On Thu, 16 Sept 2021 at 18:47, Jakub Kicinski <kuba@xxxxxxxxxx> wrote: > > Won't applications end up building something like skb_header_pointer() > based on bpf_xdp_adjust_data(), anyway? In which case why don't we > provide them what they need? > > say: > > void *xdp_mb_pointer(struct xdp_buff *xdp_md, u32 flags, > u32 offset, u32 len, void *stack_buf) > > flags and offset can be squashed into one u64 as needed. Helper returns > pointer to packet data, either real one or stack_buf. Verifier has to > be taught that the return value is NULL or a pointer which is safe with > offsets up to @len. > > If the reason for access is write we'd also need: > > void *xdp_mb_pointer_flush(struct xdp_buff *xdp_md, u32 flags, > u32 offset, u32 len, void *stack_buf) Yes! This would be so much better than bpf_skb_load/store_bytes(), especially if we can use it for both XDP and skb contexts as stated elsewhere in this thread. -- Lorenz Bauer | Systems Engineer 6th Floor, County Hall/The Riverside Building, SE1 7PB, UK www.cloudflare.com
