On 07/22/2016 01:48 AM, Ananyev, Konstantin wrote: > >> This is an ABI deprecation notice for DPDK 16.11 in librte_ether about >> changes in rte_eth_dev and rte_eth_desc_lim structures. >> >> As discussed in that thread: >> >> http://dpdk.org/ml/archives/dev/2015-September/023603.html >> >> Different NIC models depending on HW offload requested might impose >> different requirements on packets to be TX-ed in terms of: >> >> - Max number of fragments per packet allowed >> - Max number of fragments per TSO segments >> - The way pseudo-header checksum should be pre-calculated >> - L3/L4 header fields filling >> - etc. >> >> >> MOTIVATION: >> ----------- >> >> 1) Some work cannot (and didn't should) be done in rte_eth_tx_burst. >> However, this work is sometimes required, and now, it's an >> application issue. >> >> 2) Different hardware may have different requirements for TX offloads, >> other subset can be supported and so on. >> >> 3) Some parameters (eg. number of segments in ixgbe driver) may hung >> device. These parameters may be vary for different devices. >> >> For example i40e HW allows 8 fragments per packet, but that is after >> TSO segmentation. While ixgbe has a 38-fragment pre-TSO limit. >> >> 4) Fields in packet may require different initialization (like eg. will >> require pseudo-header checksum precalculation, sometimes in a >> different way depending on packet type, and so on). Now application >> needs to care about it. >> >> 5) Using additional API (rte_eth_tx_prep) before rte_eth_tx_burst let to >> prepare packet burst in acceptable form for specific device. >> >> 6) Some additional checks may be done in debug mode keeping tx_burst >> implementation clean. >> >> >> PROPOSAL: >> --------- >> >> To help user to deal with all these varieties we propose to: >> >> 1. Introduce rte_eth_tx_prep() function to do necessary preparations of >> packet burst to be safely transmitted on device for desired HW >> offloads (set/reset checksum field according to the hardware >> requirements) and check HW constraints (number of segments per >> packet, etc). >> >> While the limitations and requirements may differ for devices, it >> requires to extend rte_eth_dev structure with new function pointer >> "tx_pkt_prep" which can be implemented in the driver to prepare and >> verify packets, in devices specific way, before burst, what should to >> prevent application to send malformed packets. >> >> 2. Also new fields will be introduced in rte_eth_desc_lim: >> nb_seg_max and nb_mtu_seg_max, providing an information about max >> segments in TSO and non-TSO packets acceptable by device. >> >> This information is useful for application to not create/limit >> malicious packet. >> >> >> APPLICATION (CASE OF USE): >> -------------------------- >> >> 1) Application should to initialize burst of packets to send, set >> required tx offload flags and required fields, like l2_len, l3_len, >> l4_len, and tso_segsz >> >> 2) Application passes burst to the rte_eth_tx_prep to check conditions >> required to send packets through the NIC. >> >> 3) The result of rte_eth_tx_prep can be used to send valid packets >> and/or restore invalid if function fails. >> >> eg. >> >> for (i = 0; i < nb_pkts; i++) { >> >> /* initialize or process packet */ >> >> bufs[i]->tso_segsz = 800; >> bufs[i]->ol_flags = PKT_TX_TCP_SEG | PKT_TX_IPV4 >> | PKT_TX_IP_CKSUM; >> bufs[i]->l2_len = sizeof(struct ether_hdr); >> bufs[i]->l3_len = sizeof(struct ipv4_hdr); >> bufs[i]->l4_len = sizeof(struct tcp_hdr); >> } >> >> /* Prepare burst of TX packets */ >> nb_prep = rte_eth_tx_prep(port, 0, bufs, nb_pkts); >> >> if (nb_prep < nb_pkts) { >> printf("tx_prep failed\n"); >> >> /* drop or restore invalid packets */ >> >> } >> >> /* Send burst of TX packets */ >> nb_tx = rte_eth_tx_burst(port, 0, bufs, nb_prep); >> >> /* Free any unsent packets. */ >> >> >> >> Signed-off-by: Tomasz Kulasek <tomaszx.kulasek at intel.com>
Acked-by: Vlad Zolotarov <vladz at scylladb.com> >> --- >> doc/guides/rel_notes/deprecation.rst | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/doc/guides/rel_notes/deprecation.rst >> b/doc/guides/rel_notes/deprecation.rst >> index f502f86..485aacb 100644 >> --- a/doc/guides/rel_notes/deprecation.rst >> +++ b/doc/guides/rel_notes/deprecation.rst >> @@ -41,3 +41,10 @@ Deprecation Notices >> * The mempool functions for single/multi producer/consumer are deprecated >> and >> will be removed in 16.11. >> It is replaced by rte_mempool_generic_get/put functions. >> + >> +* In 16.11 ABI changes are plained: the ``rte_eth_dev`` structure will be >> + extended with new function pointer ``tx_pkt_prep`` allowing verification >> + and processing of packet burst to meet HW specific requirements before >> + transmit. Also new fields will be added to the ``rte_eth_desc_lim`` >> structure: >> + ``nb_seg_max`` and ``nb_mtu_seg_max`` provideing information about number >> of >> + segments limit to be transmitted by device for TSO/non-TSO packets. >> -- > Acked-by: Konstantin Ananyev <konstantin.ananyev at intel.com> > >> 1.7.9.5
