UDP数据包从内核到Linux中用户空间的路径

Question

I'm maintaining some network driver and I've got some problems with lost of data. The effect is that when I send for example ICMP or UDP ping using ping or nping some of the udp/icmp packets are lost.

I'm sure that on ping/nping side of the transmission the ping reply is received by my driver and the kernel (tcpdump shows incoming udp or icmp packets as a reply).

But application ping/nping shows sometimes that for example 80% packets are lost. I suspect that those packets are lost somewhere between kernel and user space.

I know that for UDP there is procedure udp_rcv() for maintenance of UDP packets, but I don't know which procedure is next in the path of delivering of the packet to user space application.

Linux kernel is in version 3.3.8.

My question is - how to trace the whole path of transition of the packet from my driver to user space socket buffer?

Answer 1

udp_rcv() is a callback that is passed to struct net_protocol as a .handler . You may either look at usage of this handler field in the structure, or you can also see if some error occurs. There is a callback err_handler . Maybe packet loss happens here and error handler will be called.

PS Remember that UDP does not guarantee 100% transmit success, and one lost packet out of 100 might be expected behavior. (: