wgengine/magicsock: clean up, add, improve DERP logs

wgengine/magicsock/magicsock.go

@@ -7,6 +7,7 @@
 package magicsock
 
 import (
+	"bytes"
 	"context"
 	"crypto/tls"
 	"encoding/binary"
@@ -17,6 +18,7 @@ import (
 	"math/rand"
 	"net"
 	"os"
+	"sort"
 	"strconv"
 	"strings"
 	"sync"
@@ -104,7 +106,19 @@ type Conn struct {
 	activeDerp    map[int]activeDerp
 	prevDerp      map[int]*syncs.WaitGroupChan
 	derpTLSConfig *tls.Config // normally nil; used by tests
-	derpRoute     map[key.Public]derpRoute
+
+	// derpRoute contains optional alternate routes to use as an
+	// optimization instead of contacting a peer via their home
+	// DERP connection.  If they sent us a message on a different
+	// DERP connection (which should really only be on our DERP
+	// home connection, or what was once our home), then we
+	// remember that route here to optimistically use instead of
+	// creating a new DERP connection back to their home.
+	derpRoute map[key.Public]derpRoute // TODO: clean up this map sometime?
+
+	// peerLastDerp tracks which DERP node we last used to speak with a
+	// peer. It's only used to quiet logging, so we only log on change.
+	peerLastDerp map[key.Public]int // TODO: clean up this map sometime?
 }
 
 // derpRoute is a route entry for a public key, saying that a certain
@@ -135,7 +149,8 @@ func (c *Conn) addDerpPeerRoute(peer key.Public, derpID int, dc *derphttp.Client
 	if c.derpRoute == nil {
 		c.derpRoute = make(map[key.Public]derpRoute)
 	}
-	c.derpRoute[peer] = derpRoute{derpID, dc}
+	r := derpRoute{derpID, dc}
+	c.derpRoute[peer] = r
 }
 
 // DerpMagicIP is a fake WireGuard endpoint IP address that means
@@ -149,10 +164,14 @@ var derpMagicIP = net.ParseIP(DerpMagicIP).To4()
 
 // activeDerp contains fields for an active DERP connection.
 type activeDerp struct {
-	c         *derphttp.Client
-	cancel    context.CancelFunc
-	writeCh   chan<- derpWriteRequest
-	lastWrite *time.Time
+	c       *derphttp.Client
+	cancel  context.CancelFunc
+	writeCh chan<- derpWriteRequest
+	// lastWrite is the time of the last request for its write
+	// channel (currently even if there was no write).
+	// It is always non-nil and initialized to a non-zero Time[
+	lastWrite  *time.Time
+	createTime time.Time
 }
 
 // udpAddr is the key in the addrsByUDP map.
@@ -218,6 +237,7 @@ func Listen(opts Options) (*Conn, error) {
 		udpRecvCh:     make(chan udpReadResult),
 		derpTLSConfig: opts.derpTLSConfig,
 		derps:         opts.DERPs,
+		peerLastDerp:  make(map[key.Public]int),
 	}
 
 	if err := c.initialBind(); err != nil {
@@ -275,11 +295,11 @@ func (c *Conn) updateEndpoints(why string) {
 		}
 
 	}()
-	c.logf("magicsock.Conn: starting endpoint update (%s)", why)
+	c.logf("magicsock: starting endpoint update (%s)", why)
 
 	endpoints, err := c.determineEndpoints(c.connCtx)
 	if err != nil {
-		c.logf("magicsock.Conn: endpoint update (%s) failed: %v", why, err)
+		c.logf("magicsock: endpoint update (%s) failed: %v", why, err)
 		// TODO(crawshaw): are there any conditions under which
 		// we should trigger a retry based on the error here?
 		return
@@ -422,7 +442,7 @@ func (c *Conn) setNearestDERP(derpNum int) (wantDERP bool) {
 	// On change, notify all currently connected DERP servers and
 	// start connecting to our home DERP if we are not already.
 	c.myDerp = derpNum
-	c.logf("home DERP server is now %v, %v", derpNum, c.derps.ServerByID(derpNum))
+	c.logf("magicsock: home DERP server is now %v (%v)", derpNum, c.derps.ServerByID(derpNum))
 	for i, ad := range c.activeDerp {
 		go ad.c.NotePreferred(i == c.myDerp)
 	}
@@ -747,6 +767,7 @@ func (c *Conn) derpWriteChanOfAddr(addr *net.UDPAddr, peer key.Public) chan<- de
 	ad, ok := c.activeDerp[nodeID]
 	if ok {
 		*ad.lastWrite = time.Now()
+		c.setPeerLastDerpLocked(peer, nodeID, nodeID)
 		return ad.writeCh
 	}
 
