctx->params->hostname }
+	};
+	size_t data_count = (ctx->params->hostname != NULL) ? 2 : 1;
+	if (data_count == 1) {
+		WARN("TLS, no hostname provided, will not verify certificate owner\n")
+	}
+
+	unsigned int status;
+	ret = gnutls_certificate_verify_peers(session, data, data_count, &status);
+	if (ret != GNUTLS_E_SUCCESS) {
+		WARN("TLS, failed to verify peer certificate\n");
+		return GNUTLS_E_CERTIFICATE_ERROR;
+	}
+
+	gnutls_datum_t msg;
+	ret = gnutls_certificate_verification_status_print(
+		status, gnutls_certificate_type_get(session), &msg, 0);
+	if (ret == GNUTLS_E_SUCCESS) {
+		DBG("TLS, %s\n", msg.data);
+	}
+	gnutls_free(msg.data);
+
+	return (status == 0) ? GNUTLS_E_SUCCESS : GNUTLS_E_CERTIFICATE_ERROR;
+}
+
+int tls_ctx_init(tls_ctx_t *ctx, const tls_params_t *params, int wait)
+{
+	if (ctx == NULL || params == NULL || !params->enable) {
+		return KNOT_EINVAL;
+	}
+
+	memset(ctx, 0, sizeof(*ctx));
+	ctx->params = params;
+	ctx->wait = wait;
+	ctx->sockfd = -1;
+
+	int ret = gnutls_certificate_allocate_credentials(&ctx->credentials);
+	if (ret != GNUTLS_E_SUCCESS) {
+		return KNOT_ENOMEM;
+	}
+
+	// Import system certificates.
+	if (ctx->params->system_ca ||
+	    (ctx->params->hostname != NULL && EMPTY_LIST(ctx->params->ca_files))) {
+		ret = gnutls_certificate_set_x509_system_trust(ctx->credentials);
+		if (ret < 0) {
+			WARN("TLS, failed to import system certificates (%s)\n",
+			     gnutls_strerror_name(ret));
+			return KNOT_ERROR;
+		} else {
+			DBG("TLS, imported %i system certificates\n", ret);
+		}
+	}
+
+	// Import provided certificate files.
+	ptrnode_t *n = NULL;
+	WALK_LIST(n, ctx->params->ca_files) {
+		const char *file = (char *)n->d;
+		ret = gnutls_certificate_set_x509_trust_file(ctx->credentials, file,
+		                                             GNUTLS_X509_FMT_PEM);
+		if (ret < 0) {
+			WARN("TLS, failed to import certificate file '%s' (%s)\n",
+			    file, gnutls_strerror_name(ret));
+			return KNOT_ERROR;
+		} else {
+			DBG("TLS, imported %i certificates from '%s'\n", ret, file);
+		}
+	}
+
+	gnutls_certificate_set_verify_function(ctx->credentials, verify_certificate);
+
+	return KNOT_EOK;
+}
+
+int tls_ctx_connect(tls_ctx_t *ctx, int sockfd,  const char *remote)
+{
+	if (ctx == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	int ret = gnutls_init(&ctx->session, GNUTLS_CLIENT | GNUTLS_NONBLOCK);
+	if (ret != GNUTLS_E_SUCCESS) {
+		return KNOT_NET_ECONNECT;
+	}
+
+	ret = gnutls_set_default_priority(ctx->session);
+	if (ret != GNUTLS_E_SUCCESS) {
+		return KNOT_NET_ECONNECT;
+	}
+
+	ret = gnutls_credentials_set(ctx->session, GNUTLS_CRD_CERTIFICATE,
+	                             ctx->credentials);
+	if (ret != GNUTLS_E_SUCCESS) {
+		return KNOT_NET_ECONNECT;
+	}
+
+	if (remote != NULL) {
+		ret = gnutls_server_name_set(ctx->session, GNUTLS_NAME_DNS, remote,
+		                             strlen(remote));
+		if (ret != GNUTLS_E_SUCCESS) {
+			return KNOT_NET_ECONNECT;
+		}
+	}
+
+	gnutls_session_set_ptr(ctx->session, ctx);
+	gnutls_transport_set_int(ctx->session, sockfd);
+	gnutls_handshake_set_timeout(ctx->session, 1000 * ctx->wait);
+
+	// Initialize poll descriptor structure.
