DHCP problems

[vladstamate]

Hey folks,

I am having trouble with DHCP (and Qemu), as in I am not getting any response back to my DHCP discover. What I have tried/verified:

- dumped the package I am sending and verified it with Wireshark that is a correct DHCP package
- tried both Virtio and RTL8139 (the 2 network cards I have drivers for in my OS)

Both cards say message sent correctly (I get an interrupt back) but I never get a response back. What I do is very simple:

- (from kernel, no sockets, all very simple) build a DHCP discover message (with multicast)
- wrap it in a UDP package
- wrap that in a IPV4 package
- wrap that in an Ethernet package
- then send it out into the ether.

....and...nothing back....total silence.

At a high level am I approaching this correctly? Do I need to send something else? I run qemu like this:

-netdev user,id=net0 -device virtio-net-pci,netdev=net0

[Octocontrabass]

- dumped the package I am sending and verified it with Wireshark that is a correct DHCP package

Did you capture traffic with the filter-dump object?

[iansjack]

Can you post a dump of the outgoing packet. There must be something wrong with it if you get no response. Did you remember to translate the endianness where necessary? Is the checksum correct?

[vladstamate]

- dumped the package I am sending and verified it with Wireshark that is a correct DHCP package

Did you capture traffic with the filter-dump object?

Hey thank you very much for that. I dumped the package, loaded it in Wireshark and guess what? QEMU is actually answering back with an Offer! So it must mean I have some issues in both my VIRTIO and RTL8139 drivers! Thank you again for pointing that out!