Initial code commit

Makefile

@@ -0,0 +1,6 @@
+CFLAGS=-std=c99 -fsanitize=address -fno-omit-frame-pointer
+
+glorytun:
+
+setcap: glorytun
+	sudo setcap cap_net_admin+ep glorytun

common.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#include <unistd.h>
+#include <errno.h>
+
+#define COUNT(x) (sizeof(x)/sizeof(x[0]))
+
+static inline size_t str_cpy (char *dst, char *src, size_t n)
+{
+    if (!dst || !src)
+        return 0;
+
+    size_t i;
+
+    for (i=0; i<n && src[i]; i++)
+        dst[i] = src[i];
+
+    dst[i] = 0;
+
+    return i;
+}

glorytun.c

@@ -0,0 +1,99 @@
+#include "common.h"
+
+#include <stdio.h>
+#include <signal.h>
+#include <poll.h>
+
+#include <sys/ioctl.h>
+#include <sys/fcntl.h>
+#include <sys/socket.h>
+
+#include <linux/if.h>
+#include <linux/if_tun.h>
+
+#define GT_NAME "glorytun"
+
+volatile sig_atomic_t running;
+
+static int gt_open_tun (char *name)
+{
+    int fd = open("/dev/net/tun", O_RDWR);
+
+    if (fd<0) {
+        printf("open /dev/net/tun: %m\n");
+        return -1;
+    }
+
+    struct ifreq ifr = {
+        .ifr_flags = IFF_TUN|IFF_NO_PI,
+    };
+
+    str_cpy(ifr.ifr_name, name, IFNAMSIZ-1);
+
+    int ret = ioctl(fd, TUNSETIFF, &ifr);
+
+    if (ret<0) {
+        printf("ioctl TUNSETIFF: %m\n");
+        return -1;
+    }
+
+    printf("tun name: %s\n", ifr.ifr_name);
+
+    return fd;
+}
+
+static void gt_sa_stop (int sig) {
+    switch (sig) {
+    case SIGINT:
+    case SIGTERM:
+        running = 0;
+    }
+}
+
+static int gt_set_signal (void)
+{
+    struct sigaction sa = {0};
+
+    running = 1;
+
+    sa.sa_handler = gt_sa_stop;
+    sigaction(SIGINT,  &sa, NULL);
+    sigaction(SIGTERM, &sa, NULL);
+
+    sa.sa_handler = SIG_IGN;
+    sigaction(SIGHUP,  &sa, NULL);
+}
+
+int main (int argc, char **argv)
+{
+    gt_set_signal();
+
+    int tun_fd = gt_open_tun(GT_NAME);
+
+    if (tun_fd==-1)
+        return 1;
+
+    struct pollfd fds[] = {
+        { .fd = tun_fd, .events = POLLIN },
+    };
+
+    while (running) {
+        int ret = poll(fds, COUNT(fds), 0);
+
+        if (ret==-1) {
+            if (errno==EINTR)
+                continue;
+            printf("poll: %m\n");
+            return 1;
+        }
+
+        if (ret==0)
+            continue;
+
+        if (fds[0].revents & POLLIN) {
+            printf("POLLIN!\n");
+        }
+    }
+
+    return 0;
+}