+	struct pollfd pfd = {
+		.fd = sockfd,
+		.events = POLLIN,
+		.revents = 0,
+	};
+
+	// Perform the TLS handshake
+	do {
+		ret = gnutls_handshake(ctx->session);
+		if (ret != GNUTLS_E_SUCCESS && gnutls_error_is_fatal(ret) == 0) {
+			if (poll(&pfd, 1, 1000 * ctx->wait) != 1) {
+				WARN("TLS, peer took too long to respond\n");
+				return KNOT_NET_ETIMEOUT;
+			}
+		}
+	} while (ret != GNUTLS_E_SUCCESS && gnutls_error_is_fatal(ret) == 0);
+	if (ret != GNUTLS_E_SUCCESS) {
+		WARN("TLS, handshake failed (%s)\n", gnutls_strerror(ret));
+		tls_ctx_close(ctx);
+		return KNOT_NET_ESOCKET;
+	}
+
+	// Save the socket descriptor.
+	ctx->sockfd = sockfd;
+
+	return KNOT_EOK;
+}
+
+int tls_ctx_send(tls_ctx_t *ctx, const uint8_t *buf, const size_t buf_len)
+{
+	if (ctx == NULL || buf == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	uint16_t msg_len = htons(buf_len);
+
+	gnutls_record_cork(ctx->session);
+
+	if (gnutls_record_send(ctx->session, &msg_len, sizeof(msg_len)) <= 0) {
+		WARN("TLS, failed to send\n");
+		return KNOT_NET_ESEND;
+	}
+	if (gnutls_record_send(ctx->session, buf, buf_len) <= 0) {
+		WARN("TLS, failed to send\n");
+		return KNOT_NET_ESEND;
+	}
+
+	while (gnutls_record_check_corked(ctx->session) > 0) {
+		int ret = gnutls_record_uncork(ctx->session, 0);
+		if (ret < 0 && gnutls_error_is_fatal(ret) != 0) {
+			WARN("TLS, failed to send (%s)\n", gnutls_strerror(ret));
+			return KNOT_NET_ESEND;
+		}
+	}
+
+	return KNOT_EOK;
+}
+
+int tls_ctx_receive(tls_ctx_t *ctx, uint8_t *buf, const size_t buf_len)
+{
+	if (ctx == NULL || buf == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	// Initialize poll descriptor structure.
+	struct pollfd pfd = {
+		.fd = ctx->sockfd,
+		.events = POLLIN,
+		.revents = 0,
+	};
+
+	uint32_t total = 0;
+	uint16_t msg_len = 0;
+
+	// Receive message header.
+	while (total < sizeof(msg_len)) {
+		ssize_t ret = gnutls_record_recv(ctx->session, &msg_len + total,
+		                                 sizeof(msg_len) - total);
+		if (ret > 0) {
+			total += ret;
+		} else if (ret == 0) {
+			WARN("TLS, peer has closed the connection\n");
+			return KNOT_NET_ERECV;
+		} else if (gnutls_error_is_fatal(ret) != 0) {
+			WARN("TLS, failed to receive reply (%s)\n",
+			     gnutls_strerror(ret));
+			return KNOT_NET_ERECV;
+		} else if (poll(&pfd, 1, 1000 * ctx->wait) != 1) {
+			WARN("TLS, peer took too long to respond\n");
+			return KNOT_NET_ETIMEOUT;
+		}
+	}
+
+	// Convert number to host format.
