gprs: Move LLC IE length fix to BSSGP level

This commit moves the fixing code of the length field of the LLC
information element to the BSSGP patching level since that is not a
part of LLC itself.

Sponsored-by: On-Waves ehf

1 files changed, 35 insertions, 20 deletions

diff --git a/openbsc/src/gprs/gb_proxy.c b/openbsc/src/gprs/gb_proxy.c
index b41bedb18..d4b5e0e40 100644
--- a/openbsc/src/gprs/gb_proxy.c
+++ b/openbsc/src/gprs/gb_proxy.c
@@ -1252,7 +1252,7 @@ static int gbprox_patch_dtap(struct msgb *msg, uint8_t *data, size_t data_len,
 }
 
 static void gbprox_patch_llc(struct msgb *msg, uint8_t *llc, size_t llc_len,
-			     struct gbprox_peer *peer,
+			     struct gbprox_peer *peer, int *len_change,
 			     struct gbprox_parse_context *parse_ctx)
 {
 	struct gprs_llc_hdr_parsed ghp = {0};
@@ -1260,7 +1260,6 @@ static void gbprox_patch_llc(struct msgb *msg, uint8_t *llc, size_t llc_len,
 	uint8_t *data;
 	size_t data_len;
 	int fcs;
-	int len_change = 0;
 	const char *err_info = NULL;
 	int err_ctr = -1;
 	uint32_t tlli = parse_ctx->tlli;
@@ -1311,7 +1310,7 @@ static void gbprox_patch_llc(struct msgb *msg, uint8_t *llc, size_t llc_len,
 
 	parse_ctx->llc_hdr_parsed = &ghp;
 
-	rc = gbprox_patch_dtap(msg, data, data_len, peer, &len_change, parse_ctx);
+	rc = gbprox_patch_dtap(msg, data, data_len, peer, len_change, parse_ctx);
 
 	if (parse_ctx->new_ptmsi &&
 	    (parse_ctx->new_ptmsi | 0xc000) != (tlli | 0xc000) &&
@@ -1325,22 +1324,8 @@ static void gbprox_patch_llc(struct msgb *msg, uint8_t *llc, size_t llc_len,
 	}
 
 	if (rc > 0) {
-		llc_len += len_change;
-		ghp.crc_length += len_change;
-
-		/* Fix LLC IE len */
-		if (llc[-2] == BSSGP_IE_LLC_PDU && llc[-1] & 0x80) {
-			/* most probably a one byte length */
-			if (llc_len > 127) {
-				err_info = "Cannot increase size";
-				err_ctr = GBPROX_PEER_CTR_PATCH_ERR;
-				goto patch_error;
-			}
-			llc[-1] = llc_len | 0x80;
-		} else {
-			llc[-2] = (llc_len >> 8) & 0x7f;
-			llc[-1] = llc_len & 0xff;
-		}
+		llc_len += *len_change;
+		ghp.crc_length += *len_change;
 
 		/* Fix FCS */
 		fcs = gprs_llc_fcs(llc, ghp.crc_length);
@@ -1373,6 +1358,8 @@ static void gbprox_patch_bssgp_message(struct msgb *msg,
 	uint8_t pdu_type;
 	uint8_t *data;
 	size_t data_len;
+	const char *err_info = NULL;
+	int err_ctr = -1;
 
 	if (!gbcfg.core_mcc && !gbcfg.core_mnc && !gbcfg.core_apn)
 		return;
@@ -1426,6 +1413,7 @@ static void gbprox_patch_bssgp_message(struct msgb *msg,
 		uint8_t *llc = (uint8_t *)TLVP_VAL(&tp, BSSGP_IE_LLC_PDU);
 		size_t llc_len = TLVP_LEN(&tp, BSSGP_IE_LLC_PDU);
 		struct gbprox_parse_context parse_ctx = {0};
+		int len_change = 0;
 		parse_ctx.bssgp_tp = &tp;
 		parse_ctx.bud_hdr = budh;
 		parse_ctx.tlli = budh ? ntohl(budh->tlli) : 0;
@@ -1436,10 +1424,37 @@ static void gbprox_patch_bssgp_message(struct msgb *msg,
 			parse_ctx.imsi_len = TLVP_LEN(&tp, BSSGP_IE_IMSI);
 		}
 
-		gbprox_patch_llc(msg, llc, llc_len, peer, &parse_ctx);
+		gbprox_patch_llc(msg, llc, llc_len, peer, &len_change, &parse_ctx);
+
+		if (len_change) {
+			llc_len += len_change;
+
+			/* Fix LLC IE len */
+			/* TODO: This is a kludge, but the a pointer to the
+			 * start of the IE is not available here */
+			if (llc[-2] == BSSGP_IE_LLC_PDU && llc[-1] & 0x80) {
+				/* most probably a one byte length */
+				if (llc_len > 127) {
+					err_info = "Cannot increase size";
+					err_ctr = GBPROX_PEER_CTR_PATCH_ERR;
+					goto patch_error;
+				}
+				llc[-1] = llc_len | 0x80;
+			} else {
+				llc[-2] = (llc_len >> 8) & 0x7f;
+				llc[-1] = llc_len & 0xff;
+			}
+		}
 		/* Note that the tp struct might contain invalid pointers here
 		 * if the LLC field has changed its size */
 	}
+	return;
+
+patch_error:
+	OSMO_ASSERT(err_ctr >= 0);
+	rate_ctr_inc(&peer->ctrg->ctr[err_ctr]);
+	LOGP(DGPRS, LOGL_ERROR,
+	     "Failed to patch BSSGP message as requested: %s.\n", err_info);
 }
 
 /* feed a message down the NS-VC associated with the specified peer */