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From: Lorenz Bauer <lmb@cloudflare.com>
To: Joe Stringer <joe@wand.net.nz>
Cc: bpf <bpf@vger.kernel.org>, Networking <netdev@vger.kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Alexei Starovoitov <ast@kernel.org>,
	Eric Dumazet <eric.dumazet@gmail.com>, Martin Lau <kafai@fb.com>
Subject: Re: [PATCHv2 bpf-next 1/5] bpf: Add socket assign support
Date: Thu, 26 Mar 2020 10:24:48 +0000	[thread overview]
Message-ID: <CACAyw989SkYaE6Qt_Lm+wjTCvpFH470ObGCkb4+hmEoijG3T8Q@mail.gmail.com> (raw)
In-Reply-To: <20200325055745.10710-2-joe@wand.net.nz>

On Wed, 25 Mar 2020 at 05:57, Joe Stringer <joe@wand.net.nz> wrote:
>
> Add support for TPROXY via a new bpf helper, bpf_sk_assign().
>
> This helper requires the BPF program to discover the socket via a call
> to bpf_sk*_lookup_*(), then pass this socket to the new helper. The
> helper takes its own reference to the socket in addition to any existing
> reference that may or may not currently be obtained for the duration of
> BPF processing. For the destination socket to receive the traffic, the
> traffic must be routed towards that socket via local route. The
> simplest example route is below, but in practice you may want to route
> traffic more narrowly (eg by CIDR):
>
>   $ ip route add local default dev lo
>
> This patch avoids trying to introduce an extra bit into the skb->sk, as
> that would require more invasive changes to all code interacting with
> the socket to ensure that the bit is handled correctly, such as all
> error-handling cases along the path from the helper in BPF through to
> the orphan path in the input. Instead, we opt to use the destructor
> variable to switch on the prefetch of the socket.
>
> Signed-off-by: Joe Stringer <joe@wand.net.nz>
> ---
> v2: Use skb->destructor to determine socket prefetch usage instead of
>       introducing a new metadata_dst
>     Restrict socket assign to same netns as TC device
>     Restrict assigning reuseport sockets
>     Adjust commit wording
> v1: Initial version
> ---
>  include/net/sock.h             |  7 +++++++
>  include/uapi/linux/bpf.h       | 25 ++++++++++++++++++++++++-
>  net/core/filter.c              | 31 +++++++++++++++++++++++++++++++
>  net/core/sock.c                |  9 +++++++++
>  net/ipv4/ip_input.c            |  3 ++-
>  net/ipv6/ip6_input.c           |  3 ++-
>  net/sched/act_bpf.c            |  2 ++
>  tools/include/uapi/linux/bpf.h | 25 ++++++++++++++++++++++++-
>  8 files changed, 101 insertions(+), 4 deletions(-)
>
> diff --git a/include/net/sock.h b/include/net/sock.h
> index b5cca7bae69b..2613d21a667a 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -1657,6 +1657,7 @@ struct sk_buff *sock_omalloc(struct sock *sk, unsigned long size,
>  void skb_orphan_partial(struct sk_buff *skb);
>  void sock_rfree(struct sk_buff *skb);
>  void sock_efree(struct sk_buff *skb);
> +void sock_pfree(struct sk_buff *skb);
>  #ifdef CONFIG_INET
>  void sock_edemux(struct sk_buff *skb);
>  #else
> @@ -2526,6 +2527,12 @@ void sock_net_set(struct sock *sk, struct net *net)
>         write_pnet(&sk->sk_net, net);
>  }
>
> +static inline bool
> +skb_sk_is_prefetched(struct sk_buff *skb)
> +{
> +       return skb->destructor == sock_pfree;
> +}
> +
>  static inline struct sock *skb_steal_sock(struct sk_buff *skb)
>  {
>         if (skb->sk) {
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 5d01c5c7e598..0c6f151deebe 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -2950,6 +2950,28 @@ union bpf_attr {
>   *             restricted to raw_tracepoint bpf programs.
>   *     Return
>   *             0 on success, or a negative error in case of failure.
> + *
> + * int bpf_sk_assign(struct sk_buff *skb, struct bpf_sock *sk, u64 flags)
> + *     Description
> + *             Assign the *sk* to the *skb*. When combined with appropriate
> + *             routing configuration to receive the packet towards the socket,
> + *             will cause *skb* to be delivered to the specified socket.
> + *             Subsequent redirection of *skb* via  **bpf_redirect**\ (),
> + *             **bpf_clone_redirect**\ () or other methods outside of BPF may
> + *             interfere with successful delivery to the socket.
> + *
> + *             This operation is only valid from TC ingress path.
> + *
> + *             The *flags* argument must be zero.
> + *     Return
> + *             0 on success, or a negative errno in case of failure.
> + *
> + *             * **-EINVAL**           Unsupported flags specified.
> + *             * **-ENETUNREACH**      Socket is unreachable (wrong netns).
> + *             * **-ENOENT**           Socket is unavailable for assignment.
> + *             * **-EOPNOTSUPP**       Unsupported operation, for example a
> + *                                     call from outside of TC ingress.
> + *             * **-ESOCKTNOSUPPORT**  Socket type not supported (reuseport).
>   */
>  #define __BPF_FUNC_MAPPER(FN)          \
>         FN(unspec),                     \
> @@ -3073,7 +3095,8 @@ union bpf_attr {
>         FN(jiffies64),                  \
>         FN(read_branch_records),        \
>         FN(get_ns_current_pid_tgid),    \
> -       FN(xdp_output),
> +       FN(xdp_output),                 \
> +       FN(sk_assign),
>
>  /* 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 96350a743539..f7f9b6631f75 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -5860,6 +5860,35 @@ static const struct bpf_func_proto bpf_tcp_gen_syncookie_proto = {
>         .arg5_type      = ARG_CONST_SIZE,
>  };
>
> +BPF_CALL_3(bpf_sk_assign, struct sk_buff *, skb, struct sock *, sk, u64, flags)
> +{
> +       if (flags != 0)
> +               return -EINVAL;
> +       if (!skb_at_tc_ingress(skb))
> +               return -EOPNOTSUPP;
> +       if (unlikely(sk->sk_reuseport))
> +               return -ESOCKTNOSUPPORT;
> +       if (unlikely(dev_net(skb->dev) != sock_net(sk)))
> +               return -ENETUNREACH;
> +       if (unlikely(!refcount_inc_not_zero(&sk->sk_refcnt)))
> +               return -ENOENT;
> +
> +       skb_orphan(skb);
> +       skb->sk = sk;
> +       skb->destructor = sock_pfree;
> +
> +       return 0;
> +}

