netdev - Re: [PATCH net] packet: in recvmsg msg_name return at least sockaddr

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Message-ID: <CAF=yD-Ji+=AJPCscPdy0wdt1YMr3scwm0skx2V=jk7U6QtRQYw@mail.gmail.com>
Date:   Mon, 29 Apr 2019 09:26:45 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     David Laight <David.Laight@...lab.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "ebiederm@...ssion.com" <ebiederm@...ssion.com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net] packet: in recvmsg msg_name return at least sockaddr_ll

On Mon, Apr 29, 2019 at 9:19 AM David Laight <David.Laight@...lab.com> wrote:
>
> > Can then also change memset to zero only two bytes in the Ethernet case.
> >
> > +                       if (msg->msg_namelen < sizeof(struct sockaddr_ll)) {
> > +                               msg->msg_namelen = sizeof(struct sockaddr_ll);
> > +                               memset(msg->msg_name + copy_len, 0,
> > +                                      msg->namelen - copy_len);
>
> copy_len not defined ....

Was a quick sketch of an iteration on the above, sorry if unclear.
Intended to be defined before the branch.

>
> > +                       }
>
> Except that has to be a real memset() not an inlined direct
> write of an 8byte register (or 2 writes on a 32bit systems).

I wasn't sure whether a 2 byte store would be optimized in a similar
manner. That might even be architecture dependent, I imagine? Will
leave as is.

Thanks for the quick response!



>
>         David
>
> -
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