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From: "Liu, Jijiang" <jijiang.liu@intel.com>
To: Olivier MATZ <olivier.matz@6wind.com>
Thread-Topic: [dpdk-dev] [PATCH v5 2/3] mbuf:add three TX ol_flags and
repalce PKT_TX_VXLAN_CKSUM
Thread-Index: AQHQDkIzZMvV7Xzwn0SVLY5kK7hoh5x9OYaAgAAV4YCAABxsgIABPOtw
Date: Thu, 4 Dec 2014 02:08:13 +0000
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Subject: Re: [dpdk-dev] [PATCH v5 2/3] mbuf:add three TX ol_flags and
repalce PKT_TX_VXLAN_CKSUM
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Hi Olivier,
> -----Original Message-----
> From: Olivier MATZ [mailto:olivier.matz@6wind.com]
> Sent: Wednesday, December 3, 2014 10:42 PM
> To: Ananyev, Konstantin; Liu, Jijiang; dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v5 2/3] mbuf:add three TX ol_flags and rep=
alce
> PKT_TX_VXLAN_CKSUM
>=20
> Hi Konstantin,
>=20
> On 12/03/2014 01:59 PM, Ananyev, Konstantin wrote:
> >> I still think having a flag IPV4 + another flag IP_CHECKSUM is not
> >> appropriate.
> >
> > Sorry, didn't get you here.
> > Are you talking about our discussion should PKT_TX_IP_CKSUM and
> PKT_TX_IPV4 be mutually exclusive or not?
>=20
> Yes
>=20
> >> I though Konstantin agreed on other flags, but I may have
> >> misunderstood:
> >>
> >> http://dpdk.org/ml/archives/dev/2014-November/009070.html
> >
> > In that mail, I was talking about my suggestion to make PKT_TX_IP_CKSU=
M,
> PKT_TX_IPV4 and PKT_TX_IPV6 to occupy 2 bits.
> > Something like:
> > #define PKT_TX_IP_CKSUM (1 << X)
> > #define PKT_TX_IPV6 (2 << X)
> > #define PKT_TX_IPV4 (3 << X)
> >
> > "Even better, if we can squeeze these 3 flags into 2 bits.
> > Would save us 2 bits, plus might be handy, as in the PMD you can do:
> >
> > switch (ol_flags & TX_L3_MASK) {
> > case TX_IPV4:
> > ...
> > break;
> > case TX_IPV6:
> > ...
> > break;
> > case TX_IP_CKSUM:
> > ...
> > break;
> > }"
> >
> > As you pointed out, it will break backward compatibility.
> > I agreed with that and self-NACKed it.
>=20
> ok, so we are back between:
>=20
> 1/ (Jijiang's patch)
> PKT_TX_IP_CKSUM /* packet is IPv4, and we want hw cksum */
> PKT_TX_IPV6 /* packet is IPv6 */
> PKT_TX_IPV4 /* packet is IPv4, and we don't want hw cksum */
>=20
> with PKT_TX_IP_CKSUM and PKT_TX_IPV4 exclusive
>=20
> and
>=20
> 2/
> PKT_TX_IP_CKSUM /* we want hw IP cksum */
> PKT_TX_IPV6 /* packet is IPv6 */
> PKT_TX_IPV4 /* packet is IPv4 */
>=20
> with PKT_TX_IP_CKSUM implies PKT_TX_IPV4
>=20
>=20
> Solution 2/ looks better from a user point of view. Anyone else has an op=
inion?
Let's think about these IPv4/6 flags in terms of checksum and IP version/ty=
pe,
=20
1. For IPv6=20
IP checksum is meaningful only for IPv4, so we define 'PKT_TX_IPV6 /*=
packet is IPv6 */' to tell driver/HW that this is IPV6 packet, here we don=
't talk about the checksum for IPv6 as it is meaningless. Right?
PKT_TX_IPV6 /* packet is IPv6 */ ------ IP type: v6; HW check=
sum: meaningless
2. For IPv4,
My patch:
PKT_TX_IP_CKSUM /* packet is IPv4, and we want hw cksum */----------------=
----------IP type: v4; HW checksum: Yes
PKT_TX_IPV4 /* packet is IPv4, and we don't want hw cksum */ ---------=
-------------- IP type: v4; HW checksum: No
You want:
PKT_TX_IP_CKSUM /* we want hw IP cksum */-------------------------- IP typ=
e: v4; HW checksum: Yes
PKT_TX_IPV4 /* packet is IPv4*/ ------------------------ IP type: v4;=
HW checksum: yes or no?
=
driver/HW don't know, just know this is packet =
with IPv4 header.=20
=
HW checksum: meaningless??
> Regards,
> Olivier