From 340c151122130b987f4d9417fd29c2f85ac20a81 Mon Sep 17 00:00:00 2001
From: Trekkie Coder <trekkie@netlox.io>
Date: Thu, 29 Feb 2024 18:47:24 +0900
Subject: [PATCH] gh-558 Added some arbitration to breakout of split-brain

---
 proto/bfd.go | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/proto/bfd.go b/proto/bfd.go
index 960836edc..dbd458ac3 100644
--- a/proto/bfd.go
+++ b/proto/bfd.go
@@ -50,6 +50,7 @@ const (
 	BFDMinSysTXIntervalUs = 100000
 	BFDDflSysTXIntervalUs = 200000
 	BFDMinSysRXIntervalUs = 200000
+	BFDIncrDiscVal        = 0x10000000
 )
 
 type ConfigArgs struct {
@@ -82,6 +83,7 @@ type bfdSession struct {
 	Instance       string
 	Cxn            net.Conn
 	State          SessionState
+	CiState        string
 	MyMulti        uint8
 	RemMulti       uint8
 	MyIP           net.IP
@@ -308,6 +310,12 @@ func (b *bfdSession) RunSessionSM(raw *WireRaw) {
 			tk.LogIt(tk.LogInfo, "%s: BFD State -> UP\n", b.RemoteName)
 		}
 		b.State = BFDUp
+		if b.CiState == "MASTER" {
+			// Force reelection
+			if b.MyDisc <= b.RemDisc {
+				oldState = BFDDown
+			}
+		}
 	}
 	newState := b.State
 	b.Mutex.Unlock()
@@ -324,8 +332,8 @@ func (b *bfdSession) checkSessTimeout() {
 	if b.State == BFDUp {
 		if time.Duration(time.Since(b.LastRxTS).Microseconds()) > time.Duration(b.TimeOut) {
 			b.State = BFDDown
-			b.MyDisc = b.RemDisc + 100
-			tk.LogIt(tk.LogInfo, "%s: BFD State -> Down\n", b.RemoteName)
+			b.MyDisc = b.RemDisc + BFDIncrDiscVal
+			tk.LogIt(tk.LogInfo, "%s: BFD State -> Down (%v:%v)\n", b.RemoteName, b.MyDisc, b.RemDisc)
 		}
 	}
 	newState := b.State
@@ -344,12 +352,17 @@ func (b *bfdSession) sendStateNotification(newState, oldState SessionState, inst
 		if b.MyDisc > b.RemDisc {
 			ciState = "MASTER"
 		}
+		tk.LogIt(tk.LogInfo, "%s: State change (%v:%v)\n", b.RemoteName, b.MyDisc, b.RemDisc)
+		b.CiState = ciState
 		b.Notify.BFDSessionNotify(inst, remote, ciState)
 	} else if newState == BFDDown && oldState == BFDUp {
 		ciState := "MASTER"
+		b.CiState = ciState
 		b.Notify.BFDSessionNotify(inst, remote, ciState)
 	} else if b.RemDisc == b.MyDisc {
-		b.Notify.BFDSessionNotify(inst, remote, "NOT_DEFINED")
+		ciState := "NOT_DEFINED"
+		b.CiState = ciState
+		b.Notify.BFDSessionNotify(inst, remote, ciState)
 	}
 }