@@ -759,12 +780,15 @@ func (c *Conn) derpWriteChanOfAddr(addr *net.UDPAddr, peer key.Public) chan<- de
 	if !peer.IsZero() && debugUseDerpRoute {
 		if r, ok := c.derpRoute[peer]; ok {
 			if ad, ok := c.activeDerp[r.derpID]; ok && ad.c == r.dc {
+				c.setPeerLastDerpLocked(peer, r.derpID, nodeID)
 				*ad.lastWrite = time.Now()
 				return ad.writeCh
 			}
 		}
 	}
 
+	c.logf("magicsock: adding connection to derp%v", nodeID)
+
 	if c.activeDerp == nil {
 		c.activeDerp = make(map[int]activeDerp)
 		c.prevDerp = make(map[int]*syncs.WaitGroupChan)
@@ -778,7 +802,7 @@ func (c *Conn) derpWriteChanOfAddr(addr *net.UDPAddr, peer key.Public) chan<- de
 	// so it is safe to do under the mu lock.
 	dc, err := derphttp.NewClient(c.privateKey, "https://"+derpSrv.HostHTTPS+"/derp", c.logf)
 	if err != nil {
-		c.logf("derphttp.NewClient: port %d, host %q invalid? err: %v", nodeID, derpSrv.HostHTTPS, err)
+		c.logf("derphttp.NewClient: node %d, host %q invalid? err: %v", nodeID, derpSrv.HostHTTPS, err)
 		return nil
 	}
 
@@ -793,7 +817,11 @@ func (c *Conn) derpWriteChanOfAddr(addr *net.UDPAddr, peer key.Public) chan<- de
 	ad.writeCh = ch
 	ad.cancel = cancel
 	ad.lastWrite = new(time.Time)
+	*ad.lastWrite = time.Now()
+	ad.createTime = time.Now()
 	c.activeDerp[nodeID] = ad
+	c.logActiveDerpLocked()
+	c.setPeerLastDerpLocked(peer, nodeID, nodeID)
 
 	// Build a startGate for the derp reader+writer
 	// goroutines, so they don't start running until any
@@ -810,10 +838,24 @@ func (c *Conn) derpWriteChanOfAddr(addr *net.UDPAddr, peer key.Public) chan<- de
 	go c.runDerpReader(ctx, addr, dc, wg, startGate)
 	go c.runDerpWriter(ctx, addr, dc, ch, wg, startGate)
 
-	*ad.lastWrite = time.Now()
 	return ad.writeCh
 }
 
+// c.mu must be held.
+func (c *Conn) setPeerLastDerpLocked(peer key.Public, nodeID, homeID int) {
+	if peer.IsZero() {
+		return
+	}
+	old := c.peerLastDerp[peer]
+	if old == nodeID {
+		return
+	}
+	c.peerLastDerp[peer] = nodeID
+
+	pubKey := wgcfg.Key(peer)
+	c.logf("magicsock: derp route for %x (home derp %v) changed from derp %d => %d", pubKey.ShortString(), homeID, old, nodeID)
+}
+
 // derpReadResult is the type sent by runDerpClient to ReceiveIPv4
 // when a DERP packet is available.
 //
@@ -1122,8 +1164,8 @@ func (c *Conn) SetPrivateKey(privateKey wgcfg.PrivateKey) error {
 	// Key changed. Close existing DERP connections and reconnect to home.
 	myDerp := c.myDerp
 	c.myDerp = 0
-	c.logf("magicsock private key set, rebooting connection to home DERP %d", myDerp)
-	c.closeAllDerpLocked()
+	c.logf("magicsock: private key set, rebooting connection to home DERP %d", myDerp)
+	c.closeAllDerpLocked("new-private-key")
 	go c.setNearestDERP(myDerp)
 
 	return nil
@@ -1137,41 +1179,87 @@ func (c *Conn) SetDERPEnabled(wantDerp bool) {
 
 	c.wantDerp = wantDerp
 	if !wantDerp {
-		c.closeAllDerpLocked()
+		c.closeAllDerpLocked("derp-disabled")
 	}
 }
 
