Subject: Re: WMM classification guideline for applications?
From: Johannes Berg <johannes@sipsolutions.net>
To: Kalle Valo <kalle.valo@iki.fi>
Cc: linux-wireless@vger.kernel.org, patrik.flykt@nokia.com
In-Reply-To: <87d42u6dnd.fsf@purkki.valot.fi>
References: <87d42u6dnd.fsf@purkki.valot.fi>
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Date: Sun, 06 Dec 2009 11:57:17 +0100
Message-ID: <1260097037.3461.10.camel@johannes.local>
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Sender: linux-wireless-owner@vger.kernel.org


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On Fri, 2009-12-04 at 16:02 +0200, Kalle Valo wrote:

> Method 3 (IPv4 DSCP field) feels most portable to us, at least most,
> if not all, wifi drivers should use it. And, in theory, the receiver
> should also benefit from the classification, unless ISPs modify it of
> course. But the standardisation for IPv4 QoS bits is a mess and I
> don't really understand where the use of DSCP bits (as used in WMM
> implementations) is specified.=20

http://tools.ietf.org/rfc/rfc2474.txt ?

> Also I was told that root privileges
> are needed to set this and that's somewhat cumbersome from application
> developer's point of view.

I don't see that IP_TOS, which will end up setting IP TOS/DSCP, requires
any elevated privileges:

        case IP_TOS:    /* This sets both TOS and Precedence */
                if (sk->sk_type =3D=3D SOCK_STREAM) {
                        val &=3D ~3;
                        val |=3D inet->tos & 3;=20
                }
                if (inet->tos !=3D val) {
                        inet->tos =3D val;
                        sk->sk_priority =3D rt_tos2priority(val);
                        sk_dst_reset(sk);
                }
                break;

whereas, for instance:

        case IP_IPSEC_POLICY:
        case IP_XFRM_POLICY:
                err =3D -EPERM;
                if (!capable(CAP_NET_ADMIN))
                        break;

In any case, I think this topic would benefit of cross-posting to
netdev :)

johannes

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