On Wed, Jul 27, 2022 at 10:14 AM <sdf@xxxxxxxxxx> wrote:
>
> On 07/26, Joanne Koong wrote:
> > 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 (writes and data slices are not permitted). For reads on the
> > dynptr, this includes reading into data in the non-linear paged buffers
> > but for writes and data slices, if the data is in a paged buffer, the
> > user must first call bpf_skb_pull_data to pull the data into the linear
> > portion.
>
> > Additionally, any helper calls that change the underlying packet buffer
> > (eg bpf_skb_pull_data) invalidates any data slices of the associated
> > dynptr.
>
> > Right now, skb dynptrs can only be constructed from skbs that are
> > the bpf program context - as such, there does not need to be any
> > reference tracking or release on skb dynptrs.
>
> > Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
> > ---
> > include/linux/bpf.h | 8 ++++-
> > include/linux/filter.h | 4 +++
> > include/uapi/linux/bpf.h | 42 ++++++++++++++++++++++++--
> > kernel/bpf/helpers.c | 54 +++++++++++++++++++++++++++++++++-
> > kernel/bpf/verifier.c | 43 +++++++++++++++++++++++----
> > net/core/filter.c | 53 ++++++++++++++++++++++++++++++---
> > tools/include/uapi/linux/bpf.h | 42 ++++++++++++++++++++++++--
> > 7 files changed, 229 insertions(+), 17 deletions(-)
>
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index 20c26aed7896..7fbd4324c848 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -407,11 +407,14 @@ enum bpf_type_flag {
> > /* Size is known at compile time. */
> > MEM_FIXED_SIZE = BIT(10 + BPF_BASE_TYPE_BITS),
>
> > + /* DYNPTR points to sk_buff */
> > + DYNPTR_TYPE_SKB = BIT(11 + BPF_BASE_TYPE_BITS),
> > +
> > __BPF_TYPE_FLAG_MAX,
> > __BPF_TYPE_LAST_FLAG = __BPF_TYPE_FLAG_MAX - 1,
> > };
>
> > -#define DYNPTR_TYPE_FLAG_MASK (DYNPTR_TYPE_LOCAL | DYNPTR_TYPE_RINGBUF)
> > +#define DYNPTR_TYPE_FLAG_MASK (DYNPTR_TYPE_LOCAL | DYNPTR_TYPE_RINGBUF |
> > DYNPTR_TYPE_SKB)
>
> > /* Max number of base types. */
> > #define BPF_BASE_TYPE_LIMIT (1UL << BPF_BASE_TYPE_BITS)
> > @@ -2556,12 +2559,15 @@ enum bpf_dynptr_type {
> > BPF_DYNPTR_TYPE_LOCAL,
> > /* Underlying data is a ringbuf record */
> > BPF_DYNPTR_TYPE_RINGBUF,
> > + /* Underlying data is a sk_buff */
> > + BPF_DYNPTR_TYPE_SKB,
> > };
>
> > void bpf_dynptr_init(struct bpf_dynptr_kern *ptr, void *data,
> > enum bpf_dynptr_type type, u32 offset, u32 size);
> > void bpf_dynptr_set_null(struct bpf_dynptr_kern *ptr);
> > int bpf_dynptr_check_size(u32 size);
> > +void bpf_dynptr_set_rdonly(struct bpf_dynptr_kern *ptr);
>
> > #ifdef CONFIG_BPF_LSM
> > void bpf_cgroup_atype_get(u32 attach_btf_id, int cgroup_atype);
> > diff --git a/include/linux/filter.h b/include/linux/filter.h
> > index a5f21dc3c432..649063d9cbfd 100644
> > --- a/include/linux/filter.h
> > +++ b/include/linux/filter.h
> > @@ -1532,4 +1532,8 @@ static __always_inline int
> > __bpf_xdp_redirect_map(struct bpf_map *map, u32 ifind
> > return XDP_REDIRECT;
> > }
>
> > +int __bpf_skb_load_bytes(const struct sk_buff *skb, u32 offset, void
> > *to, u32 len);
> > +int __bpf_skb_store_bytes(struct sk_buff *skb, u32 offset, const void
> > *from,
> > + u32 len, u64 flags);
> > +
> > #endif /* __LINUX_FILTER_H__ */
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 59a217ca2dfd..0730cd198a7f 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -5241,11 +5241,22 @@ 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:
> > + * * if *offset* + *len* extends into the skb's paged buffers, the
> > user
> > + * should manually pull the skb with bpf_skb_pull and then try
> > again.
