26. ABI and API Deprecation

See the guidelines document for details of the ABI policy. API and ABI deprecation notices are to be posted here.

26.1. Deprecation Notices

  • kvargs: The function rte_kvargs_process will get a new parameter for returning key match count. It will ease handling of no-match case.

  • eal: The function rte_eal_remote_launch will return new error codes after read or write error on the pipe, instead of calling rte_panic.

  • rte_atomicNN_xxx: These APIs do not take memory order parameter. This does not allow for writing optimized code for all the CPU architectures supported in DPDK. DPDK will adopt C11 atomic operations semantics and provide wrappers using C11 atomic built-ins. These wrappers must be used for patches that need to be merged in 20.08 onwards. This change will not introduce any performance degradation.

  • rte_smp_*mb: These APIs provide full barrier functionality. However, many use cases do not require full barriers. To support such use cases, DPDK will adopt C11 barrier semantics and provide wrappers using C11 atomic built-ins. These wrappers must be used for patches that need to be merged in 20.08 onwards. This change will not introduce any performance degradation.

  • lib: will fix extending some enum/define breaking the ABI. There are multiple samples in DPDK that enum/define terminated with a .*MAX.* value which is used by iterators, and arrays holding these values are sized with this .*MAX.* value. So extending this enum/define increases the .*MAX.* value which increases the size of the array and depending on how/where the array is used this may break the ABI. RTE_ETH_FLOW_MAX is one sample of the mentioned case, adding a new flow type will break the ABI because of flex_mask[RTE_ETH_FLOW_MAX] array usage in following public struct hierarchy: rte_eth_fdir_flex_conf -> rte_fdir_conf -> rte_eth_conf (in the middle). Need to identify this kind of usages and fix in 20.11, otherwise this blocks us extending existing enum/define. One solution can be using a fixed size array instead of .*MAX.* value.

  • ethdev: The flow director API, including rte_eth_conf.fdir_conf field, and the related structures (rte_fdir_* and rte_eth_fdir_*), will be removed in DPDK 20.11.

  • ethdev: New offload flags DEV_RX_OFFLOAD_FLOW_MARK will be added in 19.11. This will allow application to enable or disable PMDs from updating rte_mbuf::hash::fdir. This scheme will allow PMDs to avoid writes to rte_mbuf fields on Rx and thereby improve Rx performance if application wishes do so. In 19.11 PMDs will still update the field even when the offload is not enabled.

  • ethdev: uint32_t max_rx_pkt_len field of struct rte_eth_rxmode, will be replaced by a new uint32_t mtu field of struct rte_eth_conf in v21.11. The new mtu field will be used to configure the initial device MTU via rte_eth_dev_configure() API. Later MTU can be changed by rte_eth_dev_set_mtu() API as done now. The existing (struct rte_eth_dev)->data->mtu variable will be used to store the configured mtu value, and this new (struct rte_eth_dev)->data->dev_conf.mtu variable will be used to store the user configuration request. Unlike max_rx_pkt_len, which was valid only when JUMBO_FRAME enabled, mtu field will be always valid. When mtu config is not provided by the application, default RTE_ETHER_MTU value will be used. (struct rte_eth_dev)->data->mtu should be updated after MTU set successfully, either by rte_eth_dev_configure() or rte_eth_dev_set_mtu().

    An application may need to configure device for a specific Rx packet size, like for cases DEV_RX_OFFLOAD_SCATTER is not supported and device received packet size can’t be bigger than Rx buffer size. To cover these cases an application needs to know the device packet overhead to be able to calculate the mtu corresponding to a Rx buffer size, for this (struct rte_eth_dev_info).max_rx_pktlen will be kept, the device packet overhead can be calculated as: (struct rte_eth_dev_info).max_rx_pktlen - (struct rte_eth_dev_info).max_mtu

  • ethdev: rx_descriptor_done dev_ops and rte_eth_rx_descriptor_done will be removed in 21.11. Existing rte_eth_rx_descriptor_status and rte_eth_tx_descriptor_status APIs can be used as replacement.

  • ethdev: The port mirroring API can be replaced with a more fine grain flow API. The structs rte_eth_mirror_conf, rte_eth_vlan_mirror and the functions rte_eth_mirror_rule_set, rte_eth_mirror_rule_reset will be marked as deprecated in DPDK 20.11, along with the associated macros ETH_MIRROR_*. This API will be fully removed in DPDK 21.11.

  • ethdev: Attribute shared of the struct rte_flow_action_count is deprecated and will be removed in DPDK 21.11. Shared counters should be managed using shared actions API (rte_flow_shared_action_create etc).

  • ethdev: The flow API matching pattern structures, struct rte_flow_item_*, should start with relevant protocol header. Some matching pattern structures implements this by duplicating protocol header fields in the struct. To clarify the intention and to be sure protocol header is intact, will replace those fields with relevant protocol header struct. In v21.02 both individual protocol header fields and the protocol header struct will be added as union, target is switch usage to the protocol header by time. In v21.11 LTS, protocol header fields will be cleaned and only protocol header struct will remain.

  • ethdev: Queue specific stats fields will be removed from struct rte_eth_stats. Mentioned fields are: q_ipackets, q_opackets, q_ibytes, q_obytes, q_errors. Instead queue stats will be received via xstats API. Current method support will be limited to maximum 256 queues. Also compile time flag RTE_ETHDEV_QUEUE_STAT_CNTRS will be removed.

  • sched: To allow more traffic classes, flexible mapping of pipe queues to traffic classes, and subport level configuration of pipes and queues changes will be made to macros, data structures and API functions defined in “rte_sched.h”. These changes are aligned to improvements suggested in the RFC https://mails.dpdk.org/archives/dev/2018-November/120035.html.

  • metrics: The function rte_metrics_init will have a non-void return in order to notify errors instead of calling rte_exit.

  • cmdline: cmdline structure will be made opaque to hide platform-specific content. On Linux and FreeBSD, supported prior to DPDK 20.11, original structure will be kept until DPDK 21.11.