Can I change the content of a packet in RouteInput() function?

[bxin Guan]

I used the RouteInput() to forward and locally deliver packet.

I want to add a header defined by myself, but the packet Ptr is 'const', so I use  packet = p->copy() , when I call the ucb (route,packet,header) , it seem working fine.

But when I enable  wifiPhy.EnableAsciiAll() in test code, it will crash with:

assert failed. cond="m_current >= delta", file=./ns3/buffer.h, line=865
terminate called without an active exception

If I don't modify the packet and call ucb (route,p,header) , it working fine.

What are the first 8 bytes of the packet, the header? I have noticed the problems of the first 8 bytes. How do I modify packets correctly?

[bxin Guan]

I want add header like this :   The first 8 bytes data (The default Ipv4 Header?) + my defined header + packet normal content.