kernel/linux.git/include/uapi/linux/if_xdp.h, branch v6.12.80

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

xsk: add support to allow unaligned chunk placement

2019-08-30T23:08:26+00:00

Currently, addresses are chunk size aligned. This means, we are very restricted in terms of where we can place chunk within the umem. For example, if we have a chunk size of 2k, then our chunks can only be placed at 0,2k,4k,6k,8k... and so on (ie. every 2k starting from 0). This patch introduces the ability to use unaligned chunks. With these changes, we are no longer bound to having to place chunks at a 2k (or whatever your chunk size is) interval. Since we are no longer dealing with aligned chunks, they can now cross page boundaries. Checks for page contiguity have been added in order to keep track of which pages are followed by a physically contiguous page. Signed-off-by: Kevin Laatz Signed-off-by: Ciara Loftus Signed-off-by: Bruce Richardson Acked-by: Jonathan Lemon Signed-off-by: Daniel Borkmann

xsk: add support for need_wakeup flag in AF_XDP rings

2019-08-17T21:07:32+00:00

This commit adds support for a new flag called need_wakeup in the AF_XDP Tx and fill rings. When this flag is set, it means that the application has to explicitly wake up the kernel Rx (for the bit in the fill ring) or kernel Tx (for bit in the Tx ring) processing by issuing a syscall. Poll() can wake up both depending on the flags submitted and sendto() will wake up tx processing only. The main reason for introducing this new flag is to be able to efficiently support the case when application and driver is executing on the same core. Previously, the driver was just busy-spinning on the fill ring if it ran out of buffers in the HW and there were none on the fill ring. This approach works when the application is running on another core as it can replenish the fill ring while the driver is busy-spinning. Though, this is a lousy approach if both of them are running on the same core as the probability of the fill ring getting more entries when the driver is busy-spinning is zero. With this new feature the driver now sets the need_wakeup flag and returns to the application. The application can then replenish the fill queue and then explicitly wake up the Rx processing in the kernel using the syscall poll(). For Tx, the flag is only set to one if the driver has no outstanding Tx completion interrupts. If it has some, the flag is zero as it will be woken up by a completion interrupt anyway. As a nice side effect, this new flag also improves the performance of the case where application and driver are running on two different cores as it reduces the number of syscalls to the kernel. The kernel tells user space if it needs to be woken up by a syscall, and this eliminates many of the syscalls. This flag needs some simple driver support. If the driver does not support this, the Rx flag is always zero and the Tx flag is always one. This makes any application relying on this feature default to the old behaviour of not requiring any syscalls in the Rx path and always having to call sendto() in the Tx path. For backwards compatibility reasons, this feature has to be explicitly turned on using a new bind flag (XDP_USE_NEED_WAKEUP). I recommend that you always turn it on as it so far always have had a positive performance impact. The name and inspiration of the flag has been taken from io_uring by Jens Axboe. Details about this feature in io_uring can be found in http://kernel.dk/io_uring.pdf, section 8.3. Signed-off-by: Magnus Karlsson Acked-by: Jonathan Lemon Signed-off-by: Daniel Borkmann

xsk: Add getsockopt XDP_OPTIONS

2019-06-27T20:53:26+00:00

Make it possible for the application to determine whether the AF_XDP socket is running in zero-copy mode. To achieve this, add a new getsockopt option XDP_OPTIONS that returns flags. The only flag supported for now is the zero-copy mode indicator. Signed-off-by: Maxim Mikityanskiy Signed-off-by: Tariq Toukan Acked-by: Saeed Mahameed Acked-by: Björn Töpel Signed-off-by: Daniel Borkmann