Change in libosmocore[master]: WIP mtu support

[daniel]

daniel has uploaded this change for review. ( https://gerrit.osmocom.org/c/libosmocore/+/22447 )


Change subject: WIP mtu support
......................................................................

WIP mtu support

Change-Id: Iaf621da527ace8b3fcaa8f51f5e8b4f26fdae9b7
---
M include/osmocom/gprs/bssgp_bvc_fsm.h
M include/osmocom/gprs/gprs_bssgp2.h
M src/gb/bssgp_bvc_fsm.c
M src/gb/gprs_bssgp2.c
4 files changed, 29 insertions(+), 6 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/libosmocore refs/changes/47/22447/1

diff --git a/include/osmocom/gprs/bssgp_bvc_fsm.h b/include/osmocom/gprs/bssgp_bvc_fsm.h
index e69c205..9d37c3d 100644
--- a/include/osmocom/gprs/bssgp_bvc_fsm.h
+++ b/include/osmocom/gprs/bssgp_bvc_fsm.h
@@ -30,6 +30,7 @@
 	BSSGP_BVCFSM_E_REQ_UNBLOCK,
 	BSSGP_BVCFSM_E_REQ_RESET,	/* data: uint8_t *cause */
 	BSSGP_BVCFSM_E_REQ_FC_BVC,	/* data: struct bssgp2_flow_ctrl */
+	BSSGP_BVCFSM_E_REQ_STATUS,	/* data: struct bssgp2_status */
 };
 
 struct bssgp_bvc_fsm_ops {
@@ -64,3 +65,5 @@
 uint32_t bssgp_bvc_get_features_advertised(struct osmo_fsm_inst *fi);
 uint32_t bssgp_bvc_get_features_received(struct osmo_fsm_inst *fi);
 uint32_t bssgp_bvc_get_features_negotiated(struct osmo_fsm_inst *fi);
+
+void bssgp_bvc_fsm_set_mtu(struct osmo_fsm_inst *fi, uint16_t mtu);
\ No newline at end of file
diff --git a/include/osmocom/gprs/gprs_bssgp2.h b/include/osmocom/gprs/gprs_bssgp2.h
index bf814cb..2396bea 100644
--- a/include/osmocom/gprs/gprs_bssgp2.h
+++ b/include/osmocom/gprs/gprs_bssgp2.h
@@ -4,6 +4,9 @@
 #include <osmocom/gprs/protocol/gsm_08_18.h>
 #include <osmocom/gprs/gprs_ns2.h>
 
+/* Set a conservative MTU as default (Ethernet MTU of 1500 - IPv6 Header - UDP Header */
+#define DEFAULT_BSSGP_MTU (1500 - 40 - 8)
+
 struct bssgp2_flow_ctrl;
 struct gprs_ns2_inst;
 struct gprs_ra_id;
@@ -38,6 +41,12 @@
 	} u;
 };
 
+struct bssgp2_status {
+	uint8_t cause;
+	/* Only used if cause is "BVCI blocked" or "BVCI unknown" */
+	const uint16_t *bvci;
+	const struct msgb *orig_msg;
+};
 
 int bssgp2_nsi_tx_ptp(struct gprs_ns2_inst *nsi, uint16_t nsei, uint16_t bvci,
 		      struct msgb *msg, uint32_t lsp);
@@ -59,7 +68,7 @@
 struct msgb *bssgp2_enc_bvc_reset_ack(uint16_t bvci, const struct gprs_ra_id *ra_id, uint16_t cell_id,
 				      const uint8_t *feat_bm, const uint8_t *ext_feat_bm);
 
-struct msgb *bssgp2_enc_status(uint8_t cause, const uint16_t *bvci, const struct msgb *orig_msg);
+struct msgb *bssgp2_enc_status(uint8_t cause, const uint16_t *bvci, const struct msgb *orig_msg, uint16_t mtu);
 
 
 int bssgp2_dec_fc_bvc(struct bssgp2_flow_ctrl *fc, const struct tlv_parsed *tp);
diff --git a/src/gb/bssgp_bvc_fsm.c b/src/gb/bssgp_bvc_fsm.c
index 6de0028..8db8866 100644
--- a/src/gb/bssgp_bvc_fsm.c
+++ b/src/gb/bssgp_bvc_fsm.c
@@ -116,6 +116,8 @@
 
