#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <linux/if_addr.h>
+/* glibc versions prior to 2.24 do not define SOL_NETLINK */
+#ifndef SOL_NETLINK
+#define SOL_NETLINK 270
+#endif
+/* linux kernel versions prior to 4.3 do not define/support NETLINK_CAP_ACK */
+#ifndef NETLINK_CAP_ACK
+#define NETLINK_CAP_ACK 10
+#endif
#endif
#include "pppd.h"
if (fd < 0)
return 0;
- /* do not ask for error message content */
+ /*
+ * Tell kernel to not send to us payload of acknowledgment error message.
+ * NETLINK_CAP_ACK option is supported since Linux kernel version 4.3 and
+ * older kernel versions always send full payload in acknowledgment netlink
+ * message. We ignore payload of this message as we need only error code,
+ * to check if our set remote peer address request succeeded or failed.
+ * So ignore return value from the following setsockopt() call as setting
+ * option NETLINK_CAP_ACK means for us just a kernel hint / optimization.
+ */
one = 1;
setsockopt(fd, SOL_NETLINK, NETLINK_CAP_ACK, &one, sizeof(one));