+#define PHASE_INITIALIZE 1
+#define PHASE_DORMANT 2
+#define PHASE_ESTABLISH 3
+#define PHASE_AUTHENTICATE 4
+#define PHASE_CALLBACK 5
+#define PHASE_NETWORK 6
+#define PHASE_TERMINATE 7
+#define PHASE_HOLDOFF 8
+
+/*
+ * The following struct gives the addresses of procedures to call
+ * for a particular protocol.
+ */
+struct protent {
+ u_short protocol; /* PPP protocol number */
+ /* Initialization procedure */
+ void (*init) __P((int unit));
+ /* Process a received packet */
+ void (*input) __P((int unit, u_char *pkt, int len));
+ /* Process a received protocol-reject */
+ void (*protrej) __P((int unit));
+ /* Lower layer has come up */
+ void (*lowerup) __P((int unit));
+ /* Lower layer has gone down */
+ void (*lowerdown) __P((int unit));
+ /* Open the protocol */
+ void (*open) __P((int unit));
+ /* Close the protocol */
+ void (*close) __P((int unit, char *reason));
+ /* Print a packet in readable form */
+ int (*printpkt) __P((u_char *pkt, int len,
+ void (*printer) __P((void *, char *, ...)),
+ void *arg));
+ /* Process a received data packet */
+ void (*datainput) __P((int unit, u_char *pkt, int len));
+ int enabled_flag; /* 0 iff protocol is disabled */
+ char *name; /* Text name of protocol */
+ /* Check requested options, assign defaults */
+ void (*check_options) __P((void));
+ /* Configure interface for demand-dial */
+ int (*demand_conf) __P((int unit));
+ /* Say whether to bring up link for this pkt */
+ int (*active_pkt) __P((u_char *pkt, int len));
+};
+
+/* Table of pointers to supported protocols */
+extern struct protent *protocols[];