Re: [PATCH v2] network: add rule to nftables backend that zeroes checksum of DHCP responses

On 10/29/24 11:12 AM, Phil Sutter wrote:

> FWIW, I just tested an alternative workaround using tc. This works for > me with a FreeBSD guest and NIC switched to either e1000 or virtio: > > # tc qd add dev vnetbr0 root handle 1: htb > # tc filter add dev vnetbr0 prio 1 protocol ip parent 1: \ > u32 match ip sport 67 ffff match ip dport 68 ffff \ > action csum ip and udp This did work for me. However, since we support bandwidth management of the interfaces connected to a virtual netowkr using tc, I decided to try doing the same on a network configured with bandwidth management enabled. I did this by adding the following to the <network> XML before starting the network: <bandwidth> <inbound average='1000' peak='2000' burst='5120'/> <outbound average='500' peak='1000' burst='2560'/> </bandwidth> This resulted in the following tc-related stuff being setup: # tc filter show dev virbr13 filter parent 1: protocol all pref 1 fw chain 0 filter parent 1: protocol all pref 1 fw chain 0 handle 0x1 classid :1 ======= # tc qd show dev virbr13 qdisc htb 1: root refcnt 2 r2q 10 default 0x2 direct_packets_stat 0 direct_qlen 1000 qdisc sfq 2: parent 1:2 limit 127p quantum 1514b depth 127 divisor 1024 perturb 10sec qdisc ingress ffff: parent ffff:fff1 ---------------- ======= # tc class show dev virbr13 class htb 1:1 root rate 8Mbit ceil 16Mbit burst 1600b cburst 1600b class htb 1:2 parent 1:1 leaf 2: prio 0 rate 8Mbit ceil 16Mbit burst 5Mb cburst 1600b ======= (obviously my network is using virbr13). Now when I try running the commands above, I see this: # tc qd add dev virbr13 root handle 1: htb Error: Exclusivity flag on, cannot modify.

So how does this all need to change in order to have our per-bridge-device bandwidth management coexist with the qdisc/filter to re-compute dhcp response checksums? (sorry for requesting that you ELI5; that's just easier than digging through all the documentation to figure out what is probably a simple solution :-P)