kernel/linux.git/include/uapi/linux/if_xdp.h, branch v6.19.11

net: xsk: introduce XDP_MAX_TX_SKB_BUDGET setsockopt

2025-07-10T12:48:29+00:00

This patch provides a setsockopt method to let applications leverage to adjust how many descs to be handled at most in one send syscall. It mitigates the situation where the default value (32) that is too small leads to higher frequency of triggering send syscall. Considering the prosperity/complexity the applications have, there is no absolutely ideal suggestion fitting all cases. So keep 32 as its default value like before. The patch does the following things: - Add XDP_MAX_TX_SKB_BUDGET socket option. - Set max_tx_budget to 32 by default in the initialization phase as a per-socket granular control. - Set the range of max_tx_budget as [32, xs->tx->nentries]. The idea behind this comes out of real workloads in production. We use a user-level stack with xsk support to accelerate sending packets and minimize triggering syscalls. When the packets are aggregated, it's not hard to hit the upper bound (namely, 32). The moment user-space stack fetches the -EAGAIN error number passed from sendto(), it will loop to try again until all the expected descs from tx ring are sent out to the driver. Enlarging the XDP_MAX_TX_SKB_BUDGET value contributes to less frequency of sendto() and higher throughput/PPS. Here is what I did in production, along with some numbers as follows: For one application I saw lately, I suggested using 128 as max_tx_budget because I saw two limitations without changing any default configuration: 1) XDP_MAX_TX_SKB_BUDGET, 2) socket sndbuf which is 212992 decided by net.core.wmem_default. As to XDP_MAX_TX_SKB_BUDGET, the scenario behind this was I counted how many descs are transmitted to the driver at one time of sendto() based on [1] patch and then I calculated the possibility of hitting the upper bound. Finally I chose 128 as a suitable value because 1) it covers most of the cases, 2) a higher number would not bring evident results. After twisting the parameters, a stable improvement of around 4% for both PPS and throughput and less resources consumption were found to be observed by strace -c -p xxx: 1) %time was decreased by 7.8% 2) error counter was decreased from 18367 to 572 [1]: https://lore.kernel.org/all/20250619093641.70700-1-kerneljasonxing@gmail.com/ Signed-off-by: Jason Xing Acked-by: Maciej Fijalkowski Link: https://patch.msgid.link/20250704160138.48677-1-kerneljasonxing@gmail.com Signed-off-by: Paolo Abeni

net: add UAPI to the header guard in various network headers

2025-04-18T02:04:50+00:00

fib_rule, ip6_tunnel, and a whole lot of if_* headers lack the customary _UAPI in the header guard. Without it YNL build can't protect from in tree and system headers both getting included. YNL doesn't need most of these but it's annoying to have to fix them one by one. Note that header installation strips this _UAPI prefix so this should result in no change to the end user. Acked-by: Jamal Hadi Salim Reviewed-by: Jason Xing Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20250416200840.1338195-1-kuba@kernel.org Signed-off-by: Jakub Kicinski

xsk: Add launch time hardware offload support to XDP Tx metadata

2025-02-20T23:13:45+00:00

Extend the XDP Tx metadata framework so that user can requests launch time hardware offload, where the Ethernet device will schedule the packet for transmission at a pre-determined time called launch time. The value of launch time is communicated from user space to Ethernet driver via launch_time field of struct xsk_tx_metadata. Suggested-by: Stanislav Fomichev Signed-off-by: Song Yoong Siang Signed-off-by: Martin KaFai Lau Acked-by: Stanislav Fomichev Acked-by: Jakub Kicinski Link: https://patch.msgid.link/20250216093430.957880-2-yoong.siang.song@intel.com

xsk: Require XDP_UMEM_TX_METADATA_LEN to actuate tx_metadata_len

2024-07-25T09:57:27+00:00

Julian reports that commit 341ac980eab9 ("xsk: Support tx_metadata_len") can break existing use cases which don't zero-initialize xdp_umem_reg padding. Introduce new XDP_UMEM_TX_METADATA_LEN to make sure we interpret the padding as tx_metadata_len only when being explicitly asked. Fixes: 341ac980eab9 ("xsk: Support tx_metadata_len") Reported-by: Julian Schindel Signed-off-by: Stanislav Fomichev Signed-off-by: Daniel Borkmann Reviewed-by: Maciej Fijalkowski Link: https://lore.kernel.org/bpf/20240713015253.121248-2-sdf@fomichev.me

xsk: Add option to calculate TX checksum in SW

2023-11-29T22:59:40+00:00

For XDP_COPY mode, add a UMEM option XDP_UMEM_TX_SW_CSUM to call skb_checksum_help in transmit path. Might be useful to debugging issues with real hardware. I also use this mode in the selftests. Signed-off-by: Stanislav Fomichev Link: https://lore.kernel.org/r/20231127190319.1190813-9-sdf@google.com Signed-off-by: Alexei Starovoitov

