Record session uptime (purely for the admin socket)

src/admin/admin.go

@@ -162,6 +162,7 @@ func (a *AdminSocket) Init(c *yggdrasil.Core, state *config.NodeState, log *log.
 				"bytes_sent":    s.BytesSent,
 				"bytes_recvd":   s.BytesRecvd,
 				"mtu":           s.MTU,
+				"uptime":        s.Uptime.Seconds(),
 				"was_mtu_fixed": s.WasMTUFixed,
 				"box_pub_key":   s.PublicKey,
 			}

src/yggdrasil/api.go

@@ -89,6 +89,7 @@ type Session struct {
 	BytesSent   uint64
 	BytesRecvd  uint64
 	MTU         uint16
+	Uptime      time.Duration
 	WasMTUFixed bool
 }
 
@@ -216,6 +217,7 @@ func (c *Core) GetSessions() []Session {
 				MTU:         sinfo.getMTU(),
 				BytesSent:   sinfo.bytesSent,
 				BytesRecvd:  sinfo.bytesRecvd,
+				Uptime:      time.Now().Sub(sinfo.timeOpened),
 				WasMTUFixed: sinfo.wasMTUFixed,
 			}
 			copy(session.PublicKey[:], sinfo.theirPermPub[:])

src/yggdrasil/session.go

@@ -34,6 +34,7 @@ type sessionInfo struct {
 	theirMTU       uint16                   //
 	myMTU          uint16                   //
 	wasMTUFixed    bool                     // Was the MTU fixed by a receive error?
+	timeOpened     time.Time                // Time the sessino was opened
 	time           time.Time                // Time we last received a packet
 	mtuTime        time.Time                // time myMTU was last changed
 	pingTime       time.Time                // time the first ping was sent since the last received packet
@@ -284,6 +285,7 @@ func (ss *sessions) createSession(theirPermKey *crypto.BoxPubKey) *sessionInfo {
 	sinfo.theirMTU = 1280
 	sinfo.myMTU = 1280
 	now := time.Now()
+	sinfo.timeOpened = now
 	sinfo.time = now
 	sinfo.mtuTime = now
 	sinfo.pingTime = now