p2p: use errors.Is for error comparison (#24882)

Co-authored-by: Felix Lange <fjl@twurst.com>

p2p/discover/lookup.go

@@ -18,6 +18,7 @@ package discover
 
 import (
 	"context"
+	"errors"
 	"time"
 
 	"github.com/ethereum/go-ethereum/p2p/enode"
@@ -141,7 +142,7 @@ func (it *lookup) slowdown() {
 func (it *lookup) query(n *node, reply chan<- []*node) {
 	fails := it.tab.db.FindFails(n.ID(), n.IP())
 	r, err := it.queryfunc(n)
-	if err == errClosed {
+	if errors.Is(err, errClosed) {
 		// Avoid recording failures on shutdown.
 		reply <- nil
 		return

p2p/discover/v4_udp.go

@@ -328,7 +328,7 @@ func (t *UDPv4) findnode(toid enode.ID, toaddr *net.UDPAddr, target v4wire.Pubke
 	// enough nodes the reply matcher will time out waiting for the second reply, but
 	// there's no need for an error in that case.
 	err := <-rm.errc
-	if err == errTimeout && rm.reply != nil {
+	if errors.Is(err, errTimeout) && rm.reply != nil {
 		err = nil
 	}
 	return nodes, err
@@ -526,7 +526,7 @@ func (t *UDPv4) readLoop(unhandled chan<- ReadPacket) {
 			continue
 		} else if err != nil {
 			// Shut down the loop for permament errors.
-			if err != io.EOF {
+			if !errors.Is(err, io.EOF) {
 				t.log.Debug("UDP read error", "err", err)
 			}
 			return

p2p/discover/v5_udp.go

@@ -305,7 +305,7 @@ func (t *UDPv5) lookupWorker(destNode *node, target enode.ID) ([]*node, error) {
 	)
 	var r []*enode.Node
 	r, err = t.findnode(unwrapNode(destNode), dists)
-	if err == errClosed {
+	if errors.Is(err, errClosed) {
 		return nil, err
 	}
 	for _, n := range r {
@@ -623,7 +623,7 @@ func (t *UDPv5) readLoop() {
 			continue
 		} else if err != nil {
 			// Shut down the loop for permament errors.
-			if err != io.EOF {
+			if !errors.Is(err, io.EOF) {
 				t.log.Debug("UDP read error", "err", err)
 			}
 			return

p2p/discover/v5wire/encoding.go

@@ -596,7 +596,7 @@ func (c *Codec) decodeMessage(fromAddr string, head *Header, headerData, msgData
 	// Try decrypting the message.
 	key := c.sc.readKey(auth.SrcID, fromAddr)
 	msg, err := c.decryptMessage(msgData, head.Nonce[:], headerData, key)
-	if err == errMessageDecrypt {
+	if errors.Is(err, errMessageDecrypt) {
 		// It didn't work. Start the handshake since this is an ordinary message packet.
 		return &Unknown{Nonce: head.Nonce}, nil
 	}