I want to measure the instantaneous size of the transmission buffer or the number of packets waiting to be sent on an Ethernet interface.
The problem is that the kernel takes the packet from the transmission queue and puts it in a Transmission Ring Buffer (Tx-Ring) before sending it out on the wire. Therefore: Total instantaneous size of transmission queue = No of packets in queue + No. of packets in the transmission ring buffer.
I am unable to obtain the size of the transmission ring buffer in the net/sched/*.c files. All the information regarding the size of the queue refers to the transmission queue and does not include the packets that have been put in the Ring-Buffer. Could someone please point me in the right direction. Thanks.