On 8/20/2021 1:46 PM, Tudor Cornea wrote: > The af_packet pmd driver binds to a raw socket and allows > sending and receiving of packets through the kernel. > > Since commit bcc6d47903 [1], the kernel strips the vlan tags early in > __netif_receive_skb_core(), so we receive untagged packets while > running with the af_packet pmd. > > Luckily for us, the skb vlan-related fields are still populated from the > stripped vlan tags, so we end up having all the information > that we need in the mbuf. > > We would like to have the the vlan tag inside the mbuf. > Let's take a shot at it by trying to reinsert the stripped vlan tag. >
PMD already sets 'mbuf->vlan_tci' and 'PKT_RX_VLAN | PKT_RX_VLAN_STRIPPED' flags, so application can be aware of the vlan tag and can consume it. Inserting the vlan tag back to packet is costly, what is the motivation to do so? > As a side note, something similar was done for the netvsc pmd. > > [1] > https://github.com/torvalds/linux/commit/bcc6d47903612c3861201cc3a866fb604f26b8b2 > > Signed-off-by: Tudor Cornea <tudor.cor...@gmail.com> > --- > drivers/net/af_packet/rte_eth_af_packet.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/net/af_packet/rte_eth_af_packet.c > b/drivers/net/af_packet/rte_eth_af_packet.c > index b73b211..d116583 100644 > --- a/drivers/net/af_packet/rte_eth_af_packet.c > +++ b/drivers/net/af_packet/rte_eth_af_packet.c > @@ -148,6 +148,10 @@ eth_af_packet_rx(void *queue, struct rte_mbuf **bufs, > uint16_t nb_pkts) > if (ppd->tp_status & TP_STATUS_VLAN_VALID) { > mbuf->vlan_tci = ppd->tp_vlan_tci; > mbuf->ol_flags |= (PKT_RX_VLAN | PKT_RX_VLAN_STRIPPED); > + > + /* the kernel always strips the vlan tag, try to > reinsert it */ > + if (rte_vlan_insert(&mbuf)) > + PMD_LOG(ERR, "Failed to reinsert vlan tag"); > } > > /* release incoming frame and advance ring buffer */ >
