move openbsc/* to repos root

This is the first step in creating this repository from the legacy openbsc.git.

Like all other Osmocom repositories, keep the autoconf and automake files in
the repository root. openbsc.git has been the sole exception, which ends now.

Change-Id: I9c6f2a448d9cb1cc088cf1cf6918b69d7e69b4e7

1 files changed, 714 insertions, 0 deletions

diff --git a/src/osmo-bsc_nat/bsc_nat_rewrite.c b/src/osmo-bsc_nat/bsc_nat_rewrite.c
new file mode 100644
index 000000000..e7c387c22
--- /dev/null
+++ b/src/osmo-bsc_nat/bsc_nat_rewrite.c
@@ -0,0 +1,714 @@
+/*
+ * Message rewriting functionality
+ */
+/*
+ * (C) 2010-2013 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2010-2013 by On-Waves
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <openbsc/bsc_nat.h>
+#include <openbsc/bsc_nat_sccp.h>
+#include <openbsc/bsc_msc.h>
+#include <openbsc/gsm_data.h>
+#include <openbsc/debug.h>
+#include <openbsc/ipaccess.h>
+#include <openbsc/nat_rewrite_trie.h>
+
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/talloc.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/gsm/gsm0808.h>
+#include <osmocom/gsm/ipa.h>
+
+#include <osmocom/gsm/protocol/gsm_08_08.h>
+#include <osmocom/gsm/protocol/gsm_04_11.h>
+
+#include <osmocom/sccp/sccp.h>
+
+static char *trie_lookup(struct nat_rewrite *trie, const char *number,
+			regoff_t off, void *ctx)
+{
+	struct nat_rewrite_rule *rule;
+
+	if (!trie) {
+		LOGP(DCC, LOGL_ERROR,
+			"Asked to do a table lookup but no table.\n");
+		return NULL;
+	}
+
+	rule = nat_rewrite_lookup(trie, number);
+	if (!rule) {
+		LOGP(DCC, LOGL_DEBUG,
+			"Couldn't find a prefix rule for %s\n", number);
+		return NULL;
+	}
+
+	return talloc_asprintf(ctx, "%s%s", rule->rewrite, &number[off]);
+}
+
+static char *match_and_rewrite_number(void *ctx, const char *number,
+				const char *imsi, struct llist_head *list,
+				struct nat_rewrite *trie)
+{
+	struct bsc_nat_num_rewr_entry *entry;
+	char *new_number = NULL;
+
+	/* need to find a replacement and then fix it */
+	llist_for_each_entry(entry, list, list) {
+		regmatch_t matches[2];
+
+		/* check the IMSI match */
+		if (regexec(&entry->msisdn_reg, imsi, 0, NULL, 0) != 0)
+			continue;
+
+		/* this regexp matches... */
+		if (regexec(&entry->num_reg, number, 2, matches, 0) == 0
+			&& matches[1].rm_eo != -1) {
+			if (entry->is_prefix_lookup)
+				new_number = trie_lookup(trie, number,
+						matches[1].rm_so, ctx);
+			else
+				new_number = talloc_asprintf(ctx, "%s%s",
+					entry->replace,
+					&number[matches[1].rm_so]);
+		}
+
+		if (new_number)
+			break;
+	}
+
+	return new_number;
+}
+
+static char *rewrite_isdn_number(struct bsc_nat *nat, struct llist_head *rewr_list,
+				void *ctx, const char *imsi,
+				struct gsm_mncc_number *called)
+{
+	char int_number[sizeof(called->number) + 2];
+	char *number = called->number;
+
+	if (llist_empty(&nat->num_rewr)) {
+		LOGP(DCC, LOGL_DEBUG, "Rewrite rules empty.\n");
+		return NULL;
+	}
+
+	/* only ISDN plan */
+	if (called->plan != 1) {
+		LOGP(DCC, LOGL_DEBUG, "Called plan is not 1 it was %d\n",
