From da6461ad47ca909d23abad7803385d2a1d61007d Mon Sep 17 00:00:00 2001
From: BodgeMaster <>
Date: Wed, 29 Jan 2025 23:40:28 +0100
Subject: [PATCH] Initial commit, start writing EtherCat

---
 .gitignore |  1 +
 README.md  |  3 +++
 build.sh   |  3 +++
 ethercat.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 65 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 README.md
 create mode 100755 build.sh
 create mode 100644 ethercat.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..de8e66b
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/ethercat
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..4946b02
--- /dev/null
+++ b/README.md
@@ -0,0 +1,3 @@
+# EtherCat
+
+a tool to interface tap interfaces with stdin and stdout
diff --git a/build.sh b/build.sh
new file mode 100755
index 0000000..0e7596b
--- /dev/null
+++ b/build.sh
@@ -0,0 +1,3 @@
+#!/usr/bin/env bash
+rm ethercat
+gcc -Wall -Wextra ethercat.c -o ethercat
diff --git a/ethercat.c b/ethercat.c
new file mode 100644
index 0000000..c5a550e
--- /dev/null
+++ b/ethercat.c
@@ -0,0 +1,58 @@
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/if.h>
+#include <linux/if_tun.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+#define DEVICE_NODE_TUN /dev/net/tun
+#define BUFFER_SIZE 0x1000
+
+#define EXIT_SUCCESS 0
+#define EXIT_USAGE 1
+#define EXIT_RUNTIME 2
+
+int file_descriptor;
+char buffer[BUFFER_SIZE];
+struct ifreq ifr;
+
+int main(int argc, char** argv) {
+  if (argc != 2) {
+    fprintf(stderr, "Usage: %s TAP\n", argv[0]);
+    return EXIT_USAGE;
+  } else if ((strlen(argv[1])==2 && strncmp(argv[1], "-h", 2)==0) || (strlen(argv[1])==6 &&strncmp(argv[1], "--help", 6))) {
+    fprintf(stdout, "Usage: %s TAP\n", argv[0]);
+    return EXIT_SUCCESS;
+  }
+
+  memset(&ifr, 0, sizeof(ifr));
+  ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
+  strncpy(ifr.ifr_name, argv[1], IFNAMSIZ);
+
+  file_descriptor = open("/dev/net/tun", O_RDWR);
+  if (file_descriptor == -1) {
+    fprintf(stderr, "An error occurred while trying to open DEVICE_NODE_TUN: %i\n", errno);
+    return EXIT_RUNTIME;
+  }
+
+  if (ioctl(file_descriptor, TUNSETIFF, &ifr) == -1) {
+    fprintf(stderr, "An error occurred while trying to ioctl: %i\n", errno);
+    close(file_descriptor);
+    return EXIT_RUNTIME;
+  }
+
+  //TODO:
+  // while input not EOF
+  // and the tap is still a valid device (it might go away)
+  // read from tap to stdout
+  // read from stdin to tap
+
+  //TODO: signal handler for SIGINT (and SIGHUP? maybe others?)
+
+  if (fcntl(fd, F_GETFD) != -1 || errno != EBADF) {
+    close(file_descriptor);
+  }
+  return EXIT_SUCCESS;
+}