Setup project skeleton

3 files changed, 194 insertions, 0 deletions

diff --git a/tools/tun2tcp/CMakeLists.txt b/tools/tun2tcp/CMakeLists.txt
new file mode 100644
index 0000000..674aef6
--- /dev/null
+++ b/tools/tun2tcp/CMakeLists.txt
@@ -0,0 +1,21 @@
+# wnix, a Unix-like operating system for WebAssembly applications.
+# Copyright (C) 2025  Xavier Del Campo Romero
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+cmake_minimum_required(VERSION 3.13)
+project(tun2tcp C)
+add_executable(${PROJECT_NAME} tun2tcp.c)
+target_compile_options(${PROJECT_NAME} PUBLIC ${cflags})
+install(TARGETS ${PROJECT_NAME} DESTINATION bin)
diff --git a/tools/tun2tcp/README.md b/tools/tun2tcp/README.md
new file mode 100644
index 0000000..9fcc641
--- /dev/null
+++ b/tools/tun2tcp/README.md
@@ -0,0 +1,13 @@
+# tun2serial
+
+```sh
+# setcap cap_net_admin+ep ./tun2serial
+# sudo ip addr add 10.0.0.1/24 dev tun0
+# sudo ip link set tun0 up
+# socat TCP-L:6699 /dev/ttyUSB0,rawer,b1200
+```
+
+## Thanks
+
+- https://backreference.org/2010/03/26/tuntap-interface-tutorial/index.html
+- https://blog.mbedded.ninja/programming/operating-systems/linux/linux-serial-ports-using-c-cpp/
diff --git a/tools/tun2tcp/tun2tcp.c b/tools/tun2tcp/tun2tcp.c
new file mode 100644
index 0000000..4b6615f
--- /dev/null
+++ b/tools/tun2tcp/tun2tcp.c
@@ -0,0 +1,160 @@
+
+/*
+ * wnix, a Unix-like operating system for WebAssembly applications.
+ * Copyright (C) 2025  Xavier Del Campo Romero
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include <netinet/ip.h>
+#include <net/if.h>
+#include <linux/if.h>
+#include <linux/if_tun.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <fcntl.h>
+#include <termios.h>
+#include <unistd.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+static int getport(const char *const s, unsigned short *const port)
+{
+    char *end;
+    unsigned long v;
+
+    errno = 0;
+    v = strtoull(s, &end, 10);
+
+    if (errno || *end || v > USHRT_MAX)
+        return -1;
+
+    *port = v;
+    return 0;
+}
+
+int main(int argc, char *argv[])
+{
+    static const char path[] = "/dev/net/tun";
+    char *s = NULL;
+    int ret = EXIT_FAILURE, cfd = -1, tfd = -1;
+    unsigned short port;
+
+    if (argc != 2)
+    {
+        fprintf(stderr, "%s <port>\n", *argv);
+        goto end;
+    }
+    else if (getport(argv[1], &port))
+    {
+        fprintf(stderr, "invalid port: %s\n", argv[1]);
+        goto end;
+    }
+    else if ((cfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
+    {
+        perror("socket(2)");
+        goto end;
+    }
+
+    const struct sockaddr_in addr =
+    {
+        .sin_family = AF_INET,
+        .sin_addr.s_addr = inet_addr("127.0.0.1"),
+        .sin_port = htons(port)
+    };
+
+    const struct ifreq ifr = {.ifr_flags = IFF_TUN |  IFF_NO_PI};
+
+    if (connect(cfd, (const struct sockaddr *)&addr, sizeof addr))
+    {
+        perror("connect(2)");
+        goto end;
+    }
+    else if ((tfd = open(path, O_RDWR)) < 0)
+    {
+        fprintf(stderr, "open(2) %s: %s\n", path, strerror(errno));
+        goto end;
+    }
+    else if (ioctl(tfd, TUNSETIFF, &ifr) < 0)
+    {
+        perror("ioctl(2)");
+        goto end;
+    }
+    else if (!(s = strdup(ifr.ifr_name)))
+    {
+        perror("strdup(3)");
+        goto end;
+    }
+
+    fprintf(stderr, "set up TUN device %s\n", s);
+    unsigned long long total = 0;
+
+    for (;;)
+    {
+        char b[1500];
+        ssize_t n = read(tfd, &b, sizeof b);
+
+        if (n < 0)
+        {
+            perror("read(2)");
+            goto end;
+        }
+
+        fprintf(stderr, "read %zu bytes\n", n);
+
+        size_t rem = n;
+
+        while (rem)
+        {
+            const void *p = b;
+
+            fprintf(stderr, "sending %zu bytes\n", rem);
+
+            if ((n = write(cfd, p, rem)) < 0)
+            {
+                perror("write(2)");
+                goto end;
+            }
+
+            fprintf(stderr, "sent %zu bytes, total: %llu\n", n, total += n);
+
+            p = (const char *)p + n;
+            rem -= n;
+        }
+    }
+
+    ret = EXIT_SUCCESS;
+
+end:
+
+    if (cfd >= 0 && close(cfd))
+    {
+        ret = EXIT_FAILURE;
+        perror("close(2)");
+    }
+
+    if (tfd >= 0 && close(tfd))
+    {
+        ret = EXIT_FAILURE;
+        fprintf(stderr, "close(2) %s: %s\n", path, strerror(errno));
+    }
+
+    free(s);
+    return ret;
+}