Follow up to my email re UDP tests: it seems like the helper doesn't check
that the sk is TCP, hence I assumed that you want to add support for
both in the same series.

Also, is it possible to check that the sk protocol matches skb protocol?

> +
> +static const struct bpf_func_proto bpf_sk_assign_proto = {
> +       .func           = bpf_sk_assign,
> +       .gpl_only       = false,
> +       .ret_type       = RET_INTEGER,
> +       .arg1_type      = ARG_PTR_TO_CTX,
> +       .arg2_type      = ARG_PTR_TO_SOCK_COMMON,
> +       .arg3_type      = ARG_ANYTHING,
> +};
> +
>  #endif /* CONFIG_INET */
>
>  bool bpf_helper_changes_pkt_data(void *func)
> @@ -6153,6 +6182,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>                 return &bpf_skb_ecn_set_ce_proto;
>         case BPF_FUNC_tcp_gen_syncookie:
>                 return &bpf_tcp_gen_syncookie_proto;
> +       case BPF_FUNC_sk_assign:
> +               return &bpf_sk_assign_proto;
>  #endif
>         default:
>                 return bpf_base_func_proto(func_id);
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 0fc8937a7ff4..cfaf60267360 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -2071,6 +2071,15 @@ void sock_efree(struct sk_buff *skb)
>  }
>  EXPORT_SYMBOL(sock_efree);
>
> +/* Buffer destructor for prefetch/receive path where reference count may
> + * not be held, e.g. for listen sockets.
> + */
> +void sock_pfree(struct sk_buff *skb)
> +{
> +       sock_edemux(skb);
> +}
> +EXPORT_SYMBOL(sock_pfree);
> +
>  kuid_t sock_i_uid(struct sock *sk)
>  {
>         kuid_t uid;
> diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
> index aa438c6758a7..b0c244af1e4d 100644
> --- a/net/ipv4/ip_input.c
> +++ b/net/ipv4/ip_input.c
> @@ -509,7 +509,8 @@ static struct sk_buff *ip_rcv_core(struct sk_buff *skb, struct net *net)
>         IPCB(skb)->iif = skb->skb_iif;
>
>         /* Must drop socket now because of tproxy. */
> -       skb_orphan(skb);
> +       if (!skb_sk_is_prefetched(skb))
> +               skb_orphan(skb);
>
>         return skb;
>
> diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
> index 7b089d0ac8cd..e96304d8a4a7 100644
> --- a/net/ipv6/ip6_input.c
> +++ b/net/ipv6/ip6_input.c
> @@ -285,7 +285,8 @@ static struct sk_buff *ip6_rcv_core(struct sk_buff *skb, struct net_device *dev,
>         rcu_read_unlock();
>
>         /* Must drop socket now because of tproxy. */
> -       skb_orphan(skb);
> +       if (!skb_sk_is_prefetched(skb))
> +               skb_orphan(skb);
>
>         return skb;
>  err:
> diff --git a/net/sched/act_bpf.c b/net/sched/act_bpf.c
> index 46f47e58b3be..6c7ed8fcc909 100644
> --- a/net/sched/act_bpf.c
> +++ b/net/sched/act_bpf.c
> @@ -53,6 +53,8 @@ static int tcf_bpf_act(struct sk_buff *skb, const struct tc_action *act,
>                 bpf_compute_data_pointers(skb);
>                 filter_res = BPF_PROG_RUN(filter, skb);
>         }
> +       if (filter_res != TC_ACT_OK)
> +               skb_orphan(skb);
>         rcu_read_unlock();
>
>         /* A BPF program may overwrite the default action opcode.
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 5d01c5c7e598..0c6f151deebe 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -2950,6 +2950,28 @@ union bpf_attr {
>   *             restricted to raw_tracepoint bpf programs.
>   *     Return
>   *             0 on success, or a negative error in case of failure.
> + *
> + * int bpf_sk_assign(struct sk_buff *skb, struct bpf_sock *sk, u64 flags)
> + *     Description
> + *             Assign the *sk* to the *skb*. When combined with appropriate
> + *             routing configuration to receive the packet towards the socket,
> + *             will cause *skb* to be delivered to the specified socket.
> + *             Subsequent redirection of *skb* via  **bpf_redirect**\ (),
> + *             **bpf_clone_redirect**\ () or other methods outside of BPF may
> + *             interfere with successful delivery to the socket.
> + *
> + *             This operation is only valid from TC ingress path.
> + *
> + *             The *flags* argument must be zero.
> + *     Return
> + *             0 on success, or a negative errno in case of failure.
> + *
> + *             * **-EINVAL**           Unsupported flags specified.
> + *             * **-ENETUNREACH**      Socket is unreachable (wrong netns).
> + *             * **-ENOENT**           Socket is unavailable for assignment.
> + *             * **-EOPNOTSUPP**       Unsupported operation, for example a
> + *                                     call from outside of TC ingress.
> + *             * **-ESOCKTNOSUPPORT**  Socket type not supported (reuseport).
>   */
>  #define __BPF_FUNC_MAPPER(FN)          \
>         FN(unspec),                     \
> @@ -3073,7 +3095,8 @@ union bpf_attr {
>         FN(jiffies64),                  \
>         FN(read_branch_records),        \
>         FN(get_ns_current_pid_tgid),    \
> -       FN(xdp_output),
> +       FN(xdp_output),                 \
> +       FN(sk_assign),
>
>  /* integer value in 'imm' field of BPF_CALL instruction selects which helper
>   * function eBPF program intends to call
> --
> 2.20.1
>