+			called->plan);
+		return NULL;
+	}
+
+	/* international, prepend */
+	if (called->type == 1) {
+		int_number[0] = '+';
+		memcpy(&int_number[1], number, strlen(number) + 1);
+		number = int_number;
+	}
+
+	return match_and_rewrite_number(ctx, number,
+					imsi, rewr_list, nat->num_rewr_trie);
+}
+
+static void update_called_number(struct gsm_mncc_number *called,
+				const char *chosen_number)
+{
+	if (strncmp(chosen_number, "00", 2) == 0) {
+		called->type = 1;
+		osmo_strlcpy(called->number, chosen_number + 2,
+			     sizeof(called->number));
+	} else {
+		/* rewrite international to unknown */
+		if (called->type == 1)
+			called->type = 0;
+		osmo_strlcpy(called->number, chosen_number,
+			     sizeof(called->number));
+	}
+}
+
+/**
+ * Rewrite non global numbers... according to rules based on the IMSI
+ */
+static struct msgb *rewrite_setup(struct bsc_nat *nat, struct msgb *msg,
+				  struct bsc_nat_parsed *parsed, const char *imsi,
+				  struct gsm48_hdr *hdr48, const uint32_t len)
+{
+	struct tlv_parsed tp;
+	unsigned int payload_len;
+	struct gsm_mncc_number called;
+	struct msgb *out;
+	char *new_number_pre = NULL, *new_number_post = NULL, *chosen_number;
+	uint8_t *outptr;
+	const uint8_t *msgptr;
+	int sec_len;
+
+	/* decode and rewrite the message */
+	payload_len = len - sizeof(*hdr48);
+	tlv_parse(&tp, &gsm48_att_tlvdef, hdr48->data, payload_len, 0, 0);
+
+	/* no number, well let us ignore it */
+	if (!TLVP_PRESENT(&tp, GSM48_IE_CALLED_BCD))
+		return NULL;
+
+	memset(&called, 0, sizeof(called));
+	gsm48_decode_called(&called,
+			    TLVP_VAL(&tp, GSM48_IE_CALLED_BCD) - 1);
+
+	/* check if it looks international and stop */
+	LOGP(DCC, LOGL_DEBUG,
+		"Pre-Rewrite for IMSI(%s) Plan(%d) Type(%d) Number(%s)\n",
+		imsi, called.plan, called.type, called.number);
+	new_number_pre = rewrite_isdn_number(nat, &nat->num_rewr, msg, imsi, &called);
+
+	if (!new_number_pre) {
+		LOGP(DCC, LOGL_DEBUG, "No IMSI(%s) match found, returning message.\n",
+			imsi);
+		return NULL;
+	}
+
+	if (strlen(new_number_pre) > sizeof(called.number)) {
+		LOGP(DCC, LOGL_ERROR, "Number %s is too long for structure.\n",
+				new_number_pre);
+		talloc_free(new_number_pre);
+		return NULL;
+	}
+	update_called_number(&called, new_number_pre);
+
+	/* another run through the re-write engine with other rules */
+	LOGP(DCC, LOGL_DEBUG,
+		"Post-Rewrite for IMSI(%s) Plan(%d) Type(%d) Number(%s)\n",
+		imsi, called.plan, called.type, called.number);
+	new_number_post = rewrite_isdn_number(nat, &nat->num_rewr_post, msg,
+					imsi, &called);
+	chosen_number = new_number_post ? new_number_post : new_number_pre;
+
+
+	if (strlen(chosen_number) > sizeof(called.number)) {
+		LOGP(DCC, LOGL_ERROR, "Number %s is too long for structure.\n",
+			chosen_number);
+		talloc_free(new_number_pre);
+		talloc_free(new_number_post);
+		return NULL;
+	}
+
+	/*
+	 * Need to create a new message now based on the old onew
+	 * with a new number. We can sadly not patch this in place
+	 * so we will need to regenerate it.
