Rollback popped innermost headers?

[Robin Jarry]

Hi Morten,

For some reason your first message went to spam. Sorry for the delay.

Morten Brørup, May 28, 2026 at 21:29:
>> Is it impossible to unpop / roll back the L3 and L2 headers that were
>> popped from the mbuf?
>
> Self answering, after having examined more details...
>
> Maybe not impossible, but it would be an ugly hack.
> rte_pktmbuf_prepend() is prohibited, and gr_mbuf_prepend() is clearly
> designed for adding a new header, not for un-popping previously popped
> headers.

Also, when the packets reach dhcp_input, it is impossible to know where
the packet came from. It may have been decapsulated from a VXLAN tunnel
or some other weirdness. And as you pointed out, gr_mbuf_prepend()
must not be used to "recall" a previously popped header.

> Sorry about the noise. Just playing around with various corners of
> Grout to get acquainted with it.
>
> Hopefully other Grout newcomers can learn from my silly questions. :-)

Glad you could figure this out on your own ;)

-- 
Robin

> Illegally parked cars will be towed at owner's expense.