-- 
Lorenz Bauer  |  Systems Engineer
6th Floor, County Hall/The Riverside Building, SE1 7PB, UK

www.cloudflare.com

  parent reply	other threads:[~2020-03-26 10:25 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-25  5:57 [PATCHv2 bpf-next 0/5] Add bpf_sk_assign eBPF helper Joe Stringer
2020-03-25  5:57 ` [PATCHv2 bpf-next 1/5] bpf: Add socket assign support Joe Stringer
2020-03-26  6:23   ` Martin KaFai Lau
2020-03-26  6:31     ` Joe Stringer
2020-03-26 10:24   ` Lorenz Bauer [this message]
2020-03-26 22:52     ` Joe Stringer
2020-03-27  2:40       ` Joe Stringer
2020-03-25  5:57 ` [PATCHv2 bpf-next 2/5] bpf: Prefetch established socket destinations Joe Stringer
2020-03-26 21:11   ` Alexei Starovoitov
2020-03-26 21:45     ` Joe Stringer
2020-03-25  5:57 ` [PATCHv2 bpf-next 3/5] net: Track socket refcounts in skb_steal_sock() Joe Stringer
2020-03-25  5:57 ` [PATCHv2 bpf-next 4/5] bpf: Don't refcount LISTEN sockets in sk_assign() Joe Stringer
2020-03-25 10:29   ` Lorenz Bauer
2020-03-25 20:46     ` Joe Stringer
2020-03-26 10:20       ` Lorenz Bauer
2020-03-26 21:37         ` Joe Stringer
2020-03-25  5:57 ` [PATCHv2 bpf-next 5/5] selftests: bpf: add test for sk_assign Joe Stringer
2020-03-25 10:35   ` Lorenz Bauer
2020-03-25 20:55     ` Joe Stringer
2020-03-26  6:25       ` Martin KaFai Lau
2020-03-26  6:38         ` Joe Stringer
2020-03-26 23:39           ` Joe Stringer
2020-03-25 18:17   ` Yonghong Song
2020-03-25 21:20     ` Joe Stringer
2020-03-25 22:00       ` Yonghong Song
2020-03-25 23:07         ` Joe Stringer
2020-03-26 10:13     ` Lorenz Bauer
2020-03-26 21:07       ` call for bpf progs. " Alexei Starovoitov
2020-03-26 23:14         ` Yonghong Song
2020-03-27 10:02         ` Lorenz Bauer
2020-03-27 16:08           ` Alexei Starovoitov
2020-03-27 19:06         ` Joe Stringer
2020-03-27 20:16           ` Daniel Borkmann
2020-03-27 22:24             ` Alexei Starovoitov
2020-03-28  0:17           ` Andrii Nakryiko
2020-03-26  2:04   ` Andrii Nakryiko
2020-03-26  2:16   ` Andrii Nakryiko
2020-03-26  5:28     ` Joe Stringer
2020-03-26  6:31       ` Martin KaFai Lau
2020-03-26 19:36       ` Andrii Nakryiko
2020-03-26 21:38         ` Joe Stringer

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