 	/* NSEI of the underlying NS Entity */
 	uint16_t nsei;
+	/* MTU of the underlying NS Entity */
+	uint16_t mtu;
 
 	/* BVCI of this BVC */
 	uint16_t bvci;
@@ -236,7 +238,7 @@
 	if (cause == BSSGP_CAUSE_UNKNOWN_BVCI || cause == BSSGP_CAUSE_BVCI_BLOCKED)
 		bvci = &bfp->bvci;
 
-	tx = bssgp2_enc_status(cause, bvci, rx);
+	tx = bssgp2_enc_status(cause, bvci, rx, bfp->mtu);
 
 	if (msgb_bvci(rx) == 0)
 		fi_tx_sig(fi, tx);
@@ -666,6 +668,7 @@
 	bfp->role_sgsn = role_sgsn;
 	bfp->nsei = nsei;
 	bfp->bvci = bvci;
+	bfp->mtu = DEFAULT_BSSGP_MTU;
 
 	return fi;
 }
diff --git a/src/gb/gprs_bssgp2.c b/src/gb/gprs_bssgp2.c
index 5a8d41f..5ae31e7 100644
--- a/src/gb/gprs_bssgp2.c
+++ b/src/gb/gprs_bssgp2.c
@@ -217,8 +217,9 @@
 /*! Encode BSSGP STATUS PDU as per TS 48.018 Section 10.4.14.
  *  \param[in] cause BSSGP Cause value
  *  \param[in] bvci optional BVCI - only encoded if non-NULL
- *  \param[in] msg optional message buffer containing PDU in error - only encoded if non-NULL */
-struct msgb *bssgp2_enc_status(uint8_t cause, const uint16_t *bvci, const struct msgb *orig_msg)
+ *  \param[in] msg optional message buffer containing PDU in error - only encoded if non-NULL
+ *  \param[in] mtu Maximum size the NS layer accepts as payload */
+struct msgb *bssgp2_enc_status(uint8_t cause, const uint16_t *bvci, const struct msgb *orig_msg, uint16_t mtu)
 {
 	struct msgb *msg = bssgp_msgb_alloc();
 	struct bssgp_normal_hdr *bgph;
@@ -229,12 +230,19 @@
 	bgph = (struct bssgp_normal_hdr *) msgb_put(msg, sizeof(*bgph));
 	bgph->pdu_type = BSSGP_PDUT_STATUS;
 	msgb_tvlv_put(msg, BSSGP_IE_CAUSE, 1, &cause);
+	/* FIXME: Require/encode BVCI only if cause is BVCI unknown/blocked
+	 * See 3GPP TS 48.018 Ch. 10.4.14 */
 	if (bvci) {
 		uint16_t _bvci = osmo_htons(*bvci);
 		msgb_tvlv_put(msg, BSSGP_IE_BVCI, 2, (uint8_t *) &_bvci);
 	}
-	if (orig_msg)
-		msgb_tvlv_put(msg, BSSGP_IE_PDU_IN_ERROR, msgb_bssgp_len(orig_msg), msgb_bssgph(orig_msg));
+	if (orig_msg) {
+		uint16_t len;
+		/* Calculate how long the orig_msg may be */
+		mtu = mtu - msgb_length(msg);
+		len = OSMO_MIN(msgb_bssgp_len(orig_msg), mtu);
+		msgb_tvlv_put(msg, BSSGP_IE_PDU_IN_ERROR, len, msgb_bssgph(orig_msg));
+	}
 
 	return msg;
 }

-- 
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Gerrit-Project: libosmocore
Gerrit-Branch: master
Gerrit-Change-Id: Iaf621da527ace8b3fcaa8f51f5e8b4f26fdae9b7
Gerrit-Change-Number: 22447
Gerrit-PatchSet: 1
Gerrit-Owner: daniel <dwillmann at sysmocom.de>
Gerrit-MessageType: newchange
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