+	 */
+
+	out = msgb_alloc_headroom(4096, 128, "changed-setup");
+	if (!out) {
+		LOGP(DCC, LOGL_ERROR, "Failed to allocate.\n");
+		talloc_free(new_number_pre);
+		talloc_free(new_number_post);
+		return NULL;
+	}
+
+	/* copy the header */
+	outptr = msgb_put(out, sizeof(*hdr48));
+	memcpy(outptr, hdr48, sizeof(*hdr48));
+
+	/* copy everything up to the number */
+	sec_len = TLVP_VAL(&tp, GSM48_IE_CALLED_BCD) - 2 - &hdr48->data[0];
+	outptr = msgb_put(out, sec_len);
+	memcpy(outptr, &hdr48->data[0], sec_len);
+
+	/* create the new number */
+	update_called_number(&called, chosen_number);
+	LOGP(DCC, LOGL_DEBUG,
+		"Chosen number for IMSI(%s) is Plan(%d) Type(%d) Number(%s)\n",
+		imsi, called.plan, called.type, called.number);
+	gsm48_encode_called(out, &called);
+
+	/* copy thre rest */
+	msgptr = TLVP_VAL(&tp, GSM48_IE_CALLED_BCD) +
+		 TLVP_LEN(&tp, GSM48_IE_CALLED_BCD);
+	sec_len = payload_len - (msgptr - &hdr48->data[0]);
+	outptr = msgb_put(out, sec_len);
+	memcpy(outptr, msgptr, sec_len);
+
+	talloc_free(new_number_pre);
+	talloc_free(new_number_post);
+	return out;
+}
+
+/**
+ * Find a new SMSC address, returns an allocated string that needs to be
+ * freed or is NULL.
+ */
+static char *find_new_smsc(struct bsc_nat *nat, void *ctx, const char *imsi,
+			   const char *smsc_addr, const char *dest_nr)
+{
+	struct bsc_nat_num_rewr_entry *entry;
+	char *new_number = NULL;
+	uint8_t dest_match = llist_empty(&nat->tpdest_match);
+
+	/* We will find a new number now */
+	llist_for_each_entry(entry, &nat->smsc_rewr, list) {
+		regmatch_t matches[2];
+
+		/* check the IMSI match */
+		if (regexec(&entry->msisdn_reg, imsi, 0, NULL, 0) != 0)
+			continue;
+
+		/* this regexp matches... */
+		if (regexec(&entry->num_reg, smsc_addr, 2, matches, 0) == 0 &&
+		    matches[1].rm_eo != -1)
+			new_number = talloc_asprintf(ctx, "%s%s",
+					entry->replace,
+					&smsc_addr[matches[1].rm_so]);
+		if (new_number)
+			break;
+	}
+
+	if (!new_number)
+		return NULL;
+
+	/*
+	 * now match the number against another list
+	 */
+	llist_for_each_entry(entry, &nat->tpdest_match, list) {
+		/* check the IMSI match */
+		if (regexec(&entry->msisdn_reg, imsi, 0, NULL, 0) != 0)
+			continue;
+
+		if (regexec(&entry->num_reg, dest_nr, 0, NULL, 0) == 0) {
+			dest_match = 1;
+			break;
+		}
+	}
+
+	if (!dest_match) {
+		talloc_free(new_number);
+		return NULL;
+	}
+
+	return new_number;
+}
+
+/**
+ * Clear the TP-SRR from the TPDU header
+ */
+static uint8_t sms_new_tpdu_hdr(struct bsc_nat *nat, const char *imsi,
+				const char *dest_nr, uint8_t hdr)
+{
+	struct bsc_nat_num_rewr_entry *entry;
+
+	/* We will find a new number now */
+	llist_for_each_entry(entry, &nat->sms_clear_tp_srr, list) {
+		/* check the IMSI match */
+		if (regexec(&entry->msisdn_reg, imsi, 0, NULL, 0) != 0)
+			continue;
+		if (regexec(&entry->num_reg, dest_nr, 0, NULL, 0) != 0)
+			continue;
+
+		/* matched phone number and imsi */
+		return hdr & ~0x20;
+	}
+
+	return hdr;
+}
+
+/**
+ * Check if we need to rewrite the number. For this SMS.
