Re: [PATCH net-next v9 2/8] hsr: Use skb_clone() while adding the HSR header

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On 2026-10-16 11:41:20 [+0200], To Daniel Machon wrote:
> If this is important, I could add to the patch description. The removed
> skb_reset_mac_header() should be obvious.
> The csum_start() removal and so on was mostly sashiko complaining about
> one thing at at time and memove() got replaced with
> skb_postpush_data_move() in the last iteration which I just learned
> about myself ;) That looks like a nice clean up.

Updated as:

| hsr_create_tagged_frame() creates a new skb where the HSR header can be
| prepended via __pskb_copy(). This does not copy the skb_shared_info part
| of the original skb so any timestamp request is lost.
|  
| An alternative is to use skb_clone() where the skb_shared_info part is
| shared and then skb_cow_head() to make the header part writeable. This
| avoids touching manually the tx_flags and tskey members.
| Using skb_clone() allows also return early (after the clone) in the
| offloaded case so this can be unified a bit.
| The clone case does not need manual adjustment of sk_buff::csum_start
| because by using skb_cow_head() the head does not move relative to the
| payload. Should the head need expansion then pskb_expand_head() will
| move it and update sk_buff::csum_start accordingly. The clone also
| preserves metadata (if available) so skb_postpush_data_move() is used
| instead of memmove() to move both. Finally skb_reset_mac_len() is added
| to set the new length of the header after expansion.
|  
| This is a preparation for PTP handling where timestamps are requested.

Is this better?

> > /Daniel
> 
Sebastian