I actually looked at one of your older replies to see where I could find the missing functions. I tried twice a fully clean checkout, same thing.
But can you check your ipq patches? Where do you have this symbol? Because it's for sure a QC addition, not mainline.
you are 100% sure you are working on a working tree?
I clean rebuilt on a new machine with all of the default items from the restart branch with no issues 
That is my experience as well, I even did it today twice as someboy PM-ed me with the same error.
@hgblob can you share your .config with the error? i'm sure we will reproduce the error in no time with that
After my build error, I tried to grep for skb_set_tc_classify_offload in the main directory. Other than the nss-drv where it was used I could not find it anywhere else.
Just rebuild everything from scratch, no compile issues at all.
Ok, so weird thing. @Ansuel has the patches needed in his tree for the ipq target
but I can't see these patches in @robimarko tree, the tc_classify_offload patch is missing: target/linux/ipq807x/patches-5.10/991-flat_to_indetify_igress.patch
I also can't see those patches, but they have been renumbered in the updates branch afaik
Lately github search has been a bit dubious but I cannot find them at all in robimarkos restart branch.
Because it's not there.
I would guess that @Apache14, @Ansuel nor I am not hitting the error as CONFIG_NET_CLS_ACT is disabled by default so that function is not called compiled in at all.
Its being triggered due to you including:
kmod-sched-core
ok now i remember i had that error while compiling a complete image for ax3600 migrating the r7800 config (where i have sched enabled)
also about that sched offload would be really good to have since now they both support flow
Can you make a clean patch adding the required kernel stuff?
I am not against including it as lot of people use cake etc.
I need to check the required package, patch and also check if they are not too large.
Sure, I understand.
i can be wrong but cake was not supported but the more standard sched was supported and offloaded
I know, its just when you enable CAKE or any other scheduler kmod it will pull in the generic support for that and then this build error will be visible
we should also consider patching the problematic package and add a custom flag to manually disable sched support...