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Diffstat (limited to 'gitlab/issues/target_missing/host_missing/accel_missing/2962.toml')
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1 files changed, 30 insertions, 0 deletions
diff --git a/gitlab/issues/target_missing/host_missing/accel_missing/2962.toml b/gitlab/issues/target_missing/host_missing/accel_missing/2962.toml new file mode 100644 index 00000000..0bd98457 --- /dev/null +++ b/gitlab/issues/target_missing/host_missing/accel_missing/2962.toml @@ -0,0 +1,30 @@ +id = 2962 +title = "DHCP UDP checksum workaround code appears to be broken" +state = "opened" +created_at = "2025-05-12T20:31:41.263Z" +closed_at = "n/a" +labels = ["Networking"] +url = "https://gitlab.com/qemu-project/qemu/-/issues/2962" +host-os = "Debian 12" +host-arch = "x86" +qemu-version = "9.2.3" +guest-os = "Linux Mint" +guest-arch = "x86" +description = """I am running dnsmasq DHCP server in an lxc-container. It is using a VETH pair for the network. The VETH device on the host is in a bridge. I create a TAP device and place it in the bridge. When booting the guest, I notice that the DHCP OFFER has an invalid UDP checksum all the way through the bridge and into the guest. I am able to fix this by disabling checksum offload inside the container, or adding an nftables rule that zeros out the checksum, or by reverting commit 7987d2be5a8bc3a502f89ba8cf3ac3e09f64d1ce.""" +reproduce = """1. From a debian 12 host, `apt-get install lxc lxc-templates` +2. `ip link add brtest type bridge` +3. `ip link set brtest up` +4. Create a container: `lxc-create -n dhcp -t debian -- --package=dnsmasq` +5. Edit the lxc container file `/var/lib/lxc/dhcp/config` and make sure the link is properly set to `lxc.net.0.link = brtest`, the type is set to `veth`, and give it an IP `lxc.net.0.ipv4.address = 192.168.255.1/24` +6. Start the container: `lxc-start -n dhcp` +7. Attach to the container: `lxc-attach -n dhcp` +8. Stop dnsmasq and networking: `systemctl stop dnsmasq.service networking.service` +9. Run a DHCP server: `dnsmasq --dhcp-authoritative --dhcp-range=192.168.255.2,192.168.255.254,255.255.255.0,1h --dns-loop-detect` +10. Exit the container: `exit` +11. Download the linux mint 22.1 installer: https://linuxmint.com/edition.php?id=319 +12. Create a TAP device and throw it in the bridge: `ip tuntap add dev taptest mode tap` .. `ip link set dev taptest up master brtest` +13. Run qemu: `qemu-system-x86_64 -enable-kvm -smp 4,sockets=1,threads=1 -machine pc-q35-9.2,accel=kvm,kernel_irqchip=on -m 4096 -device virtio-net-pci,netdev=nic91 -netdev tap,id=nic91,ifname=taptest,script=no,downscript=no -cdrom linuxmint-22.1-cinnamon-64bit.iso` .. I run it with vnc as this is on a headless server. +14. Once the guest has booted, you can run a tcpdump on the NIC and see that the guest receives the DHCP offer, but the UDP checksum is bunk.""" +additional = """I was able to test reverting the commit 7987d2be5a8bc3a502f89ba8cf3ac3e09f64d1ce and that appears to function once again. + +{width=901 height=38}""" |