nat: Extract the message re-writing from the utils to a dedicated file

Move the code around to make it more clear what the routines should do.

4 files changed, 630 insertions, 590 deletions

diff --git a/openbsc/src/osmo-bsc_nat/Makefile.am b/openbsc/src/osmo-bsc_nat/Makefile.am
index d5b06da6a..8d9f73237 100644
--- a/openbsc/src/osmo-bsc_nat/Makefile.am
+++ b/openbsc/src/osmo-bsc_nat/Makefile.am
@@ -6,7 +6,7 @@ bin_PROGRAMS = osmo-bsc_nat
 
 
 osmo_bsc_nat_SOURCES = bsc_filter.c bsc_mgcp_utils.c bsc_nat.c bsc_nat_utils.c \
-		  bsc_nat_vty.c bsc_sccp.c bsc_ussd.c bsc_nat_ctrl.c
+		  bsc_nat_vty.c bsc_sccp.c bsc_ussd.c bsc_nat_ctrl.c bsc_nat_rewrite.c
 osmo_bsc_nat_LDADD = $(top_builddir)/src/libcommon/libcommon.a \
 		$(top_builddir)/src/libmgcp/libmgcp.a \
 		$(top_builddir)/src/libbsc/libbsc.a \
diff --git a/openbsc/src/osmo-bsc_nat/bsc_nat_rewrite.c b/openbsc/src/osmo-bsc_nat/bsc_nat_rewrite.c
new file mode 100644
index 000000000..79f03c2e8
--- /dev/null
+++ b/openbsc/src/osmo-bsc_nat/bsc_nat_rewrite.c
@@ -0,0 +1,628 @@
+/*
+ * Message rewriting functionality
+ */
+/*
+ * (C) 2010-2011 by Holger Hans Peter Freyther <zecke@selfish.org>
+ * (C) 2010-2011 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 <osmocom/core/linuxlist.h>
+#include <osmocom/core/talloc.h>
+#include <osmocom/gsm/gsm0808.h>
+
+#include <osmocom/gsm/protocol/gsm_08_08.h>
+#include <osmocom/gsm/protocol/gsm_04_11.h>
+
+#include <osmocom/sccp/sccp.h>
+
+static char *match_and_rewrite_number(void *ctx, const char *number,
+				      const char *imsi,
+				      struct llist_head *list)
+{
+	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)
+			new_number = talloc_asprintf(ctx, "%s%s",
+					entry->replace,
+					&number[matches[1].rm_so]);
+		if (new_number)
+			break;
+	}
+
+	return new_number;
+}
+
+static char *rewrite_non_international(struct bsc_nat *nat, void *ctx, const char *imsi,
+				       struct gsm_mncc_number *called)
+{
+	if (llist_empty(&nat->num_rewr))
+		return NULL;
+
+	if (called->plan != 1)
+		return NULL;
+	if (called->type == 1)
+		return NULL;
+
+	return match_and_rewrite_number(ctx, called->number,
+					imsi, &nat->num_rewr);
+}
+
+
+/**
+ * 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 = NULL;
+	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 */
+	new_number = rewrite_non_international(nat, msg, imsi, &called);
+
+	if (!new_number) {
+		LOGP(DNAT, LOGL_DEBUG, "No IMSI match found, returning message.\n");
+		return NULL;
+	}
+
+	if (strlen(new_number) > sizeof(called.number)) {
+		LOGP(DNAT, LOGL_ERROR, "Number is too long for structure.\n");
+		talloc_free(new_number);
+		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(DNAT, LOGL_ERROR, "Failed to allocate.\n");
+		talloc_free(new_number);
+		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 */
+	if (strncmp(new_number, "00", 2) == 0) {
+		called.type = 1;
+		strncpy(called.number, new_number + 2, sizeof(called.number));
+	} else {
+		strncpy(called.number, new_number, sizeof(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);
+	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);
+}
+
+/**
+ * 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 = hdr48->proto_discr & 0x0f;
+	msg_type = hdr48->msg_type & 0xbf;
+
+	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;
+	}
+
+	ipaccess_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,
+				"Allication 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;
+		}
+
+		/* 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);
+	}
+}
diff --git a/openbsc/src/osmo-bsc_nat/bsc_nat_utils.c b/openbsc/src/osmo-bsc_nat/bsc_nat_utils.c
index 96b937c2b..c1c233bfa 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_nat_utils.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_nat_utils.c
@@ -782,592 +782,3 @@ int bsc_write_cb(struct osmo_fd *bfd, struct msgb *msg)
 	return rc;
 }
 
-static char *match_and_rewrite_number(void *ctx, const char *number,
-				      const char *imsi,
-				      struct llist_head *list)
-{
-	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)
-			new_number = talloc_asprintf(ctx, "%s%s",
-					entry->replace,
-					&number[matches[1].rm_so]);
-		if (new_number)
-			break;
-	}
-
-	return new_number;
-}
-
-static char *rewrite_non_international(struct bsc_nat *nat, void *ctx, const char *imsi,
-				       struct gsm_mncc_number *called)
-{
-	if (llist_empty(&nat->num_rewr))
-		return NULL;
-
-	if (called->plan != 1)
-		return NULL;
-	if (called->type == 1)
-		return NULL;
-
-	return match_and_rewrite_number(ctx, called->number,
-					imsi, &nat->num_rewr);
-}
-
-
-/**
- * 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 = NULL;
-	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 */
-	new_number = rewrite_non_international(nat, msg, imsi, &called);
-
-	if (!new_number) {
-		LOGP(DNAT, LOGL_DEBUG, "No IMSI match found, returning message.\n");
-		return NULL;
-	}
-
-	if (strlen(new_number) > sizeof(called.number)) {
-		LOGP(DNAT, LOGL_ERROR, "Number is too long for structure.\n");
-		talloc_free(new_number);
-		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(DNAT, LOGL_ERROR, "Failed to allocate.\n");
-		talloc_free(new_number);
-		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 */
-	if (strncmp(new_number, "00", 2) == 0) {
-		called.type = 1;
-		strncpy(called.number, new_number + 2, sizeof(called.number));
-	} else {
-		strncpy(called.number, new_number, sizeof(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);
-	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);
-}
-
-/**
- * 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 = hdr48->proto_discr & 0x0f;
-	msg_type = hdr48->msg_type & 0xbf;
-
-	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;
-	}
-
-	ipaccess_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,
-				"Allication 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;
-		}
-
-		/* 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);
-	}
-}
diff --git a/openbsc/tests/bsc-nat/Makefile.am b/openbsc/tests/bsc-nat/Makefile.am
index 6c6f4337c..e9fcb41ad 100644
--- a/openbsc/tests/bsc-nat/Makefile.am
+++ b/openbsc/tests/bsc-nat/Makefile.am
@@ -10,6 +10,7 @@ bsc_nat_test_SOURCES = bsc_nat_test.c \
 			$(top_srcdir)/src/osmo-bsc_nat/bsc_filter.c \
 			$(top_srcdir)/src/osmo-bsc_nat/bsc_sccp.c \
 			$(top_srcdir)/src/osmo-bsc_nat/bsc_nat_utils.c \
+			$(top_srcdir)/src/osmo-bsc_nat/bsc_nat_rewrite.c \
 			$(top_srcdir)/src/osmo-bsc_nat/bsc_mgcp_utils.c
 bsc_nat_test_LDADD = $(top_builddir)/src/libbsc/libbsc.a \
 			$(top_srcdir)/src/libmgcp/libmgcp.a \