type SharedStream struct {
    Stream *network.Stream
    Lock   *sync.Mutex
}
...
// Inside the TUN-read loop:
if found {
    dst = route.Target.ID
    go node.sendPacket(dst, packet, plen)
}
...
func (node *Node) sendPacket(dst peer.ID, packet []byte, plen int) {
    // Check if we already have an open connection to the destination peer.
    ms, ok := node.activeStreams[dst]
    if ok {
        if func() bool {
            ms.Lock.Lock()
            defer ms.Lock.Unlock()
            // Write out the packet's length to the libp2p stream to ensure
            // we know the full size of the packet at the other end.
            err := binary.Write(*ms.Stream, binary.LittleEndian, uint16(plen))
            if err == nil {
                // Write the packet out to the libp2p stream.
                _, err = (*ms.Stream).Write(packet[:plen])
                ...
            }
            ...
        }() { return }
    }
    ...
}