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hyper-vdpdk

How to set a loop forwarding mode from one NIC to another in DPDK testpmd?

Testpmd is running in a Hyper-V VM, and there are two NICs which connect to "internal virtual switch". I just want to test the availability of netvsc PMD.

./app/dpdk-testpmd -l 2,3 -- --total-num-mbufs=2048 -i --portmask=0x3 --port-topology=loop

I have used "start" or "start tx_first", and then used "show port stats all" to check. There are no Tx-packets or Rx-packets on two NICs.

Then I used "set fwd txonly", and I could find Tx-packets on two NICs, but it is not my want. So what steps can I do?

I want this

Solution

  • Typically, one wants to use a packet generator on the side that is opposite to a pair of ports harnessed by testpmd. Such a generator starts sending packets, whilst testpmd simply receives them on one port and transmits them back from the other one. This is what port-topology of type paired stands for, and this port-topology is used by default in testpmd. Another parameter, forward-mode, in turn, is set to io by default, which means that testpmd does not change the received packets before transmitting them back (in example, does not swap MAC addresses, etc.).

    However, in your case there's no packet generator employed, and that means that testpmd must generate and send a batch of packets itself in order to kick-start forwarding. This is accomplished by specifying option --tx-first.

    But apart from omitting option --tx-first you for some reason use option --port-topology=loop, which might be the reason behind your setup being non-functional. Variant loop means that packets received by a given port (say, Port 0) must be transmitted back from the very same port (that is, from Port 0). What you might want here is --port-topology=paired, which, as I stated before, is anyway used by default.

    So, the short of it, you should probably try running testpmd as follows:

    ./app/dpdk-testpmd -l 2,3 -- --total-num-mbufs=2048 -i --portmask=0x3 --tx-first

    Please note that this way forwarding is started automatically but you get no testpmd> prompt to enter command in. Should you wish to start forwarding automatically and, at the same time, get an interactive command prompt, please try running testpmd this way:

    ./app/dpdk-testpmd -l 2,3 -- --total-num-mbufs=2048 -i --portmask=0x3 --tx-first --auto-start -i