Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20200118000128.15746-1-matthew.cover@stackpath.com> <20200121202038.26490-1-matthew.cover@stackpath.com>
In-Reply-To: <20200121202038.26490-1-matthew.cover@stackpath.com>
From:   Matt Cover <werekraken@gmail.com>
Date:   Tue, 21 Jan 2020 13:35:22 -0700
Message-ID: <CAGyo_hpVm7q3ghW+je23xs3ja_COP_BMZoE_=phwGRzjSTih8w@mail.gmail.com>
Subject: Re: [PATCH bpf-next v2 1/2] bpf: add bpf_ct_lookup_{tcp,udp}() helpers
To:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andriin@fb.com>,
        "David S. Miller" <davem@davemloft.net>,
        Shuah Khan <shuah@kernel.org>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        John Fastabend <john.fastabend@gmail.com>,
        Jakub Sitnicki <jakub@cloudflare.com>,
        Quentin Monnet <quentin.monnet@netronome.com>,
        Matthew Cover <matthew.cover@stackpath.com>,
        Stanislav Fomichev <sdf@google.com>,
        Andrey Ignatov <rdna@fb.com>,
        Lorenz Bauer <lmb@cloudflare.com>, netdev@vger.kernel.org,
        bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org,
        Pablo Neira Ayuso <pablo@netfilter.org>,
        Jozsef Kadlecsik <kadlec@netfilter.org>,
        Florian Westphal <fw@strlen.de>, coreteam@netfilter.org
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Jan 21, 2020 at 1:20 PM Matthew Cover <werekraken@gmail.com> wrote:
>
> Allow looking up an nf_conn. This allows eBPF programs to leverage
> nf_conntrack state for similar purposes to socket state use cases,
> as provided by the socket lookup helpers. This is particularly
> useful when nf_conntrack state is locally available, but socket
> state is not.
>
> v2:
>   - Fix functions in need of and missing static inline (kbuild)
>   - Move tests to separate patch and submit as a series (John)
>   - Improve clarity in helper documentation (John)
>   - Add CONFIG_NF_CONNTRACK=m support (Daniel)

Sorry, missed additional maintainers for v2 changes.

+Pablo Neira Ayuso <pablo@netfilter.org>
+Jozsef Kadlecsik <kadlec@netfilter.org>
+Florian Westphal <fw@strlen.de>
+coreteam@netfilter.org

>
> Signed-off-by: Matthew Cover <matthew.cover@stackpath.com>
> ---
>  include/linux/bpf.h               |  29 ++++
>  include/linux/netfilter.h         |  12 ++
>  include/uapi/linux/bpf.h          | 111 ++++++++++++++-
>  kernel/bpf/verifier.c             | 105 ++++++++++++++-
>  net/core/filter.c                 | 277 ++++++++++++++++++++++++++++++++++++++
>  net/netfilter/core.c              |  16 +++
>  net/netfilter/nf_conntrack_core.c |   1 +
>  scripts/bpf_helpers_doc.py        |   4 +
>  tools/include/uapi/linux/bpf.h    | 111 ++++++++++++++-
>  9 files changed, 658 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 8e3b8f4..f502e1f 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -239,6 +239,7 @@ enum bpf_arg_type {
>         ARG_PTR_TO_LONG,        /* pointer to long */
>         ARG_PTR_TO_SOCKET,      /* pointer to bpf_sock (fullsock) */
>         ARG_PTR_TO_BTF_ID,      /* pointer to in-kernel struct */
> +       ARG_PTR_TO_NF_CONN,     /* pointer to bpf_nf_conn */
>  };
>
>  /* type of values returned from helper functions */
> @@ -250,6 +251,7 @@ enum bpf_return_type {
>         RET_PTR_TO_SOCKET_OR_NULL,      /* returns a pointer to a socket or NULL */
>         RET_PTR_TO_TCP_SOCK_OR_NULL,    /* returns a pointer to a tcp_sock or NULL */
>         RET_PTR_TO_SOCK_COMMON_OR_NULL, /* returns a pointer to a sock_common or NULL */
> +       RET_PTR_TO_NF_CONN_OR_NULL,     /* returns a pointer to a nf_conn or NULL */
>  };
>