+ */
+static char *sms_new_dest_nr(struct bsc_nat *nat, void *ctx,
+			     const char *imsi, const char *dest_nr)
+{
+	return match_and_rewrite_number(ctx, dest_nr, imsi,
+					&nat->sms_num_rewr, NULL);
+}
+
+/**
+ * This is a helper for GSM 04.11 8.2.5.2 Destination address element
+ */
+void sms_encode_addr_element(struct msgb *out, const char *new_number,
+			     int format, int tp_data)
+{
+	uint8_t new_addr_len;
+	uint8_t new_addr[26];
+
+	/*
+	 * Copy the new number. We let libosmocore encode it, then set
+	 * the extension followed after the length. Depending on if
+	 * we want to write RP we will let the TLV code add the
+	 * length for us or we need to use strlen... This is not very clear
+	 * as of 03.40 and 04.11.
+	 */
+	new_addr_len = gsm48_encode_bcd_number(new_addr, ARRAY_SIZE(new_addr),
+					       1, new_number);
+	new_addr[1] = format;
+	if (tp_data) {
+		uint8_t *data = msgb_put(out, new_addr_len);
+		memcpy(data, new_addr, new_addr_len);
+		data[0] = strlen(new_number);
+	} else {
+		msgb_lv_put(out, new_addr_len - 1, new_addr + 1);
+	}
+}
+
+static struct msgb *sms_create_new(uint8_t type, uint8_t ref,
+				   struct gsm48_hdr *old_hdr48,
+				   const uint8_t *orig_addr_ptr,
+				   int orig_addr_len, const char *new_number,
+				   const uint8_t *data_ptr, int data_len,
+				   uint8_t tpdu_first_byte,
+				   const int old_dest_len, const char *new_dest_nr)
+{
+	struct gsm48_hdr *new_hdr48;
+	struct msgb *out;
+
+	/*
+	 * We need to re-create the patched structure. This is why we have
+	 * saved the above pointers.
+	 */
+	out = msgb_alloc_headroom(4096, 128, "changed-smsc");
+	if (!out) {
+		LOGP(DNAT, LOGL_ERROR, "Failed to allocate.\n");
+		return NULL;
+	}
+
+	out->l2h = out->data;
+	msgb_v_put(out, GSM411_MT_RP_DATA_MO);
+	msgb_v_put(out, ref);
+	msgb_lv_put(out, orig_addr_len, orig_addr_ptr);
+
+	sms_encode_addr_element(out, new_number, 0x91, 0);
+
+
+	/* Patch the TPDU from here on */
+
+	/**
+	 * Do we need to put a new TP-Destination-Address (TP-DA) here or
+	 * can we copy the old thing? For the TP-DA we need to find out the
+	 * new size.
