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 01:23:55 +0200 Message-ID: <1210029835.8012.30.camel@johannes.berg> References: <1210021066.4181.41.camel@johannes.berg> <20080505.153730.186617868.davem@davemloft.net> <1210027447.8012.15.camel@johannes.berg> <20080505.161458.46071527.davem@davemloft.net> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-GpBbEZhH4YPp3KVAxfc8" Cc: tomasw-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, linville-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-wireless-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: David Miller Return-path: In-Reply-To: <20080505.161458.46071527.davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org> Sender: linux-wireless-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org --=-GpBbEZhH4YPp3KVAxfc8 Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Mon, 2008-05-05 at 16:14 -0700, David Miller wrote: > > 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? >=20 > skb_header_cloned() will return false always if the buffer is not > cloned. Right, it's less than skb_cloned(). > If it is cloned, it makes sure the data reference count allows > for modification of the buffer. Which buffer? skb->data..skb->tail? And isn't that, in mac80211's case, at least currently all the buffer anyway? > For normal traffic, you should see skb_header_cloned() always return > false unless a network tap like tcpdump is registered. Interesting point. I'll have to see when socket filters are run, wpa_supplicant could have a tap open I think. Maybe that's why I'm seeing so many cloned packets. I think I'll stacktrace skb_clone and print that out. johannes --=-GpBbEZhH4YPp3KVAxfc8 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+XCqVg1VMiehFYAQKp1RAAhlAKc45MkvYo7TK4dhGkzjQVTn3B9dLO 4MBPAvyL1Bphsf/AWIVVwcJOuGhy9SRGLmE4bpAq+rsN4IGQoFKmQDEMo+NH4dXG 50TPuEHnQu5r+ti+NlvcFW72HR5RtPoQ5jz/9/rlYEBrhez/FjbJWRcmcSqC06ke qsvtuSZVMtC+7f5A3WL5MwPnrbHw2o6uvTLgsRHHO4xdzmX4wVaet+Eqw6e4eGV6 DtjVWd4whKoQOumQTegGJI1lMAK8pQfGSrTX67acvbcfWmf2MUaa7Y+s1fVgMMkp BxZBOqVLvrrnQRYpbnIcM8vVQxZ8KDkIJbzcdUjjHAc6p/3yc34mpFdPUvf3wGyt aqR3wAKWgN42nVbX42rRbm5FnClJpT3WMOPh5Rw4LR1Mn1+TiOJxBxH4s5GX4iXK ybBCO/4DjrWEsgwpdNVYjB0DuJWHknJtNqoGOZJy0xAKtF2W02siXKGWwJGaXqMw iHlxTq/CV5J8wrjmondlJNqVGYSck2ilnYn4/R4ED9aTH7HcH9IorTYGjQRESYv7 pZbE9h2wYHb6uXOXVaKhL44npkc+CTx07oK9CEfpI1bPV7D8nCzo3UfuCzYFsVb5 BODxFGnGxPaILbXpqKe3xh/rZPrsORNdGqXpMKLYKH+snYoEY3DWDTm7yipbsoIR /sdtKOKkyHo= =RhVy -----END PGP SIGNATURE----- --=-GpBbEZhH4YPp3KVAxfc8-- -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html