Re: [dpdk-dev] [PATCH v3] mbuf: fix of enabling all newly added RX error flags

["Zhang, Helin" <helin.zhang@intel.com>]

Hi Thomas

> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> Sent: Monday, December 8, 2014 6:51 PM
> To: Zhang, Helin
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v3] mbuf: fix of enabling all newly added RX
> error flags
> 
> Hi Helin,
> 
> 2014-12-06 09:33, Helin Zhang:
> > Before redefining mbuf structure, there was lack of free bits in 'ol_flags'
> > (32 bits in total) for new RX or TX flags. So it tried to reuse
> > existant bits as most as possible, or even assigning 0 to some of bit
> > flags. After new mbuf structure defined, there are quite a lot of free
> > bits. So those newly added bit flags should be assigned with correct
> > and valid bit values, and getting their names should be enabled as
> > well. Note that 'RECIP' should be removed, as nowhere will use it.
> > 'PKT_RX_ERR' is defined to replace all other error bit flags, e.g. MAC
> > error, Oversize error, header buffer overflow error.
> >
> > Signed-off-by: Helin Zhang <helin.zhang@intel.com>
> [...]
> > --- a/lib/librte_mbuf/rte_mbuf.h
> > +++ b/lib/librte_mbuf/rte_mbuf.h
> > @@ -84,11 +84,6 @@ extern "C" {
> >  #define PKT_RX_FDIR          (1ULL << 2)  /**< RX packet with FDIR
> match indicate. */
> >  #define PKT_RX_L4_CKSUM_BAD  (1ULL << 3)  /**< L4 cksum of RX pkt.
> is
> > not OK. */  #define PKT_RX_IP_CKSUM_BAD  (1ULL << 4)  /**< IP cksum
> of
> > RX pkt. is not OK. */ -#define PKT_RX_EIP_CKSUM_BAD (0ULL << 0)  /**<
> External IP header checksum error. */
> > -#define PKT_RX_OVERSIZE      (0ULL << 0)  /**< Num of desc of an RX
> pkt oversize. */
> > -#define PKT_RX_HBUF_OVERFLOW (0ULL << 0)  /**< Header buffer
> overflow. */
> > -#define PKT_RX_RECIP_ERR     (0ULL << 0)  /**< Hardware processing
> error. */
> > -#define PKT_RX_MAC_ERR       (0ULL << 0)  /**< MAC error. */
> >  #define PKT_RX_IPV4_HDR      (1ULL << 5)  /**< RX packet with IPv4
> header. */
> >  #define PKT_RX_IPV4_HDR_EXT  (1ULL << 6)  /**< RX packet with
> extended IPv4 header. */
> >  #define PKT_RX_IPV6_HDR      (1ULL << 7)  /**< RX packet with IPv6
> header. */
> > @@ -99,6 +94,8 @@ extern "C" {
> >  #define PKT_RX_TUNNEL_IPV6_HDR (1ULL << 12) /**< RX tunnel packet
> with IPv6 header. */
> >  #define PKT_RX_FDIR_ID       (1ULL << 13) /**< FD id reported if FDIR
> match. */
> >  #define PKT_RX_FDIR_FLX      (1ULL << 14) /**< Flexible bytes reported
> if FDIR match. */
> > +#define PKT_RX_EIP_CKSUM_BAD (1ULL << 15)  /**< External IP header
> > +checksum error. */
> 
> Could PKT_RX_EIP_CKSUM_BAD be aggregated with
> PKT_RX_IP_CKSUM_BAD?
I tend to say no, but I would listen to comments from others.
For tunneling case (e.g. IP over IP), it is a bit similar to the case of L3/L4 (e.g. UDP over IP).
For L3/L4 case, we have PKT_RX_IP_CKSUM_BAD and PKT_RX_L4_CKSUM_BAD to
indicate the checksum error is in L3 or L4.
So I'd prefer to have PKT_RX_IP_CKSUM_BAD and PKT_RX_EIP_CKSUM_BAD to indicate
the checksum error is in outer or inner header.
Otherwise we have no chance to know where the checksum error is, based on mbuf.

> The conclusion is the same: the packet is corrupted.
> And some hardwares could not detect the encapsulation and use
> PKT_RX_IP_CKSUM_BAD.
If the hardware don't know it is a tunneling packet, it will just treat it as an IP packet. But if
hardware supports tunneling, it would be better for apps to know that more about the
packet which can be offloaded by hardware.

> 
> Another interesting improvement would be to have PKT_RX_IP_CKSUM_OK.
> I think we'll have to think about this kind of flag for next version.
For checksum OK, if no 'BAD' indicated, we can assume it is OK. Any other hints from you?

> 
> Note that this patch is an API change and shouldn't be applied for 1.8.0.
> But we can do an exception as it has no impact on existing applications and
> fixes the 0 flags.
Agree with you!

> 
> --
> Thomas

Thank you very much for thinking so much about this!

Regards,
Helin