Update mud

This allows to build easily with other libc.

.build.sh

@@ -11,5 +11,8 @@ cd ..
 [ -x glorytun ] || exit 1
 
 mkdir -p deploy
+
+cp glorytun deploy/glorytun-$(cat VERSION)-$(uname -m).debug.bin
+
 strip -s glorytun
-mv glorytun deploy/glorytun-$(cat VERSION)-$(uname -m).bin
+cp glorytun deploy/glorytun-$(cat VERSION)-$(uname -m).bin

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "mud"]
+	path = mud
+	url = https://github.com/angt/mud.git

Makefile.am

@@ -7,7 +7,6 @@ glorytun_LDADD = $(libsodium_LIBS)
 glorytun_SOURCES = \
     src/common.h \
     src/common.c \
-    src/buffer.h \
     src/ip.h \
     src/str.h \
     src/main.c \
@@ -16,9 +15,11 @@ glorytun_SOURCES = \
     src/tun.c \
     src/tun.h \
     src/db.c \
-    src/db.h \
-    src/state.c \
-    src/state.h
+    src/db.h
+
+glorytun_SOURCES += \
+    mud/mud.h \
+    mud/mud.c
 
 EXTRA_DIST = \
     LICENSE \

README.md

@@ -1,10 +1,6 @@
-# π₁(Glorytun)=ℤ²
+# π₁(Glorytun)=0
 
-Small, Simple and Stupid TCP VPN.
-
-#### Work In Progress
-
-This code will probably format your harddisk!
+Small, Simple and Stupid VPN over [mud](https://github.com/angt/mud).
 
 #### Build and Install
 
@@ -12,7 +8,7 @@ Glorytun depends on [libsodium](https://github.com/jedisct1/libsodium) version >
 
 To build and install the latest version:
 
-    $ git clone https://github.com/angt/glorytun
+    $ git clone https://github.com/angt/glorytun --recursive --branch mud
     $ cd glorytun
     $ ./autogen.sh
     $ ./configure

configure.ac

@@ -14,7 +14,6 @@ AM_SILENT_RULES([yes])
 AM_PROG_CC_C_O
 AC_PROG_CC_C99
 AC_USE_SYSTEM_EXTENSIONS
-AC_SEARCH_LIBS([getaddrinfo], [resolv nsl])
 AC_SEARCH_LIBS([socket], [socket])
 AC_CHECK_LIB([rt], [clock_gettime])
 AC_CHECK_FUNCS([clock_gettime])

src/buffer.h

@@ -1,66 +0,0 @@
-#pragma once
-
-#include "common.h"
-
-typedef struct buffer buffer_t;
-
-struct buffer {
-    uint8_t *data;
-    uint8_t *read;
-    uint8_t *write;
-    uint8_t *end;
-};
-
-static inline void buffer_setup (buffer_t *buffer, void *data, size_t size)
-{
-    if (!data)
-        data = malloc(ALIGN(size));
-
-    buffer->data  = data;
-    buffer->read  = data;
-    buffer->write = data;
-    buffer->end   = data;
-    buffer->end  += size;
-}
-
-static inline void buffer_format (buffer_t *buffer)
-{
-    buffer->write = buffer->data;
-    buffer->read  = buffer->data;
-}
-
-_pure_
-static inline size_t buffer_size (buffer_t *buffer)
-{
-    return buffer->end-buffer->data;
-}
-
-_pure_
-static inline size_t buffer_write_size (buffer_t *buffer)
-{
-    return buffer->end-buffer->write;
-}
-
-_pure_
-static inline size_t buffer_read_size (buffer_t *buffer)
-{
-    return buffer->write-buffer->read;
-}
-
-static inline void buffer_shift (buffer_t *buffer)
-{
-    if (buffer->read==buffer->data)
-        return;
-
-    if (buffer->read==buffer->write) {
-        buffer_format(buffer);
-        return;
-    }
-
-    const size_t size = buffer_read_size(buffer);
-
-    memmove(buffer->data, buffer->read, size);
-
-    buffer->read  = buffer->data;
-    buffer->write = buffer->data+size;
-}

src/common.c

@@ -1,9 +1,10 @@
 #include "common.h"
 
-#include <stdio.h>
 #include <stdarg.h>
+#include <stdio.h>
 
-int gt_print (const char *fmt, ...)
+int
+gt_print(const char *fmt, ...)
 {
     va_list ap;
     va_start(ap, fmt);
@@ -16,7 +17,8 @@ int gt_print (const char *fmt, ...)
     return ret;
 }
 
