+sys_init()
+{
+ /* Get an internet socket for doing socket ioctl's on. */
+ if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
+ fatal("Couldn't create IP socket: %m");
+
+ FD_ZERO(&in_fds);
+ max_in_fd = 0;
+}
+
+/*
+ * sys_cleanup - restore any system state we modified before exiting:
+ * mark the interface down, delete default route and/or proxy arp entry.
+ * This should call die() because it's called from die().
+ */
+void
+sys_cleanup()
+{
+ struct ifreq ifr;
+
+ if (if_is_up) {
+ strlcpy(ifr.ifr_name, sizeof(ifr.ifr_name), ifname);
+ if (ioctl(sockfd, SIOCGIFFLAGS, &ifr) >= 0
+ && ((ifr.ifr_flags & IFF_UP) != 0)) {
+ ifr.ifr_flags &= ~IFF_UP;
+ ioctl(sockfd, SIOCSIFFLAGS, &ifr);
+ }
+ }
+ if (ifaddrs[0] != 0)
+ cifaddr(0, ifaddrs[0], ifaddrs[1]);
+ if (default_route_gateway)
+ cifdefaultroute(0, 0, default_route_gateway);
+ if (proxy_arp_addr)
+ cifproxyarp(0, proxy_arp_addr);
+}
+
+/*
+ * sys_close - Clean up in a child process before execing.
+ */
+void
+sys_close()
+{
+ close(sockfd);
+ if (loop_slave >= 0) {
+ close(loop_slave);
+ close(loop_master);
+ }
+}
+
+/*
+ * sys_check_options - check the options that the user specified
+ */
+int
+sys_check_options()
+{
+#ifndef CDTRCTS
+ if (crtscts == 2) {
+ warn("DTR/CTS flow control is not supported on this system");
+ return 0;
+ }
+#endif
+ return 1;
+}
+
+/*
+ * ppp_available - check whether the system has any ppp interfaces
+ * (in fact we check whether we can do an ioctl on ppp0).
+ */
+int
+ppp_available()
+{
+ int s, ok;
+ struct ifreq ifr;
+ extern char *no_ppp_msg;
+
+ if ((s = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
+ return 1; /* can't tell */
+
+ strlcpy(ifr.ifr_name, sizeof (ifr.ifr_name), "ppp0");
+ ok = ioctl(s, SIOCGIFFLAGS, (caddr_t) &ifr) >= 0;
+ close(s);
+
+ no_ppp_msg = "\
+This system lacks kernel support for PPP. To include PPP support\n\
+in the kernel, please follow the steps detailed in the README.bsd\n\
+file in the ppp-2.2 distribution.\n";
+ return ok;
+}
+
+/*
+ * establish_ppp - Turn the serial port into a ppp interface.
+ */
+int
+establish_ppp(fd)
+ int fd;