kernel/linux.git/tools/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

selftests/bpf: Fix bpf selftest build warning

2025-05-28T08:00:14+00:00

On linux-next, build for bpf selftest displays a warning: Warning: Kernel ABI header at 'tools/include/uapi/linux/if_xdp.h' differs from latest version at 'include/uapi/linux/if_xdp.h'. Commit 8066e388be48 ("net: add UAPI to the header guard in various network headers") changed the header guard from _LINUX_IF_XDP_H to _UAPI_LINUX_IF_XDP_H in include/uapi/linux/if_xdp.h. To resolve the warning, update tools/include/uapi/linux/if_xdp.h to align with the changes in include/uapi/linux/if_xdp.h Fixes: 8066e388be48 ("net: add UAPI to the header guard in various network headers") Reported-by: Venkat Rao Bagalkote Closes: https://lore.kernel.org/all/c2bc466d-dff2-4d0d-a797-9af7f676c065@linux.ibm.com/ Tested-by: Venkat Rao Bagalkote Signed-off-by: Saket Kumar Bhaskar Acked-by: Daniel Borkmann Link: https://patch.msgid.link/20250527054138.1086006-1-skb99@linux.ibm.com Signed-off-by: Paolo Abeni

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

tools: Sync if_xdp.h uapi tooling header

2025-01-17T14:49:16+00:00

Sync if_xdp.h uapi header to remove following warning: Warning: Kernel ABI header at 'tools/include/uapi/linux/if_xdp.h' differs from latest version at 'include/uapi/linux/if_xdp.h' Fixes: 48eb03dd2630 ("xsk: Add TX timestamp and TX checksum offload support") Signed-off-by: Vishal Chourasia Signed-off-by: Song Yoong Siang Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20250115032248.125742-1-yoong.siang.song@intel.com

selftests/bpf: Add XDP_UMEM_TX_METADATA_LEN to XSK TX metadata test

2024-07-25T09:57:33+00:00

This flag is now required to use tx_metadata_len. Fixes: 40808a237d9c ("selftests/bpf: Add TX side to xdp_metadata") Reported-by: Julian Schindel Signed-off-by: Stanislav Fomichev Signed-off-by: Daniel Borkmann Reviewed-by: Maciej Fijalkowski Link: https://lore.kernel.org/bpf/20240713015253.121248-3-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

selftests/xsk: add basic multi-buffer test

2023-07-19T16:56:50+00:00

Add the first basic multi-buffer test that sends a stream of 9K packets and validates that they are received at the other end. In order to enable sending and receiving multi-buffer packets, code that sets the MTU is introduced as well as modifications to the XDP programs so that they signal that they are multi-buffer enabled. Signed-off-by: Magnus Karlsson Link: https://lore.kernel.org/r/20230719132421.584801-20-maciej.fijalkowski@intel.com Signed-off-by: Alexei Starovoitov

selftests/xsk: transmit and receive multi-buffer packets

2023-07-19T16:56:50+00:00

Add the ability to send and receive packets that are larger than the size of a umem frame, using the AF_XDP /XDP multi-buffer support. There are three pieces of code that need to be changed to achieve this: the Rx path, the Tx path, and the validation logic. Both the Rx path and Tx could only deal with a single fragment per packet. The Tx path is extended with a new function called pkt_nb_frags() that can be used to retrieve the number of fragments a packet will consume. We then create these many fragments in a loop and fill the N-1 first ones to the max size limit to use the buffer space efficiently, and the Nth one with whatever data that is left. This goes on until we have filled in at the most BATCH_SIZE worth of descriptors and fragments. If we detect that the next packet would lead to BATCH_SIZE number of fragments sent being exceeded, we do not send this packet and finish the batch. This packet is instead sent in the next iteration of BATCH_SIZE fragments. For Rx, we loop over all fragments we receive as usual, but for every descriptor that we receive we call a new validation function called is_frag_valid() to validate the consistency of this fragment. The code then checks if the packet continues in the next frame. If so, it loops over the next packet and performs the same validation. once we have received the last fragment of the packet we also call the function is_pkt_valid() to validate the packet as a whole. If we get to the end of the batch and we are not at the end of the current packet, we back out the partial packet and end the loop. Once we get into the receive loop next time, we start over from the beginning of that packet. This so the code becomes simpler at the cost of some performance. The validation function is_frag_valid() checks that the sequence and packet numbers are correct at the start and end of each fragment. Signed-off-by: Magnus Karlsson Link: https://lore.kernel.org/r/20230719132421.584801-19-maciej.fijalkowski@intel.com Signed-off-by: Alexei Starovoitov