-void gt_log (const char *fmt, ...)
+void
+gt_log(const char *fmt, ...)
 {
     va_list ap;
     va_start(ap, fmt);
@@ -24,7 +26,8 @@ void gt_log (const char *fmt, ...)
     va_end(ap);
 }
 
-void gt_fatal (const char *fmt, ...)
+void
+gt_fatal(const char *fmt, ...)
 {
     va_list ap;
     va_start(ap, fmt);
@@ -34,17 +37,19 @@ void gt_fatal (const char *fmt, ...)
     exit(EXIT_FAILURE);
 }
 
-void gt_na (const char *name)
+void
+gt_na(const char *name)
 {
     gt_log("%s is not available on your platform\n", name);
 }
 
-int gt_tohex (char *dst, size_t dst_size, const uint8_t *src, size_t src_size)
+int
+gt_tohex(char *dst, size_t dst_size, const uint8_t *src, size_t src_size)
 {
-    if _0_(!dst_size)
+    if (_0_(!dst_size))
         return -1;
 
-    if _0_(((dst_size-1)/2)<src_size)
+    if (_0_(((dst_size - 1) / 2) < src_size))
         return -1;
 
     static const char tbl[] = "0123456789ABCDEF";
@@ -59,8 +64,8 @@ int gt_tohex (char *dst, size_t dst_size, const uint8_t *src, size_t src_size)
     return 0;
 }
 
-_const_
-static inline int fromhex (const char c)
+_const_ static inline int
+fromhex(const char c)
 {
     if (c >= '0' && c <= '9')
         return c - '0';
@@ -74,19 +79,20 @@ static inline int fromhex (const char c)
     return -1;
 }
 
-int gt_fromhex (uint8_t *dst, size_t dst_size, const char *src, size_t src_size)
+int
+gt_fromhex(uint8_t *dst, size_t dst_size, const char *src, size_t src_size)
 {
-    if _0_(src_size&1)
+    if (_0_(src_size & 1))
         return -1;
 
-    if _0_(dst_size<(src_size/2))
+    if (_0_(dst_size < (src_size / 2)))
         return -1;
 
     for (size_t i = 0; i < src_size; i += 2) {
         const int a = fromhex(src[i]);
         const int b = fromhex(src[i + 1]);
 
-        if _0_(a==-1 || b==-1)
+        if (_0_(a == -1 || b == -1))
             return -1;
 
         *dst++ = (a << 4) | b;

src/common.h

@@ -29,6 +29,12 @@
 #define _const_        __attribute__ ((const))
 #define _align_(...)   __attribute__ ((aligned(__VA_ARGS__)))
 
+#undef MAX
+#define MAX(x,y) ({ __typeof__(x) X=(x); __typeof__(y) Y=(y); X > Y ? X : Y; })
+
+#undef MIN
+#define MIN(x,y) ({ __typeof__(x) X=(x); __typeof__(y) Y=(y); X < Y ? X : Y; })
+
 int  gt_print (const char *, ...) _printf_(1,2);
 void gt_log   (const char *, ...) _printf_(1,2);
 void gt_fatal (const char *, ...) _printf_(1,2) _noreturn_;

src/db.c

@@ -12,14 +12,14 @@ struct node {
     uint32_t point;
 };
 
-_pure_
-static inline size_t db_size (const uint8_t *a)
+_pure_ static inline size_t
+db_size(const uint8_t *a)
 {
     return (a[0] ?: str_len((char *)a + 1)) + 1;
 }
 
-_pure_
-static inline size_t db_cmp (const uint8_t *a, const uint8_t *b)
+_pure_ static inline size_t
+db_cmp(const uint8_t *a, const uint8_t *b)
 {
     const size_t size = a[0];
 
@@ -39,8 +39,8 @@ static inline size_t db_cmp (const uint8_t *a, const uint8_t *b)
     return 0;
 }
 
-_pure_
-static inline int db_dir (const uint32_t point, uint8_t *data, const size_t size)
+_pure_ static inline int
+db_dir(const uint32_t point, uint8_t *data, const size_t size)
 {
     const size_t pos = point >> 8;
 
@@ -50,9 +50,10 @@ static inline int db_dir (const uint32_t point, uint8_t *data, const size_t size
     return ((point | data[pos]) & 255) == 255;
 }
 
