site_archiver@lists.apple.com Delivered-To: darwin-kernel@lists.apple.com The packet header field is a big disaster. When an ethernet driver inputs a packet it usually: -josh On Sep 18, 2006, at 1:46 PM, Bhavesh Davda wrote: For certain packets that my iff_input_func is receiving, when I looked at the entire mbuf structure received in parameter 4, I noticed that the m_hdr.mh_data field offsets 14 bytes beyond the start of the ethernet frame. This is causing my mbuf_dup() cloned mbuf to not contain the 14 bytes of ethernet header in my NKE. Looking in the original mbuf received in my iff_input_func, the 14 bytes of ethernet header are in the mbuf body at mbuf->M_dat.MH.MH_dat.MH_databuf[0..13]. Thanks! - Bhavesh _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.a... This email sent to site_archiver@lists.apple.com - has the whole packet copied in to the mbuf - Sets the mbuf's packet header to point to where the ethernet frame starts in the mbuf - uses mbuf_adj or something similar to move the start of the mbuf pointer to the end of the ethernet header If you're doing to use mbuf_dup on one of these packets your best bet is probably to: - mbuf_prepend for the length of the ethernet header - copy the ethernet header in to the preceeding space you just created using mbuf_prepend - duplicate the packet - set the packet header's header field to the mbuf_data value - mbuf_adj for the size of the ethernet header If there was one thing I could undo it would be the wacky way in which this header stuff is handled. It is especially frustrating when you're working with interface filters. On the outbound path, you get the entire packet in the mbuf chain. On the inbound path, the ethernet header is separate, in the packet header's header field. It usually points to some place in the allocated space for the first mbuf, but there are no guarantees this will be the case. What am I doing wrong? How do I clone the mbuf to include the DLIL header? -- Bhavesh P. Davda _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-kernel/jgraessley% 40apple.com This email sent to jgraessley@apple.com smime.p7s