From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [RFC v2] mac80211: assign needed_headroom/tailroom for netdevs Date: Mon, 05 May 2008 16:14:58 -0700 (PDT) Message-ID: <20080505.161458.46071527.davem@davemloft.net> References: <1210021066.4181.41.camel@johannes.berg> <20080505.153730.186617868.davem@davemloft.net> <1210027447.8012.15.camel@johannes.berg> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: tomasw-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, linville-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-wireless-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: johannes-cdvu00un1VgdHxzADdlk8Q@public.gmane.org Return-path: In-Reply-To: <1210027447.8012.15.camel-YfaajirXv214zXjbi5bjpg@public.gmane.org> Sender: linux-wireless-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org From: Johannes Berg Date: Tue, 06 May 2008 00:44:07 +0200 > 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? skb_header_cloned() will return false always if the buffer is not cloned. If it is cloned, it makes sure the data reference count allows for modification of the buffer. For normal traffic, you should see skb_header_cloned() always return false unless a network tap like tcpdump is registered. -- 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