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: Mon, 05 May 2008 22:10:14 +0200 Message-ID: <1210018214.4181.27.camel@johannes.berg> References: <1210014316.4181.14.camel@johannes.berg> <20080505.125013.129139559.davem@davemloft.net> <1210017456.4181.23.camel@johannes.berg> <20080505.130225.159803012.davem@davemloft.net> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-ZTs7XAeDZZT35+d9sBNl" 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]:52702 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759638AbYEEULL (ORCPT ); Mon, 5 May 2008 16:11:11 -0400 In-Reply-To: <20080505.130225.159803012.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: --=-ZTs7XAeDZZT35+d9sBNl Content-Type: text/plain Content-Transfer-Encoding: quoted-printable > And the copy is necessary because you need more tailroom or something? >=20 > I don't understand why simply having all the space you need is not > better and faster :-) >=20 > Even if you have a clone, you can muck with the data in the IP and TCP > header areas, so long as skb_header_cloned() is false. I think it's probably all because I don't understand skb_cloned() vs. skb_header_cloned() and mac80211 came with checks for skb_cloned() that I didn't spot. So you're saying the check there to see if we can add 802.11 headers should depend on skb_header_cloned() and not skb_cloned()? > So I can only conclude that your problematic case is that of > encryption, right? That's the only situation where I can imagine you > need to modify with packet data outside of the protocol headers. When is protocol header equivalent to skb header and when not? johannes --=-ZTs7XAeDZZT35+d9sBNl Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Comment: Johannes Berg (powerbook) iQIVAwUASB9ppaVg1VMiehFYAQKrRg/7Bb7CD0xyv81194rsV4HdhdM3bSlelN6D XkXYgvWh5/WZwQKWUvzDd0VW+uOOAsPU578KXyGmNjH7XQRHT78DvAgppbxXi2Mb acyb4gDM7/FZSBCyrHcdEIZKvRJa5wwt9LSmWMoS7FDxkXkKj8ABmLsc7fiudY99 YkGFcUe4n+ZsMKVwPQuFnLparqFVW4C3RHi08dwj4jPLTuxgZGxyEx7pJArze0Od NmVZTvamTSTiOsmu7mKRyoICqW7/gtZLX8dt8JAqO3Nw6wxDeknGF7oK371aYLOH WdJRe8a8VKcs/KC7C3ApfBbvGua0Il2w0KDaHnTQnMz0r1tzkjLm7JMbHDrvC/HP ByxosYF1+P0cBeeaB1adO+XlUm3m6nTrXlkQxeKqltt3LKCh7spByLuI4ZL59/sG Rd2v1eIUDDKoEg7B7T9DEF1XAyVMQOBWsxia/033OG409NQK+6qAre0tIq1ssXI4 LW7y5Omy2acVFxornWSBHhmUuk3Go76Qa3Qj6EjJhElrpkX9tYF6uL2/h4pGG1I6 SbFkeWjYwlhipiSqPgqQZprZqGz7A0x1WQSJyUepOR2DMd7BTUEV2Wf0ZoeozWnK yDv8k97LcyzPTJuZABB1CdgScBEe23CxYvaKWwUeS9H1AFIRiHXgylAzqIoQe4W2 uEOyVnIskGM= =LeRX -----END PGP SIGNATURE----- --=-ZTs7XAeDZZT35+d9sBNl--