Add example to use TAP interface on Linux

examples/mip-tap/main.c

@@ -0,0 +1,91 @@
+// Copyright (c) 2022 Cesanta Software Limited
+// All rights reserved
+//
+// example using MIP and a TUN/TAP interface
+
+#include "mongoose.h"
+#include <linux/if.h>
+#include <linux/if_tun.h>
+#include <sys/ioctl.h>
+
+static int s_signo;
+void signal_handler(int signo) {
+  s_signo = signo;
+}
+
+static size_t tap_tx(const void *buf, size_t len, void *userdata) {
+  ssize_t res = write((int) userdata, buf, len);
+  if (res < 0) {
+    MG_ERROR(("tap_tx failed: %d", errno));
+    return 0;
+  }
+  return (size_t) res;
+}
+
+static bool tap_up(void *userdata) {
+  return userdata ? true : false;
+}
+
+static size_t tap_rx(void *buf, size_t len, void *userdata) {
+  ssize_t received = read((int) userdata, buf, len);
+  usleep(1);  // This is to avoid 100% CPU
+  if (received < 0) return 0;
+  return (size_t) received;
+}
+
+int main(int argc, char *argv[]) {
+  const char *iface = "tap0";             // Network iface
+  const char *mac = "00:00:01:02:03:77";  // MAC address
+
+  // Parse options
+  for (int i = 1; i < argc; i++) {
+    if (strcmp(argv[i], "-i") == 0 && i + 1 < argc) {
+      iface = argv[++i];
+    } else if (strcmp(argv[i], "-mac") == 0 && i + 1 < argc) {
+      mac = argv[++i];
+    } else if (strcmp(argv[i], "-v") == 0 && i + 1 < argc) {
+      mg_log_set(atoi(argv[++i]));
+    } else {
+      MG_ERROR(("unknown option %s", argv[i]));
+      return EXIT_FAILURE;
+    }
+  }
+
+  // Open network interface
+  int fd = open("/dev/net/tun", O_RDWR);
+  struct ifreq ifr;
+  memset(&ifr, 0, sizeof(ifr));
+  strncpy(ifr.ifr_name, iface, IFNAMSIZ);
+  ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
+  if (ioctl(fd, TUNSETIFF, (void *) &ifr) < 0) {
+    MG_ERROR(("Failed to setup TAP interface: %s", ifr.ifr_name));
+    return EXIT_FAILURE;
+  }
+  fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_NONBLOCK);  // Non-blocking mode
+
+  MG_INFO(("Opened TAP interface: %s", iface));
+  signal(SIGINT, signal_handler);
+  signal(SIGTERM, signal_handler);
+
+  struct mg_mgr mgr;  // Event manager
+  mg_mgr_init(&mgr);  // Initialise event manager
+
+  struct mip_cfg c = {.ip = 0, .mask = 0, .gw = 0};
+  sscanf(mac, "%hhx:%hhx:%hhx:%hhx:%hhx:%hhx", &c.mac[0], &c.mac[1], &c.mac[2],
+         &c.mac[3], &c.mac[4], &c.mac[5]);
+
+  struct mip_driver driver = {.tx = tap_tx, .up = tap_up, .rx = tap_rx};
+  mip_init(&mgr, &c, &driver, (void *) fd);
+  MG_INFO(("Init done, starting main loop"));
+
+  extern void device_dashboard_fn(struct mg_connection *, int, void *, void *);
+  mg_http_listen(&mgr, "http://0.0.0.0:8000", device_dashboard_fn, &mgr);
+
+  while (s_signo == 0) mg_mgr_poll(&mgr, 100);  // Infinite event loop
+
+  mg_mgr_free(&mgr);
+  close(fd);
+  printf("Exiting on signal %d\n", s_signo);
+
+  return 0;
+}