+/* All the IP options documented in Linux ip(7). */
+#define IP_ADD_MEMBERSHIP 0
+#define IP_DROP_MEMBERSHIP 1
+#define IP_HDRINCL 2
+#define IP_MTU 3
+#define IP_MTU_DISCOVER 4
+#define IP_MULTICAST_IF 5
+#define IP_MULTICAST_LOOP 6
+#define IP_MULTICAST_TTL 7
+#define IP_NODEFRAG 8
+#define IP_OPTIONS 9
+#define IP_PKTINFO 10
+#define IP_RECVERR 11
+#define IP_RECVOPTS 12
+#define IP_RECVTOS 13
+#define IP_RECVTTL 14
+#define IP_RETOPTS 15
+#define IP_ROUTER_ALERT 16
+#define IP_TOS 17
+#define IP_TTL 18
+