include packet info in tun but discard it so that tun can work on platforms

that include packet info

llarp/ev.cpp

@@ -120,5 +120,6 @@ llarp_ev_add_tun(struct llarp_ev_loop *loop, struct llarp_tun_io *tun)
 bool
 llarp_ev_tun_async_write(struct llarp_tun_io *tun, const void *pkt, size_t sz)
 {
-  return static_cast< llarp::ev_io * >(tun->impl)->queue_write(pkt, sz);
+  // TODO: queue write
+  return static_cast< llarp::ev_io * >(tun->impl)->do_write(pkt, sz);
 }

llarp/ev.hpp

@@ -1,6 +1,8 @@
 #ifndef LLARP_EV_HPP
 #define LLARP_EV_HPP
 #include <llarp/ev.h>
+// witev
+#include <sys/uio.h>
 
 #ifndef _MSC_VER
 #include <unistd.h>
@@ -41,9 +43,16 @@ namespace llarp
 
     /// used for tun interface
     bool
-    queue_write(const void* data, size_t sz)
+    do_write(void* data, size_t sz)
     {
-      return write(fd, data, sz) != -1;
+      iovec vecs[2];
+      // TODO: IPV6
+      uint32_t t       = htonl(AF_INET);
+      vecs[0].iov_base = &t;
+      vecs[0].iov_len  = sizeof(t);
+      vecs[1].iov_base = data;
+      vecs[1].iov_len  = sz;
+      return writev(fd, vecs, 2) != -1;
     }
 
     /// called in event loop when fd is ready for writing
@@ -55,7 +64,7 @@ namespace llarp
       m_writeq.Process([&](WriteBuffer& buffer) {
       // todo: wtf???
 #ifndef _WIN32
-        write(fd, buffer.buf, buffer.bufsz);
+        do_write(buffer.buf, buffer.bufsz);
         // if we would block we save the entries for later
 
         // discard entry

llarp/ev_epoll.hpp

@@ -96,9 +96,10 @@ namespace llarp
     read(void* buf, size_t sz)
     {
       ssize_t ret = tuntap_read(tunif, buf, sz);
-      if(ret > 0 && t->recvpkt)
+      if(ret > 4 && t->recvpkt)
       {
-        t->recvpkt(t, buf, ret);
+        // don't include packet info
+        t->recvpkt(t, ((byte_t*)buf) + 4, ret - 4);
       }
       return ret;
     }

vendor/libtuntap-master/tuntap-unix-linux.c

@@ -72,7 +72,7 @@ tuntap_sys_start(struct device *dev, int mode, int tun)
     tuntap_log(TUNTAP_LOG_ERR, "Invalid parameter 'mode'");
     return -1;
   }
-  ifr.ifr_flags |= IFF_NO_PI;
+  // ifr.ifr_flags |= IFF_NO_PI;
 
   if(tun < 0)
   {