netdev - Re: [PATCH v3 2/4] wifi: libertas: only add RSN/WPA IE in lbs_add_wpa

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Date:   Wed, 18 Jan 2023 10:14:12 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Doug Brown <doug@...morgal.com>
Cc:     Kalle Valo <kvalo@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Dan Williams <dcbw@...hat.com>,
        libertas-dev@...ts.infradead.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH v3 2/4] wifi: libertas: only add RSN/WPA IE in
 lbs_add_wpa_tlv

On Tue, Jan 17, 2023 at 10:35:56PM -0800, Doug Brown wrote:
> On 1/17/2023 12:59 AM, Simon Horman wrote:
> > On Mon, Jan 16, 2023 at 12:21:24PM -0800, Doug Brown wrote:
> > > [You don't often get email from doug@...morgal.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> > > 
> > > The existing code only converts the first IE to a TLV, but it returns a
> > > value that takes the length of all IEs into account. When there is more
> > > than one IE (which happens with modern wpa_supplicant versions for
> > > example), the returned length is too long and extra junk TLVs get sent
> > > to the firmware, resulting in an association failure.
> > > 
> > > Fix this by finding the first RSN or WPA IE and only adding that. This
> > > has the extra benefit of working properly if the RSN/WPA IE isn't the
> > > first one in the IE buffer.
> > > 
> > > While we're at it, clean up the code to use the available structs like
> > > the other lbs_add_* functions instead of directly manipulating the TLV
> > > buffer.
> > > 
> > > Signed-off-by: Doug Brown <doug@...morgal.com>
> > > ---
> > >   drivers/net/wireless/marvell/libertas/cfg.c | 28 +++++++++++++--------
> > >   1 file changed, 18 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/drivers/net/wireless/marvell/libertas/cfg.c b/drivers/net/wireless/marvell/libertas/cfg.c
> > > index 3e065cbb0af9..3f35dc7a1d7d 100644
> > > --- a/drivers/net/wireless/marvell/libertas/cfg.c
> > > +++ b/drivers/net/wireless/marvell/libertas/cfg.c
> > 
> > ...
> > 
> > > @@ -428,14 +438,12 @@ static int lbs_add_wpa_tlv(u8 *tlv, const u8 *ie, u8 ie_len)
> > >           *   __le16  len
> > >           *   u8[]    data
> > >           */
> > > -       *tlv++ = *ie++;
> > > -       *tlv++ = 0;
> > > -       tlv_len = *tlv++ = *ie++;
> > > -       *tlv++ = 0;
> > > -       while (tlv_len--)
> > > -               *tlv++ = *ie++;
> > > -       /* the TLV is two bytes larger than the IE */
> > > -       return ie_len + 2;
> > > +       wpatlv->header.type = cpu_to_le16(wpaie->id);
> > > +       wpatlv->header.len = cpu_to_le16(wpaie->datalen);
> > > +       memcpy(wpatlv->data, wpaie->data, wpaie->datalen);
> > 
> > Hi Doug,
> > 
> > Thanks for fixing the endiness issues with cpu_to_le16()
> > This part looks good to me now. Likewise for patch 4/4.
> > 
> > One suggestion I have, which is probably taking things to far,
> > is a helper for what seems to be repeated code-pattern.
> > But I don't feel strongly about that.
> 
> Thanks Simon. Is this basically what you're suggesting for a helper?
> 
> static int lbs_add_ie_tlv(u8 *tlvbuf, const struct element *ie, u16 tlvtype)
> {
> 	struct mrvl_ie_data *tlv = (struct mrvl_ie_data *)tlvbuf;
> 	tlv->header.type = cpu_to_le16(tlvtype);
> 	tlv->header.len = cpu_to_le16(ie->datalen);
> 	memcpy(tlv->data, ie->data, ie->datalen);
> 	return sizeof(struct mrvl_ie_header) + ie->datalen;
> }
> 
> And then in the two functions where I'm doing that, at the bottom:
> 
> return lbs_add_ie_tlv(tlv, wpaie, wpaie->id);
> return lbs_add_ie_tlv(tlv, wpsie, TLV_TYPE_WPS_ENROLLEE);
> 
> I could definitely do that to avoid repeating the chunk of code that
> fills out the struct in the two functions. A lot of the other
> lbs_add_*_tlv functions follow a similar pattern of setting up a struct
> pointer and filling out the header, so I don't think it's too crazy to
> just repeat the code twice. On the other hand, the example above does
> look pretty darn clean. I don't feel strongly either way myself.

Hi Doug,

yes, I was thinking about something like that.
And wondering if it might be reused elsewhere (in the same file).

But again, I don't feel strongly about this.
So perhaps it's something to consider in future.