Change in libosmocore[master]: gprs_ns2: improve handling of TLV errors on new nsvcs

[laforge]

laforge has submitted this change. ( https://gerrit.osmocom.org/c/libosmocore/+/21724 )

Change subject: gprs_ns2: improve handling of TLV errors on new nsvcs
......................................................................

gprs_ns2: improve handling of TLV errors on new nsvcs

The specification says the PDU should be ignored if the PDU type is
unknown.

Change-Id: I2992d06b37ed122b7ff315d4852e86acc936800b
---
M src/gb/gprs_ns2.c
1 file changed, 20 insertions(+), 8 deletions(-)

Approvals:
  Jenkins Builder: Verified
  laforge: Looks good to me, approved
  daniel: Looks good to me, but someone else must approve



diff --git a/src/gb/gprs_ns2.c b/src/gb/gprs_ns2.c
index 9d5a97c..49606d8 100644
--- a/src/gb/gprs_ns2.c
+++ b/src/gb/gprs_ns2.c
@@ -793,19 +793,17 @@
 	uint16_t nsvci;
 	uint16_t nsei;
 
-	int rc;
+	int rc, tlv;
 
 	if (msg->len < sizeof(struct gprs_ns_hdr))
 		return GPRS_NS2_CS_ERROR;
 
-	rc = ns2_tlv_parse(&tp, nsh->data,
+	/* parse the tlv early to allow reject status msg to
+	 * work with valid tp.
+	 * Ignore the return code until the pdu type is parsed because
+	 * an unknown pdu type should be ignored */
+	tlv = ns2_tlv_parse(&tp, nsh->data,
 			   msgb_l2len(msg) - sizeof(*nsh), 0, 0);
-	if (rc < 0) {
-		LOGP(DLNS, LOGL_ERROR, "Rx NS RESET Error %d during "
-		     "TLV Parse\n", rc);
-		/* TODO: send invalid message back */
-		return GPRS_NS2_CS_REJECTED;
-	}
 
 	switch (nsh->pdu_type) {
 	case NS_PDUT_STATUS:
@@ -849,6 +847,20 @@
 		return GPRS_NS2_CS_REJECTED;
 	}
 
+	if (tlv < 0) {
+		/* TODO: correct behaviour would checking what's wrong.
+		 * If it's an essential TLV for the PDU return NS_CAUSE_INVAL_ESSENT_IE.
+		 * Otherwise ignore the non-essential TLV. */
+		LOGP(DLNS, LOGL_ERROR, "Rx NS RESET Error %d during "
+				       "TLV Parse\n", tlv);
+		rc = reject_status_msg(msg, &tp, reject, NS_CAUSE_PROTO_ERR_UNSPEC);
+		if (rc < 0) {
+			LOGP(DLNS, LOGL_ERROR, "Failed to generate reject message (%d)\n", rc);
+			return rc;
+		}
+		return GPRS_NS2_CS_REJECTED;
+	}
+
 	if (!TLVP_PRES_LEN(&tp, NS_IE_CAUSE, 1) ||
 	    !TLVP_PRES_LEN(&tp, NS_IE_VCI, 2) || !TLVP_PRES_LEN(&tp, NS_IE_NSEI, 2)) {
 		LOGP(DLNS, LOGL_ERROR, "NS RESET Missing mandatory IE\n");

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Gerrit-Project: libosmocore
Gerrit-Branch: master
Gerrit-Change-Id: I2992d06b37ed122b7ff315d4852e86acc936800b
Gerrit-Change-Number: 21724
Gerrit-PatchSet: 3
Gerrit-Owner: lynxis lazus <lynxis at fe80.eu>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: daniel <dwillmann at sysmocom.de>
Gerrit-Reviewer: laforge <laforge at osmocom.org>
Gerrit-Reviewer: pespin <pespin at sysmocom.de>
Gerrit-MessageType: merged
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