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.
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| @@ -53,12 +53,28 @@ enum netdev_xdp_rx_metadata { · 52 unmodified lines | ||
| 53 | 53 | NETDEV_XDP_RX_METADATA_MASK = 3, |
| 54 | 54 | }; |
| 55 | 55 | |
| 56 | +/** | |
| 57 | + * enum netdev_xsk_flags | |
| 58 | + * @NETDEV_XSK_FLAGS_TX_TIMESTAMP: HW timestamping egress packets is supported | |
| 59 | + * by the driver. | |
| 60 | + * @NETDEV_XSK_FLAGS_TX_CHECKSUM: L3 checksum HW offload is supported by the | |
| 61 | + * driver. | |
| 62 | + */ | |
| 63 | +enum netdev_xsk_flags { | |
| 64 | + NETDEV_XSK_FLAGS_TX_TIMESTAMP = 1, | |
| 65 | + NETDEV_XSK_FLAGS_TX_CHECKSUM = 2, | |
| 66 | + | |
| 67 | + /* private: */ | |
| 68 | + NETDEV_XSK_FLAGS_MASK = 3, | |
| 69 | +}; | |
| 70 | + | |
| 56 | 71 | enum { |
| 57 | 72 | NETDEV_A_DEV_IFINDEX = 1, |
| 58 | 73 | NETDEV_A_DEV_PAD, |
| 59 | 74 | NETDEV_A_DEV_XDP_FEATURES, |
| 60 | 75 | NETDEV_A_DEV_XDP_ZC_MAX_SEGS, |
| 61 | 76 | NETDEV_A_DEV_XDP_RX_METADATA_FEATURES, |
| 77 | + NETDEV_A_DEV_XSK_FEATURES, | |
| 62 | 78 | |
| 63 | 79 | __NETDEV_A_DEV_MAX, |
| 64 | 80 | NETDEV_A_DEV_MAX = (__NETDEV_A_DEV_MAX - 1) |