From 56a866c46e19233cebda59342d0cbf06f2fb22c0 Mon Sep 17 00:00:00 2001
From: Kenny Barlee <kbarlee@users.noreply.github.com>
Date: Wed, 9 Sep 2020 13:28:19 +0100
Subject: [PATCH] Fix for SGWC and SMF round robin selection - select only PFCP
 associated SGWU/UPF nodes (#556)

---
 src/sgwc/context.c | 40 +++++++++++++++++++++++++++++-----------
 src/smf/context.c  | 40 +++++++++++++++++++++++++++++-----------
 2 files changed, 58 insertions(+), 22 deletions(-)

diff --git a/src/sgwc/context.c b/src/sgwc/context.c
index f442e9283..54436051b 100644
--- a/src/sgwc/context.c
+++ b/src/sgwc/context.c
@@ -451,19 +451,37 @@ static ogs_pfcp_node_t *selected_sgwu_node(
     ogs_assert(current);
     ogs_assert(sess);
 
-    next = ogs_list_next(current);
-    for (node = next; node; node = ogs_list_next(node)) {
-        if (OGS_FSM_CHECK(&node->sm, sgwc_pfcp_state_associated) &&
-            compare_ue_info(node, sess) == true) return node;
+    int RR=0, selected=0;
+
+    while(!selected){
+        // continue search from current position
+        next = ogs_list_next(current);
+        for (node = next; node; node = ogs_list_next(node)) {
+            if (!RR){
+                if (OGS_FSM_CHECK(&node->sm, sgwc_pfcp_state_associated) &&
+                    compare_ue_info(node, sess) == true) return node;
+            }else{
+                if (OGS_FSM_CHECK(&node->sm, sgwc_pfcp_state_associated)) return node;
+            }
+        }
+        // cyclic search from top to current position
+        for (node = ogs_list_first(&ogs_pfcp_self()->peer_list);
+                node != next; node = ogs_list_next(node)) {
+            if (!RR){
+                if (OGS_FSM_CHECK(&node->sm, sgwc_pfcp_state_associated) &&
+                    compare_ue_info(node, sess) == true) return node;
+            }else{
+                if (OGS_FSM_CHECK(&node->sm, sgwc_pfcp_state_associated)) return node;
+            }
+        }
+        // if a round robin search has already been carried out
+        if(RR) break;
+        // re-run search in round robin mode, find and use next PFCP associated node
+        RR = 1;
     }
 
-    for (node = ogs_list_first(&ogs_pfcp_self()->peer_list);
-            node != next; node = ogs_list_next(node)) {
-        if (OGS_FSM_CHECK(&node->sm, sgwc_pfcp_state_associated) &&
-            compare_ue_info(node, sess) == true) return node;
-    }
-
-    return next ? next : ogs_list_first(&ogs_pfcp_self()->peer_list);
+    ogs_error("No SGWUs are PFCP associated");
+    return ogs_list_first(&ogs_pfcp_self()->peer_list);
 }
 
 void sgwc_sess_select_sgwu(sgwc_sess_t *sess)
diff --git a/src/smf/context.c b/src/smf/context.c
index fdddfe9c0..31bc2d357 100644
--- a/src/smf/context.c
+++ b/src/smf/context.c
@@ -635,19 +635,37 @@ static ogs_pfcp_node_t *selected_upf_node(
     ogs_assert(current);
     ogs_assert(sess);
 
-    next = ogs_list_next(current);
-    for (node = next; node; node = ogs_list_next(node)) {
-        if (OGS_FSM_CHECK(&node->sm, smf_pfcp_state_associated) &&
-            compare_ue_info(node, sess) == true) return node;
+    int RR=0, selected=0;
+
+    while(!selected){
+        // continue search from current position
+        next = ogs_list_next(current);
+        for (node = next; node; node = ogs_list_next(node)) {
+            if (!RR){
+                if (OGS_FSM_CHECK(&node->sm, smf_pfcp_state_associated) &&
+                    compare_ue_info(node, sess) == true) return node;
+            }else{
+                if (OGS_FSM_CHECK(&node->sm, smf_pfcp_state_associated)) return node;
+            }
+        }
+        // cyclic search from top to current position
+        for (node = ogs_list_first(&ogs_pfcp_self()->peer_list);
+                node != next; node = ogs_list_next(node)) {
+            if (!RR){
+                if (OGS_FSM_CHECK(&node->sm, smf_pfcp_state_associated) &&
+                    compare_ue_info(node, sess) == true) return node;
+            }else{
+                if (OGS_FSM_CHECK(&node->sm, smf_pfcp_state_associated)) return node;
+            }
+        }
+        // if a round robin search has already been carried out
+        if(RR) break;
+        // re-run search in round robin mode, find and use next PFCP associated node
+        RR = 1;
     }
 
-    for (node = ogs_list_first(&ogs_pfcp_self()->peer_list);
-            node != next; node = ogs_list_next(node)) {
-        if (OGS_FSM_CHECK(&node->sm, smf_pfcp_state_associated) &&
-            compare_ue_info(node, sess) == true) return node;
-    }
-
-    return next ? next : ogs_list_first(&ogs_pfcp_self()->peer_list);
+    ogs_error("No UPFs are PFCP associated");
+    return ogs_list_first(&ogs_pfcp_self()->peer_list);
 }
 
 void smf_sess_select_upf(smf_sess_t *sess)