diff options
| author | Jakub Sitnicki <jakub@cloudflare.com> | 2025-08-14 11:59:27 +0200 |
|---|---|---|
| committer | Martin KaFai Lau <martin.lau@kernel.org> | 2025-08-18 10:29:42 -0700 |
| commit | 89d912e494f786e79f69ed9d567a8842c71dbb03 (patch) | |
| tree | 28268338451d686c8842efc36e7596ae4d63b4dc /kernel/bpf/helpers.c | |
| parent | 8f5ae30d69d7543eee0d70083daf4de8fe15d585 (diff) | |
bpf: Add dynptr type for skb metadata
Add a dynptr type, similar to skb dynptr, but for the skb metadata access.
The dynptr provides an alternative to __sk_buff->data_meta for accessing
the custom metadata area allocated using the bpf_xdp_adjust_meta() helper.
More importantly, it abstracts away the fact where the storage for the
custom metadata lives, which opens up the way to persist the metadata by
relocating it as the skb travels through the network stack layers.
Writes to skb metadata invalidate any existing skb payload and metadata
slices. While this is more restrictive that needed at the moment, it leaves
the door open to reallocating the metadata on writes, and should be only a
minor inconvenience to the users.
Only the program types which can access __sk_buff->data_meta today are
allowed to create a dynptr for skb metadata at the moment. We need to
modify the network stack to persist the metadata across layers before
opening up access to other BPF hooks.
Once more BPF hooks gain access to skb_meta dynptr, we will also need to
add a read-only variant of the helper similar to
bpf_dynptr_from_skb_rdonly.
skb_meta dynptr ops are stubbed out and implemented by subsequent changes.
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Jesse Brandeburg <jbrandeburg@cloudflare.com>
Link: https://patch.msgid.link/20250814-skb-metadata-thru-dynptr-v7-1-8a39e636e0fb@cloudflare.com
Diffstat (limited to 'kernel/bpf/helpers.c')
| -rw-r--r-- | kernel/bpf/helpers.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 6b4877e85a68..9552b32208c5 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -1780,6 +1780,8 @@ static int __bpf_dynptr_read(void *dst, u32 len, const struct bpf_dynptr_kern *s return __bpf_skb_load_bytes(src->data, src->offset + offset, dst, len); case BPF_DYNPTR_TYPE_XDP: return __bpf_xdp_load_bytes(src->data, src->offset + offset, dst, len); + case BPF_DYNPTR_TYPE_SKB_META: + return -EOPNOTSUPP; /* not implemented */ default: WARN_ONCE(true, "bpf_dynptr_read: unknown dynptr type %d\n", type); return -EFAULT; @@ -1836,6 +1838,8 @@ int __bpf_dynptr_write(const struct bpf_dynptr_kern *dst, u32 offset, void *src, if (flags) return -EINVAL; return __bpf_xdp_store_bytes(dst->data, dst->offset + offset, src, len); + case BPF_DYNPTR_TYPE_SKB_META: + return -EOPNOTSUPP; /* not implemented */ default: WARN_ONCE(true, "bpf_dynptr_write: unknown dynptr type %d\n", type); return -EFAULT; @@ -1882,6 +1886,7 @@ BPF_CALL_3(bpf_dynptr_data, const struct bpf_dynptr_kern *, ptr, u32, offset, u3 return (unsigned long)(ptr->data + ptr->offset + offset); case BPF_DYNPTR_TYPE_SKB: case BPF_DYNPTR_TYPE_XDP: + case BPF_DYNPTR_TYPE_SKB_META: /* skb and xdp dynptrs should use bpf_dynptr_slice / bpf_dynptr_slice_rdwr */ return 0; default: @@ -2710,6 +2715,8 @@ __bpf_kfunc void *bpf_dynptr_slice(const struct bpf_dynptr *p, u32 offset, bpf_xdp_copy_buf(ptr->data, ptr->offset + offset, buffer__opt, len, false); return buffer__opt; } + case BPF_DYNPTR_TYPE_SKB_META: + return NULL; /* not implemented */ default: WARN_ONCE(true, "unknown dynptr type %d\n", type); return NULL; |