+	 */
+	if (new_dest_nr) {
+		uint8_t *data, *new_size;
+
+		/* reserve the size and write the header */
+		new_size = msgb_put(out, 1);
+		out->l3h = new_size + 1;
+		msgb_v_put(out, tpdu_first_byte);
+		msgb_v_put(out, data_ptr[1]);
+
+		/* encode the new number and put it */
+		if (strncmp(new_dest_nr, "00", 2) == 0)
+			sms_encode_addr_element(out, new_dest_nr + 2, 0x91, 1);
+		else
+			sms_encode_addr_element(out, new_dest_nr, 0x81, 1);
+
+		/* Copy the rest after the TP-DS */
+		data = msgb_put(out, data_len - 2 - 1 - old_dest_len);
+		memcpy(data, &data_ptr[2 + 1 + old_dest_len], data_len - 2 - 1 - old_dest_len);
+
+		/* fill in the new size */
+		new_size[0] = msgb_l3len(out);
+	} else {
+		msgb_v_put(out, data_len);
+		msgb_tv_fixed_put(out, tpdu_first_byte, data_len - 1, &data_ptr[1]);
+	}
+
+	/* prepend GSM 04.08 header */
+	new_hdr48 = (struct gsm48_hdr *) msgb_push(out, sizeof(*new_hdr48) + 1);
+	memcpy(new_hdr48, old_hdr48, sizeof(*old_hdr48));
+	new_hdr48->data[0] = msgb_l2len(out);
+
+	return out;
+}
+
+/**
+ * Parse the SMS and check if it needs to be rewritten
+ */
+static struct msgb *rewrite_sms(struct bsc_nat *nat, struct msgb *msg,
+				struct bsc_nat_parsed *parsed, const char *imsi,
+				struct gsm48_hdr *hdr48, const uint32_t len)
+{
+	unsigned int payload_len;
+	unsigned int cp_len;
+
+	uint8_t ref;
+	uint8_t orig_addr_len, *orig_addr_ptr;
+	uint8_t dest_addr_len, *dest_addr_ptr;
+	uint8_t data_len, *data_ptr;
+	char smsc_addr[30];
+
+
+	uint8_t dest_len, orig_dest_len;
+	char _dest_nr[30];
+	char *dest_nr;
+	char *new_dest_nr;
+
+	char *new_number = NULL;
+	uint8_t tpdu_hdr;
+	struct msgb *out;
+
+	payload_len = len - sizeof(*hdr48);
+	if (payload_len < 1) {
+		LOGP(DNAT, LOGL_ERROR, "SMS too short for things. %d\n", payload_len);
+		return NULL;
+	}
+
+	cp_len = hdr48->data[0];
+	if (payload_len + 1 < cp_len) {
+		LOGP(DNAT, LOGL_ERROR, "SMS RPDU can not fit in: %d %d\n", cp_len, payload_len);
+		return NULL;
+	}
+
+	if (hdr48->data[1] != GSM411_MT_RP_DATA_MO)
+		return NULL;
+
+	if (cp_len < 5) {
+		LOGP(DNAT, LOGL_ERROR, "RD-DATA can not fit in the CP len: %d\n", cp_len);
+		return NULL;
+	}
+
+	/* RP */
+	ref = hdr48->data[2];
+	orig_addr_len = hdr48->data[3];
+	orig_addr_ptr = &hdr48->data[4];
+
+	/* the +1 is for checking if the following element has some space */
+	if (cp_len < 3 + orig_addr_len + 1) {
+		LOGP(DNAT, LOGL_ERROR, "RP-Originator addr does not fit: %d\n", orig_addr_len);
+		return NULL;
+	}
+
+	dest_addr_len = hdr48->data[3 + orig_addr_len + 1];
+	dest_addr_ptr = &hdr48->data[3 + orig_addr_len + 2];
+
+	if (cp_len < 3 + orig_addr_len + 1 + dest_addr_len + 1) {
+		LOGP(DNAT, LOGL_ERROR, "RP-Destination addr does not fit: %d\n", dest_addr_len);
+		return NULL;
+	}
+	gsm48_decode_bcd_number(smsc_addr, ARRAY_SIZE(smsc_addr), dest_addr_ptr - 1, 1);
+
+	data_len = hdr48->data[3 + orig_addr_len + 1 + dest_addr_len + 1];
+	data_ptr = &hdr48->data[3 + orig_addr_len + 1 + dest_addr_len + 2];
+
+	if (cp_len < 3 + orig_addr_len + 1 + dest_addr_len + 1 + data_len) {
+		LOGP(DNAT, LOGL_ERROR, "RP-Data does not fit: %d\n", data_len);
+		return NULL;
+	}
+
+	if (data_len < 3) {
+		LOGP(DNAT, LOGL_ERROR, "SMS-SUBMIT is too short.\n");
+		return NULL;
+	}
+
+	/* TP-PDU starts here */
+	if ((data_ptr[0] & 0x03) != GSM340_SMS_SUBMIT_MS2SC)
+		return NULL;
+
+	/*
+	 * look into the phone number. The length is in semi-octets, we will
+	 * need to add the byte for the number type as well.
