From c113e3b5b12619c80b962a3b6e895a14a13eaa75 Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@twurst.com>
Date: Mon, 17 Feb 2025 09:47:12 +0100
Subject: [PATCH] p2p: fix marshaling of NAT in TOML (#31192)

This fixes an issue where a nat.Interface unmarshaled from the TOML
config file could not be re-marshaled to TOML correctly.

Fixes #31183
---
 p2p/config.go | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/p2p/config.go b/p2p/config.go
index 5ea62e12f5..68a9c0bb5f 100644
--- a/p2p/config.go
+++ b/p2p/config.go
@@ -18,6 +18,7 @@ package p2p
 
 import (
 	"crypto/ecdsa"
+	"encoding"
 	"fmt"
 
 	"github.com/ethereum/go-ethereum/common/mclock"
@@ -135,6 +136,13 @@ type configNAT struct {
 	nat.Interface
 }
 
+func (w *configNAT) MarshalText() ([]byte, error) {
+	if tm, ok := w.Interface.(encoding.TextMarshaler); ok {
+		return tm.MarshalText()
+	}
+	return nil, fmt.Errorf("NAT specification %#v cannot be marshaled", w.Interface)
+}
+
 func (w *configNAT) UnmarshalText(input []byte) error {
 	n, err := nat.Parse(string(input))
 	if err != nil {