On Thu, Jan 17, 2019 at 03:31:57PM -0800, Eric Dumazet wrote:
> This adds the ability to read gso_segs from a BPF program.
>
> v2: refined Eddie Hao patch to address Alexei feedback.
>
> Signed-off-by: Eric Dumazet <[email protected]>
> Cc: Eddie Hao <[email protected]>
> Cc: Vlad Dumitrescu <[email protected]>
> Cc: Xiaotian Pei <[email protected]>
> Cc: Yuchung Cheng <[email protected]>
> ---
> include/uapi/linux/bpf.h | 1 +
> net/core/filter.c | 21 ++++++++++++
> tools/include/uapi/linux/bpf.h | 1 +
> tools/testing/selftests/bpf/test_verifier.c | 36 +++++++++++++++++++++
> 4 files changed, 59 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index
> 91c43884f295f60a85268ddf0020bf8aa47f8329..2940a9854f6d8e493518ca894e0c9c630ae4ab7a
> 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -2540,6 +2540,7 @@ struct __sk_buff {
> __bpf_md_ptr(struct bpf_flow_keys *, flow_keys);
> __u64 tstamp;
> __u32 wire_len;
> + __u32 gso_segs;
> };
>
> struct bpf_tunnel_key {
> diff --git a/net/core/filter.c b/net/core/filter.c
> index
> 2b3b436ef5457bf44c99780d6dec0b5f403f005c..a6ff5d9a04cf06926ee75cbc523456d12baf25ae
> 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -6700,6 +6700,27 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type
> type,
> target_size));
> break;
>
> + case offsetof(struct __sk_buff, gso_segs):
> + /* si->dst_reg = skb_shinfo(SKB); */
> +#ifdef NET_SKBUFF_DATA_USES_OFFSET
> + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, head),
> + si->dst_reg, si->src_reg,
> + offsetof(struct sk_buff, head));
> + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end),
> + BPF_REG_TMP, si->src_reg,
> + offsetof(struct sk_buff, end));
I am not sure BPF_REG_TMP can be used for non-classic BPF.
The earlier insn could be using BPF_REG_TMP (which is BPF_REG_2) and
R2 would become loss after this BPF_LDX_MEM.
Daniel, can BPF_REG_AX be used here as a tmp?
> + *insn++ = BPF_ALU64_REG(BPF_ADD, si->dst_reg, BPF_REG_TMP);
> +#else
> + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end),
> + si->dst_reg, si->src_reg,
> + offsetof(struct sk_buff, end));
> +#endif
> + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct skb_shared_info,
> gso_segs),
> + si->dst_reg, si->dst_reg,
> + bpf_target_off(struct skb_shared_info,
> + gso_segs, 2,
> + target_size));
> + break;
> case offsetof(struct __sk_buff, wire_len):
> BUILD_BUG_ON(FIELD_SIZEOF(struct qdisc_skb_cb, pkt_len) != 4);
>
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index
> 91c43884f295f60a85268ddf0020bf8aa47f8329..2940a9854f6d8e493518ca894e0c9c630ae4ab7a
> 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -2540,6 +2540,7 @@ struct __sk_buff {
> __bpf_md_ptr(struct bpf_flow_keys *, flow_keys);
> __u64 tstamp;
> __u32 wire_len;
> + __u32 gso_segs;
> };
>
> struct bpf_tunnel_key {
> diff --git a/tools/testing/selftests/bpf/test_verifier.c
> b/tools/testing/selftests/bpf/test_verifier.c
> index
> 2fd90d4568926d13542783c870507d43a6d6bb64..2c46531044bdf9ec1e4fa47e2c94c9edb0ac3d08
> 100644
> --- a/tools/testing/selftests/bpf/test_verifier.c
> +++ b/tools/testing/selftests/bpf/test_verifier.c
> @@ -5663,6 +5663,42 @@ static struct bpf_test tests[] = {
> .result = ACCEPT,
> .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
> },
> + {
> + "read gso_segs from CGROUP_SKB",
> + .insns = {
> + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
> + offsetof(struct __sk_buff, gso_segs)),
> + BPF_MOV64_IMM(BPF_REG_0, 0),
> + BPF_EXIT_INSN(),
> + },
> + .result = ACCEPT,
> + .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
> + },
> + {
> + "write gso_segs from CGROUP_SKB",
> + .insns = {
> + BPF_MOV64_IMM(BPF_REG_0, 0),
> + BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_0,
> + offsetof(struct __sk_buff, gso_segs)),
> + BPF_MOV64_IMM(BPF_REG_0, 0),
> + BPF_EXIT_INSN(),
> + },
> + .result = REJECT,
> + .result_unpriv = REJECT,
> + .errstr = "invalid bpf_context access off=164 size=4",
> + .prog_type = BPF_PROG_TYPE_CGROUP_SKB,
> + },
> + {
> + "read gso_segs from CLS",
> + .insns = {
> + BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
> + offsetof(struct __sk_buff, gso_segs)),
> + BPF_MOV64_IMM(BPF_REG_0, 0),
> + BPF_EXIT_INSN(),
> + },
> + .result = ACCEPT,
> + .prog_type = BPF_PROG_TYPE_SCHED_CLS,
> + },
> {
> "multiple registers share map_lookup_elem result",
> .insns = {
> --
> 2.20.1.321.g9e740568ce-goog
>
