From 2c406718df23e96260b2802b49df8fcdc707c27f Mon Sep 17 00:00:00 2001
From: Tim Beatham <tcb1@st-andrews.ac.uk>
Date: Fri, 24 Nov 2023 12:37:54 +0000
Subject: [PATCH] 29-only-ping-clients-who-have-updated-their-config

Only consider clients who have updated their config when synchronising
with peers. Consider a dead time where we don't have a handshake and
a prune time when we remove them from the WireGuard configuration.
---
 pkg/automerge/automerge.go | 23 +++++++++++++++++++++--
 pkg/conf/conf.go           | 15 ++++++++++++---
 pkg/mesh/types.go          |  1 +
 3 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/pkg/automerge/automerge.go b/pkg/automerge/automerge.go
index 8188d37..9e2fc3c 100644
--- a/pkg/automerge/automerge.go
+++ b/pkg/automerge/automerge.go
@@ -58,11 +58,30 @@ func (c *CrdtMeshManager) isPeer(nodeId string) bool {
 	return nodeType.Str() == string(conf.PEER_ROLE)
 }
 
+// isAlive: checks that the node's configuration has been updated
+// since the rquired keep alive time
+func (c *CrdtMeshManager) isAlive(nodeId string) bool {
+	node, err := c.doc.Path("nodes").Map().Get(nodeId)
+
+	if err != nil || node.Kind() != automerge.KindMap {
+		return false
+	}
+
+	timestamp, err := node.Map().Get("timestamp")
+
+	if err != nil || timestamp.Kind() != automerge.KindInt64 {
+		return false
+	}
+
+	keepAliveTime := timestamp.Int64()
+	return (time.Now().Unix() - keepAliveTime) < int64(c.conf.DeadTime)
+}
+
 func (c *CrdtMeshManager) GetPeers() []string {
 	keys, _ := c.doc.Path("nodes").Map().Keys()
 
-	keys = lib.Filter(keys, func(s string) bool {
-		return c.isPeer(s)
+	keys = lib.Filter(keys, func(publicKey string) bool {
+		return c.isPeer(publicKey) && c.isAlive(publicKey)
 	})
 
 	return keys
diff --git a/pkg/conf/conf.go b/pkg/conf/conf.go
index 4afad08..8ae48c3 100644
--- a/pkg/conf/conf.go
+++ b/pkg/conf/conf.go
@@ -64,8 +64,11 @@ type WgMeshConfiguration struct {
 	KeepAliveTime int `yaml:"keepAliveTime"`
 	// Timeout number of seconds before we consider the node as dead
 	Timeout int `yaml:"timeout"`
-	// PruneTime number of seconds before we consider the 'node' as dead
+	// PruneTime number of seconds before we remove nodes that are likely to be dead
 	PruneTime int `yaml:"pruneTime"`
+	// DeadTime: number of seconds before we consider the node as dead and stop considering it
+	// when picking a random peer
+	DeadTime int `yaml:"deadTime"`
 	// Profile whether or not to include a http server that profiles the code
 	Profile bool `yaml:"profile"`
 	// StubWg whether or not to stub the WireGuard types
@@ -145,9 +148,15 @@ func ValidateConfiguration(c *WgMeshConfiguration) error {
 		}
 	}
 
-	if c.PruneTime <= 1 {
+	if c.PruneTime < 1 {
 		return &WgMeshConfigurationError{
-			msg: "Prune time cannot be <= 1",
+			msg: "Prune time cannot be < 1",
+		}
+	}
+
+	if c.DeadTime < 1 {
+		return &WgMeshConfigurationError{
+			msg: "Dead time cannot be < 1",
 		}
 	}
 
diff --git a/pkg/mesh/types.go b/pkg/mesh/types.go
index daf99b4..cd5d0ed 100644
--- a/pkg/mesh/types.go
+++ b/pkg/mesh/types.go
@@ -101,6 +101,7 @@ type MeshProvider interface {
 	// Prune: prunes all nodes that have not updated their timestamp in
 	// pruneAmount seconds
 	Prune(pruneAmount int) error
+	// GetPeers: get a list of contactable peers
 	GetPeers() []string
 }