Hi Didier > -----Original Message----- > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of didier.pallard > Sent: Tuesday, December 02, 2014 2:53 PM > To: Liu, Jijiang; dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH v4 3/3] mbuf:replace the inner_l2_len and the > inner_l3_len fields > > Hello, > > On 12/02/2014 07:52 AM, Jijiang Liu wrote: > > Replace the inner_l2_len and the inner_l3_len field with the outer_l2_len > > and outer_l3_len field, and rework csum forward engine > and i40e PMD due to these changes. > > > > Signed-off-by: Jijiang Liu <jijiang.liu at intel.com> > [...] > > --- a/lib/librte_mbuf/rte_mbuf.h > > +++ b/lib/librte_mbuf/rte_mbuf.h > > @@ -276,8 +276,8 @@ struct rte_mbuf { > > uint64_t tso_segsz:16; /**< TCP TSO segment size */ > > > > /* fields for TX offloading of tunnels */ > > - uint64_t inner_l3_len:9; /**< inner L3 (IP) Hdr Length. > > */ > > - uint64_t inner_l2_len:7; /**< inner L2 (MAC) Hdr > > Length. */ > > + uint64_t outer_l3_len:9; /**< Outer L3 (IP) Hdr Length. > > */ > > + uint64_t outer_l2_len:7; /**< Outer L2 (MAC) Hdr > > Length. */ > > > > /* uint64_t unused:8; */ > > }; > > Sorry for entering lately this discussion, but i'm not convinced by the > choice of outer_lx_len rather than inner_lx_len for new fields. > I agree with Olivier that new flags should only be related to the use of > new fields, to maintain coherency with oldest implementations. > But from a stack point of view, i think it is better to have lx_len > fields that target the outer layers, and to name new fields inner_lx_len. > > Let's discuss the two possibilities. > > 1) outer_lx_len fields are introduced. > In this case, the stack should have knowledge that it is processing > tunneled packets to use outer_lx_len rather than lx_len, > or stack should always use outer_lx_len packet and move those fields to > lx_len packets if no tunneling occurs... > I think it will induce extra processing that does not seem to be really > needed. > > 2) inner_lx_len fields are introduced. > In this case, the stack first uses lx_len fields. When packet should be > tunneled, lx_len fields are moved to inner_lx_len fields. > Then the stack can process the outer layer and still use the lx_len fields.
Not sure, that I understood why 2) is better than 1). Let say, you have a 'normal' (non-tunnelling) packet: ether/IP/TCP In that case you still use mbuf's l2_len/l3_len/l4_len fields and setup ol_flags as usual. Then later, you decided to 'tunnel' that packet. So you just fill mbuf's outer_l2_len/outer_l3_len, setup TX_OUTER_* and TX_TUNNEL_* bits in ol_flags and probably update l2_len. l3_len/l4_len and ol_flags bits set for them remain intact. That's with 1) With 2) - you'll have to move l3_len/l4_len to inner_lx_len. And I suppose ol_flags values too: ol_flags &= ~PKT_ IP_CKSUM; ol_flgas |= PKT_INNER_IP_CKSUM ? And same for L4_CKSUM flags too? Konstantin > > For example: > an eth/IP/TCP forged packet will look like this: > > Ether/IP/UDP/xxx > m->flags = IP_CKSUM > m->l2_len = sizeof(ether) > m->l3_len = sizeof(ip) > m->l4_len = sizeof(udp) > m->inner_l2_len = 0 > m->inner_l3_len = 0 > > When entering tunnel for example a VXLAN interface, lx_len will be moved > to inner_lx_len > > Ether/IP/UDP/xxx > m->flags = INNER_IP_CKSUM > m->l2_len = 0 > m->l3_len = 0 > m->l4_len = 0 > m->inner_l2_len = sizeof(ether) > m->inner_l3_len = sizeof(ip) > > > once complete encapsulation is processed by the stack, the packet will > look like > > Ether/IP/UDP/VXLAN/Ether/IP/UDP/xxx > m->flags = IP_CKSUM | INNER_IP_CKSUM > m->l2_len = sizeof(ether) > m->l3_len = sizeof(ip) > m->l4_len = sizeof(udp) > m->inner_l2_len = sizeof(ether) + sizeof (vxlan) > m->inner_l3_len = sizeof(ip) > > > didier >
