diff --git a/include/osmocom/abis/ipa.h b/include/osmocom/abis/ipa.h
index 7b5b1e8..69888f5 100644
--- a/include/osmocom/abis/ipa.h
+++ b/include/osmocom/abis/ipa.h
@@ -20,10 +20,10 @@
 	enum ipa_link_state	state;
 	const char		*addr;
 	uint16_t		port;
-	int (*process)(struct ipa_link *link, struct msgb *msg);
+	int (*cb)(struct ipa_link *link, struct msgb *msg);
 };
 
-struct ipa_link *ipa_client_link_create(void *ctx, const char *addr, uint16_t port);
+struct ipa_link *ipa_client_link_create(void *ctx, struct e1inp_line *line, const char *addr, uint16_t port, int (*cb)(struct ipa_link *link, struct msgb *msgb));
 void ipa_client_link_destroy(struct ipa_link *link);
 
 int ipa_client_link_open(struct ipa_link *link);
diff --git a/src/input/hsl.c b/src/input/hsl.c
index cb1aa51..f8c009e 100644
--- a/src/input/hsl.c
+++ b/src/input/hsl.c
@@ -302,6 +302,12 @@
         return ret;
 }
 
+static int hsl_bts_process(struct ipa_link *link, struct msgb *msg)
+{
+	/* XXX: not implemented yet. */
+	return 0;
+}
+
 static int hsl_line_update(struct e1inp_line *line,
 			   enum e1inp_line_role role, const char *addr)
 {
@@ -331,7 +337,8 @@
 
 		LOGP(DINP, LOGL_NOTICE, "enabling hsl BTS mode\n");
 
-		link = ipa_client_link_create(tall_hsl_ctx, addr, HSL_TCP_PORT);
+		link = ipa_client_link_create(tall_hsl_ctx, line, addr,
+						HSL_TCP_PORT, hsl_bts_process);
 		if (link == NULL) {
 			LOGP(DINP, LOGL_ERROR, "cannot create BTS link: %s\n",
 				strerror(errno));
diff --git a/src/input/ipa.c b/src/input/ipa.c
index 7318e07..536490e 100644
--- a/src/input/ipa.c
+++ b/src/input/ipa.c
@@ -113,8 +113,8 @@
 		ipa_client_retry(link);
 		return;
 	}
-	if (link->process)
-		link->process(link, msg);
+	if (link->cb)
+		link->cb(link, msg);
 }
 
 static void ipa_client_write(struct ipa_link *link)
@@ -177,7 +177,9 @@
 static void ipa_link_timer_cb(void *data);
 
 struct ipa_link *
-ipa_client_link_create(void *ctx, const char *addr, uint16_t port)
+ipa_client_link_create(void *ctx, struct e1inp_line *line,
+		       const char *addr, uint16_t port,
+		       int (*cb)(struct ipa_link *link, struct msgb *msgb))
 {
 	struct ipa_link *ipa_link;
 
@@ -193,6 +195,8 @@
 	ipa_link->timer.data = ipa_link;
 	ipa_link->addr = talloc_strdup(ipa_link, addr);
 	ipa_link->port = port;
+	ipa_link->cb = cb;
+	ipa_link->line = line;
 
 	return ipa_link;
 }
diff --git a/src/input/ipaccess.c b/src/input/ipaccess.c
index 71db51d..19e5a53 100644
--- a/src/input/ipaccess.c
+++ b/src/input/ipaccess.c
@@ -428,6 +428,56 @@
 	return 0;
 }
 
+static int ipaccess_bts_cb(struct ipa_link *link, struct msgb *msg)
+{
+	struct ipaccess_head *hh = (struct ipaccess_head *) msg->data;
+	struct e1inp_ts *e1i_ts = NULL;
+	struct e1inp_sign_link *sign_link;
+
+	/* special handling for IPA CCM. */
+	if (hh->proto == IPAC_PROTO_IPACCESS) {
+		uint8_t msg_type = *(msg->l2h);
+
+		/* ping, pong and acknowledgment cases. */
+		ipaccess_rcvmsg_base(msg, &link->ofd);
+
+		/* this is a request for identification from the BSC. */
+		if (msg_type == IPAC_MSGT_ID_GET) {
+			LOGP(DINP, LOGL_NOTICE, "received ID get\n");
+			if (!link->line->ops.sign_link_up) {
+				LOGP(DINP, LOGL_ERROR, "Fix your application, "
+					"no action set if the signalling link "
+					"becomes ready\n");
+				return -EINVAL;
+			}
+			link->line->ops.sign_link_up(msg, link->line);
+		}
+		return 0;
+	} else if (link->port == IPA_TCP_PORT_OML)
+		e1i_ts = &link->line->ts[0];
+	else if (link->port == IPA_TCP_PORT_RSL)
+		e1i_ts = &link->line->ts[1];
+
+	/* look up for some existing signaling link. */
+	sign_link = e1inp_lookup_sign_link(e1i_ts, hh->proto, 0);
+	if (sign_link == NULL) {
+		LOGP(DINP, LOGL_ERROR, "no matching signalling link for "
+			"hh->proto=0x%02x\n", hh->proto);
+		msgb_free(msg);
+		return -EIO;
+	}
+	msg->dst = sign_link;
+
+	/* XXX better use e1inp_ts_rx? */
+	if (!link->line->ops.sign_link) {
+		LOGP(DINP, LOGL_ERROR, "Fix your application, "
+			"no action set for signalling messages.\n");
+		return -ENOENT;
+	}
+	link->line->ops.sign_link(msg, sign_link);
+	return 0;
+}
+
 static int ipaccess_line_update(struct e1inp_line *line,
 				enum e1inp_line_role role, const char *addr)
 {
@@ -473,8 +523,9 @@
 
 		LOGP(DINP, LOGL_NOTICE, "enabling ipaccess BTS mode\n");
 
-		link = ipa_client_link_create(tall_ipa_ctx,
-						addr, IPA_TCP_PORT_OML);
+		link = ipa_client_link_create(tall_ipa_ctx, line,
+					      addr, IPA_TCP_PORT_OML,
+					      ipaccess_bts_cb);
 		if (link == NULL) {
 			LOGP(DINP, LOGL_ERROR, "cannot create OML "
 				"BTS link: %s\n", strerror(errno));
@@ -487,8 +538,9 @@
 			ipa_client_link_destroy(link);
 			return -EIO;
 		}
-		rsl_link = ipa_client_link_create(tall_ipa_ctx,
-						  addr, IPA_TCP_PORT_RSL);
+		rsl_link = ipa_client_link_create(tall_ipa_ctx, line,
+						  addr, IPA_TCP_PORT_RSL,
+						  ipaccess_bts_cb);
 		if (rsl_link == NULL) {
 			LOGP(DINP, LOGL_ERROR, "cannot create RSL "
 				"BTS link: %s\n", strerror(errno));