Messages in this thread | | | Date | Tue, 23 Apr 2024 21:24:51 -0400 | From | Willem de Bruijn <> | Subject | Re: [RFC] net: add TCP fraglist GRO support |
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Felix Fietkau wrote: > On 23.04.24 16:34, Paolo Abeni wrote: > > On Tue, 2024-04-23 at 14:23 +0200, Felix Fietkau wrote: > >> On 23.04.24 14:11, Eric Dumazet wrote: > >> > On Tue, Apr 23, 2024 at 1:55 PM Felix Fietkau <nbd@nbd.name> wrote: > >> > > > >> > > In the world of consumer-grade WiFi devices, there are a lot of chipsets > >> > > with limited or nonexistent SG support, and very limited checksum > >> > > offload capabilities on Ethernet. The WiFi side of these devices is > >> > > often even worse. I think fraglist GRO is a decent fallback for the > >> > > inevitable corner cases. > >> > > >> > What about netfilter and NAT ? Are they okay with NETIF_F_FRAGLIST_GRO already ? > >> > > >> > Many of these devices are probably using NAT. > >> > >> In my tests, nftables NAT works just fine, both with and without > >> flowtable offloading. I didn't see anything in netfilter that would have > >> a problem with this. > > > > I see you handle explicitly NAT changes in __tcpv4_gso_segment_csum(), > > like the current UDP code. > > > > The TCP header has many other fields that could be updated affecting > > the TCP csum. > > Handling every possible mutation looks cumbersome and will likely > > reduce the performance benefits. > > > > What is your plan WRT other TCP header fields update? > > I think that should be easy enough to handle. My patch already only > combines packets where tcp_flag_word(th) is identical. So when > segmenting, I could handle all flags changes with a single > inet_proto_csum_replace4 call. > > > Strictly WRT the patch, I guess it deserves to be split in series, > > moving UDP helpers in common code and possibly factoring out more > > helpers with separate patches. > Will do.
A significant chunk of the complexity is in the tcp[46]_check_fraglist_gro sk match. Is this heuristic worth the complexity?
It seems that the platforms that will enable NETIF_F_FRAGLIST will be mainly forwarding planes.
If keeping, this refinement can probably a separate follow-on patch in the series too:
- refactor existing udp code - add segmentation support to handle such packets on tx - add coalescing support that starts building such packets on rx - refine coalescing choice
> > e.g. in __tcpv4_gso_segment_csum() is quite similar > > __udpv4_gso_segment_csum() - even too much, as the tcp csum should be > > always be updated when the ports or addresses change ;) > > Will fix that. > > Thanks, > > - Felix
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