RE: [PATCH v6 1/6] wifi: mac80211: Use struct instead of macro for PREQ frame

[Ping-Ke Shih <pkshih@realtek.com>]

> > +             orig_addr = preq_elem_top->orig_addr;
> > +             orig_sn = get_unaligned_le32(&preq_elem_top->orig_sn);
> > +             orig_lifetime = get_unaligned_le32(&preq_elem_bottom->lifetime);
> > +             orig_metric = get_unaligned_le32(&preq_elem_bottom->metric);
> 
> Ok, oops, I just realized my other thought on this was wrong - the
> previous PREQ_IE_LIFETIME() was u32_field_get() which loaded an entirely
> u32 from there using get_unaligned_le32().
> 
> However, another comment: You don't need get_unaligned_le32() here since
> the struct is __packed, so you can simplify all of these to just
> 
>         orig_sn = le32_to_cpu(preq_elem_top->orig_sn);
> 

I think the __packed can cause unaligned. Consider the offset below I added. 

struct ieee80211_mesh_hwmp_preq_top {
       u8 flags;					// offset = 0
       u8 hopcount;					// offset = 1
       u8 ttl;						// offset = 2
       __le32 preq_id;				// offset = 3 (unaligned)
       u8 orig_addr[ETH_ALEN];		// offset = 7
       __le32 orig_sn;				// offset = 13 (unaligned)

       /* optional AE, lifetime, metric, target */
       u8 variable[];
} __packed;

Not sure if the pointer preq_elem_top can adjust offset back to be aligned?
(But I think we don't make this assumption.)

Ping-Ke