[v3,bpf-next,1/3] bpf: Add get_netns_id helper function for sock_ops

Currently 5-tuple(sip+dip+sport+dport+proto) can't identify a
uniq connection because there may be multi net namespace.
For example, there may be a chance that netns a and netns b all
listen on 127.0.0.1:8080 and the client with same port 40782
connect to them. Without netns number, sock ops program
can't distinguish them.
Using bpf_get_netns_id helper to get current connection
netns id to distinguish connections.

Signed-off-by: Lingpeng Chen <forrest0579@gmail.com>
---
 include/uapi/linux/bpf.h |  9 ++++++++-
 net/core/filter.c        | 20 ++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

On Wed, Feb 19, 2020 at 11:11 PM Lingpeng Chen <forrest0579@gmail.com> wrote:
>
> Currently 5-tuple(sip+dip+sport+dport+proto) can't identify a
> uniq connection because there may be multi net namespace.
> For example, there may be a chance that netns a and netns b all
> listen on 127.0.0.1:8080 and the client with same port 40782
> connect to them. Without netns number, sock ops program
> can't distinguish them.
> Using bpf_get_netns_id helper to get current connection
> netns id to distinguish connections.
>
> Signed-off-by: Lingpeng Chen <forrest0579@gmail.com>
> ---
>  include/uapi/linux/bpf.h |  9 ++++++++-
>  net/core/filter.c        | 20 ++++++++++++++++++++
>  2 files changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index f1d74a2bd234..e79082f78b74 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -2892,6 +2892,12 @@ union bpf_attr {
>   *             Obtain the 64bit jiffies
>   *     Return
>   *             The 64 bit jiffies
> + *
> + * u64 bpf_get_netns_id(struct bpf_sock_ops *bpf_socket)
> + *  Description
> + *      Obtain netns id of sock
> + * Return
> + *      The current netns inum
>   */
>  #define __BPF_FUNC_MAPPER(FN)          \
>         FN(unspec),                     \
> @@ -3012,7 +3018,8 @@ union bpf_attr {
>         FN(probe_read_kernel_str),      \
>         FN(tcp_send_ack),               \
>         FN(send_signal_thread),         \
> -       FN(jiffies64),
> +       FN(jiffies64),                  \
> +       FN(get_netns_id),
>
>  /* integer value in 'imm' field of BPF_CALL instruction selects which helper
>   * function eBPF program intends to call
> diff --git a/net/core/filter.c b/net/core/filter.c
> index c180871e606d..5302ec9f7c0d 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -4421,6 +4421,24 @@ static const struct bpf_func_proto bpf_sock_ops_cb_flags_set_proto = {
>         .arg2_type      = ARG_ANYTHING,
>  };
>
> +BPF_CALL_1(bpf_get_netns_id_sock_ops, struct bpf_sock_ops_kern *, bpf_sock)

I guess we only need bpf_get_netns_id,

> +{
> +#ifdef CONFIG_NET_NS
> +       struct sock *sk = bpf_sock->sk;
> +
> +       return (u64)sk->sk_net.net->ns.inum;
> +#else
> +       return 0;
> +#endif
> +}
> +
> +static const struct bpf_func_proto bpf_get_netns_id_sock_ops_proto = {
and bpf_get_netns_id_proto.

> +       .func           = bpf_get_netns_id_sock_ops,
> +       .gpl_only       = false,
> +       .ret_type       = RET_INTEGER,
> +       .arg1_type      = ARG_PTR_TO_CTX,
> +};
> +
>  const struct ipv6_bpf_stub *ipv6_bpf_stub __read_mostly;
>  EXPORT_SYMBOL_GPL(ipv6_bpf_stub);
>
> @@ -6218,6 +6236,8 @@ sock_ops_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>         case BPF_FUNC_tcp_sock:
>                 return &bpf_tcp_sock_proto;
>  #endif /* CONFIG_INET */
> +       case BPF_FUNC_get_netns_id:
> +               return &bpf_get_netns_id_sock_ops_proto;
>         default:
>                 return bpf_base_func_proto(func_id);
>         }
> --
> 2.20.1
>

Currently 5-tuple(sip+dip+sport+dport+proto) can't identify a
uniq connection because there may be multi net namespace.
For example, there may be a chance that netns a and netns b all
listen on 127.0.0.1:8080 and the client with same port 40782
connect to them. Without netns number, sock ops program
can't distinguish them.
Using bpf_get_netns_id helpers to get current connection
netns number to distinguish connections.

Changes in v4:
- rename get_netns_id_sock_ops to get_getns_id
- rebase from bpf-next

Changes in v3:
- rename sock_ops_get_netns to get_netns_id

Changes in v2:
- Return u64 instead of u32 for sock_ops_get_netns
- Fix build bug when CONFIG_NET_NS not set
- Add selftest for sock_ops_get_netns

Lingpeng Chen (3):
  bpf: Add get_netns_id helper function for sock_ops
  bpf: Sync uapi bpf.h to tools/
  selftests/bpf: add selftest for get_netns_id helper

 include/uapi/linux/bpf.h                      |  9 +++-
 net/core/filter.c                             | 20 ++++++++
 tools/include/uapi/linux/bpf.h                |  9 +++-
 .../selftests/bpf/progs/test_tcpbpf_kern.c    | 11 +++++
 .../testing/selftests/bpf/test_tcpbpf_user.c  | 46 ++++++++++++++++++-
 5 files changed, 92 insertions(+), 3 deletions(-)


base-commit e0360423d020
("selftests/bpf: Run SYN cookies with reuseport BPF test only for TCP")