From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: netlink stats: Ability to get stats for a single device?
Date: Tue, 26 Oct 2010 22:37:12 +0200
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Cc: David Miller <davem@davemloft.net>, netdev@vger.kernel.org
To: Ben Greear <greearb@candelatech.com>
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Le mardi 26 octobre 2010 =C3=A0 13:29 -0700, Ben Greear a =C3=A9crit :

> I'm trying to craft my own netlink message...basically:
>=20
>     memset(&snl, 0, sizeof(snl));
>     snl.nl_family =3D AF_NETLINK;
>     snl.nl_pid    =3D 0;
>     snl.nl_groups =3D 0;
>=20
>     memset(&buffer, 0, sizeof(buffer));
>     nlh->nlmsg_type =3D msg_type;
>     nlh->nlmsg_flags =3D NLM_F_MATCH|NLM_F_REQUEST;

dont use F_MATCH : check net/core/rtnetlink.c

vi +1660 net/core/rtnetlink.c

You _dont_ want to call 'dumpit' : so dont use a bit present in
NLM_F_DUMP at all:

        if (kind =3D=3D 2 && nlh->nlmsg_flags&NLM_F_DUMP) {
                struct sock *rtnl;
                rtnl_dumpit_func dumpit;

                dumpit =3D rtnl_get_dumpit(family, type);
                if (dumpit =3D=3D NULL)
                        return -EOPNOTSUPP;

                __rtnl_unlock();
                rtnl =3D net->rtnl;
                err =3D netlink_dump_start(rtnl, skb, nlh, dumpit, NULL=
);
                rtnl_lock();
                return err;
        }

You want instead to call the 'doit' handler  (one device only)

        doit =3D rtnl_get_doit(family, type);
        if (doit =3D=3D NULL)
                return -EOPNOTSUPP;

        return doit(skb, nlh, (void *)&rta_buf[0]);