On 01/20/2016 04:02 PM, Montorsi, Francesco wrote: > Hi all, > > I need to get access to the Ethernet CRC of received packets. > To do this, I'm configuring: > > port_conf.rxmode.hw_strip_crc = 0; > > Now my question is: how am I supposed to access the Ethernet CRC from a DPDK > mbuf? > Is the CRC just the 4 final bytes of the packets? > > Is this correct: > > uint32_t crc = rte_pktmbuf_mtod_offset (mymbuf, uint32_t*, > mymbuf->pkt_len) ; > > ? > > Thanks, > Francesco Montorsi > Hi Francesco,
You would be right... if the PMDs did not transparently strip the CRC in software when hardware CRC stripping is disabled at port configuration (as described above). See for instance how the function ixgbe_recv_pkts_lro() in file drivers/net/ixgbe/ixgbe_rxtx.c deals with crc_len. Considering your need, I think now that PMDs should keep the CRC that are stored in received packets when hardware CRC stripping is disabled by the application, so that the application can access it as needed. Note that this would impose that the input packet processing of such DPDK applications be aware of the CRC presence (+4 in the packet length , for instance). Let's see what others, if any, that might care think about such a change into the CRC stripping semantics. Ivan -- Ivan Boule 6WIND Development Engineer