> > + *
> > + * * *flags* are a combination of **BPF_F_RECOMPUTE_CSUM**
> > (automatically
> > + * recompute the checksum for the packet after storing the bytes) and
> > + * **BPF_F_INVALIDATE_HASH** (set *skb*\ **->hash**, *skb*\
> > + * **->swhash** and *skb*\ **->l4hash** to 0).
> > * 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, -EAGAIN if for
> > + * skb-type dynptrs the write extends into the skb's paged buffers.
> > *
> > * void *bpf_dynptr_data(struct bpf_dynptr *ptr, u32 offset, u32 len)
> > * Description
> > @@ -5253,10 +5264,19 @@ union bpf_attr {
> > *
> > * *len* must be a statically known value. The returned data slice
> > * is invalidated whenever the dynptr is invalidated.
> > + *
> > + * For skb-type dynptrs:
> > + * * if *offset* + *len* extends into the skb's paged buffers,
> > + * the user should manually pull the skb with bpf_skb_pull and
> > then
> > + * try again.
> > + *
> > + * * the data slice is automatically invalidated anytime a
> > + * helper call that changes the underlying packet buffer
> > + * (eg bpf_skb_pull) is called.
> > * 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
> > - * is out of bounds.
> > + * is out of bounds or in a paged buffer for skb-type dynptrs.
> > *
> > * s64 bpf_tcp_raw_gen_syncookie_ipv4(struct iphdr *iph, struct tcphdr
> > *th, u32 th_len)
> > * Description
> > @@ -5331,6 +5351,21 @@ union bpf_attr {
> > * **-EACCES** if the SYN cookie is not valid.
> > *
> > * **-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin.
> > + *
> > + * long bpf_dynptr_from_skb(struct sk_buff *skb, u64 flags, struct
> > bpf_dynptr *ptr)
> > + * Description
> > + * Get a dynptr to the data in *skb*. *skb* must be the BPF program
> > + * context. Depending on program type, the dynptr may be read-only,
> > + * in which case trying to obtain a direct data slice to it through
> > + * bpf_dynptr_data will return an error.
> > + *
> > + * Calls that change the *skb*'s underlying packet buffer
> > + * (eg bpf_skb_pull_data) do not invalidate the dynptr, but they do
> > + * invalidate any data slices associated with the dynptr.
> > + *
> > + * *flags* is currently unused, it must be 0 for now.
> > + * Return
> > + * 0 on success or -EINVAL if flags is not 0.
