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Date: Fri, 11 Apr 2014 11:01:21 +0000 From: Dennis Punjabi <linuxdev@...s.bz> To: "netdev@...r.kernel.org" <netdev@...r.kernel.org> Subject: 802.1AD packets - Kernel changes ether type from 88A8 to 8100 on all packets. Background: 1) I need to setup a Linux software bridge and ensure that packets coming in on one bridge port exit unchanged on another bridge port, like a normal HW bridge. 2) I need to use the new vlan filtering capability of the bridge. Good news of this feature is made in the kernel announcement of release 3.9 @ http://kernelnewbies.org/Linux_3.9 3) I need to test what presently happens to 802.1AD tagged packets when bridge vlan filtering is enabled because I also need support for Q-in-Q. I am using a packet generator (Ostinato) and creating 802.1AD packets as follows: (MAC_HDR) (8021AD_HDR) (8021Q HDR) (PAYLOAD) (DA | SA | TYPE) (TCI | TPID) (TCI | TPID) (TEST PAYLOAD - ARP BCAST PACKET) (DA | SA | 88A8) (TCI | 8100) (TCI | 0806) (TEST PAYLOAD - ARP BCAST PACKET) (hopefully the alignment is ok above, if not I apologize and hope its clear enough) Even before setting up the the bridge, I want to ensure that packets are being received properly to my system. I do a tcpdump output for the port receiving the generated packets. What I notice is that the 88A8 TPIC/ether type get changed to 8100. Ie, all packets with ether type 802.1AD get changed to 802.1Q type, ie 8100. I initially tested this on a 3.14 vanilla kernel. I recompiled my 8139too.c driver and printed printk the packets in the driver before they are handed over to netif_receive_skb. Before being passed to the kernel networking stack the packet is as it is supposed to be, ie it has the correct 88A8 ether type. I went ahead and tested this on kernel 3.12, 3.11, 3.10. I Saw the same result. I also tested it on 3.9, 3.8 and 2.6 and these kernels did not change the 88A8 to 8100. Is this intentional or a bug? Does this have something to do with the addition of the new feature (vlan: Add 802.1ad support) announced in kernel 3.10? http://kernelnewbies.org/Linux_3.10 I have been following the net-dev mailing lists and want to test the bridge 802.1AD filtering feature discussed here http://www.spinics.net/lists/linux-ethernet-bridging/msg05207.html but cannot do so if the bridge does not even get the 802.1AD tagged packets to begin with. Assuming I don't want to use filtering and just want a simple bridge. The expected behaviour is that the bridge must not change my packet and should simply pass it along. Is my thinking correct? Thanks for any help provided. Dennis -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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