Am 2018-09-24 14:01, schrieb Michael Walle:
Hi,I'm using the AF_PACKET socket with setsockopt(PACKET_AUXDATA) to get the incoming VLAN tag. Correct me if I'm wrong, but as far as I see the first VLAN tag is always stripped - either in hardware or in net/core/dev.c in __netif_receive_skb_core() - and stored in skb->vlan_tci. Therefore, it won't be in the packet data anymore. If I use the socket with ETH_P_ALL as protocol, everything works as expected. But if I'm using an actual protocol number, instead of the catch all, the tp_vlan_tci field inside the auxdata will be zero. I've traced this to commit d4b812dea4a236f729526facf97df1a9d18e191c (vlan: mask vlan prio bits): + if (unlikely(vlan_tx_tag_present(skb))) { + if (vlan_tx_tag_get_id(skb)) + skb->pkt_type = PACKET_OTHERHOST; + /* Note: we might in the future use prio bits + * and set skb->priority like in vlan_do_receive() + * For the time being, just ignore Priority Code Point + */ + skb->vlan_tci = 0; + } The ptype_all callbacks (which are working as expected) are before this code and the ptype_specific callbacks (which are not working) are after this piece of code. I don't know it this is a bug or not, I guess it is one, at least from the AF_PACKET socket point of view. If not, how I'm supposed to get the original VLAN tag with socket(AF_PACKET, my_protocol)? I also don't understand the commit (message) as the subject suggesets only the prio bits should be masked, but with "skb->vlan_tci = 0" everything is masked. Therefore, I've put the original (hopefully the mail addresses are still valid) authors in CC.
ping? :) -michael
