gbproxy: Unify TLLI tracking

This patch unifies the TLLI tracking for all LLC messages. The TLLI
state handling is moved into separate functions.

Only Detach Accept messages are taken into account to release a TLLI,
which is safe but not optimal.

Sponsored-by: On-Waves ehf

1 files changed, 121 insertions, 76 deletions

diff --git a/openbsc/src/gprs/gb_proxy.c b/openbsc/src/gprs/gb_proxy.c
index 40ff8c0f9..1b3654fb0 100644
--- a/openbsc/src/gprs/gb_proxy.c
+++ b/openbsc/src/gprs/gb_proxy.c
@@ -1057,8 +1057,13 @@ static int gbprox_parse_dtap(uint8_t *data, size_t data_len,
 	case GSM48_MT_GSM_ACT_PDP_REQ:
 		return gbprox_parse_gsm_act_pdp_req(data, data_len, parse_ctx);
 
-	case GSM48_MT_GMM_DETACH_ACK:
 	case GSM48_MT_GMM_DETACH_REQ:
+		/* TODO: Check power off if !to_bss, if yes invalidate */
+		parse_ctx->llc_msg_name = "DETACH_REQ";
+		break;
+
+	case GSM48_MT_GMM_DETACH_ACK:
+		parse_ctx->llc_msg_name = "DETACH_ACK";
 		parse_ctx->invalidate_tlli = 1;
 		break;
 
@@ -1082,6 +1087,11 @@ static int allow_message_patching(struct gbproxy_peer *peer, int msg_type)
 	}
 }
 
+static void gbprox_update_state(struct gbproxy_peer *peer,
+				struct gbproxy_parse_context *parse_ctx);
+static void gbprox_update_state_after(struct gbproxy_peer *peer,
+				      struct gbproxy_parse_context *parse_ctx);
+
 static void gbprox_patch_llc(struct msgb *msg, uint8_t *llc, size_t llc_len,
 			     struct gbproxy_peer *peer, int *len_change,
 			     struct gbproxy_parse_context *parse_ctx) __attribute__((nonnull));
@@ -1095,9 +1105,6 @@ static void gbprox_patch_llc(struct msgb *msg, uint8_t *llc, size_t llc_len,
 	uint8_t *data;
 	size_t data_len;
 	int fcs;
-	const char *err_info = NULL;
-	int err_ctr = -1;
-	uint32_t tlli = parse_ctx->tlli;
 	int have_patched = 0;
 
 	/* parse LLC */
@@ -1118,12 +1125,8 @@ static void gbprox_patch_llc(struct msgb *msg, uint8_t *llc, size_t llc_len,
 	if (ghp.sapi != GPRS_SAPI_GMM)
 		return;
 
-	if (peer->cfg->core_apn && parse_ctx->to_bss && tlli && parse_ctx->imsi)
-		gbprox_register_tlli(peer, tlli,
-				     parse_ctx->imsi, parse_ctx->imsi_len);
-
 	if (ghp.cmd != GPRS_LLC_UI)
-		return;
+		goto update_tlli_mapping;
 
 	if (ghp.is_encrypted) {
 		if (patching_is_required(peer, GBPROX_PATCH_LLC_ATTACH)) {
@@ -1132,12 +1135,12 @@ static void gbprox_patch_llc(struct msgb *msg, uint8_t *llc, size_t llc_len,
 			 * so we possibly fail to patch the LLC part of the
 			 * message. */
 
-			err_info = "GMM message is encrypted";
-			err_ctr = GBPROX_PEER_CTR_PATCH_CRYPT_ERR;
-			goto patch_error;
+			rate_ctr_inc(&peer->ctrg->ctr[GBPROX_PEER_CTR_PATCH_CRYPT_ERR]);
+			LOGP(DGPRS, LOGL_ERROR,
+			     "Failed to patch BSSGP/GMM message as requested: "
+			     "GMM message is encrypted\n");
 		}
-
-		return;
+		goto update_tlli_mapping;
 	}
 
 	/* fix DTAP GMM/GSM */
@@ -1147,87 +1150,129 @@ static void gbprox_patch_llc(struct msgb *msg, uint8_t *llc, size_t llc_len,
 	parse_ctx->llc_hdr_parsed = &ghp;
 
 	rc = gbprox_parse_dtap(data, data_len, parse_ctx);
-	if (!rc)
-		return;
 