-uint8_t *db_search (uint8_t **p, uint8_t *data)
+uint8_t *
+db_search(uint8_t **p, uint8_t *data)
 {
-    if _0_(!*p)
+    if (_0_(!*p))
         return NULL;
 
     uint8_t *r = *p;
@@ -69,12 +70,13 @@ uint8_t *db_search (uint8_t **p, uint8_t *data)
     return NULL;
 }
 
-uint8_t *db_insert (uint8_t **p, uint8_t *data)
+uint8_t *
+db_insert(uint8_t **p, uint8_t *data)
 {
-    if _0_(CBIT(data))
+    if (_0_(CBIT(data)))
         return NULL;
 
-    if _0_(!*p) {
+    if (_0_(!*p)) {
         *p = data;
         return data;
     }
@@ -89,7 +91,7 @@ uint8_t *db_insert (uint8_t **p, uint8_t *data)
 
     const size_t diff = db_cmp(r, data);
 
-    if _0_(!diff)
+    if (_0_(!diff))
         return r;
 
     const size_t pos = diff - 1;
@@ -107,7 +109,7 @@ uint8_t *db_insert (uint8_t **p, uint8_t *data)
 
     struct node *node = malloc(sizeof(struct node));
 
-    if _0_(!node)
+    if (_0_(!node))
         return NULL;
 
     const int dir = (mask | r[pos]) == 255;
@@ -121,9 +123,10 @@ uint8_t *db_insert (uint8_t **p, uint8_t *data)
     return data;
 }
 
-uint8_t *db_remove (uint8_t **p, uint8_t *data)
+uint8_t *
+db_remove(uint8_t **p, uint8_t *data)
 {
-    if _0_(!*p)
+    if (_0_(!*p))
         return NULL;
 
     const size_t size = db_size(data);
@@ -139,7 +142,7 @@ uint8_t *db_remove (uint8_t **p, uint8_t *data)
         p = node->child + dir;
     }
 
-    if _0_(db_cmp(data, *p))
+    if (_0_(db_cmp(data, *p)))
         return NULL;
 
     uint8_t *r = *p;

src/ip.h

@@ -4,13 +4,14 @@
 
 struct ip_common {
     uint8_t version;
+    uint8_t tc;
     uint8_t proto;
     uint8_t hdr_size;
     uint16_t size;
 };
 
-_pure_
-static inline uint8_t ip_get_version (const uint8_t *data, size_t size)
+_pure_ static inline uint8_t
+ip_get_version(const uint8_t *data, size_t size)
 {
     if (size < 20)
         return 0;
@@ -18,17 +19,22 @@ static inline uint8_t ip_get_version (const uint8_t *data, size_t size)
     return data[0] >> 4;
 }
 
-static inline int ip_get_common (struct ip_common *ic, const uint8_t *data, size_t size)
+static inline int
+ip_get_common(struct ip_common *ic, const uint8_t *data, size_t size)
 {
     ic->version = ip_get_version(data, size);
 
     switch (ic->version) {
     case 4:
+        ic->tc = data[1];
         ic->proto = data[9];
         ic->hdr_size = (data[0] & 0xF) << 2;
         ic->size = ((data[2] << 8) | data[3]);
+        if (ic->size >= 20)
             return 0;
+        break;
     case 6:
+        ic->tc = ((data[0] & 0xF) << 4) | (data[1] >> 4);
         ic->proto = data[6];
         ic->hdr_size = 40;
         ic->size = ((data[4] << 8) | data[5]) + 40;

src/option.c

@@ -3,7 +3,8 @@
 #include "option.h"
 #include "str.h"
 
-int option_str (void *data, int argc, char **argv)
+int
+option_str(void *data, int argc, char **argv)
 {
     if (argc < 2 || str_empty(argv[1])) {
         gt_print("option `%s' need a string argument\n", argv[0]);
@@ -15,7 +16,8 @@ int option_str (void *data, int argc, char **argv)
     return 1;
 }
 
-int option_long (void *data, int argc, char **argv)
+int
+option_long(void *data, int argc, char **argv)
 {
     if (argc < 2 || str_empty(argv[1])) {
         gt_print("option `%s' need an integer argument\n", argv[0]);
@@ -36,7 +38,8 @@ int option_long (void *data, int argc, char **argv)
     return 1;
 }
 