> > */
> > #define __BPF_FUNC_MAPPER(FN) \
> > FN(unspec), \
> > @@ -5541,6 +5576,7 @@ union bpf_attr {
> > FN(tcp_raw_gen_syncookie_ipv6), \
> > FN(tcp_raw_check_syncookie_ipv4), \
> > FN(tcp_raw_check_syncookie_ipv6), \
> > + FN(dynptr_from_skb), \
> > /* */
>
> > /* integer value in 'imm' field of BPF_CALL instruction selects which
> > helper
> > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> > index 1f961f9982d2..21a806057e9e 100644
> > --- a/kernel/bpf/helpers.c
> > +++ b/kernel/bpf/helpers.c
> > @@ -1425,11 +1425,21 @@ static bool bpf_dynptr_is_rdonly(struct
> > bpf_dynptr_kern *ptr)
> > return ptr->size & DYNPTR_RDONLY_BIT;
> > }
>
> > +void bpf_dynptr_set_rdonly(struct bpf_dynptr_kern *ptr)
> > +{
> > + ptr->size |= DYNPTR_RDONLY_BIT;
> > +}
> > +
> > static void bpf_dynptr_set_type(struct bpf_dynptr_kern *ptr, enum
> > bpf_dynptr_type type)
> > {
> > ptr->size |= type << DYNPTR_TYPE_SHIFT;
> > }
>
> > +static enum bpf_dynptr_type bpf_dynptr_get_type(const struct
> > bpf_dynptr_kern *ptr)
> > +{
> > + return (ptr->size & ~(DYNPTR_RDONLY_BIT)) >> DYNPTR_TYPE_SHIFT;
> > +}
> > +
> > static u32 bpf_dynptr_get_size(struct bpf_dynptr_kern *ptr)
> > {
> > return ptr->size & DYNPTR_SIZE_MASK;
> > @@ -1500,6 +1510,7 @@ static const struct bpf_func_proto
> > bpf_dynptr_from_mem_proto = {
> > BPF_CALL_5(bpf_dynptr_read, void *, dst, u32, len, struct
> > bpf_dynptr_kern *, src,
> > u32, offset, u64, flags)
> > {
> > + enum bpf_dynptr_type type;
> > int err;
>
> > if (!src->data || flags)
> > @@ -1509,6 +1520,11 @@ BPF_CALL_5(bpf_dynptr_read, void *, dst, u32, len,
> > struct bpf_dynptr_kern *, src
> > if (err)
> > return err;
>
> > + type = bpf_dynptr_get_type(src);
> > +
> > + if (type == BPF_DYNPTR_TYPE_SKB)
> > + return __bpf_skb_load_bytes(src->data, src->offset + offset, dst, len);
> > +
> > memcpy(dst, src->data + src->offset + offset, len);
>
> > return 0;
> > @@ -1528,15 +1544,38 @@ static const struct bpf_func_proto
> > bpf_dynptr_read_proto = {
> > BPF_CALL_5(bpf_dynptr_write, struct bpf_dynptr_kern *, dst, u32, offset,
> > void *, src,
> > u32, len, u64, flags)
> > {
> > + enum bpf_dynptr_type type;
> > int err;
>
> > - if (!dst->data || flags || bpf_dynptr_is_rdonly(dst))
> > + if (!dst->data || bpf_dynptr_is_rdonly(dst))
> > return -EINVAL;
>
> > err = bpf_dynptr_check_off_len(dst, offset, len);
> > if (err)
> > return err;
>
> > + type = bpf_dynptr_get_type(dst);
> > +
> > + if (flags) {
> > + if (type == BPF_DYNPTR_TYPE_SKB) {
> > + if (flags & ~(BPF_F_RECOMPUTE_CSUM | BPF_F_INVALIDATE_HASH))
> > + return -EINVAL;
> > + } else {
> > + return -EINVAL;
> > + }
> > + }
> > +
> > + if (type == BPF_DYNPTR_TYPE_SKB) {
> > + struct sk_buff *skb = dst->data;
> > +
> > + /* if the data is paged, the caller needs to pull it first */
> > + if (dst->offset + offset + len > skb->len - skb->data_len)
>
> Use skb_headlen instead of 'skb->len - skb->data_len' ?
Awesome, will replace this (and the one in bpf_dynptr_data) with
skb_headlen() for v2. thanks!
>
> > + return -EAGAIN;
> > +
> > + return __bpf_skb_store_bytes(skb, dst->offset + offset, src, len,
> > + flags);
> > + }
> > +
> > memcpy(dst->data + dst->offset + offset, src, len);
>
> > return 0;
> > @@ -1555,6 +1594,7 @@ static const struct bpf_func_proto
> > bpf_dynptr_write_proto = {
>
> > BPF_CALL_3(bpf_dynptr_data, struct bpf_dynptr_kern *, ptr, u32, offset,
> > u32, len)
> > {
> > + enum bpf_dynptr_type type;
> > int err;
>
> > if (!ptr->data)
> > @@ -1567,6 +1607,18 @@ BPF_CALL_3(bpf_dynptr_data, struct bpf_dynptr_kern
> > *, ptr, u32, offset, u32, len
> > if (bpf_dynptr_is_rdonly(ptr))
> > return 0;
>
> > + type = bpf_dynptr_get_type(ptr);
> > +
> > + if (type == BPF_DYNPTR_TYPE_SKB) {
> > + struct sk_buff *skb = ptr->data;
> > +
> > + /* if the data is paged, the caller needs to pull it first */
> > + if (ptr->offset + offset + len > skb->len - skb->data_len)
> > + return 0;
>
> Same here?