 // c.mu must be held.
-func (c *Conn) closeAllDerpLocked() {
+func (c *Conn) closeAllDerpLocked(why string) {
+	if len(c.activeDerp) == 0 {
+		return // without the useless log statement
+	}
 	for i := range c.activeDerp {
-		c.closeDerpLocked(i)
+		c.closeDerpLocked(i, why)
 	}
+	c.logActiveDerpLocked()
 }
 
 // c.mu must be held.
-func (c *Conn) closeDerpLocked(node int) {
+// It is the responsibility of the caller to call logActiveDerpLocked after any set of closes.
+func (c *Conn) closeDerpLocked(node int, why string) {
 	if ad, ok := c.activeDerp[node]; ok {
-		c.logf("closing connection to derp%v", node)
+		c.logf("magicsock: closing connection to derp%v (%v), age %v", node, why, time.Since(ad.createTime).Round(time.Second))
 		go ad.c.Close()
 		ad.cancel()
 		delete(c.activeDerp, node)
 	}
 }
 
+var bufPool = sync.Pool{New: func() interface{} { return new(bytes.Buffer) }}
+
+// c.mu must be held.
+func (c *Conn) logActiveDerpLocked() {
+	buf := bufPool.Get().(*bytes.Buffer)
+	defer bufPool.Put(buf)
+	now := time.Now()
+	buf.Reset()
+	buf.WriteString(": ")
+	c.foreachActiveDerpSortedLocked(func(node int, ad activeDerp) {
+		fmt.Fprintf(buf, "derp%d=cr%v,wr%v ", node, simpleDur(now.Sub(ad.createTime)), simpleDur(now.Sub(*ad.lastWrite)))
+	})
+	var details []byte
+	if buf.Len() > len(": ") {
+		details = bytes.TrimSpace(buf.Bytes())
+	}
+	c.logf("magicsock: %v active derp conns%s", len(c.activeDerp), details)
+}
+
+// c.mu must be held.
+func (c *Conn) foreachActiveDerpSortedLocked(fn func(nodeID int, ad activeDerp)) {
+	if len(c.activeDerp) < 2 {
+		for id, ad := range c.activeDerp {
+			fn(id, ad)
+		}
+		return
+	}
+	ids := make([]int, 0, len(c.activeDerp))
+	for id := range c.activeDerp {
+		ids = append(ids, id)
+	}
+	sort.Ints(ids)
+	for _, id := range ids {
+		fn(id, c.activeDerp[id])
+	}
+}
+
 func (c *Conn) cleanStaleDerp() {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 	const inactivityTime = 60 * time.Second
 	tooOld := time.Now().Add(-inactivityTime)
+	dirty := false
 	for i, ad := range c.activeDerp {
 		if i == c.myDerp {
 			continue
 		}
 		if ad.lastWrite.Before(tooOld) {
-			c.logf("closing stale DERP connection to derp%v", i)
-			c.closeDerpLocked(i)
+			c.closeDerpLocked(i, "idle")
+			dirty = true
 		}
 	}
+	if dirty {
+		c.logActiveDerpLocked()
+	}
 }
 
 // DERPs reports the number of active DERP connections.
@@ -1198,7 +1286,7 @@ func (c *Conn) Close() error {
 
 	c.closed = true
 	c.connCtxCancel()
-	c.closeAllDerpLocked()
+	c.closeAllDerpLocked("conn-close")
 	if c.pconn6 != nil {
 		c.pconn6.Close()
 	}
@@ -1687,3 +1775,14 @@ func (c *RebindingUDPConn) WriteTo(b []byte, addr net.Addr) (int, error) {
 		return n, err
 	}
 }
+
+// simpleDur rounds d such that it stringifies to something short.
+func simpleDur(d time.Duration) time.Duration {
+	if d < time.Second {
+		return d.Round(time.Millisecond)
+	}
+	if d < time.Minute {
+		return d.Round(time.Second)
+	}
+	return d.Round(time.Minute)
+}