From bef9ccfa713695f3b75f41cda5ae3887980aa97d Mon Sep 17 00:00:00 2001
From: Jakob Borg <jakob@nym.se>
Date: Sun, 15 Dec 2013 16:19:45 +0100
Subject: [PATCH] Do ping check after 5 minute inactivity

---
 protocol/protocol.go | 59 +++++++++++++++++++++++++++++++++++---------
 1 file changed, 48 insertions(+), 11 deletions(-)

diff --git a/protocol/protocol.go b/protocol/protocol.go
index 20a605f93..2c35b8453 100644
--- a/protocol/protocol.go
+++ b/protocol/protocol.go
@@ -5,6 +5,7 @@ import (
 	"errors"
 	"io"
 	"sync"
+	"time"
 
 	"github.com/calmh/syncthing/buffers"
 )
@@ -40,17 +41,19 @@ type Model interface {
 }
 
 type Connection struct {
-	receiver   Model
-	reader     io.Reader
-	mreader    *marshalReader
-	writer     io.Writer
-	mwriter    *marshalWriter
-	wLock      sync.RWMutex
-	closed     bool
-	closedLock sync.RWMutex
-	awaiting   map[int]chan asyncResult
-	nextId     int
-	ID         string
+	ID          string
+	receiver    Model
+	reader      io.Reader
+	mreader     *marshalReader
+	writer      io.Writer
+	mwriter     *marshalWriter
+	wLock       sync.RWMutex
+	closed      bool
+	closedLock  sync.RWMutex
+	awaiting    map[int]chan asyncResult
+	nextId      int
+	lastReceive time.Time
+	peerLatency time.Duration
 }
 
 var ErrClosed = errors.New("Connection closed")
@@ -60,6 +63,9 @@ type asyncResult struct {
 	err error
 }
 
+const pingTimeout = 30 * time.Second
+const pingIdleTime = 5 * time.Minute
+
 func NewConnection(nodeID string, reader io.Reader, writer io.Writer, receiver Model) *Connection {
 	flrd := flate.NewReader(reader)
 	flwr, err := flate.NewWriter(writer, flate.BestSpeed)
@@ -78,6 +84,7 @@ func NewConnection(nodeID string, reader io.Reader, writer io.Writer, receiver M
 	}
 
 	go c.readerLoop()
+	go c.pingerLoop()
 
 	return &c
 }
@@ -166,6 +173,10 @@ func (c *Connection) readerLoop() {
 			break
 		}
 
+		c.wLock.Lock()
+		c.lastReceive = time.Now()
+		c.wLock.Unlock()
+
 		switch hdr.msgType {
 		case messageTypeIndex:
 			files := c.mreader.readIndex()
@@ -237,3 +248,29 @@ func (c *Connection) processRequest(msgID int) {
 		}()
 	}
 }
+
+func (c *Connection) pingerLoop() {
+	var rc = make(chan time.Duration)
+	for !c.isClosed() {
+		c.wLock.RLock()
+		lr := c.lastReceive
+		c.wLock.RUnlock()
+
+		if time.Since(lr) > pingIdleTime {
+			go func() {
+				t0 := time.Now()
+				c.Ping()
+				rc <- time.Since(t0)
+			}()
+			select {
+			case lat := <-rc:
+				c.wLock.Lock()
+				c.peerLatency = (c.peerLatency + lat) / 2
+				c.wLock.Unlock()
+			case <-time.After(pingTimeout):
+				c.close()
+			}
+		}
+		time.Sleep(time.Second)
+	}
+}