-	switch (parse_ctx->g48_hdr->msg_type) {
-	case GSM48_MT_GMM_ATTACH_REQ:
-		rate_ctr_inc(&peer->ctrg->ctr[GBPROX_PEER_CTR_ATTACH_REQS]);
-		break;
+update_tlli_mapping:
 
-	case GSM48_MT_GMM_ATTACH_REJ:
-		rate_ctr_inc(&peer->ctrg->ctr[GBPROX_PEER_CTR_ATTACH_REJS]);
-		break;
+	gbprox_update_state(peer, parse_ctx);
 
-	default:
-		break;
-	}
+	if (parse_ctx->g48_hdr &&
+	    allow_message_patching(peer, parse_ctx->g48_hdr->msg_type)) {
+		if (parse_ctx->raid_enc) {
+			gbprox_patch_raid(parse_ctx->raid_enc, peer,
+					  parse_ctx->to_bss,
+					  parse_ctx->llc_msg_name);
+			have_patched = 1;
+		}
 
-	if (parse_ctx->ptmsi_enc &&
-	    peer->cfg->core_apn && parse_ctx->to_bss && parse_ctx->imsi) {
-		/* A new TLLI (PTMSI) has been signaled in the message */
-		uint32_t new_ptmsi;
-		if (!parse_mi_tmsi(parse_ctx->ptmsi_enc, GSM48_TMSI_LEN,
-				   &new_ptmsi)) {
-			err_info = "Failed to parse new P-TMSI";
-			err_ctr = GBPROX_PEER_CTR_PATCH_ERR;
-			goto patch_error;
+		if (parse_ctx->apn_ie &&
+		    peer->cfg->core_apn &&
+		    !parse_ctx->to_bss &&
+		    gbprox_check_tlli(peer, parse_ctx->tlli)) {
+			size_t new_len;
+			gbprox_patch_apn_ie(msg,
+					    parse_ctx->apn_ie,
+					    parse_ctx->apn_ie_len, peer,
+					    &new_len, parse_ctx->llc_msg_name);
+			*len_change += (int)new_len - (int)parse_ctx->apn_ie_len;
+
+			have_patched = 1;
 		}
 
-		LOGP(DGPRS, LOGL_INFO,
-		     "Got new TLLI/PTMSI %08x (current is %08x)\n",
-		     new_ptmsi, tlli);
-		gbprox_register_tlli(peer, new_ptmsi,
-				     parse_ctx->imsi, parse_ctx->imsi_len);
-	} else if (parse_ctx->invalidate_tlli) {
-		gbprox_unregister_tlli(peer, parse_ctx->tlli);
+		if (have_patched) {
+			llc_len += *len_change;
+			ghp.crc_length += *len_change;
+
+			/* Fix FCS */
+			fcs = gprs_llc_fcs(llc, ghp.crc_length);
+			LOGP(DLLC, LOGL_DEBUG,
+			     "Updated LLC message, CRC: %06x -> %06x\n",
+			     ghp.fcs, fcs);
+
+			llc[llc_len - 3] = fcs & 0xff;
+			llc[llc_len - 2] = (fcs >> 8) & 0xff;
+			llc[llc_len - 1] = (fcs >> 16) & 0xff;
+		}
 	}
 
-	if (!allow_message_patching(peer, parse_ctx->g48_hdr->msg_type))
-		return;
+	gbprox_update_state_after(peer, parse_ctx);
 
-	if (parse_ctx->raid_enc) {
-		gbprox_patch_raid(parse_ctx->raid_enc, peer, parse_ctx->to_bss,
-				  parse_ctx->llc_msg_name);
-		have_patched = 1;
+	return;
+}
+
+static void gbprox_update_state(struct gbproxy_peer *peer,
+				struct gbproxy_parse_context *parse_ctx)
+{
+	const char *msg_name = "LLC";
+
+	if (parse_ctx->llc_msg_name)
+		msg_name = parse_ctx->llc_msg_name;
+
+	if (parse_ctx->g48_hdr) {
+		switch (parse_ctx->g48_hdr->msg_type) {
+		case GSM48_MT_GMM_ATTACH_REQ:
+			rate_ctr_inc(&peer->ctrg->ctr[GBPROX_PEER_CTR_ATTACH_REQS]);
+			break;
+
+		case GSM48_MT_GMM_ATTACH_REJ:
+			rate_ctr_inc(&peer->ctrg->ctr[GBPROX_PEER_CTR_ATTACH_REJS]);
+			break;
+
+		default:
+			break;
+		}
 	}
 