-int option_is_set (struct option *opts, const char *name)
+int
+option_is_set(struct option *opts, const char *name)
 {
     for (int k = 0; opts[k].name; k++) {
         if (!str_cmp(opts[k].name, name))
@@ -46,7 +49,8 @@ int option_is_set (struct option *opts, const char *name)
     return 0;
 }
 
-int option_option (void *data, int argc, char **argv)
+int
+option_option(void *data, int argc, char **argv)
 {
     if (!data)
         return 0;
@@ -87,7 +91,8 @@ int option_option (void *data, int argc, char **argv)
     return argc;
 }
 
-static int option_usage (struct option *opts, int slen)
+static int
+option_usage(struct option *opts, int slen)
 {
     if (!opts)
         return 0;
@@ -114,7 +119,8 @@ static int option_usage (struct option *opts, int slen)
     return len;
 }
 
-int option (struct option *opts, int argc, char **argv)
+int
+option(struct option *opts, int argc, char **argv)
 {
     int ret = option_option(opts, argc, argv);
 

src/state.c

@@ -1,62 +0,0 @@
-#include "common.h"
-
-#include "state.h"
-#include "str.h"
-
-#include <stdio.h>
-#include <fcntl.h>
-#include <sys/stat.h>
-
-int state_create (const char *filename)
-{
-    if (str_empty(filename))
-        return -1;
-
-    int fd = open(filename, O_WRONLY);
-
-    if (fd==-1) {
-        if (errno!=EINTR)
-            perror("open");
-        return -1;
-    }
-
-    struct stat st = {0};
-
-    if (fstat(fd, &st)==-1) {
-        perror("fstat");
-        close(fd);
-        return -1;
-    }
-
-    if (!S_ISFIFO(st.st_mode)) {
-        gt_log("`%s' is not a fifo\n", filename);
-        close(fd);
-        return -1;
-    }
-
-    return fd;
-}
-
-void state_send (int fd, const char *state, const char *info)
-{
-    if (str_empty(state))
-        return;
-
-    if (fd==-1) {
-        gt_print("%s %s\n", state, info);
-        return;
-    }
-
-    const char *strs[] = { state, " ", info, "\n" };
-    char *str = str_cat(strs, COUNT(strs));
-
-    if (!str) {
-        perror("str_cat");
-        return;
-    }
-
-    if (write(fd, str, str_len(str))==-1 && errno!=EINTR)
-        perror("write");
-
-    free(str);
-}

src/state.h

@@ -1,4 +0,0 @@
-#pragma once
-
-int  state_create (const char *);
-void state_send   (int, const char *, const char *);

src/str.h

@@ -2,7 +2,8 @@
 
 #include "common.h"
 
-static inline size_t str_cpy (char *restrict dst, const char *restrict src, size_t len)
+static inline size_t
+str_cpy(char *restrict dst, const char *restrict src, size_t len)
 {
     if (!dst || !src)
         return 0;
@@ -17,14 +18,14 @@ static inline size_t str_cpy (char *restrict dst, const char *restrict src, size
     return i;
 }
 
-_pure_
-static inline int str_empty (const char *restrict str)
+_pure_ static inline int
+str_empty(const char *restrict str)
 {
     return !str || !str[0];
 }
 
-_pure_
-static inline size_t str_cmp (const char *restrict sa, const char *restrict sb)
+_pure_ static inline size_t
+str_cmp(const char *restrict sa, const char *restrict sb)
 {
     if (!sa || !sb)
         return 1;
@@ -38,8 +39,8 @@ static inline size_t str_cmp (const char *restrict sa, const char *restrict sb)
     return i + 1;
 }
 
-_pure_
-static inline size_t str_len (const char *restrict str)
+_pure_ static inline size_t
+str_len(const char *restrict str)
 {
     if (!str)
         return 0;
@@ -47,7 +48,8 @@ static inline size_t str_len (const char *restrict str)
     return strlen(str);
 }
 
-static inline char *str_cat (const char **strs, size_t count)
+static inline char *
+str_cat(const char **strs, size_t count)
 {
     size_t size = 1;
 

src/tun.c

@@ -1,25 +1,28 @@
 #include "common.h"
 
-#include "tun.h"
-#include "str.h"
 #include "ip.h"
+#include "str.h"
+#include "tun.h"
 
-#include <stdio.h>
 #include <fcntl.h>
+#include <stdio.h>
 
 #include <sys/ioctl.h>
 #include <sys/socket.h>
 #include <sys/uio.h>
 
+#include <net/if.h>
+
 #ifdef __linux__
-#include <linux/if.h>
-#include <linux/if_tun.h>
+#define IFF_TUN 0x0001
+#define IFF_NO_PI 0x1000
+#define TUNSETIFF _IOW('T', 202, int)
 #endif
 
