From 9847be464a041c0f040d435dfbe595106d25541b Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Wed, 22 Sep 2021 18:56:59 +0100
Subject: [PATCH] remove dependency on the backoff library

---
 client.go | 48 +++++++++++++++++++++++-------------------------
 go.mod    |  1 -
 go.sum    |  2 --
 3 files changed, 23 insertions(+), 28 deletions(-)

diff --git a/client.go b/client.go
index d22fcc98..34b50b41 100644
--- a/client.go
+++ b/client.go
@@ -3,11 +3,11 @@ package zeroconf
 import (
 	"context"
 	"fmt"
+	"math/rand"
 	"net"
 	"strings"
 	"time"
 
-	"github.com/cenkalti/backoff/v4"
 	"github.com/miekg/dns"
 	"golang.org/x/net/ipv4"
 	"golang.org/x/net/ipv6"
@@ -365,31 +365,16 @@ func (c *client) recv(ctx context.Context, l interface{}, msgCh chan *dns.Msg) {
 // TODO: move error reporting to shutdown function as periodicQuery is called from
 // go routine context.
 func (c *client) periodicQuery(ctx context.Context, params *lookupParams) error {
-	bo := backoff.NewExponentialBackOff()
-	bo.InitialInterval = 4 * time.Second
-	bo.MaxInterval = 60 * time.Second
-	bo.MaxElapsedTime = 0
-	bo.Reset()
-
-	var timer *time.Timer
-	defer func() {
-		if timer != nil {
-			timer.Stop()
-		}
-	}()
-	for {
-		// Do periodic query.
-		if err := c.query(params); err != nil {
-			return err
-		}
-		// Backoff logic
-		wait := bo.NextBackOff()
-		if timer == nil {
-			timer = time.NewTimer(wait)
-		} else {
-			timer.Reset(wait)
-		}
+	// Do the first query immediately.
+	if err := c.query(params); err != nil {
+		return err
+	}
 
+	const maxInterval = 60 * time.Second
+	interval := 4 * time.Second
+	timer := time.NewTimer(interval)
+	defer timer.Stop()
+	for {
 		select {
 		case <-timer.C:
 			// Wait for next iteration.
@@ -403,6 +388,19 @@ func (c *client) periodicQuery(ctx context.Context, params *lookupParams) error
 			}
 			return ctx.Err()
 		}
+
+		if err := c.query(params); err != nil {
+			return err
+		}
+		// Exponential increase of the interval with jitter:
+		// the new interval will be between 1.5x and 2.5x the old interval, capped at maxInterval.
+		if interval != maxInterval {
+			interval += time.Duration(rand.Int63n(interval.Nanoseconds())) + interval/2
+			if interval > maxInterval {
+				interval = maxInterval
+			}
+		}
+		timer.Reset(interval)
 	}
 }
 
diff --git a/go.mod b/go.mod
index 76f7fafc..97770765 100644
--- a/go.mod
+++ b/go.mod
@@ -3,7 +3,6 @@ module github.com/libp2p/zeroconf/v2
 go 1.16
 
 require (
-	github.com/cenkalti/backoff/v4 v4.1.1
 	github.com/miekg/dns v1.1.41
 	golang.org/x/net v0.0.0-20210423184538-5f58ad60dda6
 	golang.org/x/sys v0.0.0-20210426080607-c94f62235c83 // indirect
diff --git a/go.sum b/go.sum
index 9f4fe9c2..72d48a5c 100644
--- a/go.sum
+++ b/go.sum
@@ -1,5 +1,3 @@
-github.com/cenkalti/backoff/v4 v4.1.1 h1:G2HAfAmvm/GcKan2oOQpBXOd2tT2G57ZnZGWa1PxPBQ=
-github.com/cenkalti/backoff/v4 v4.1.1/go.mod h1:scbssz8iZGpm3xbr14ovlUdkxfGXNInqkPWOWmG2CLw=
 github.com/miekg/dns v1.1.41 h1:WMszZWJG0XmzbK9FEmzH2TVcqYzFesusSIB41b8KHxY=
 github.com/miekg/dns v1.1.41/go.mod h1:p6aan82bvRIyn+zDIv9xYNUpwa73JcSh9BKwknJysuI=
 golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=