>  /* eBPF function prototype used by verifier to allow BPF_CALLs from eBPF programs
> @@ -316,6 +318,8 @@ enum bpf_reg_type {
>         PTR_TO_TP_BUFFER,        /* reg points to a writable raw tp's buffer */
>         PTR_TO_XDP_SOCK,         /* reg points to struct xdp_sock */
>         PTR_TO_BTF_ID,           /* reg points to kernel struct */
> +       PTR_TO_NF_CONN,          /* reg points to struct nf_conn */
> +       PTR_TO_NF_CONN_OR_NULL,  /* reg points to struct nf_conn or NULL */
>  };
>
>  /* The information passed from prog-specific *_is_valid_access
> @@ -1513,4 +1517,29 @@ enum bpf_text_poke_type {
>  int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
>                        void *addr1, void *addr2);
>
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
> +bool bpf_nf_conn_is_valid_access(int off, int size, enum bpf_access_type type,
> +                                struct bpf_insn_access_aux *info);
> +
> +u32 bpf_nf_conn_convert_ctx_access(enum bpf_access_type type,
> +                                  const struct bpf_insn *si,
> +                                  struct bpf_insn *insn_buf,
> +                                  struct bpf_prog *prog, u32 *target_size);
> +#else
> +static inline bool bpf_nf_conn_is_valid_access(int off, int size,
> +                               enum bpf_access_type type,
> +                               struct bpf_insn_access_aux *info)
> +{
> +       return false;
> +}
> +
> +static inline u32 bpf_nf_conn_convert_ctx_access(enum bpf_access_type type,
> +                               const struct bpf_insn *si,
> +                               struct bpf_insn *insn_buf,
> +                               struct bpf_prog *prog, u32 *target_size)
> +{
> +       return 0;
> +}
> +#endif /* CONFIG_NF_CONNTRACK */
> +
>  #endif /* _LINUX_BPF_H */
> diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
> index eb312e7..a360ced 100644
> --- a/include/linux/netfilter.h
> +++ b/include/linux/netfilter.h
> @@ -451,6 +451,9 @@ static inline int nf_hook(u_int8_t pf, unsigned int hook, struct net *net,
>  struct nf_conntrack_tuple;
>  bool nf_ct_get_tuple_skb(struct nf_conntrack_tuple *dst_tuple,
>                          const struct sk_buff *skb);
> +struct nf_conntrack_tuple_hash *
> +nf_ct_find_get(struct net *net, const struct nf_conntrack_zone *zone,
> +              const struct nf_conntrack_tuple *tuple);
>  #else
>  static inline void nf_ct_attach(struct sk_buff *new, struct sk_buff *skb) {}
>  struct nf_conntrack_tuple;
> @@ -459,6 +462,12 @@ static inline bool nf_ct_get_tuple_skb(struct nf_conntrack_tuple *dst_tuple,
>  {
>         return false;
>  }
> +static inline struct nf_conntrack_tuple_hash *
> +nf_ct_find_get(struct net *net, const struct nf_conntrack_zone *zone,
> +              const struct nf_conntrack_tuple *tuple)
> +{
> +       return NULL;
> +}
>  #endif
>
>  struct nf_conn;
> @@ -469,6 +478,9 @@ struct nf_ct_hook {
>         void (*destroy)(struct nf_conntrack *);
>         bool (*get_tuple_skb)(struct nf_conntrack_tuple *,
>                               const struct sk_buff *);
> +       struct nf_conntrack_tuple_hash *
> +       (*find_get)(struct net *net, const struct nf_conntrack_zone *zone,
> +                    const struct nf_conntrack_tuple *tuple);
>  };
>  extern struct nf_ct_hook __rcu *nf_ct_hook;
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 033d90a..85c4b3f 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -2885,6 +2885,88 @@ struct bpf_stack_build_id {
>   *             **-EPERM** if no permission to send the *sig*.
