begin generic tun impl

ww/tundevice/tun.h

@@ -0,0 +1,19 @@
+#pragma once
+#include "hloop.h"
+#include "hplatform.h"
+#include <stdint.h>
+
+typedef union {
+    int   fd;     // Unix file descriptor
+    void *handle; // Windows handle (void* can hold HANDLE)
+} tun_handle_t;
+
+typedef struct tun_device_s
+{
+    char        *name;
+    hio_t       *io;
+    tun_handle_t handle;
+
+} tun_device_t;
+
+tun_device_t *createTunDevice(hloop_t *loop, const char *name, bool offload);

ww/tundevice/tun_unix.c

@@ -0,0 +1,48 @@
+#include "tun.h"
+#include "ww.h"
+#include <arpa/inet.h>
+#include <fcntl.h>
+#include <linux/if.h>
+#include <linux/if_tun.h>
+#include <netinet/ip.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+tun_device_t *createTunDevice(hloop_t *loop, const char *name, bool offload)
+{
+    (void) offload; // todo (send/receive offloading)
+
+    struct ifreq ifr;
+
+    int fd = open("/dev/net/tun", O_RDWR);
+    if (fd < 0)
+    {
+        perror("Opening /dev/net/tun");
+        return NULL;
+    }
+
+    memset(&ifr, 0, sizeof(ifr));
+
+    ifr.ifr_flags = IFF_TUN | IFF_NO_PI; // TUN device, no packet information
+    if (*name)
+    {
+        strncpy(ifr.ifr_name, name, IFNAMSIZ);
+    }
+
+    int err = ioctl(fd, TUNSETIFF, (void *) &ifr);
+    if (err < 0)
+    {
+        perror("ioctl(TUNSETIFF)");
+        close(fd);
+        return NULL;
+    }
+
+    tun_device_t *tdev = globalMalloc(sizeof(tun_device_t));
+    *tdev = (tun_device_t) {.name = strdup(ifr.ifr_name), .handle = (tun_handle_t) {.fd = fd}, .io = hio_get(loop, fd)};
+
+    return tdev;
+}
+