package/ell: fix build with older toolchains

Older toolchains need to include sys/types.h and sys/socket.h before
linux/if.h, RTA_PREF was introduces with linux-4.1.x.

Fixes:

  http://autobuild.buildroot.net/results/2d1/2d1a3f82abb8475d39908b22f775c2dac781f330

  In file included from ell/rtnl.c:28:0:
  .../host/arm-buildroot-linux-gnueabi/sysroot/usr/include/linux/if.h:185:19: error: field 'ifru_addr' has incomplete type
  .../host/arm-buildroot-linux-gnueabi/sysroot/usr/include/linux/if.h:186:19: error: field 'ifru_dstaddr' has incomplete type
  .../host/arm-buildroot-linux-gnueabi/sysroot/usr/include/linux/if.h:187:19: error: field 'ifru_broadaddr' has incomplete type
  .../host/arm-buildroot-linux-gnueabi/sysroot/usr/include/linux/if.h:188:19: error: field 'ifru_netmask' has incomplete type
  .../arm-buildroot-linux-gnueabi/sysroot/usr/include/linux/if.h:189:20: error: field 'ifru_hwaddr' has incomplete type
  ell/rtnl.c: In function 'l_rtnl_route_extract':
  ell/rtnl.c:120:8: error: 'RTA_PREF' undeclared (first use in this function)

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/ell/0002-ell-rtnl-fix-compile-with-older-toolchains.patch

@@ -0,0 +1,67 @@
+From 60b4cd4c703be380aef194d31a1ffc4b42431bde Mon Sep 17 00:00:00 2001
+From: Peter Seiderer <ps.report@gmx.net>
+Date: Thu, 9 Apr 2020 22:21:36 +0200
+Subject: [PATCH] ell/rtnl: fix compile with older toolchains
+
+Older toolchains need to include sys/types.h and sys/socket.h before
+linux/if.h, RTA_PREF was introduces with linux-4.1.x.
+
+Fixes:
+
+  In file included from ell/rtnl.c:28:0:
+  .../host/arm-buildroot-linux-gnueabi/sysroot/usr/include/linux/if.h:185:19: error: field 'ifru_addr' has incomplete type
+  .../host/arm-buildroot-linux-gnueabi/sysroot/usr/include/linux/if.h:186:19: error: field 'ifru_dstaddr' has incomplete type
+  .../host/arm-buildroot-linux-gnueabi/sysroot/usr/include/linux/if.h:187:19: error: field 'ifru_broadaddr' has incomplete type
+  .../host/arm-buildroot-linux-gnueabi/sysroot/usr/include/linux/if.h:188:19: error: field 'ifru_netmask' has incomplete type
+  .../arm-buildroot-linux-gnueabi/sysroot/usr/include/linux/if.h:189:20: error: field 'ifru_hwaddr' has incomplete type
+  ell/rtnl.c: In function 'l_rtnl_route_extract':
+  ell/rtnl.c:120:8: error: 'RTA_PREF' undeclared (first use in this function)
+
+Signed-off-by: Peter Seiderer <ps.report@gmx.net>
+---
+ configure.ac | 2 ++
+ ell/rtnl.c   | 7 ++++++-
+ 2 files changed, 8 insertions(+), 1 deletion(-)
+
+diff --git a/configure.ac b/configure.ac
+index 0351f89..3be35a4 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -113,6 +113,8 @@ AC_CHECK_LIB(dl, dlopen, dummy=yes,
+ 
+ AC_CHECK_HEADERS(linux/types.h linux/if_alg.h)
+ 
++AC_CHECK_DECLS([RTA_PREF], [], [], [[#include <linux/rtnetlink.h>]])
++
+ AC_ARG_ENABLE(glib, AC_HELP_STRING([--enable-glib],
+ 				[enable ell/glib main loop example]),
+ 					[enable_glib=${enableval}])
+diff --git a/ell/rtnl.c b/ell/rtnl.c
+index dc83937..3493d34 100644
+--- a/ell/rtnl.c
++++ b/ell/rtnl.c
+@@ -25,8 +25,9 @@
+ #endif
+ 
+ #define _GNU_SOURCE
+-#include <linux/if.h>
++#include <sys/types.h>
+ #include <sys/socket.h>
++#include <linux/if.h>
+ #include <arpa/inet.h>
+ 
+ #include "util.h"
+@@ -35,6 +36,10 @@
+ #include "rtnl.h"
+ #include "private.h"
+ 
++#if defined HAVE_DECL_RTA_PREF && !HAVE_DECL_RTA_PREF
++#define RTA_PREF 20
++#endif
++
+ static size_t rta_add_u8(void *rta_buf, unsigned short type, uint8_t value)
+ {
+ 	struct rtattr *rta = rta_buf;
+-- 
+2.26.0
+