2 files changed, 188 insertions, 0 deletions
diff --git a/yocto/esp32tun/Makefile b/yocto/esp32tun/Makefile
new file mode 100755
index 0000000..574c480
--- /dev/null
+++ b/yocto/esp32tun/Makefile
@@ -0,0 +1,15 @@
+#CFLAGS =
+LDFLAGS = -pthread -lgpiod
+TARGET = esp32tun
+obj = esp32tun.o
+
+all: $(TARGET)
+
+%.o: %.c %.h
+	$(CC) $(CFLAGS) -c $<
+
+$(TARGET): $(obj)
+	$(CC) $(obj) $(LDFLAGS) -o $@
+
+clean:
+	rm -f $(TARGET) *.o
diff --git a/yocto/esp32tun/esp32tun.c b/yocto/esp32tun/esp32tun.c
new file mode 100755
index 0000000..8f9e3bd
--- /dev/null
+++ b/yocto/esp32tun/esp32tun.c
@@ -0,0 +1,173 @@
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <assert.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+
+#include <linux/if.h>
+#include <linux/if_tun.h>
+
+#include <pthread.h>
+
+#define TUN_NAME            "tun0"
+
+#define ESP32_MTU           1500
+#define ESP32_FNAMSIZ       64
+#define ESP32_DEVFN         "/dev/esp32.?"
+#define ESP32_MTYPE_TUN     1
+#define ESP32_MAX_MTYPE     8
+
+static pthread_t tun_handler_thd, esp32_handler_thd;
+
+static int tun_fd, esp32_fd;
+static char tun_name[IFNAMSIZ];
+
+/* Arguments taken by the function:
+ *
+ * char *dev: the name of an interface (or '\0'). MUST have enough
+ *   space to hold the interface name if '\0' is passed
+ * int flags: interface flags (eg, IFF_TUN etc.)
+ */
+int tun_alloc(char *dev, int flags) {
+    struct ifreq ifr;
+    int fd, rv;
+    char *clonedev = "/dev/net/tun";
+
+    fd = open(clonedev, O_RDWR);
+    if (fd < 0) return fd;
+
+    memset(&ifr, 0, sizeof(ifr));
+    ifr.ifr_flags = flags;  /* IFF_TUN or IFF_TAP, plus maybe IFF_NO_PI */
+
+    if (*dev) {
+        /* if a device name was specified, put it in the structure; otherwise,
+         * the kernel will try to allocate the "next" device of the
+         * specified type */
+        strncpy(ifr.ifr_name, dev, IFNAMSIZ);
+    }
+
+    /* try to create the device */
+    rv = ioctl(fd, TUNSETIFF, (void *) &ifr);
+    if (rv < 0) {
+        close(fd);
+        return rv;
+    }
+
+    /* if the operation was successful, write back the name of the
+     * interface to the variable "dev", so the caller can know
+     * it. Note that the caller MUST reserve space in *dev (see calling
+     * code below) */
+    strcpy(dev, ifr.ifr_name);
+
+    /* this is the special file descriptor that the caller will use to talk
+     * with the virtual interface */
+    return fd;
+}
+
+ssize_t tun_read(unsigned char *buffer, size_t buf_size) {
+    return read(tun_fd, buffer, buf_size);
+}
+
+ssize_t tun_write(unsigned char *buffer, size_t buf_len) {
+    return write(tun_fd, buffer, buf_len);
+}
+
+int tun_init(char *name) {
+    if (strlen(name) + 1 > sizeof(tun_name)) return -1;
+
+    strcpy(tun_name, name);
+    tun_fd = tun_alloc(tun_name, IFF_TUN | IFF_NO_PI);
+
+    if (tun_fd < 0) return tun_fd;
+    return 0;
+}
+
+ssize_t esp32_read(unsigned char *buffer, size_t buf_size) {
+    return read(esp32_fd, buffer, buf_size);
+}
+
+ssize_t esp32_write(unsigned char *buffer, size_t buf_len) {
+    return write(esp32_fd, buffer, buf_len);
+}
+
+int esp32_fname(char *fname, int mtype) {
+    if (mtype >= ESP32_MAX_MTYPE) return -1;
+
+    strcpy(fname, ESP32_DEVFN);
+    fname[strlen(fname) - 1] = '0' + mtype;
+
+    return 0;
+}
+
+int esp32_init(void) {
+    char fname[ESP32_FNAMSIZ];
+    int rv;
+
+    rv = esp32_fname(fname, ESP32_MTYPE_TUN);
+    if (rv) return rv;
+
+	esp32_fd = open(fname, O_RDWR);
+
+    if (esp32_fd < 0) return esp32_fd;
+    return 0;
+}
+
+void *tun_handler(void *arg) {
+    unsigned char buffer[ESP32_MTU];
+    ssize_t len, rv;
+
+    while (1) {
+        len = tun_read(buffer, ESP32_MTU);
+        if (len < 0) {
+            perror("tun read");
+            continue;
+        }
+        rv = esp32_write(buffer, len);
+        if (rv < 0) {
+            perror("esp32 write");
+            continue;
+        }
+    }
+
+    return NULL;
+}
+
+void *esp32_handler(void *arg) {
+    unsigned char buffer[ESP32_MTU];
+    ssize_t len, rv;
+
+    while (1) {
+        len = esp32_read(buffer, ESP32_MTU);
+        if (len < 0) {
+            perror("esp32 read");
+            continue;
+        }
+        rv = tun_write(buffer, len);
+        if (rv < 0) {
+            perror("tun write");
+            continue;
+        }
+    }
+
+    return NULL;
+}
+
+int main(int argc, char *argv[]) {
+    int rv;
+
+    rv = tun_init(TUN_NAME);
+    assert(rv == 0);
+
+    rv = esp32_init();
+    assert(rv == 0);
+
+    rv = pthread_create(&tun_handler_thd, NULL, tun_handler, NULL);
+    assert(rv == 0);
+
+    rv = pthread_create(&esp32_handler_thd, NULL, esp32_handler, NULL);
+    assert(rv == 0);
+
+    while(1);
+}