From 15a7ff83de3723ea94176183ef99471b52114741 Mon Sep 17 00:00:00 2001
From: Josh Bleecher Snyder <josh@tailscale.com>
Date: Mon, 24 May 2021 14:31:24 -0700
Subject: [PATCH] internal/deephash: remove netaddr special cases
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All netaddr types that we are concerned with now implement AppendTo.
Use the AppendTo method if available, and remove all references to netaddr.

This is slower but cleaner, and more readily re-usable by others.

name              old time/op    new time/op    delta
Hash-8              12.6µs ± 0%    14.8µs ± 1%  +18.05%  (p=0.000 n=8+10)
HashMapAcyclic-8    21.4µs ± 1%    21.9µs ± 1%   +2.39%  (p=0.000 n=10+9)

name              old alloc/op   new alloc/op   delta
Hash-8                408B ± 0%      408B ± 0%     ~     (p=1.000 n=10+10)
HashMapAcyclic-8     1.00B ± 0%     1.00B ± 0%     ~     (all equal)

name              old allocs/op  new allocs/op  delta
Hash-8                6.00 ± 0%      6.00 ± 0%     ~     (all equal)
HashMapAcyclic-8      0.00           0.00          ~     (all equal)

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
---
 internal/deephash/deephash.go | 49 +++++++++--------------------------
 1 file changed, 12 insertions(+), 37 deletions(-)

diff --git a/internal/deephash/deephash.go b/internal/deephash/deephash.go
index f3e596144..630eddacc 100644
--- a/internal/deephash/deephash.go
+++ b/internal/deephash/deephash.go
@@ -16,7 +16,6 @@ import (
 	"strconv"
 	"sync"
 
-	"inet.af/netaddr"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/wgkey"
 )
@@ -47,14 +46,16 @@ func printTo(w *bufio.Writer, v interface{}, scratch []byte) {
 }
 
 var (
-	netaddrIPType       = reflect.TypeOf(netaddr.IP{})
-	netaddrIPPrefix     = reflect.TypeOf(netaddr.IPPrefix{})
-	netaddrIPPort       = reflect.TypeOf(netaddr.IPPort{})
 	wgkeyKeyType        = reflect.TypeOf(wgkey.Key{})
 	wgkeyPrivateType    = reflect.TypeOf(wgkey.Private{})
 	tailcfgDiscoKeyType = reflect.TypeOf(tailcfg.DiscoKey{})
+	appenderToType      = reflect.TypeOf((*appenderTo)(nil)).Elem()
 )
 
+type appenderTo interface {
+	AppendTo([]byte) []byte
+}
+
 // print hashes v into w.
 // It reports whether it was able to do so without hitting a cycle.
 func print(w *bufio.Writer, v reflect.Value, visited map[uintptr]bool, scratch []byte) (acyclic bool) {
@@ -62,42 +63,16 @@ func print(w *bufio.Writer, v reflect.Value, visited map[uintptr]bool, scratch [
 		return true
 	}
 
-	// Special case some common types.
 	if v.CanInterface() {
-		switch v.Type() {
-		case netaddrIPType:
-			scratch = scratch[:0]
-			if v.CanAddr() {
-				x := v.Addr().Interface().(*netaddr.IP)
-				scratch = x.AppendTo(scratch)
-			} else {
-				x := v.Interface().(netaddr.IP)
-				scratch = x.AppendTo(scratch)
-			}
-			w.Write(scratch)
-			return true
-		case netaddrIPPrefix:
-			scratch = scratch[:0]
-			if v.CanAddr() {
-				x := v.Addr().Interface().(*netaddr.IPPrefix)
-				scratch = x.AppendTo(scratch)
-			} else {
-				x := v.Interface().(netaddr.IPPrefix)
-				scratch = x.AppendTo(scratch)
-			}
-			w.Write(scratch)
-			return true
-		case netaddrIPPort:
-			scratch = scratch[:0]
-			if v.CanAddr() {
-				x := v.Addr().Interface().(*netaddr.IPPort)
-				scratch = x.AppendTo(scratch)
-			} else {
-				x := v.Interface().(netaddr.IPPort)
-				scratch = x.AppendTo(scratch)
-			}
+		// Use AppendTo methods, if available and cheap.
+		if v.CanAddr() && v.Type().Implements(appenderToType) {
+			a := v.Addr().Interface().(appenderTo)
+			scratch = a.AppendTo(scratch[:0])
 			w.Write(scratch)
 			return true
+		}
+		// Special case some common types.
+		switch v.Type() {
 		case wgkeyKeyType:
 			if v.CanAddr() {
 				x := v.Addr().Interface().(*wgkey.Key)