From b6d689d677144613a83b382d3e09b423c159f220 Mon Sep 17 00:00:00 2001
From: Pau Espin Pedrol <pespin@sysmocom.de>
Date: Mon, 17 Feb 2025 19:12:44 +0100
Subject: [PATCH] Introduce hashtable to look up gtp_tundev by local TEID

Use this hashtable while looking up for tunend based on
<access.local.teid, access.remote.teid, access.remote.addr>.
This kind of look up is used every time a session is added or removed,
which means potentially thousands of tunend sessions were being iterated
linerarly every time.

For simplification (easier/quicker hashtable key generation), reduce the
whole key presented above to a more general one based on
"access.local.teid". This is usually enough since we are anyways
allocating local TEIDs globally per tunnel without caring about remote
address.

Change-Id: Ib12ecc8ce87175071c52c0ed2217a29d901f0f05
---
 include/osmocom/upf/upf_gtp.h | 3 +++
 src/osmo-upf/upf_gtp.c        | 9 +++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/osmocom/upf/upf_gtp.h b/include/osmocom/upf/upf_gtp.h
index b4cd3df..1162861 100644
--- a/include/osmocom/upf/upf_gtp.h
+++ b/include/osmocom/upf/upf_gtp.h
@@ -24,6 +24,7 @@
 #pragma once
 
 #include <osmocom/core/linuxlist.h>
+#include <osmocom/core/hashtable.h>
 #include <osmocom/core/select.h>
 #include <osmocom/core/logging.h>
 
@@ -55,6 +56,8 @@ struct upf_gtp_dev {
 
 	/* list of struct upf_gtp_tunend */
 	struct llist_head tunnels;
+	/* hashtable of (struct upf_gtp_tunen) with key desc.access.local.teid */
+	DECLARE_HASHTABLE(tunnels_by_local_f_teid, 10);
 };
 
 /* Description of a GTP encapsulation / decapsulation.
diff --git a/src/osmo-upf/upf_gtp.c b/src/osmo-upf/upf_gtp.c
index 528937b..4cbebcd 100644
--- a/src/osmo-upf/upf_gtp.c
+++ b/src/osmo-upf/upf_gtp.c
@@ -134,6 +134,7 @@ static struct upf_gtp_dev *upf_gtp_dev_alloc(const char *name, const char *local
 		.gtpv1.ofd.fd = -1,
 	};
 	INIT_LLIST_HEAD(&dev->tunnels);
+	hash_init(dev->tunnels_by_local_f_teid);
 
 	osmo_sockaddr_str_from_str(&addr_conv, local_addr, PORT_GTP0_U);
 
@@ -318,7 +319,8 @@ int upf_gtp_genl_ensure_open()
 }
 
 struct upf_gtp_tunend {
-	struct llist_head entry;
+	struct llist_head entry; /* item in (struct upf_gtp_dev)->tunnels */
+	struct hlist_node node_by_local_f_teid; /* item in g_upf->gtp.pdrs_by_local_f_teid */
 
 	struct upf_gtp_dev *dev;
 	struct upf_tunend desc;
@@ -349,6 +351,7 @@ static int upf_gtp_tunend_destruct(struct upf_gtp_tunend *tun)
 {
 	if (tun->active)
 		upf_gtp_tunend_deactivate(tun);
+	hash_del(&tun->node_by_local_f_teid);
 	llist_del(&tun->entry);
 	return 0;
 }
@@ -369,6 +372,7 @@ static struct upf_gtp_tunend *upf_gtp_tunend_alloc(struct upf_gtp_dev *dev, cons
 		.dev = dev,
 		.desc = *desc,
 	};
+	hash_add(dev->tunnels_by_local_f_teid, &tun->node_by_local_f_teid, tun->desc.access.local.teid);
 	llist_add(&tun->entry, &dev->tunnels);
 	talloc_set_destructor(tun, upf_gtp_tunend_destruct);
 	return tun;
@@ -425,7 +429,8 @@ static struct upf_gtp_tunend *upf_gtp_dev_tunend_find(struct upf_gtp_dev *dev, c
 {
 	struct upf_gtp_tunend *tun;
 	tunend_validate(tunend);
-	llist_for_each_entry(tun, &dev->tunnels, entry) {
+
+	hash_for_each_possible(dev->tunnels_by_local_f_teid, tun, node_by_local_f_teid, tunend->access.local.teid) {
 		if (upf_gtp_tunend_cmp(tunend, &tun->desc))
 			continue;
 		return tun;