From 3a983d3b3a569f5429e6d9fd57e409f5b262f551 Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@twurst.com>
Date: Fri, 13 Dec 2024 00:14:16 +0100
Subject: [PATCH] p2p: add test for dialing with DNS hostname

---
 p2p/dial.go      |  1 +
 p2p/dial_test.go | 29 +++++++++++++++++++++++++++++
 p2p/peer_test.go | 30 +++++++++++++++---------------
 3 files changed, 45 insertions(+), 15 deletions(-)

diff --git a/p2p/dial.go b/p2p/dial.go
index 606cfcd3ec..b1338c46bb 100644
--- a/p2p/dial.go
+++ b/p2p/dial.go
@@ -490,6 +490,7 @@ func (d *dialScheduler) dnsResolveHostname(n *enode.Node) (*enode.Node, error) {
 	if foundIP6.IsValid() {
 		rec.Set(enr.IPv6Addr(foundIP6))
 	}
+	rec.SetSeq(n.Seq()) // ensure seq not bumped by update
 	newNode := enode.SignNull(rec, n.ID()).WithHostname(n.Hostname())
 	d.log.Trace("Node updated from DNS lookup", "id", n.ID(), "name", n.Hostname(), "ip", newNode.IP())
 	return newNode, nil
diff --git a/p2p/dial_test.go b/p2p/dial_test.go
index 13908f11ea..f18dacce2a 100644
--- a/p2p/dial_test.go
+++ b/p2p/dial_test.go
@@ -22,6 +22,7 @@ import (
 	"fmt"
 	"math/rand"
 	"net"
+	"net/netip"
 	"reflect"
 	"sync"
 	"testing"
@@ -394,6 +395,34 @@ func TestDialSchedResolve(t *testing.T) {
 	})
 }
 
+func TestDialSchedDNSHostname(t *testing.T) {
+	t.Parallel()
+
+	config := dialConfig{
+		maxActiveDials: 1,
+		maxDialPeers:   1,
+	}
+	node := newNode(uintID(0x01), ":30303").WithHostname("node-hostname")
+	resolved := newNode(uintID(0x01), "1.2.3.4:30303").WithHostname("node-hostname")
+	runDialTest(t, config, []dialTestRound{
+		{
+			update: func(d *dialScheduler) {
+				d.dnsLookupFunc = func(ctx context.Context, network string, name string) ([]netip.Addr, error) {
+					if name != "node-hostname" {
+						t.Error("wrong hostname in DNS lookup:", name)
+					}
+					result := []netip.Addr{netip.MustParseAddr("1.2.3.4")}
+					return result, nil
+				}
+				d.addStatic(node)
+			},
+			wantNewDials: []*enode.Node{
+				resolved,
+			},
+		},
+	})
+}
+
 // -------
 // Code below here is the framework for the tests above.
 
diff --git a/p2p/peer_test.go b/p2p/peer_test.go
index 4308bbd2eb..dea72875fe 100644
--- a/p2p/peer_test.go
+++ b/p2p/peer_test.go
@@ -60,22 +60,22 @@ func uintID(i uint16) enode.ID {
 // newNode creates a node record with the given address.
 func newNode(id enode.ID, addr string) *enode.Node {
 	var r enr.Record
-	if addr != "" {
-		// Set the port if present.
-		if strings.Contains(addr, ":") {
-			hs, ps, err := net.SplitHostPort(addr)
-			if err != nil {
-				panic(fmt.Errorf("invalid address %q", addr))
-			}
-			port, err := strconv.Atoi(ps)
-			if err != nil {
-				panic(fmt.Errorf("invalid port in %q", addr))
-			}
-			r.Set(enr.TCP(port))
-			r.Set(enr.UDP(port))
-			addr = hs
+	// Set the port if present.
+	if strings.Contains(addr, ":") {
+		hs, ps, err := net.SplitHostPort(addr)
+		if err != nil {
+			panic(fmt.Errorf("invalid address %q", addr))
 		}
-		// Set the IP.
+		port, err := strconv.Atoi(ps)
+		if err != nil {
+			panic(fmt.Errorf("invalid port in %q", addr))
+		}
+		r.Set(enr.TCP(port))
+		r.Set(enr.UDP(port))
+		addr = hs
+	}
+	// Set the IP.
+	if addr != "" {
 		ip := net.ParseIP(addr)
 		if ip == nil {
 			panic(fmt.Errorf("invalid IP %q", addr))