xsk: Add TX timestamp and TX checksum offload support

2023-11-29T22:59:40+00:00

This change actually defines the (initial) metadata layout that should be used by AF_XDP userspace (xsk_tx_metadata). The first field is flags which requests appropriate offloads, followed by the offload-specific fields. The supported per-device offloads are exported via netlink (new xsk-flags). The offloads themselves are still implemented in a bit of a framework-y fashion that's left from my initial kfunc attempt. I'm introducing new xsk_tx_metadata_ops which drivers are supposed to implement. The drivers are also supposed to call xsk_tx_metadata_request/xsk_tx_metadata_complete in the right places. Since xsk_tx_metadata_{request,_complete} are static inline, we don't incur any extra overhead doing indirect calls. The benefit of this scheme is as follows: - keeps all metadata layout parsing away from driver code - makes it easy to grep and see which drivers implement what - don't need any extra flags to maintain to keep track of what offloads are implemented; if the callback is implemented - the offload is supported (used by netlink reporting code) Two offloads are defined right now: 1. XDP_TXMD_FLAGS_CHECKSUM: skb-style csum_start+csum_offset 2. XDP_TXMD_FLAGS_TIMESTAMP: writes TX timestamp back into metadata area upon completion (tx_timestamp field) XDP_TXMD_FLAGS_TIMESTAMP is also implemented for XDP_COPY mode: it writes SW timestamp from the skb destructor (note I'm reusing hwtstamps to pass metadata pointer). The struct is forward-compatible and can be extended in the future by appending more fields. Reviewed-by: Song Yoong Siang Signed-off-by: Stanislav Fomichev Acked-by: Jakub Kicinski Link: https://lore.kernel.org/r/20231127190319.1190813-3-sdf@google.com Signed-off-by: Alexei Starovoitov

xsk: Support tx_metadata_len

2023-11-29T22:59:40+00:00

For zerocopy mode, tx_desc->addr can point to an arbitrary offset and carry some TX metadata in the headroom. For copy mode, there is no way currently to populate skb metadata. Introduce new tx_metadata_len umem config option that indicates how many bytes to treat as metadata. Metadata bytes come prior to tx_desc address (same as in RX case). The size of the metadata has mostly the same constraints as XDP: - less than 256 bytes - 8-byte aligned (compared to 4-byte alignment on xdp, due to 8-byte timestamp in the completion) - non-zero This data is not interpreted in any way right now. Reviewed-by: Song Yoong Siang Signed-off-by: Stanislav Fomichev Reviewed-by: Jakub Kicinski Link: https://lore.kernel.org/r/20231127190319.1190813-2-sdf@google.com Signed-off-by: Alexei Starovoitov

xsk: introduce XSK_USE_SG bind flag for xsk socket

2023-07-19T16:56:48+00:00

As of now xsk core drops any xdp_buff with data size greater than the xsk frame_size as set by the af_xdp application. With multi-buffer support introduced in the next patch xsk core can now split those buffers into multiple descriptors provided the af_xdp application can handle them. Such capability of the application needs to be independent of the xdp_prog's frag support capability since there are cases where even a single xdp_buffer may need to be split into multiple descriptors owing to a smaller xsk frame size. For e.g., with NIC rx_buffer size set to 4kB, a 3kB packet will constitute of a single buffer and so will be sent as such to AF_XDP layer irrespective of 'xdp.frags' capability of the XDP program. Now if the xsk frame size is set to 2kB by the AF_XDP application, then the packet will need to be split into 2 descriptors if AF_XDP application can handle multi-buffer, else it needs to be dropped. Applications can now advertise their frag handling capability to xsk core so that xsk core can decide if it should drop or split xdp_buffs that exceed xsk frame size. This is done using a new 'XSK_USE_SG' bind flag for the xdp socket. Signed-off-by: Tirthendu Sarkar Link: https://lore.kernel.org/r/20230719132421.584801-3-maciej.fijalkowski@intel.com Signed-off-by: Alexei Starovoitov

xsk: prepare 'options' in xdp_desc for multi-buffer use

2023-07-19T16:56:48+00:00

Use the 'options' field in xdp_desc as a packet continuity marker. Since 'options' field was unused till now and was expected to be set to 0, the 'eop' descriptor will have it set to 0, while the non-eop descriptors will have to set it to 1. This ensures legacy applications continue to work without needing any change for single-buffer packets. Add helper functions and extend xskq_prod_reserve_desc() to use the 'options' field. Signed-off-by: Tirthendu Sarkar Link: https://lore.kernel.org/r/20230719132421.584801-2-maciej.fijalkowski@intel.com Signed-off-by: Alexei Starovoitov

xsk: Add new statistics

2020-07-13T22:32:56+00:00

It can be useful for the user to know the reason behind a dropped packet. Introduce new counters which track drops on the receive path caused by: 1. rx ring being full 2. fill ring being empty Also, on the tx path introduce a counter which tracks the number of times we attempt pull from the tx ring when it is empty. Signed-off-by: Ciara Loftus Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20200708072835.4427-2-ciara.loftus@intel.com