>
> > +
> > + return (unsigned long)(skb->data + ptr->offset + offset);
> > + }
> > +
> > return (unsigned long)(ptr->data + ptr->offset + offset);
> > }
>
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 0d523741a543..0838653eeb4e 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -263,6 +263,7 @@ struct bpf_call_arg_meta {
> > u32 subprogno;
> > struct bpf_map_value_off_desc *kptr_off_desc;
> > u8 uninit_dynptr_regno;
> > + enum bpf_dynptr_type type;
> > };
>
> > struct btf *btf_vmlinux;
> > @@ -678,6 +679,8 @@ static enum bpf_dynptr_type arg_to_dynptr_type(enum
> > bpf_arg_type arg_type)
> > return BPF_DYNPTR_TYPE_LOCAL;
> > case DYNPTR_TYPE_RINGBUF:
> > return BPF_DYNPTR_TYPE_RINGBUF;
> > + case DYNPTR_TYPE_SKB:
> > + return BPF_DYNPTR_TYPE_SKB;
> > default:
> > return BPF_DYNPTR_TYPE_INVALID;
> > }
> > @@ -5820,12 +5823,14 @@ int check_func_arg_reg_off(struct
> > bpf_verifier_env *env,
> > return __check_ptr_off_reg(env, reg, regno, fixed_off_ok);
> > }
>
> > -static u32 stack_slot_get_id(struct bpf_verifier_env *env, struct
> > bpf_reg_state *reg)
> > +static void stack_slot_get_dynptr_info(struct bpf_verifier_env *env,
> > struct bpf_reg_state *reg,
> > + struct bpf_call_arg_meta *meta)
> > {
> > struct bpf_func_state *state = func(env, reg);
> > int spi = get_spi(reg->off);
>
> > - return state->stack[spi].spilled_ptr.id;
> > + meta->ref_obj_id = state->stack[spi].spilled_ptr.id;
> > + meta->type = state->stack[spi].spilled_ptr.dynptr.type;
> > }
>
> > static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
> > @@ -6052,6 +6057,9 @@ static int check_func_arg(struct bpf_verifier_env
> > *env, u32 arg,
> > case DYNPTR_TYPE_RINGBUF:
> > err_extra = "ringbuf ";
> > break;
> > + case DYNPTR_TYPE_SKB:
> > + err_extra = "skb ";
> > + break;
> > default:
> > break;
> > }
> > @@ -6065,8 +6073,10 @@ static int check_func_arg(struct bpf_verifier_env
> > *env, u32 arg,
> > verbose(env, "verifier internal error: multiple refcounted args in
> > BPF_FUNC_dynptr_data");
> > return -EFAULT;
> > }
> > - /* Find the id of the dynptr we're tracking the reference of */
> > - meta->ref_obj_id = stack_slot_get_id(env, reg);
> > + /* Find the id and the type of the dynptr we're tracking
> > + * the reference of.
> > + */
> > + stack_slot_get_dynptr_info(env, reg, meta);
> > }
> > }
> > break;
> > @@ -7406,7 +7416,11 @@ static int check_helper_call(struct
> > bpf_verifier_env *env, struct bpf_insn *insn
> > regs[BPF_REG_0].type = PTR_TO_TCP_SOCK | ret_flag;
> > } else if (base_type(ret_type) == RET_PTR_TO_ALLOC_MEM) {
> > mark_reg_known_zero(env, regs, BPF_REG_0);
> > - regs[BPF_REG_0].type = PTR_TO_MEM | ret_flag;
> > + if (func_id == BPF_FUNC_dynptr_data &&
> > + meta.type == BPF_DYNPTR_TYPE_SKB)
> > + regs[BPF_REG_0].type = PTR_TO_PACKET | ret_flag;
> > + else
> > + regs[BPF_REG_0].type = PTR_TO_MEM | ret_flag;
> > regs[BPF_REG_0].mem_size = meta.mem_size;
> > } else if (base_type(ret_type) == RET_PTR_TO_MEM_OR_BTF_ID) {
> > const struct btf_type *t;
> > @@ -14132,6 +14146,25 @@ static int do_misc_fixups(struct
> > bpf_verifier_env *env)
> > goto patch_call_imm;
> > }
>
>
> [..]
