From 532968d766549fc05916c38a08e11fd7f241181f Mon Sep 17 00:00:00 2001
From: Neels Janosch Hofmeyr <nhofmeyr@sysmocom.de>
Date: Mon, 8 Apr 2024 02:34:57 +0200
Subject: [PATCH] nft_kpi: add rate_ctr gtpu:ue_bytes:ul,dl

So far we have the nftables based counters for total GTP-U bytes (UL,
DL), as well as a packet count.

Add another counter for the computed UE payload bytes:
  total_bytes - packets * (20 + 8 + 8)

Related: SYS#6773
Change-Id: Ib2f0a9252715ea4b2fe9c367aa65f771357768ca
---
 include/osmocom/hnbgw/hnbgw.h   |  2 ++
 include/osmocom/hnbgw/nft_kpi.h |  3 ++-
 src/osmo-hnbgw/hnbgw.c          |  8 ++++++++
 src/osmo-hnbgw/nft_kpi.c        | 16 +++++++++++++++-
 4 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/include/osmocom/hnbgw/hnbgw.h b/include/osmocom/hnbgw/hnbgw.h
index d323bdf..c9142e9 100644
--- a/include/osmocom/hnbgw/hnbgw.h
+++ b/include/osmocom/hnbgw/hnbgw.h
@@ -139,8 +139,10 @@ enum hnb_rate_ctr {
 
 	HNB_CTR_GTPU_PACKETS_UL,
 	HNB_CTR_GTPU_TOTAL_BYTES_UL,
+	HNB_CTR_GTPU_UE_BYTES_UL,
 	HNB_CTR_GTPU_PACKETS_DL,
 	HNB_CTR_GTPU_TOTAL_BYTES_DL,
+	HNB_CTR_GTPU_UE_BYTES_DL,
 };
 
 enum hnb_stat {
diff --git a/include/osmocom/hnbgw/nft_kpi.h b/include/osmocom/hnbgw/nft_kpi.h
index 95304ce..7b3153d 100644
--- a/include/osmocom/hnbgw/nft_kpi.h
+++ b/include/osmocom/hnbgw/nft_kpi.h
@@ -6,7 +6,8 @@ struct hnb_persistent;
 
 struct nft_kpi_val {
 	uint64_t packets;
-	uint64_t bytes;
+	uint64_t total_bytes;
+	uint64_t ue_bytes;
 
 	bool handle_present;
 	int64_t handle;
diff --git a/src/osmo-hnbgw/hnbgw.c b/src/osmo-hnbgw/hnbgw.c
index a3ea265..6340d10 100644
--- a/src/osmo-hnbgw/hnbgw.c
+++ b/src/osmo-hnbgw/hnbgw.c
@@ -468,6 +468,10 @@ const struct rate_ctr_desc hnb_ctr_description[] = {
 		"gtpu:total_bytes:ul",
 		"Count of total GTP-U bytes received from the HNB, including the GTP-U/UDP/IP headers",
 	},
+	[HNB_CTR_GTPU_UE_BYTES_UL] = {
+		"gtpu:ue_bytes:ul",
+		"Assuming an IP header length of 20 bytes, GTP-U bytes received from the HNB, excluding the GTP-U/UDP/IP headers",
+	},
 	[HNB_CTR_GTPU_PACKETS_DL] = {
 		"gtpu:packets:dl",
 		"Count of GTP-U packets sent to the HNB",
@@ -476,6 +480,10 @@ const struct rate_ctr_desc hnb_ctr_description[] = {
 		"gtpu:total_bytes:dl",
 		"Count of total GTP-U bytes sent to the HNB, including the GTP-U/UDP/IP headers",
 	},
+	[HNB_CTR_GTPU_UE_BYTES_DL] = {
+		"gtpu:ue_bytes:dl",
+		"Assuming an IP header length of 20 bytes, GTP-U bytes sent to the HNB, excluding the GTP-U/UDP/IP headers",
+	},
 
 };
 
diff --git a/src/osmo-hnbgw/nft_kpi.c b/src/osmo-hnbgw/nft_kpi.c
index 2eb5496..4a9dc34 100644
--- a/src/osmo-hnbgw/nft_kpi.c
+++ b/src/osmo-hnbgw/nft_kpi.c
@@ -268,7 +268,21 @@ static void hnb_update_counters(struct hnb_persistent *hnbp, bool ul, int64_t pa
 		   &val->packets, packets);
 	update_ctr(hnbp->ctrs,
 		   ul ? HNB_CTR_GTPU_TOTAL_BYTES_UL : HNB_CTR_GTPU_TOTAL_BYTES_DL,
-		   &val->bytes, bytes);
+		   &val->total_bytes, bytes);
+
+	/* Assuming an IP header of 20 bytes, derive the GTP-U payload size:
+	 *
+	 *  [...]             \              \
+	 *  [ UDP ][ TCP ]    | UE payload   | nft reports these bytes
+	 *  [ IP ]            /              |
+	 *  -- payload --                    |
+	 *  [ GTP-U 8 bytes ]                |   \
+	 *  [ UDP 8 bytes ]                  |   | need to subtract these, ~20 + 8 + 8
+	 *  [ IP 20 bytes ]                  /   /
+	 */
+	update_ctr(hnbp->ctrs,
+		   ul ? HNB_CTR_GTPU_UE_BYTES_UL : HNB_CTR_GTPU_UE_BYTES_DL,
+		   &val->ue_bytes, bytes - OSMO_MIN(bytes, packets * (20 + 8 + 8)));
 }
 
 /* In the string section *pos .. end, find the first occurrence of after_str and return the following token, which ends