From 37975e38306a04644868fd5e48c96fbf1e2408dd Mon Sep 17 00:00:00 2001
From: Karl Mehltretter <kmehltretter@gmail.com>
Date: Sun, 24 May 2026 13:59:33 +0200
Subject: [PATCH] Fix bind_interface support guard

The bind_interface parser guard still checked SO_BINDTODEVICE, but the runtime implementation no longer uses SO_BINDTODEVICE. It uses getifaddrs() on non-Windows/non-AIX platforms instead.

This caused bind_interface to be rejected at config parse time on platforms where the runtime implementation is available, including macOS.

Add a HAVE_BIND_INTERFACE guard and use it consistently for parsing, the ifaddrs include, the bind helper, and the call site. This fixes test/broker/16-config-huge.py on macOS.

Assisted-by: OpenAI Codex (GPT-5)
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
---
 config.h   |  4 ++++
 src/conf.c |  2 +-
 src/net.c  | 14 +++++++-------
 3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/config.h b/config.h
index 45145fe79a..851fba020d 100644
--- a/config.h
+++ b/config.h
@@ -16,6 +16,10 @@
 #  define HAVE_NETINET_IN_H
 #endif
 
+#if !defined(WIN32) && !defined(_AIX)
+#  define HAVE_BIND_INTERFACE
+#endif
+
 #define OPENSSL_LOAD_CONF
 
 /* ============================================================
diff --git a/src/conf.c b/src/conf.c
index 05627df458..bc2fddf792 100644
--- a/src/conf.c
+++ b/src/conf.c
@@ -1291,7 +1291,7 @@ static int config__read_file_core(struct mosquitto__config *config, bool reload,
 						return MOSQ_ERR_INVAL;
 					}
 				}else if(!strcmp(token, "bind_interface")){
-#ifdef SO_BINDTODEVICE
+#ifdef HAVE_BIND_INTERFACE
 					if(reload){
 						continue;        /* Rebinding listeners not valid during reloading. */
 					}
diff --git a/src/net.c b/src/net.c
index 611e295d62..2011eea409 100644
--- a/src/net.c
+++ b/src/net.c
@@ -20,9 +20,6 @@ SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 
 #ifndef WIN32
 #  include <arpa/inet.h>
-#  ifndef _AIX
-#    include <ifaddrs.h>
-#  endif
 #  include <netdb.h>
 #  include <netinet/tcp.h>
 #  include <strings.h>
@@ -45,6 +42,10 @@ SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 #  include <netinet/in.h>
 #endif
 
+#ifdef HAVE_BIND_INTERFACE
+#  include <ifaddrs.h>
+#endif
+
 #if defined(WITH_UNIX_SOCKETS) || defined(WITH_TLS)
 #  include "sys/stat.h"
 #endif
@@ -718,15 +719,14 @@ int net__tls_load_verify(struct mosquitto__listener *listener)
 }
 
 
-#if !defined(WIN32) && !defined(_AIX)
+#ifdef HAVE_BIND_INTERFACE
 
 
 static int net__bind_interface(struct mosquitto__listener *listener, struct addrinfo *rp)
 {
 	/*
 	 * This binds the listener sock to a network interface.
-	 * The use of SO_BINDTODEVICE requires root access, which we don't have, so instead
-	 * use getifaddrs to find the interface addresses, and use IP of the
+	 * Use getifaddrs to find the interface addresses, then use the IP of the
 	 * matching interface in the later bind().
 	 */
 	struct ifaddrs *ifaddr;
@@ -874,7 +874,7 @@ static int net__socket_listen_tcp(struct mosquitto__listener *listener)
 			return 1;
 		}
 
-#if !defined(WIN32) && !defined(_AIX)
+#ifdef HAVE_BIND_INTERFACE
 		if(listener->bind_interface){
 			/* It might be possible that an interface does not support all relevant sa_families.
 			 * We should successfully find at least one. */