From 7aa7806c0958ed943965e8180fdeeecea8171516 Mon Sep 17 00:00:00 2001
From: ozpool <151670776+ozpool@users.noreply.github.com>
Date: Thu, 2 Jul 2026 21:50:25 +0530
Subject: [PATCH] cmd/devp2p: close the iterator in discv4 LookupRandom
 (#35206)

The LookupRandom RPC handler obtains a node iterator from
RandomNodes() but never closes it.

RandomNodes() returns a lookupIterator backed by a cancelable
context derived from the listener's lifetime context
(newLookupIterator -> context.WithCancel). The iterator's
Close() is what calls the cancel func, so each LookupRandom call
that never closes leaks the cancel func (and any in-flight lookup
goroutine) until the discv4 listener shuts down. When the listener
serves the RPC API (discv4 --rpc) it is long-lived, so repeated
LookupRandom calls accumulate the leak.

Close the iterator when the handler returns. This matches how the
crawler already releases the same RandomNodes() iterators
(crawl.go closes every iterator it consumes).
---
 cmd/devp2p/discv4cmd.go | 1 +
 1 file changed, 1 insertion(+)

diff --git a/cmd/devp2p/discv4cmd.go b/cmd/devp2p/discv4cmd.go
index 1089210c57..98b04311b4 100644
--- a/cmd/devp2p/discv4cmd.go
+++ b/cmd/devp2p/discv4cmd.go
@@ -430,6 +430,7 @@ type discv4API struct {
 
 func (api *discv4API) LookupRandom(n int) (ns []*enode.Node) {
 	it := api.host.RandomNodes()
+	defer it.Close()
 	for len(ns) < n && it.Next() {
 		ns = append(ns, it.Node())
 	}