+	 */
+	orig_dest_len = data_ptr[2];
+	dest_len = ((orig_dest_len + 1) / 2) + 1;
+	if (data_len < dest_len + 3 || dest_len < 2) {
+		LOGP(DNAT, LOGL_ERROR, "SMS-SUBMIT can not have TP-DestAddr.\n");
+		return NULL;
+	}
+
+	if ((data_ptr[3] & 0x80) == 0) {
+		LOGP(DNAT, LOGL_ERROR, "TP-DestAddr has extension. Not handled.\n");
+		return NULL;
+	}
+
+	if ((data_ptr[3] & 0x0F) == 0) {
+		LOGP(DNAT, LOGL_ERROR, "TP-DestAddr is of unknown type.\n");
+		return NULL;
+	}
+
+	/**
+	 * Besides of what I think I read in GSM 03.40 and 04.11 the TP-DA
+	 * contains the semi-octets as length (strlen), change it to the
+	 * the number of bytes, but then change it back.
+	 */
+	data_ptr[2] = dest_len;
+	gsm48_decode_bcd_number(_dest_nr + 2, ARRAY_SIZE(_dest_nr) - 2,
+				&data_ptr[2], 1);
+	data_ptr[2] = orig_dest_len;
+	if ((data_ptr[3] & 0x70) == 0x10) {
+		_dest_nr[0] = _dest_nr[1] = '0';
+		dest_nr = &_dest_nr[0];
+	} else {
+		dest_nr = &_dest_nr[2];
+	}
+
+	/**
+	 * Call functions to rewrite the data
+	 */
+	tpdu_hdr = sms_new_tpdu_hdr(nat, imsi, dest_nr, data_ptr[0]);
+	new_number = find_new_smsc(nat, msg, imsi, smsc_addr, dest_nr);
+	new_dest_nr = sms_new_dest_nr(nat, msg, imsi, dest_nr);
+
+	if (tpdu_hdr == data_ptr[0] && !new_number && !new_dest_nr)
+		return NULL;
+
+	out = sms_create_new(GSM411_MT_RP_DATA_MO, ref, hdr48,
+			orig_addr_ptr, orig_addr_len,
+			new_number ? new_number : smsc_addr,
+			data_ptr, data_len, tpdu_hdr,
+			dest_len, new_dest_nr);
+	talloc_free(new_number);
+	talloc_free(new_dest_nr);
+	return out;
+}
+
+struct msgb *bsc_nat_rewrite_msg(struct bsc_nat *nat, struct msgb *msg, struct bsc_nat_parsed *parsed, const char *imsi)
+{
+	struct gsm48_hdr *hdr48;
+	uint32_t len;
+	uint8_t msg_type, proto;
+	struct msgb *new_msg = NULL, *sccp;
+	uint8_t link_id;
+
+	if (!imsi || strlen(imsi) < 5)
+		return msg;
+
+	/* only care about DTAP messages */
+	if (parsed->bssap != BSSAP_MSG_DTAP)
+		return msg;
+	if (!parsed->dest_local_ref)
+		return msg;
+
+	hdr48 = bsc_unpack_dtap(parsed, msg, &len);
+	if (!hdr48)
+		return msg;
+
+	link_id = msg->l3h[1];
+	proto = gsm48_hdr_pdisc(hdr48);
+	msg_type = gsm48_hdr_msg_type(hdr48);
+
+	if (proto == GSM48_PDISC_CC && msg_type == GSM48_MT_CC_SETUP)
+		new_msg = rewrite_setup(nat, msg, parsed, imsi, hdr48, len);
+	else if (proto == GSM48_PDISC_SMS && msg_type == GSM411_MT_CP_DATA)
+		new_msg = rewrite_sms(nat, msg, parsed, imsi, hdr48, len);
+
+	if (!new_msg)
+		return msg;
+
+	/* wrap with DTAP, SCCP, then IPA. TODO: Stop copying */
+	gsm0808_prepend_dtap_header(new_msg, link_id);
