Re: [PATCH bpf-next 1/2] bpf: Expose bpf_get_socket_cookie to tracing programs

[Yonghong Song]

On 11/26/20 9:02 AM, Florent Revest wrote:
This creates a new helper proto because the existing
bpf_get_socket_cookie_sock_proto has a ARG_PTR_TO_CTX argument and only
works for BPF programs where the context is a sock.

This helper could also be useful to other BPF program types such as LSM.

Signed-off-by: Florent Revest <rev...@google.com>
---
  kernel/trace/bpf_trace.c | 4 ++++
  net/core/filter.c        | 7 +++++++
  2 files changed, 11 insertions(+)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index d255bc9b2bfa..14ad96579813 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1725,6 +1725,8 @@ raw_tp_prog_func_proto(enum bpf_func_id func_id, const 
struct bpf_prog *prog)
        }
  }
  
+extern const struct bpf_func_proto bpf_get_socket_cookie_sock_tracing_proto;
+
  const struct bpf_func_proto *
  tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
  {
@@ -1748,6 +1750,8 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const 
struct bpf_prog *prog)
                return &bpf_sk_storage_get_tracing_proto;
        case BPF_FUNC_sk_storage_delete:
                return &bpf_sk_storage_delete_tracing_proto;
+       case BPF_FUNC_get_socket_cookie:
+               return &bpf_get_socket_cookie_sock_tracing_proto;
  #endif
        case BPF_FUNC_seq_printf:
                return prog->expected_attach_type == BPF_TRACE_ITER ?
diff --git a/net/core/filter.c b/net/core/filter.c
index 2ca5eecebacf..177c4e5e529d 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4631,6 +4631,13 @@ static const struct bpf_func_proto 
bpf_get_socket_cookie_sock_proto = {
        .arg1_type      = ARG_PTR_TO_CTX,
  };
  
+const struct bpf_func_proto bpf_get_socket_cookie_sock_tracing_proto = {
+       .func           = bpf_get_socket_cookie_sock,
+       .gpl_only       = false,
+       .ret_type       = RET_INTEGER,
+       .arg1_type      = ARG_PTR_TO_BTF_ID_SOCK_COMMON,
+};

This seems correct to me. Could you add another helper description in 
uapi bpf.h? Currently we already have:
  u64 bpf_get_socket_cookie(struct sk_buff *skb)
  u64 bpf_get_socket_cookie(struct bpf_sock_addr *ctx)
  u64 bpf_get_socket_cookie(struct bpf_sock_ops *ctx)

The btf-id based helper will be something like below
  u64 bpf_get_socket_cookie(void *sk)


+
  BPF_CALL_1(bpf_get_socket_cookie_sock_ops, struct bpf_sock_ops_kern *, ctx)
  {
        return __sock_gen_cookie(ctx->sk);