+/* flags in inp_flags: */
+#define INP_RECVOPTS 0x01 /* receive incoming IP options */
+#define INP_RECVRETOPTS 0x02 /* receive IP options for reply */
+#define INP_RECVDSTADDR 0x04 /* receive IP dst address */
+#define INP_CONTROLOPTS (INP_RECVOPTS|INP_RECVRETOPTS|INP_RECVDSTADDR)
+#define INP_HDRINCL 0x08 /* user supplies entire IP header */
+