Add MTU negotiation

src/main.c

@@ -325,11 +325,16 @@ int main (int argc, char **argv)
         return 1;
     }
 
+    if (tun_set_mtu(tun_name, mtu)==-1) {
+        perror("tun_set_mtu");
+        return 1;
+    }
+
     fd_set_nonblock(tun_fd);
 
     int chacha = option_is_set(opts, "chacha20");
 
-    struct mud *mud = mud_create(bind_port, v4, v6, !chacha);
+    struct mud *mud = mud_create(bind_port, v4, v6, !chacha, mtu);
 
     if (!mud) {
         gt_log("couldn't create mud\n");
@@ -440,8 +445,6 @@ int main (int argc, char **argv)
 
                 send_size += r;
 
-                int update_tc = (ic.tc&0xFC)>(send_tc&0xFC);
-
                 if (send_size<=mtu) {
                     send_limit = send_size;
                     if ((ic.tc&0xFC)>(send_tc&0xFC))
@@ -453,25 +456,76 @@ int main (int argc, char **argv)
             }
         }
 
-        if (send_limit && mud_send(mud, send.buf, send_limit, send_tc)==send_limit) {
+        if (send_limit) {
-            if (send_size>send_limit)
+            int r = mud_send(mud, send.buf, send_limit, send_tc);
-                memmove(&send.buf[0], &send.buf[send_limit], send_size-send_limit);
+
-            send_size -= send_limit;
+            if (r==send_limit) {
-            send_limit = send_size;
+                if (send_size>send_limit)
-            send_tc = send_next_tc;
+                    memmove(send.buf, &send.buf[send_limit], send_size-send_limit);
-            send_next_tc = 0;
+                send_size -= send_limit;
+                send_limit = send_size;
+                send_tc = send_next_tc;
+                send_next_tc = 0;
+            } else if (r==-1) {
+                if (errno==EMSGSIZE) {
+                    long new_mtu = mud_get_mtu(mud);
+                    if (new_mtu!=mtu) {
+                        size_t total = send_size;
+
+                        if (tun_set_mtu(tun_name, new_mtu)==-1) {
+                            perror("tun_set_mtu");
+                            gt.quit |= 1;
+                            break;
+                        }
+
+                        gt_log("MTU changed: %li\n", new_mtu);
+
+                        mtu = new_mtu;
+                        send_size = 0;
+                        send_limit = 0;
+                        send_tc = 0;
+                        send_next_tc = 0;
+
+                        while (send_size<total) {
+                            struct ip_common ic;
+
+                            if (ip_get_common(&ic, send.buf+send_size, mtu))
+                                break;
+
+                            send_size += ic.size;
+
+                            if (send_size<=mtu) {
+                                send_limit = send_size;
+                                if ((ic.tc&0xFC)>(send_tc&0xFC))
+                                    send_tc = ic.tc;
+                            } else {
+                                if ((ic.tc&0xFC)>(send_next_tc&0xFC))
+                                    send_next_tc = ic.tc;
+                            }
+                        }
+                    }
+                } else if (errno!=EAGAIN) {
+                    perror("mud_send");
+                }
+            }
         }
 
-        mud_push(mud);
+        if (mud_push(mud)==-1 && errno!=EAGAIN)
+            perror("mud_push");
 
-        if (FD_ISSET(mud_fd, &rfds))
+        if (FD_ISSET(mud_fd, &rfds)) {
-            mud_pull(mud);
+            if (mud_pull(mud)==-1 && errno!=EAGAIN)
+                perror("mud_pull");
+        }
 
         while (!gt.quit) {
             const int size = mud_recv(mud, recv.buf, mtu);
 
-            if (size<=0)
+            if (size<=0) {
+                if (size==-1 && errno!=EAGAIN)
+                    perror("mud_recv");
                 break;
+            }
 
             int p = 0;
 

src/tun.c

@@ -240,3 +240,25 @@ ssize_t tun_write (int fd, const void *data, size_t size)
     return ret;
 #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

@@ -2,6 +2,7 @@
 
 #include <unistd.h>
 
-int     tun_create (char *, char **, int);
+int     tun_create  (char *, char **, int);
-ssize_t tun_read   (int, void *, size_t);
+ssize_t tun_read    (int, void *, size_t);
-ssize_t tun_write  (int, const void *, size_t);
+ssize_t tun_write   (int, const void *, size_t);
+int     tun_set_mtu (char *, int);