-	if (parse_ctx->apn_ie &&
-	    peer->cfg->core_apn &&
-	    !parse_ctx->to_bss &&
-	    gbprox_check_tlli(peer, parse_ctx->tlli)) {
-		size_t new_len;
-		gbprox_patch_apn_ie(msg,
-				    parse_ctx->apn_ie, parse_ctx->apn_ie_len,
-				    peer, &new_len, parse_ctx->llc_msg_name);
-		*len_change += (int)new_len - (int)parse_ctx->apn_ie_len;
-
-		have_patched = 1;
+	if (parse_ctx->tlli) {
+		LOGP(DGPRS, LOGL_DEBUG, "%s: Got TLLI %08x\n",
+		     msg_name, parse_ctx->tlli);
 	}
 
-	if (have_patched) {
-		llc_len += *len_change;
-		ghp.crc_length += *len_change;
+	if (parse_ctx->ptmsi_enc) {
+		uint32_t new_ptmsi = GSM_RESERVED_TMSI;
+		int ok;
+		ok = parse_mi_tmsi(parse_ctx->ptmsi_enc, GSM48_TMSI_LEN,
+				   &new_ptmsi);
+		LOGP(DGPRS, LOGL_DEBUG, "%s: Got new PTMSI %08x%s\n",
+		     msg_name, new_ptmsi, ok ? "" : " (parse error)");
+	}
 
-		/* Fix FCS */
-		fcs = gprs_llc_fcs(llc, ghp.crc_length);
-		LOGP(DLLC, LOGL_DEBUG, "Updated LLC message, CRC: %06x -> %06x\n",
-		     ghp.fcs, fcs);
+	if (parse_ctx->imsi) {
+		char mi_buf[200];
+		mi_buf[0] = '\0';
+		gsm48_mi_to_string(mi_buf, sizeof(mi_buf),
+				   parse_ctx->imsi, parse_ctx->imsi_len);
+		LOGP(DGPRS, LOGL_DEBUG, "%s: Got IMSI %s\n",
+		     msg_name, mi_buf);
+	}
 
-		llc[llc_len - 3] = fcs & 0xff;
-		llc[llc_len - 2] = (fcs >> 8) & 0xff;
-		llc[llc_len - 1] = (fcs >> 16) & 0xff;
+	if (parse_ctx->ptmsi_enc && parse_ctx->to_bss && parse_ctx->imsi) {
+		/* A new TLLI (PTMSI) has been signaled in the message */
+		uint32_t new_ptmsi;
+		if (!parse_mi_tmsi(parse_ctx->ptmsi_enc, GSM48_TMSI_LEN,
+				   &new_ptmsi)) {
+			LOGP(DGPRS, LOGL_ERROR,
+			     "Failed to parse new TLLI/PTMSI (current is %08x)\n",
+			     parse_ctx->tlli);
+			return;
+		}
+		LOGP(DGPRS, LOGL_INFO,
+		     "Got new TLLI/PTMSI %08x (current is %08x)\n",
+		     new_ptmsi, parse_ctx->tlli);
+		gbprox_register_tlli(peer, new_ptmsi,
+				     parse_ctx->imsi, parse_ctx->imsi_len);
+	} else if (parse_ctx->tlli && parse_ctx->imsi) {
+		gbprox_register_tlli(peer, parse_ctx->tlli,
+				     parse_ctx->imsi, parse_ctx->imsi_len);
 	}
 
 	return;
+}
 
-patch_error:
-	OSMO_ASSERT(err_ctr >= 0);
-	rate_ctr_inc(&peer->ctrg->ctr[err_ctr]);
-	LOGP(DGPRS, LOGL_ERROR,
-	     "Failed to patch BSSGP/GMM message as requested: %s.\n", err_info);
-
-	return;
+static void gbprox_update_state_after(struct gbproxy_peer *peer,
+				      struct gbproxy_parse_context *parse_ctx)
+{
+	if (parse_ctx->invalidate_tlli)
+		gbprox_unregister_tlli(peer, parse_ctx->tlli);
 }
 
 /* patch BSSGP message to use core_mcc/mnc on the SGSN side */