Remove unused wakers

These wakers are uselessly allocated and passed around; nothing ever
listens for notifications on them. The code here appears to be
vestigial, so removing it and allowing a nil waker to be passed seems
appropriate.

PiperOrigin-RevId: 249879320
Change-Id: Icd209fb77cc0dd4e5c49d7a9f2adc32bf88b4b71

4 files changed, 9 insertions, 24 deletions

diff --git a/pkg/tcpip/stack/linkaddrcache.go b/pkg/tcpip/stack/linkaddrcache.go
index 42b9768ae..b952ad20f 100644
--- a/pkg/tcpip/stack/linkaddrcache.go
+++ b/pkg/tcpip/stack/linkaddrcache.go
@@ -138,8 +138,10 @@ func (e *linkAddrEntry) changeState(ns entryState) {
 	e.s = ns
 }
 
-func (e *linkAddrEntry) addWaker(w *sleep.Waker) {
-	e.wakers[w] = struct{}{}
+func (e *linkAddrEntry) maybeAddWaker(w *sleep.Waker) {
+	if w != nil {
+		e.wakers[w] = struct{}{}
+	}
 }
 
 func (e *linkAddrEntry) removeWaker(w *sleep.Waker) {
@@ -217,7 +219,7 @@ func (c *linkAddrCache) get(k tcpip.FullAddress, linkRes LinkAddressResolver, lo
 			return "", nil, tcpip.ErrNoLinkAddress
 		case incomplete:
 			// Address resolution is still in progress.
-			entry.addWaker(waker)
+			entry.maybeAddWaker(waker)
 			return "", entry.done, tcpip.ErrWouldBlock
 		default:
 			panic(fmt.Sprintf("invalid cache entry state: %s", s))
@@ -230,7 +232,7 @@ func (c *linkAddrCache) get(k tcpip.FullAddress, linkRes LinkAddressResolver, lo
 
 	// Add 'incomplete' entry in the cache to mark that resolution is in progress.
 	e := c.makeAndAddEntry(k, "")
-	e.addWaker(waker)
+	e.maybeAddWaker(waker)
 
 	go c.startAddressResolution(k, linkRes, localAddr, linkEP, e.done) // S/R-SAFE: link non-savable; wakers dropped synchronously.
 
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index cc384dd3d..e2b90ef10 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -18,7 +18,6 @@ import (
 	"encoding/binary"
 	"sync"
 
-	"gvisor.googlesource.com/gvisor/pkg/sleep"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/header"
@@ -274,13 +273,8 @@ func (e *endpoint) Write(p tcpip.Payload, opts tcpip.WriteOptions) (uintptr, <-c
 	}
 
 	if route.IsResolutionRequired() {
-		waker := &sleep.Waker{}
-		if ch, err := route.Resolve(waker); err != nil {
+		if ch, err := route.Resolve(nil); err != nil {
 			if err == tcpip.ErrWouldBlock {
-				// Link address needs to be resolved.
-				// Resolution was triggered the background.
-				// Better luck next time.
-				route.RemoveWaker(waker)
 				return 0, ch, tcpip.ErrNoLinkAddress
 			}
 			return 0, nil, err
diff --git a/pkg/tcpip/transport/raw/endpoint.go b/pkg/tcpip/transport/raw/endpoint.go
index e7b383ad5..1daf5823f 100644
--- a/pkg/tcpip/transport/raw/endpoint.go
+++ b/pkg/tcpip/transport/raw/endpoint.go
@@ -29,7 +29,6 @@ package raw
 import (
 	"sync"
 
-	"gvisor.googlesource.com/gvisor/pkg/sleep"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/header"
@@ -259,13 +258,8 @@ func (ep *endpoint) finishWrite(payload tcpip.Payload, route *stack.Route) (uint
 	// network address). If that requires blocking (e.g. to use ARP),
 	// return a channel on which the caller can wait.
 	if route.IsResolutionRequired() {
-		waker := &sleep.Waker{}
-		if ch, err := route.Resolve(waker); err != nil {
+		if ch, err := route.Resolve(nil); err != nil {
 			if err == tcpip.ErrWouldBlock {
-				// Link address needs to be resolved.
-				// Resolution was triggered the background.
-				// Better luck next time.
-				route.RemoveWaker(waker)
 				return 0, ch, tcpip.ErrNoLinkAddress
 			}
 			return 0, nil, err
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index d9ca097c9..3d52a4f31 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -18,7 +18,6 @@ import (
 	"math"
 	"sync"
 
-	"gvisor.googlesource.com/gvisor/pkg/sleep"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/header"
@@ -346,12 +345,8 @@ func (e *endpoint) Write(p tcpip.Payload, opts tcpip.WriteOptions) (uintptr, <-c
 	}
 
 	if route.IsResolutionRequired() {
-		waker := &sleep.Waker{}
-		if ch, err := route.Resolve(waker); err != nil {
+		if ch, err := route.Resolve(nil); err != nil {
 			if err == tcpip.ErrWouldBlock {
-				// Link address needs to be resolved. Resolution was triggered the background.
-				// Better luck next time.
-				route.RemoveWaker(waker)
 				return 0, ch, tcpip.ErrNoLinkAddress
 			}
 			return 0, nil, err