 #ifdef __APPLE__
-#include <sys/sys_domain.h>
-#include <sys/kern_control.h>
 #include <net/if_utun.h>
+#include <sys/kern_control.h>
+#include <sys/sys_domain.h>
 #endif
 
 #if defined(__APPLE__) || defined(__OpenBSD__)
@@ -28,7 +31,8 @@
 
 #ifdef __APPLE__
 
-static int tun_create_by_id (char *name, size_t size, unsigned id, _unused_ int mq)
+static int
+tun_create_by_id(char *name, size_t size, unsigned id)
 {
     int fd = socket(PF_SYSTEM, SOCK_DGRAM, SYSPROTO_CONTROL);
 
@@ -41,7 +45,9 @@ static int tun_create_by_id (char *name, size_t size, unsigned id, _unused_ int
     str_cpy(ci.ctl_name, UTUN_CONTROL_NAME, sizeof(ci.ctl_name) - 1);
 
     if (ioctl(fd, CTLIOCGINFO, &ci)) {
+        int err = errno;
         close(fd);
+        errno = err;
         return -1;
     }
 
@@ -54,7 +60,9 @@ static int tun_create_by_id (char *name, size_t size, unsigned id, _unused_ int
     };
 
     if (connect(fd, (struct sockaddr *)&sc, sizeof(sc))) {
+        int err = errno;
         close(fd);
+        errno = err;
         return -1;
     }
 
@@ -63,21 +71,25 @@ static int tun_create_by_id (char *name, size_t size, unsigned id, _unused_ int
     return fd;
 }
 
-static int tun_create_by_name (char *name, size_t size, char *dev_name, int mq)
+static int
+tun_create_by_name(char *name, size_t size, char *dev_name)
 {
     unsigned id = 0;
 
-    if (sscanf(dev_name, "utun%u", &id)!=1)
+    if (sscanf(dev_name, "utun%u", &id) != 1) {
+        errno = EINVAL;
         return -1;
+    }
 
-    return tun_create_by_id(name, size, id, mq);
+    return tun_create_by_id(name, size, id);
 }
 
 #else /* not __APPLE__ */
 
 #ifdef __linux__
 
-static int tun_create_by_name (char *name, size_t size, char *dev_name, int mq)
+static int
+tun_create_by_name(char *name, size_t size, char *dev_name)
 {
     int fd = open("/dev/net/tun", O_RDWR);
 
@@ -88,12 +100,6 @@ static int tun_create_by_name (char *name, size_t size, char *dev_name, int mq)
         .ifr_flags = IFF_TUN | IFF_NO_PI,
     };
 
-    if (mq) {
-#ifdef IFF_MULTI_QUEUE
-        ifr.ifr_flags |= IFF_MULTI_QUEUE;
-#endif
-    }
-
     str_cpy(ifr.ifr_name, dev_name, IFNAMSIZ - 1);
 
     if (ioctl(fd, TUNSETIFF, &ifr)) {
@@ -108,7 +114,8 @@ static int tun_create_by_name (char *name, size_t size, char *dev_name, int mq)
 
 #else /* not __linux__ not __APPLE__ */
 
-static int tun_create_by_name (char *name, size_t size, char *dev_name, _unused_ int mq)
+static int
+tun_create_by_name(char *name, size_t size, char *dev_name)
 {
     char path[64];
 
@@ -120,32 +127,29 @@ static int tun_create_by_name (char *name, size_t size, char *dev_name, _unused_
 
 #endif /* not __APPLE__ */
 
-static int tun_create_by_id (char *name, size_t size, unsigned id, int mq)
+static int
+tun_create_by_id(char *name, size_t size, unsigned id)
 {
     char dev_name[64];
 
     snprintf(dev_name, sizeof(dev_name), "tun%u", id);
 
-    return tun_create_by_name(name, size, dev_name, mq);
+    return tun_create_by_name(name, size, dev_name);
 }
 
 #endif
 
-int tun_create (char *dev_name, char **ret_name, int mq)
+int
+tun_create(char *dev_name, char **ret_name)
 {
     char name[64] = {0};
     int fd = -1;
 
