https://bugs.gentoo.org/904843
https://github.com/nm-l2tp/NetworkManager-l2tp/commit/36a427c316a8ccd3168606f6e7fd6c8ae2b9bebf

From 36a427c316a8ccd3168606f6e7fd6c8ae2b9bebf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Eivind=20N=C3=A6ss?= <eivnaes@yahoo.com>
Date: Fri, 3 Mar 2023 05:22:13 +0000
Subject: [PATCH] Adding support for compiling against pppd-2.5.0 (current
 master)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Signed-off-by: Eivind Næss <eivnaes@yahoo.com>
---
 Makefile.am                                   |  5 +-
 src/nm-l2tp-pppd-compat.h                     | 93 +++++++++++++++++++
 src/nm-l2tp-pppd-plugin.c                     |  7 +-
 ...{nm-ppp-status.h => nm-l2tp-pppd-status.h} |  0
 src/nm-l2tp-service.c                         |  2 +-
 5 files changed, 100 insertions(+), 7 deletions(-)
 create mode 100644 src/nm-l2tp-pppd-compat.h
 rename src/{nm-ppp-status.h => nm-l2tp-pppd-status.h} (100%)

diff --git a/Makefile.am b/Makefile.am
index 8201ca7..1feb9be 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -99,7 +99,7 @@ src_nm_l2tp_service_SOURCES = \
 	shared/nm-l2tp-crypto-nss.c \
 	shared/utils.h \
 	shared/utils.c \
-	src/nm-ppp-status.h \
+	src/nm-l2tp-pppd-status.h \
 	src/nm-l2tp-service.h \
 	src/nm-l2tp-service.c
 src_nm_l2tp_service_CPPFLAGS = $(src_cppflags) $(NSS_CFLAGS) $(OPENSSL_CFLAGS)
@@ -118,7 +118,8 @@ pppd_plugin_LTLIBRARIES = src/nm-l2tp-pppd-plugin.la
 src_nm_l2tp_pppd_plugin_la_SOURCES = \
 	$(shared_sources) \
 	src/nm-l2tp-pppd-plugin.c \
-	src/nm-ppp-status.h
+	src/nm-l2tp-pppd-compat.h \
+	src/nm-l2tp-pppd-status.h
 src_nm_l2tp_pppd_plugin_la_CPPFLAGS = $(src_cppflags)
 src_nm_l2tp_pppd_plugin_la_LDFLAGS = \
 	-module -avoid-version
diff --git a/src/nm-l2tp-pppd-compat.h b/src/nm-l2tp-pppd-compat.h
new file mode 100644
index 0000000..80e2891
--- /dev/null
+++ b/src/nm-l2tp-pppd-compat.h
@@ -0,0 +1,93 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* -*- Mode: C; tab-width: 4; indent-tabs-mode: t; c-basic-offset: 4 -*- */
+/* nm-sstp-service - sstp (and other pppd) integration with NetworkManager
+ *
+ * Copyright (C) 2023 Eivind Naess, eivnaes@yahoo.com
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#ifndef __NM_L2TP_PPPD_COMPAT_H__
+#define __NM_L2TP_PPPD_COMPAT_H__
+
+// PPP < 2.5.0 defines and exports VERSION which overlaps with current package VERSION define.
+//   this silly macro magic is to work around that.
+
+#define INET6	1
+
+#undef VERSION
+#include <pppd/pppd.h>
+#ifndef PPPD_VERSION
+#define PPPD_VERSION VERSION
+#endif
+
+#include <pppd/fsm.h>
+#include <pppd/ccp.h>
+#include <pppd/eui64.h>
+#include <pppd/ipcp.h>
+#include <pppd/ipv6cp.h>
+#include <pppd/eap.h>
+#include <pppd/upap.h>
+
+#ifdef HAVE_PPPD_CHAP_H
+ #include <pppd/chap.h>
+#endif
+
+#ifdef HAVE_PPPD_CHAP_NEW_H
+ #include <pppd/chap-new.h>
+#endif
+
+#ifdef HAVE_PPPD_CHAP_MS_H
+ #include <pppd/chap_ms.h>
+#endif
+
+#ifndef PPP_PROTO_CHAP
+#define PPP_PROTO_CHAP              0xc223
+#endif 
+
+#ifndef PPP_PROTO_EAP
+#define PPP_PROTO_EAP               0xc227
+#endif
+
+#if WITH_PPP_VERSION < PPP_VERSION(2,5,0)
+
+static inline bool debug_on(void)
+{
+    return debug;
+}
+
+static inline const char *ppp_ipparam(void)
+{
+    return ipparam;
+}
+
+static inline int ppp_ifunit(void)
+{
+    return ifunit;
+}
+
+static inline const char *ppp_ifname(void)
+{
+    return ifname;
+}
+
+static inline int ppp_get_mtu(int idx)
+{
+    return netif_get_mtu(idx);
+}
+
+#endif // #if WITH_PPP_VERSION < PPP_VERSION(2,5,0)
+#endif // #ifdef __NM_L2TP_PPPD_COMPAT_H__
diff --git a/src/nm-l2tp-pppd-plugin.c b/src/nm-l2tp-pppd-plugin.c
index dd752a1..f1d588e 100644
--- a/src/nm-l2tp-pppd-plugin.c
+++ b/src/nm-l2tp-pppd-plugin.c
@@ -9,8 +9,6 @@
 #include <config.h>
 #define ___CONFIG_H__
 
-#include "nm-default.h"
-
 #include <string.h>
 #include <stdlib.h>
 #include <sys/socket.h>
@@ -18,10 +16,11 @@
 #include <arpa/inet.h>
 #include <dlfcn.h>
 
-#include "nm-l2tp-service.h"
-#include "nm-ppp-status.h"
+#include "nm-l2tp-pppd-status.h"
 #include "nm-l2tp-pppd-compat.h"
 
+#include "nm-default.h"
+#include "nm-l2tp-service.h"
 #include "nm-utils/nm-shared-utils.h"
 #include "nm-utils/nm-vpn-plugin-macros.h"
 
diff --git a/src/nm-ppp-status.h b/src/nm-l2tp-pppd-status.h
similarity index 100%
rename from src/nm-ppp-status.h
rename to src/nm-l2tp-pppd-status.h
diff --git a/src/nm-l2tp-service.c b/src/nm-l2tp-service.c
index 55f9542..629923c 100644
--- a/src/nm-l2tp-service.c
+++ b/src/nm-l2tp-service.c
@@ -36,7 +36,7 @@
 #include <arpa/inet.h>
 #include <netdb.h>
 
-#include "nm-ppp-status.h"
+#include "nm-l2tp-pppd-status.h"
 #include "nm-l2tp-pppd-service-dbus.h"
 #include "nm-utils/nm-shared-utils.h"
 #include "nm-utils/nm-secret-utils.h"