+	sccp = sccp_create_dt1(parsed->dest_local_ref, new_msg->data, new_msg->len);
+	talloc_free(new_msg);
+
+	if (!sccp) {
+		LOGP(DNAT, LOGL_ERROR, "Failed to allocate.\n");
+		return msg;
+	}
+
+	ipa_prepend_header(sccp, IPAC_PROTO_SCCP);
+
+	/* the parsed hangs off from msg but it needs to survive */
+	talloc_steal(sccp, parsed);
+	msgb_free(msg);
+	return sccp;
+}
+
+static void num_rewr_free_data(struct bsc_nat_num_rewr_entry *entry)
+{
+	regfree(&entry->msisdn_reg);
+	regfree(&entry->num_reg);
+	talloc_free(entry->replace);
+}
+
+void bsc_nat_num_rewr_entry_adapt(void *ctx, struct llist_head *head,
+				  const struct osmo_config_list *list)
+{
+	struct bsc_nat_num_rewr_entry *entry, *tmp;
+	struct osmo_config_entry *cfg_entry;
+
+	/* free the old data */
+	llist_for_each_entry_safe(entry, tmp, head, list) {
+		num_rewr_free_data(entry);
+		llist_del(&entry->list);
+		talloc_free(entry);
+	}
+
+
+	if (!list)
+		return;
+
+	llist_for_each_entry(cfg_entry, &list->entry, list) {
+		char *regexp;
+		if (cfg_entry->text[0] == '+') {
+			LOGP(DNAT, LOGL_ERROR,
+				"Plus is not allowed in the number\n");
+			continue;
+		}
+
+		entry = talloc_zero(ctx, struct bsc_nat_num_rewr_entry);
+		if (!entry) {
+			LOGP(DNAT, LOGL_ERROR,
+				"Allocation of the num_rewr entry failed.\n");
+			continue;
+		}
+
+		entry->replace = talloc_strdup(entry, cfg_entry->text);
+		if (!entry->replace) {
+			LOGP(DNAT, LOGL_ERROR,
+				"Failed to copy the replacement text.\n");
+			talloc_free(entry);
+			continue;
+		}
+
+		if (strcmp("prefix_lookup", entry->replace) == 0)
+			entry->is_prefix_lookup = 1;
+
+		/* we will now build a regexp string */
+		if (cfg_entry->mcc[0] == '^') {
+			regexp = talloc_strdup(entry, cfg_entry->mcc);
+		} else {
+			regexp = talloc_asprintf(entry, "^%s%s",
+					cfg_entry->mcc[0] == '*' ?
+						"[0-9][0-9][0-9]" : cfg_entry->mcc,
+					cfg_entry->mnc[0] == '*' ?
+						"[0-9][0-9]" : cfg_entry->mnc);
+		}
+
+		if (!regexp) {
+			LOGP(DNAT, LOGL_ERROR, "Failed to create a regexp string.\n");
+			talloc_free(entry);
+			continue;
+		}
+
+		if (regcomp(&entry->msisdn_reg, regexp, 0) != 0) {
+			LOGP(DNAT, LOGL_ERROR,
+				"Failed to compile regexp '%s'\n", regexp);
+			talloc_free(regexp);
+			talloc_free(entry);
+			continue;
+		}
+
+		talloc_free(regexp);
+		if (regcomp(&entry->num_reg, cfg_entry->option, REG_EXTENDED) != 0) {
+			LOGP(DNAT, LOGL_ERROR,
+				"Failed to compile regexp '%s'\n", cfg_entry->option);
+			regfree(&entry->msisdn_reg);
+			talloc_free(entry);
+			continue;
+		}
+
+		/* we have copied the number */
+		llist_add_tail(&entry->list, head);
+	}
+}