-#ifndef IFF_MULTI_QUEUE
-    if (mq)
-        gt_na("IFF_MULTI_QUEUE");
-#endif
-
     if (str_empty(dev_name)) {
         for (unsigned id = 0; id < 32 && fd == -1; id++)
-            fd = tun_create_by_id(name, sizeof(name), id, mq);
+            fd = tun_create_by_id(name, sizeof(name), id);
     } else {
-        fd = tun_create_by_name(name, sizeof(name), dev_name, mq);
+        fd = tun_create_by_name(name, sizeof(name), dev_name);
     }
 
     if (fd != -1 && ret_name)
@@ -154,48 +158,45 @@ int tun_create (char *dev_name, char **ret_name, int mq)
     return fd;
 }
 
-ssize_t tun_read (int fd, void *data, size_t size)
+int
+tun_read(int fd, void *data, size_t size)
 {
     if (!size)
-        return -1;
+        return 0;
 
 #ifdef GT_BSD_TUN
     uint32_t family;
 
     struct iovec iov[2] = {
-        { .iov_base = &family, .iov_len = sizeof(family) },
-        { .iov_base = data, .iov_len = size }
+        {
+            .iov_base = &family,
+            .iov_len = sizeof(family),
+        },
+        {
+            .iov_base = data,
+            .iov_len = size,
+        },
     };
 
     ssize_t ret = readv(fd, iov, 2);
-#else
-    ssize_t ret = read(fd, data, size);
-#endif
 
-    if (ret==-1) {
-        if (errno==EAGAIN || errno==EINTR)
-            return -1;
+    if (ret <= (ssize_t)0)
+        return ret;
 
-        if (errno)
-            perror("tun read");
-
-        return 0;
-    }
-
-#ifdef GT_BSD_TUN
-    if (ret<(ssize_t) sizeof(family))
+    if (ret <= (ssize_t)sizeof(family))
         return 0;
 
     return ret - sizeof(family);
 #else
-    return ret;
+    return read(fd, data, size);
 #endif
 }
 
-ssize_t tun_write (int fd, const void *data, size_t size)
+int
+tun_write(int fd, const void *data, size_t size)
 {
     if (!size)
-        return -1;
+        return 0;
 
 #ifdef GT_BSD_TUN
     uint32_t family;
@@ -208,35 +209,54 @@ ssize_t tun_write (int fd, const void *data, size_t size)
         family = htonl(AF_INET6);
         break;
     default:
+        errno = EINVAL;
         return -1;
     }
 
     struct iovec iov[2] = {
-        { .iov_base = &family, .iov_len = sizeof(family) },
-        { .iov_base = (void *) data, .iov_len = size },
+        {
+            .iov_base = &family,
+            .iov_len = sizeof(family),
+        },
+        {
+            .iov_base = (void *)data,
+            .iov_len = size,
+        },
     };
 
     ssize_t ret = writev(fd, iov, 2);
-#else
-    ssize_t ret = write(fd, data, size);
-#endif
 
-    if (ret==-1) {
-        if (errno==EAGAIN || errno==EINTR)
-            return -1;
+    if (ret <= (ssize_t)0)
+        return ret;
 
-        if (errno)
-            perror("tun write");
-
-        return 0;
-    }
-
-#ifdef GT_BSD_TUN
-    if (ret<(ssize_t) sizeof(family))
+    if (ret <= (ssize_t)sizeof(family))
         return 0;
 
     return ret - sizeof(family);
 #else
-    return ret;
+    return write(fd, data, size);
 #endif
 }
+
+int
+tun_set_mtu(char *dev_name, int mtu)
+{
+    struct ifreq ifr = {
+        .ifr_mtu = mtu,
+    };
+
+    str_cpy(ifr.ifr_name, dev_name, IFNAMSIZ - 1);
+
+    int fd = socket(AF_INET, SOCK_DGRAM, 0);
+
+    if (fd == -1)
+        return -1;
+
+    int ret = ioctl(fd, SIOCSIFMTU, &ifr);
+
+    int err = errno;
+    close(fd);
+    errno = err;
+
+    return ret;
+}

src/tun.h

@@ -1,7 +1,6 @@
 #pragma once
 
-#include <unistd.h>
-
-int     tun_create (char *, char **, int);
-ssize_t tun_read   (int, void *, size_t);
-ssize_t tun_write  (int, const void *, size_t);
+int tun_create  (char *, char **);
+int tun_read    (int, void *, size_t);
+int tun_write   (int, const void *, size_t);
+int tun_set_mtu (char *, int);