From dddc68ec2d72ba18668103ce1147c6dea422d7ea Mon Sep 17 00:00:00 2001
From: owent <admin@owent.net>
Date: Fri, 9 Oct 2020 17:48:39 +0800
Subject: [PATCH] netlink: check for RTA_PREF before use

Old kernels like v3.10 don't have it

 [#2079](https://github.com/warmcat/libwebsockets/issues/2079)
---
 CMakeLists.txt        | 5 +++++
 cmake/lws_config.h.in | 1 +
 2 files changed, 6 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 28bbdab61..b78c9ac57 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -632,6 +632,11 @@ CHECK_C_SOURCE_COMPILES("#include <stddef.h>
 		return p != NULL;
 	}" LWS_HAS_GETOPT_LONG)
 
+CHECK_C_SOURCE_COMPILES("#include <linux/rtnetlink.h>
+	int main(void) {
+		int test = RTA_PREF;
+		return 0;
+	}" LWS_HAVE_RTA_PREF)
 
 if (NOT PID_T_SIZE)
 	set(pid_t int)
diff --git a/cmake/lws_config.h.in b/cmake/lws_config.h.in
index 3382f74f2..05e183200 100644
--- a/cmake/lws_config.h.in
+++ b/cmake/lws_config.h.in
@@ -196,4 +196,5 @@
 #cmakedefine LWS_WITH_EVLIB_PLUGINS
 #cmakedefine LWS_WITH_LIBUV_INTERNAL
 #cmakedefine LWS_WITH_PLUGINS_API
+#cmakedefine LWS_HAVE_RTA_PREF