[dpdk-users] Is it possible to TX through a port with no RX connected?

[Andrea Bigagli]

Hi everyone.
Moving first steps with DPDK, so forgive my noobness or if this is a dumb question, but I’ve searched around before posting and didn’t find anything that could help me.

I have 4 Intel 10Gbps cards for a total of 8 RX/TX ports.
What I’m trying to do is a kind of “8->4 tapping-concentrator”: 8 fibers are tapped through an optical splitter and connected to the 8 RX ports, some packet analysis is performed and based on certain properties of the packets, traffic is re-routed on only 4 TX ports.
The application guarantees that overall input bandwidth is less than 30Gbps, so using only 4 TXs is not a problem (the balancing is almost pretty even).
The problem I’m facing is that the 8 monitored RX are not always up. The system being monitored at times shuts down some of those 8 connections and so on some of the 8 RXs the link goes down, and when that happens, the corresponding TX stops working.
I’m not a great expert of the inner working of the 10Gbps cards, I’ve skimmed through the 82599 datasheet and tried to play with some registers (i.e. setting the “FORCE-LINK-UP” bit in the AUTOC register), but couldn’t find a way to keep the TX ports running without something “alive” on the corresponding RX port.

Is there any way (maybe diving down at the PHY layer, which I’m really not familiar with) to have TX ports working regardless of their corresponding RX port status?
Looping back something in the RX port is not feasible in my case because the RX port has to be dedicated to the tapped traffic, for when there’s actually traffic on it.

Hope I was able to explain myself, and hope someone could point me in some direction as I’m totally stuck at the moment.


Thanks,
Andrea.