From b5964b968ac64c2ec2debee7518499113b27c34e Mon Sep 17 00:00:00 2001 From: Joanne Koong Date: Wed, 1 Mar 2023 07:49:50 -0800 Subject: bpf: Add skb dynptrs Add skb dynptrs, which are dynptrs whose underlying pointer points to a skb. The dynptr acts on skb data. skb dynptrs have two main benefits. One is that they allow operations on sizes that are not statically known at compile-time (eg variable-sized accesses). Another is that parsing the packet data through dynptrs (instead of through direct access of skb->data and skb->data_end) can be more ergonomic and less brittle (eg does not need manual if checking for being within bounds of data_end). For bpf prog types that don't support writes on skb data, the dynptr is read-only (bpf_dynptr_write() will return an error) For reads and writes through the bpf_dynptr_read() and bpf_dynptr_write() interfaces, reading and writing from/to data in the head as well as from/to non-linear paged buffers is supported. Data slices through the bpf_dynptr_data API are not supported; instead bpf_dynptr_slice() and bpf_dynptr_slice_rdwr() (added in subsequent commit) should be used. For examples of how skb dynptrs can be used, please see the attached selftests. Signed-off-by: Joanne Koong Link: https://lore.kernel.org/r/20230301154953.641654-8-joannelkoong@gmail.com Signed-off-by: Alexei Starovoitov --- include/uapi/linux/bpf.h | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 62ce1f5d1b1d..d0351d30e551 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -5325,11 +5325,17 @@ union bpf_attr { * Description * Write *len* bytes from *src* into *dst*, starting from *offset* * into *dst*. - * *flags* is currently unused. + * + * *flags* must be 0 except for skb-type dynptrs. + * + * For skb-type dynptrs: + * * For *flags*, please see the flags accepted by + * **bpf_skb_store_bytes**\ (). * Return * 0 on success, -E2BIG if *offset* + *len* exceeds the length * of *dst*'s data, -EINVAL if *dst* is an invalid dynptr or if *dst* - * is a read-only dynptr or if *flags* is not 0. + * is a read-only dynptr or if *flags* is not correct. For skb-type dynptrs, + * other errors correspond to errors returned by **bpf_skb_store_bytes**\ (). * * void *bpf_dynptr_data(const struct bpf_dynptr *ptr, u32 offset, u32 len) * Description @@ -5337,6 +5343,9 @@ union bpf_attr { * * *len* must be a statically known value. The returned data slice * is invalidated whenever the dynptr is invalidated. + * + * skb type dynptrs may not use bpf_dynptr_data. They should + * instead use bpf_dynptr_slice and bpf_dynptr_slice_rdwr. * Return * Pointer to the underlying dynptr data, NULL if the dynptr is * read-only, if the dynptr is invalid, or if the offset and length -- cgit v1.2.3