netdev - Re: [PATCH,v2,net-next 2/2] tun: enable napi_gro

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Date:   Fri, 22 Sep 2017 10:06:28 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Petar Penkov <peterpenkov96@...il.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Mahesh Bandewar <maheshb@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        David Miller <davem@...emloft.net>, ppenkov@...nford.edu
Subject: Re: [PATCH,v2,net-next 2/2] tun: enable napi_gro_frags() for TUN/TAP driver

> @@ -2061,6 +2174,9 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
>         if (tfile->detached)
>                 return -EINVAL;
>
> +       if ((ifr->ifr_flags & IFF_NAPI_FRAGS) && !capable(CAP_NET_ADMIN))
> +               return -EPERM;
> +

This should perhaps be moved into the !dev branch, directly below the
ns_capable check.

>         dev = __dev_get_by_name(net, ifr->ifr_name);
>         if (dev) {
>                 if (ifr->ifr_flags & IFF_TUN_EXCL)
> @@ -2185,6 +2301,9 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
>         tun->flags = (tun->flags & ~TUN_FEATURES) |
>                 (ifr->ifr_flags & TUN_FEATURES);
>
> +       if (!(tun->flags & IFF_NAPI) || (tun->flags & TUN_TYPE_MASK) != IFF_TAP)
> +               tun->flags = tun->flags & ~IFF_NAPI_FRAGS;
> +

Similarly, this check only need to be performed in that branch.
Instead of reverting to non-frags mode, a tun_set_iff with the wrong
set of flags should probably fail hard.