>
> > + if (insn->imm == BPF_FUNC_dynptr_from_skb) {
> > + if (!may_access_direct_pkt_data(env, NULL, BPF_WRITE))
> > + insn_buf[0] = BPF_MOV32_IMM(BPF_REG_4, true);
> > + else
> > + insn_buf[0] = BPF_MOV32_IMM(BPF_REG_4, false);
> > + insn_buf[1] = *insn;
> > + cnt = 2;
> > +
> > + new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
> > + if (!new_prog)
> > + return -ENOMEM;
> > +
> > + delta += cnt - 1;
> > + env->prog = new_prog;
> > + prog = new_prog;
> > + insn = new_prog->insnsi + i + delta;
> > + goto patch_call_imm;
> > + }
>
> Would it be easier to have two separate helpers:
> - BPF_FUNC_dynptr_from_skb
> - BPF_FUNC_dynptr_from_skb_readonly
>
> And make the verifier rewrite insn->imm to
> BPF_FUNC_dynptr_from_skb_readonly when needed?
>
> if (insn->imm == BPF_FUNC_dynptr_from_skb) {
> if (!may_access_direct_pkt_data(env, NULL, BPF_WRITE))
> insn->imm = BPF_FUNC_dynptr_from_skb_readonly;
> }
>
> Or it's also ugly because we'd have to leak that new helper into UAPI?
> (I wonder whether that hidden 4th argument is too magical, but probably
> fine?)
To me, having 2 separate helpers feels more cluttered and having to
expose it in the uapi (though I think there is probably some way to
avoid this by doing some sort of ad hoc processing) doesn't seem
ideal. If you feel strongly about this though, I am happy to change
this to use two separate helpers. We do this sort of manual
instruction patching for the sleepable flags in
bpf_task/sk/inode_storage_get and for the callback args in
bpf_timer_set_callback as well - if we use separate helpers here, we
should do that for the other cases as well to maintain consistency.
>
> > +
> > /* BPF_EMIT_CALL() assumptions in some of the map_gen_lookup
> > * and other inlining handlers are currently limited to 64 bit
> > * only.
> > diff --git a/net/core/filter.c b/net/core/filter.c
> > index 5669248aff25..312f99deb759 100644
> > --- a/net/core/filter.c
> > +++ b/net/core/filter.c
> > @@ -1681,8 +1681,8 @@ static inline void bpf_pull_mac_rcsum(struct
> > sk_buff *skb)
> > skb_postpull_rcsum(skb, skb_mac_header(skb), skb->mac_len);
> > }
>
> > -BPF_CALL_5(bpf_skb_store_bytes, struct sk_buff *, skb, u32, offset,
> > - const void *, from, u32, len, u64, flags)
> > +int __bpf_skb_store_bytes(struct sk_buff *skb, u32 offset, const void
> > *from,
> > + u32 len, u64 flags)
> > {
> > void *ptr;
>
> > @@ -1707,6 +1707,12 @@ BPF_CALL_5(bpf_skb_store_bytes, struct sk_buff *,
> > skb, u32, offset,
> > return 0;
> > }
>
> > +BPF_CALL_5(bpf_skb_store_bytes, struct sk_buff *, skb, u32, offset,
> > + const void *, from, u32, len, u64, flags)
> > +{
> > + return __bpf_skb_store_bytes(skb, offset, from, len, flags);
> > +}
> > +
> > static const struct bpf_func_proto bpf_skb_store_bytes_proto = {
> > .func = bpf_skb_store_bytes,
> > .gpl_only = false,
> > @@ -1718,8 +1724,7 @@ static const struct bpf_func_proto
> > bpf_skb_store_bytes_proto = {
> > .arg5_type = ARG_ANYTHING,
> > };
>
> > -BPF_CALL_4(bpf_skb_load_bytes, const struct sk_buff *, skb, u32, offset,
> > - void *, to, u32, len)
> > +int __bpf_skb_load_bytes(const struct sk_buff *skb, u32 offset, void
> > *to, u32 len)
> > {
> > void *ptr;
>
> > @@ -1738,6 +1743,12 @@ BPF_CALL_4(bpf_skb_load_bytes, const struct
