From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Berg Subject: Re: [RFC v2] mac80211: assign needed_headroom/tailroom for netdevs Date: Tue, 06 May 2008 00:44:07 +0200 Message-ID: <1210027447.8012.15.camel@johannes.berg> References: <1210018214.4181.27.camel@johannes.berg> <20080505.134420.194001886.davem@davemloft.net> <1210021066.4181.41.camel@johannes.berg> <20080505.153730.186617868.davem@davemloft.net> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-JCrzFm5tGATrOBhgOvbY" Cc: tomasw@gmail.com, linville@tuxdriver.com, netdev@vger.kernel.org, linux-wireless@vger.kernel.org To: David Miller Return-path: Received: from xc.sipsolutions.net ([83.246.72.84]:33556 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1764060AbYEEWo4 (ORCPT ); Mon, 5 May 2008 18:44:56 -0400 In-Reply-To: <20080505.153730.186617868.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: --=-JCrzFm5tGATrOBhgOvbY Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Mon, 2008-05-05 at 15:37 -0700, David Miller wrote: > From: Johannes Berg > Date: Mon, 05 May 2008 22:57:46 +0200 >=20 > > But I cannot modify the ethernet header that'll live on in the skb data > > so that's not useful. >=20 > Actually, you can, if skb_header_cloned() returns false. >=20 > When skb_header_cloned() returns false you can change the > headers however you like. >=20 > I'm not sure if it helps the bridging case or not, but in > any event, the following patch should work and reduce the > number of cases where pskb_expand_head() is necessary on > TX. Right, that makes sense. But will it ever return false? skb_cloned() returns true often enough, and we only accept linear skbs, but I think I don't understand yet what skb_header_cloned() vs. skb_cloned() refers to. Which exactly is the header space I'm allowed to modify when skb_header_cloned() returns false? johannes --=-JCrzFm5tGATrOBhgOvbY Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Comment: Johannes Berg (powerbook) iQIVAwUASB+NtaVg1VMiehFYAQIhyQ/9GuNcaKx0zmTXy1LXbVDmBC+dCJo9LIky A0P5toUodoN4FkrwVhttExnnhkvjNicYbs+YzJyIOxjKvqBZjY8gmYe17BBibpnE 5fcsgVPg0gOh96oYaqAkmitEYt3+yQ3sZMo5MhRhE7O1ug7BuChsqQKbktAPQv9g GsRvXAisUD1/j0wxj5gia1S2byo+oa+PQw/Pnp+Quld1IDgQ3I2wU/+pB0pM5LT8 OpRr7ogGOmIbGw6jny4aDwDsyiyvuELlLssMJnpCyLxvAdxtLzuZ9K2VvL07zmfB wOZf5QDNtH7RlGD8g0psZTsk8TPBa1Bpa2B4ZFDiYd6JejgYr7UKyNaLODOWqC8l v2Yy+4sySnJnl5NKLK2JGRNxcvoEYobxKXoGrtTJrKLOeFLYKUMPWeOZHa+6UKX5 WWVsaOepTP1iM7Q/viRhsV/2C7OQuM/ua2htO693Zk9PzYtB9lBP0n3mmDkB8DMo hq78D/U1pEcj70u0PetuyN22z5xE8r+4Z9aEOxS75Fj73IbvHmBjnLe/hElEWBre oUQzR9DsacUI/K/5deFelMh/Xvnt25NYJEFRlynRn8UmyBH1nRq6t0lTr/k1SDDz lnA0eTiH7QZArDMNwNE4P3/kWpy2/yplZ8PZCRNPROrIovd9BtzWtiGgl9pYkcBw mfxz5HQc4lU= =l5/x -----END PGP SIGNATURE----- --=-JCrzFm5tGATrOBhgOvbY--