From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-2?Q?Micha=B3_Miros=B3aw?= Subject: Re: [GIT] Networking Date: Thu, 2 May 2013 18:22:47 +0200 Message-ID: References: <20130502.041625.412316202038784117.davem@davemloft.net> <20130502083619.GA22010@macbook.localnet> <87d2t9bvj1.fsf@nemi.mork.no> <20130502.051727.949429506738234701.davem@davemloft.net> <1367490491.5106.137.camel@deadeye.wl.decadent.org.uk> <87zjwda9bl.fsf@nemi.mork.no> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Ben Hutchings , David Miller , kaber@trash.net, torvalds@linux-foundation.org, hayeswang@realtek.com, akpm@linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: =?ISO-8859-1?Q?Bj=F8rn_Mork?= , =?UTF-8?Q?Pavel_=C5=A0imerda?= Return-path: In-Reply-To: <87zjwda9bl.fsf@nemi.mork.no> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 2013/5/2 Bj=C3=B8rn Mork : > Ben Hutchings writes: >> On Thu, 2013-05-02 at 05:17 -0400, David Miller wrote: >>> From: Bj=C3=B8rn Mork >>> Date: Thu, 02 May 2013 11:06:42 +0200 >>> >>> > Adding the new netdev features will make it go from 1 to 2: >>> >>> We already had more than 31 feature bits before Patrick's >>> changes, and I'm pretty sure this was the case when we added >>> that ethtool API. >> >> It wasn't, but this should be OK. Userland is supposed to query the >> number of features using ETHTOOL_GSSET_INFO and then work out the nu= mber >> of words/blocks using FEATURE_BITS_TO_BLOCKS(). > > > Looking at > http://cgit.freedesktop.org/NetworkManager/NetworkManager/tree/src/pl= atform/nm-linux-platform.c#n1025 > there seems to be a couple of bugs in this area. This is certainly > abusing the exported API, but it does mean that NM breaks if you ever > move NETIF_F_VLAN_CHALLENGED (like the 802.1ad patch did): > > ---- > #define NETIF_F_VLAN_CHALLENGED (1 << 10) > > static gboolean > link_supports_vlans (NMPlatform *platform, int ifindex) > { > auto_nl_object struct rtnl_link *rtnllink =3D link_get (platf= orm, ifindex); > const char *name =3D nm_platform_link_get_name (ifindex); > struct { > struct ethtool_gfeatures features; > struct ethtool_get_features_block features_block; > } edata =3D { .features =3D { .cmd =3D ETHTOOL_GFEATURES, .si= ze =3D 1 } }; > > /* Only ARPHRD_ETHER links can possibly support VLANs. */ > if (!rtnllink || rtnl_link_get_arptype (rtnllink) !=3D ARPHRD= _ETHER) > return FALSE; > > if (!name || !ethtool_get (name, &edata)) > return FALSE; > > return !(edata.features.features[0].active & NETIF_F_VLAN_CHA= LLENGED); > } > ---- > > > Not that I see how this particular bug matters unless you need VLAN > support in NM. But there could be similar issues around. I guess > avoiding unnecessary renumbering of the NETIF_F bits can save us some > trouble. Although you can certainly argue that those bits never were > intended to be part of the API, and that using them like this is a us= er > application bug. This is certainly a bug in NM, and a fresh one: commit b636ea86b1c0a28b77eda311c84d3b2417cad22e from 2013-04-10 14:40:58 (GMT). Userspace is expected to use ETHTOOL_GSTRINGS for ETH_SS_FEATURES and find a corresponding bit position by feature name ("vlan-challenged" in this case). Cc: commit's author. Best Regards, Micha=C5=82 Miros=C5=82aw