> > sk_buff *, skb, u32, offset,
> > return -EFAULT;
> > }
>
> > +BPF_CALL_4(bpf_skb_load_bytes, const struct sk_buff *, skb, u32, offset,
> > + void *, to, u32, len)
> > +{
> > + return __bpf_skb_load_bytes(skb, offset, to, len);
> > +}
> > +
> > static const struct bpf_func_proto bpf_skb_load_bytes_proto = {
> > .func = bpf_skb_load_bytes,
> > .gpl_only = false,
> > @@ -1849,6 +1860,32 @@ static const struct bpf_func_proto
> > bpf_skb_pull_data_proto = {
> > .arg2_type = ARG_ANYTHING,
> > };
>
> > +/* is_rdonly is set by the verifier */
> > +BPF_CALL_4(bpf_dynptr_from_skb, struct sk_buff *, skb, u64, flags,
> > + struct bpf_dynptr_kern *, ptr, u32, is_rdonly)
> > +{
> > + if (flags) {
> > + bpf_dynptr_set_null(ptr);
> > + return -EINVAL;
> > + }
> > +
> > + bpf_dynptr_init(ptr, skb, BPF_DYNPTR_TYPE_SKB, 0, skb->len);
> > +
> > + if (is_rdonly)
> > + bpf_dynptr_set_rdonly(ptr);
> > +
> > + return 0;
> > +}
> > +
> > +static const struct bpf_func_proto bpf_dynptr_from_skb_proto = {
> > + .func = bpf_dynptr_from_skb,
> > + .gpl_only = false,
> > + .ret_type = RET_INTEGER,
> > + .arg1_type = ARG_PTR_TO_CTX,
> > + .arg2_type = ARG_ANYTHING,
> > + .arg3_type = ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_SKB | MEM_UNINIT,
> > +};
> > +
> > BPF_CALL_1(bpf_sk_fullsock, struct sock *, sk)
> > {
> > return sk_fullsock(sk) ? (unsigned long)sk : (unsigned long)NULL;
> > @@ -7808,6 +7845,8 @@ sk_filter_func_proto(enum bpf_func_id func_id,
> > const struct bpf_prog *prog)
> > return &bpf_get_socket_uid_proto;
> > case BPF_FUNC_perf_event_output:
> > return &bpf_skb_event_output_proto;
> > + case BPF_FUNC_dynptr_from_skb:
> > + return &bpf_dynptr_from_skb_proto;
> > default:
> > return bpf_sk_base_func_proto(func_id);
> > }
> > @@ -7991,6 +8030,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id,
> > const struct bpf_prog *prog)
> > return &bpf_tcp_raw_check_syncookie_ipv6_proto;
> > #endif
> > #endif
> > + case BPF_FUNC_dynptr_from_skb:
> > + return &bpf_dynptr_from_skb_proto;
> > default:
> > return bpf_sk_base_func_proto(func_id);
> > }
> > @@ -8186,6 +8227,8 @@ sk_skb_func_proto(enum bpf_func_id func_id, const
> > struct bpf_prog *prog)
> > case BPF_FUNC_skc_lookup_tcp:
> > return &bpf_skc_lookup_tcp_proto;
> > #endif
> > + case BPF_FUNC_dynptr_from_skb:
> > + return &bpf_dynptr_from_skb_proto;
> > default:
> > return bpf_sk_base_func_proto(func_id);
> > }
> > @@ -8224,6 +8267,8 @@ lwt_out_func_proto(enum bpf_func_id func_id, const
> > struct bpf_prog *prog)
> > return &bpf_get_smp_processor_id_proto;
> > case BPF_FUNC_skb_under_cgroup:
> > return &bpf_skb_under_cgroup_proto;
> > + case BPF_FUNC_dynptr_from_skb:
> > + return &bpf_dynptr_from_skb_proto;
> > default:
> > return bpf_sk_base_func_proto(func_id);
> > }
> > diff --git a/tools/include/uapi/linux/bpf.h
> > b/tools/include/uapi/linux/bpf.h
> > index 59a217ca2dfd..0730cd198a7f 100644
> > --- a/tools/include/uapi/linux/bpf.h
> > +++ b/tools/include/uapi/linux/bpf.h
> > @@ -5241,11 +5241,22 @@ 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:
> > + * * if *offset* + *len* extends into the skb's paged buffers, the
> > user
> > + * should manually pull the skb with bpf_skb_pull and then try
> > again.