+	msg_len = ntohs(msg_len);
+	if (msg_len > buf_len) {
+		return KNOT_ESPACE;
+	}
+
+	total = 0;
+
+	// Receive data over TLS
+	while (total < msg_len) {
+		ssize_t ret = gnutls_record_recv(ctx->session, buf + total,
+		                                 msg_len - total);
+		if (ret > 0) {
+			total += ret;
+		} else if (ret == 0) {
+			WARN("TLS, peer has closed the connection\n");
+			return KNOT_NET_ERECV;
+		} else if (gnutls_error_is_fatal(ret) != 0) {
+			WARN("TLS, failed to receive reply (%s)\n",
+			     gnutls_strerror(ret));
+			return KNOT_NET_ERECV;
+		} else if (poll(&pfd, 1, 1000 * ctx->wait) != 1) {
+			WARN("TLS, peer took too long to respond\n");
+			return KNOT_NET_ETIMEOUT;
+		}
+	}
+
+	return total;
+}
+
+void tls_ctx_close(tls_ctx_t *ctx)
+{
+	if (ctx == NULL || ctx->session == NULL) {
+		return;
+	}
+
+	gnutls_bye(ctx->session, GNUTLS_SHUT_RDWR);
+	gnutls_deinit(ctx->session);
+}
+
+void tls_ctx_deinit(tls_ctx_t *ctx)
+{
+	if (ctx == NULL) {
+		return;
+	}
+
+	if (ctx->credentials != NULL) {
+		gnutls_certificate_free_credentials(ctx->credentials);
+	}
+}
+
+void print_tls(const tls_ctx_t *ctx)
+{
+	if (ctx == NULL || ctx->session == NULL) {
+		return;
+	}
+
+	char *msg = gnutls_session_get_desc(ctx->session);
+	printf(";; TLS session %s\n", msg);
+	gnutls_free(msg);
+}
diff --git a/src/utils/common/tls.h b/src/utils/common/tls.h
new file mode 100644
index 0000000..487a0de
--- /dev/null
+++ b/src/utils/common/tls.h
@@ -0,0 +1,64 @@
+/*  Copyright (C) 2018 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <stdint.h>
+#include <gnutls/gnutls.h>
+
+#include "contrib/ucw/lists.h"
+
+/*! \brief TLS parameters. */
+typedef struct {
+	/*! Use TLS indicator. */
+	bool enable;
+	/*! Import system certificates indicator. */
+	bool system_ca;
+	/*! Certificate files to import. */
+	list_t ca_files;
+	/*! Pinned certificates. */
+	list_t pins;
+	/*! Required server hostname. */
+	char *hostname;
+	/*! Optional server name indicator. */
+	char *sni;
+} tls_params_t;
+
+/*! \brief TLS context. */
+typedef struct {
+	/*! TLS handshake timeout. */
+	int wait;
+	/*! Socket descriptor. */
+	int sockfd;
+	/*! TLS parameters. */
+	const tls_params_t *params;
+	/*! GnuTLS session handle. */
+	gnutls_session_t session;
+	/*! GnuTLS credentials handle. */
+	gnutls_certificate_credentials_t credentials;
+} tls_ctx_t;
+
+void tls_params_init(tls_params_t *params);
+int tls_params_copy(tls_params_t *dst, const tls_params_t *src);
+void tls_params_clean(tls_params_t *params);
+
+int tls_ctx_init(tls_ctx_t *ctx, const tls_params_t *params, int wait);
+int tls_ctx_connect(tls_ctx_t *ctx, int sockfd, const char *remote);
+int tls_ctx_send(tls_ctx_t *ctx, const uint8_t *buf, const size_t buf_len);
+int tls_ctx_receive(tls_ctx_t *ctx, uint8_t *buf, const size_t buf_len);
+void tls_ctx_close(tls_ctx_t *ctx);
+void tls_ctx_deinit(tls_ctx_t *ctx);
+void print_tls(const tls_ctx_t *ctx);
diff --git a/src/utils/common/token.c b/src/utils/common/token.c
new file mode 100644
index 0000000..0bba3c7
--- /dev/null
+++ b/src/utils/common/token.c
@@ -0,0 +1,115 @@
+/*  Copyright (C) 2017 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "utils/common/token.h"
+#include "utils/common/msg.h"
+#include "libknot/libknot.h"
+#include "contrib/ctype.h"
+
+int tok_scan(const char* lp, const char **tbl, int *lpm)
+{
+	if (lp == NULL || tbl == NULL || *tbl == NULL || lpm == NULL) {
+		DBG_NULL;
