diff options
| author | Daniel Borkmann <daniel@iogearbox.net> | 2018-05-04 01:08:15 +0200 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2018-05-03 16:49:19 -0700 |
| commit | 4e1ec56cdc59746943b2acfab3c171b930187bbe (patch) | |
| tree | c7bc363b064ec1d5a3917de49d90696c8794e361 /net/core | |
| parent | e0cea7ce988cf48cc4052235d2ad2550b3bc4fa0 (diff) | |
bpf: add skb_load_bytes_relative helper
This adds a small BPF helper similar to bpf_skb_load_bytes() that
is able to load relative to mac/net header offset from the skb's
linear data. Compared to bpf_skb_load_bytes(), it takes a fifth
argument namely start_header, which is either BPF_HDR_START_MAC
or BPF_HDR_START_NET. This allows for a more flexible alternative
compared to LD_ABS/LD_IND with negative offset. It's enabled for
tc BPF programs as well as sock filter program types where it's
mainly useful in reuseport programs to ease access to lower header
data.
Reference: https://lists.iovisor.org/pipermail/iovisor-dev/2017-March/000698.html
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'net/core')
| -rw-r--r-- | net/core/filter.c | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/net/core/filter.c b/net/core/filter.c index a49729842b3d..6877426c23a6 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -1684,6 +1684,47 @@ static const struct bpf_func_proto bpf_skb_load_bytes_proto = { .arg4_type = ARG_CONST_SIZE, }; +BPF_CALL_5(bpf_skb_load_bytes_relative, const struct sk_buff *, skb, + u32, offset, void *, to, u32, len, u32, start_header) +{ + u8 *ptr; + + if (unlikely(offset > 0xffff || len > skb_headlen(skb))) + goto err_clear; + + switch (start_header) { + case BPF_HDR_START_MAC: + ptr = skb_mac_header(skb) + offset; + break; + case BPF_HDR_START_NET: + ptr = skb_network_header(skb) + offset; + break; + default: + goto err_clear; + } + + if (likely(ptr >= skb_mac_header(skb) && + ptr + len <= skb_tail_pointer(skb))) { + memcpy(to, ptr, len); + return 0; + } + +err_clear: + memset(to, 0, len); + return -EFAULT; +} + +static const struct bpf_func_proto bpf_skb_load_bytes_relative_proto = { + .func = bpf_skb_load_bytes_relative, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_CTX, + .arg2_type = ARG_ANYTHING, + .arg3_type = ARG_PTR_TO_UNINIT_MEM, + .arg4_type = ARG_CONST_SIZE, + .arg5_type = ARG_ANYTHING, +}; + BPF_CALL_2(bpf_skb_pull_data, struct sk_buff *, skb, u32, len) { /* Idea is the following: should the needed direct read/write @@ -4061,6 +4102,8 @@ sk_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) switch (func_id) { case BPF_FUNC_skb_load_bytes: return &bpf_skb_load_bytes_proto; + case BPF_FUNC_skb_load_bytes_relative: + return &bpf_skb_load_bytes_relative_proto; case BPF_FUNC_get_socket_cookie: return &bpf_get_socket_cookie_proto; case BPF_FUNC_get_socket_uid: @@ -4078,6 +4121,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_skb_store_bytes_proto; case BPF_FUNC_skb_load_bytes: return &bpf_skb_load_bytes_proto; + case BPF_FUNC_skb_load_bytes_relative: + return &bpf_skb_load_bytes_relative_proto; case BPF_FUNC_skb_pull_data: return &bpf_skb_pull_data_proto; case BPF_FUNC_csum_diff: |