> > + *
> > + * * *flags* are a combination of **BPF_F_RECOMPUTE_CSUM**
> > (automatically
> > + * recompute the checksum for the packet after storing the bytes) and
> > + * **BPF_F_INVALIDATE_HASH** (set *skb*\ **->hash**, *skb*\
> > + * **->swhash** and *skb*\ **->l4hash** to 0).
> > * 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, -EAGAIN if for
> > + * skb-type dynptrs the write extends into the skb's paged buffers.
> > *
> > * void *bpf_dynptr_data(struct bpf_dynptr *ptr, u32 offset, u32 len)
> > * Description
> > @@ -5253,10 +5264,19 @@ union bpf_attr {
> > *
> > * *len* must be a statically known value. The returned data slice
> > * is invalidated whenever the dynptr is invalidated.
> > + *
> > + * For skb-type dynptrs:
> > + * * if *offset* + *len* extends into the skb's paged buffers,
> > + * the user should manually pull the skb with bpf_skb_pull and
> > then
> > + * try again.
> > + *
> > + * * the data slice is automatically invalidated anytime a
> > + * helper call that changes the underlying packet buffer
> > + * (eg bpf_skb_pull) is called.
> > * 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
> > - * is out of bounds.
> > + * is out of bounds or in a paged buffer for skb-type dynptrs.
> > *
> > * s64 bpf_tcp_raw_gen_syncookie_ipv4(struct iphdr *iph, struct tcphdr
> > *th, u32 th_len)
> > * Description
> > @@ -5331,6 +5351,21 @@ union bpf_attr {
> > * **-EACCES** if the SYN cookie is not valid.
> > *
> > * **-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin.
> > + *
> > + * long bpf_dynptr_from_skb(struct sk_buff *skb, u64 flags, struct
> > bpf_dynptr *ptr)
> > + * Description
> > + * Get a dynptr to the data in *skb*. *skb* must be the BPF program
> > + * context. Depending on program type, the dynptr may be read-only,
> > + * in which case trying to obtain a direct data slice to it through
> > + * bpf_dynptr_data will return an error.
> > + *
> > + * Calls that change the *skb*'s underlying packet buffer
> > + * (eg bpf_skb_pull_data) do not invalidate the dynptr, but they do
> > + * invalidate any data slices associated with the dynptr.
> > + *
> > + * *flags* is currently unused, it must be 0 for now.
> > + * Return
> > + * 0 on success or -EINVAL if flags is not 0.
> > */
> > #define __BPF_FUNC_MAPPER(FN) \
> > FN(unspec), \
> > @@ -5541,6 +5576,7 @@ union bpf_attr {
> > FN(tcp_raw_gen_syncookie_ipv6), \
> > FN(tcp_raw_check_syncookie_ipv4), \
> > FN(tcp_raw_check_syncookie_ipv6), \
> > + FN(dynptr_from_skb), \
> > /* */
>
> > /* integer value in 'imm' field of BPF_CALL instruction selects which
> > helper
> > --
> > 2.30.2
>