+		return -1;
+	}
+
+	const char *prefix = lp; /* Ptr to line start. */
+	int i = 0, pl = 1;       /* Match index, prefix length. */
+	unsigned char len = 0;   /* Read length. */
+	for(;;) {
+		const char *tok = tbl[i];
+		if (*lp == '\0' || is_space(*lp)) {
+			if (tok && TOK_L(tok) == len) { /* Consumed whole w? */
+				return i; /* Identifier */
+			} else { /* Word is shorter than cmd? */
+				break;
+			}
+		}
+
+		/* Find next prefix match. */
+		++len;
+		while (tok) {
+			if (TOK_L(tok) >= len) {  /* Is prefix of current token */
+				if (*lp < tok[pl]) {  /* Terminate early. */
+					tok = NULL;
+					break; /* No match could be found. */
+				}
+				if (*lp == tok[pl]) { /* Match */
+					if(lpm) *lpm = i;
+					++pl;
+					break;
+				}
+			}
+
+			/* No early cut, no match - seek next. */
+			while ((tok = tbl[++i]) != NULL) {
+				if (TOK_L(tok) >= len &&
+				    memcmp(TOK_S(tok), prefix, len) == 0) {
+					break;
+				}
+			}
+		}
+
+		if (tok == NULL) {
+			break; /* All tokens exhausted. */
+		} else {
+			++lp;  /* Next char */
+		}
+	}
+
+	return -1;
+}
+
+int tok_find(const char *lp, const char **tbl)
+{
+	if (lp == NULL || tbl == NULL || *tbl == NULL) {
+		DBG_NULL;
+		return KNOT_EINVAL;
+	}
+
+	int lpm = -1;
+	int bp = 0;
+	if ((bp = tok_scan(lp, tbl, &lpm)) < 0) {
+		if (lpm > -1) {
+			ERR("unexpected literal: '%s', did you mean '%s' ?\n",
+			    lp, TOK_S(tbl[lpm]));
+		} else {
+			ERR("unexpected literal: '%s'\n", lp);
+		}
+
+		return KNOT_EPARSEFAIL;
+	}
+
+	return bp;
+}
+
+const char *tok_skipspace(const char *lp)
+{
+	if (lp == NULL) {
+		DBG_NULL;
+		return NULL;
+	}
+
+	while (is_space(*lp)) {
+		lp += 1;
+	}
+
+	return lp;
+}
diff --git a/src/utils/common/token.h b/src/utils/common/token.h
new file mode 100644
index 0000000..b4d33d2
--- /dev/null
+++ b/src/utils/common/token.h
@@ -0,0 +1,77 @@
+/*  Copyright (C) 2011 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+/*!
+ * \file token.h
+ *
+ * \author Marek Vavrusa <marek.vavrusa@nic.cz>
+ *
+ * \brief String tokenizer and simple scanner.
+ *
+ * \addtogroup knot_utils
+ * @{
+ */
+
+#pragma once
+
+#include <stdio.h>
+
+/*!
+ * \brief Example of token table:
+ *
+ * \warning Table _must_ be lexicographically ordered.
+ *
+ * const char *tok_tbl[] = {
+ * // LEN  STRING
+ *   "\x4" "abcd",
+ *   "\x5" "class",
+ *   NULL // END
+ * }
+ */
+/*! \brief String part of the token. */
+#define TOK_S(x) ((x)+1)
+/*! \brief Len of the token. */
+#define TOK_L(x) ((unsigned char)(x)[0])
+
+/*!
+ * \brief Scan for matching token described by a match table.
+ *
+ * Table consists of strings, prefixed with 1B length.
+ *
+ * \param lp Pointer to current line.
+ * \param tbl Match description table.
+ * \param lpm Pointer to longest prefix match.
+ * \retval index to matching record.
+ * \retval -1 if no match is found, lpm may be set to longest prefix match.
+ */
+int tok_scan(const char* lp, const char **tbl, int *lpm);
+
+/*!
+ * \brief Find token from table in a line buffer.
+ * \param lp Pointer to current line.
+ * \param tbl Match description table.
+ * \retval index to matching record.
+ * \retval error code if no match is found
+ */
+int tok_find(const char *lp, const char **tbl);
+
+/*!
+ * \brief Return pointer to next non-blank character.
+ * \param lp Pointer to current line.
+ * \return ptr to next non-blank character.
+ */
+const char *tok_skipspace(const char *lp);
+
+/*! @} */