>   *
>   *             **-EAGAIN** if bpf program can try again.
> + *
> + * struct bpf_nf_conn *bpf_ct_lookup_tcp(void *ctx, struct bpf_nf_conntrack_tuple *tuple, u32 tuple_size, u64 netns, u64 flags)
> + *     Description
> + *             Look for TCP nf_conntrack entry matching *tuple*, optionally in
> + *             a child network namespace *netns*. The return value must be
> + *             checked, and if non-**NULL**, released via
> + *             **bpf_ct_release**\ ().
> + *
> + *             The *ctx* should point to the context of the program, such as
> + *             the skb or xdp_md (depending on the hook in use). This is used
> + *             to determine the base network namespace for the lookup.
> + *
> + *             *tuple_size* must be one of:
> + *
> + *             **sizeof**\ (*tuple*\ **->ipv4**)
> + *                     Look for an IPv4 nf_conn.
> + *             **sizeof**\ (*tuple*\ **->ipv6**)
> + *                     Look for an IPv6 nf_conn.
> + *
> + *             If the *netns* is a negative signed 32-bit integer, then the
> + *             nf_conn lookup table in the netns associated with the *ctx* will
> + *             will be used. For the TC hooks, this is the netns of the device
> + *             in the skb. For XDP hooks, this is the netns of the device in
> + *             the xdp_md. If *netns* is any other signed 32-bit value greater
> + *             than or equal to zero then it specifies the ID of the netns
> + *             relative to the netns associated with the *ctx*. *netns* values
> + *             beyond the range of 32-bit integers are reserved for future
> + *             use.
> + *
> + *             All values for *flags* are reserved for future usage, and must
> + *             be left at zero.
> + *
> + *             This helper will always return NULL if the kernel was compiled
> + *             without **CONFIG_NF_CONNTRACK**.
> + *     Return
> + *             Pointer to **struct bpf_nf_conn**, or **NULL** in case of
> + *             failure.
> + *
> + * struct bpf_nf_conn *bpf_ct_lookup_udp(void *ctx, struct bpf_nf_conntrack_tuple *tuple, u32 tuple_size, u64 netns, u64 flags)
> + *     Description
> + *             Look for UDP nf_conntrack entry matching *tuple*, optionally in
> + *             a child network namespace *netns*. The return value must be
> + *             checked, and if non-**NULL**, released via
> + *             **bpf_ct_release**\ ().
> + *
> + *             The *ctx* should point to the context of the program, such as
> + *             the skb or xdp_md (depending on the hook in use). This is used
> + *             to determine the base network namespace for the lookup.
> + *
> + *             *tuple_size* must be one of:
> + *
> + *             **sizeof**\ (*tuple*\ **->ipv4**)
> + *                     Look for an IPv4 nf_conn.
> + *             **sizeof**\ (*tuple*\ **->ipv6**)
> + *                     Look for an IPv6 nf_conn.
> + *
> + *             If the *netns* is a negative signed 32-bit integer, then the
> + *             nf_conn lookup table in the netns associated with the *ctx* will
> + *             will be used. For the TC hooks, this is the netns of the device
> + *             in the skb. For XDP hooks, this is the netns of the device in
> + *             the xdp_md. If *netns* is any other signed 32-bit value greater
> + *             than or equal to zero then it specifies the ID of the netns
> + *             relative to the netns associated with the *ctx*. *netns* values
> + *             beyond the range of 32-bit integers are reserved for future
> + *             use.
> + *
> + *             All values for *flags* are reserved for future usage, and must
> + *             be left at zero.
> + *
> + *             This helper will always return NULL if the kernel was compiled
> + *             without **CONFIG_NF_CONNTRACK**.
> + *     Return
> + *             Pointer to **struct bpf_nf_conn**, or **NULL** in case of
> + *             failure.
> + *
> + * int bpf_ct_release(struct bpf_nf_conn *ct)
> + *     Description
> + *             Release the reference held by *ct*. *ct* must be a
> + *             non-**NULL** pointer that was returned from
> + *             **bpf_ct_lookup_xxx**\ ().
> + *     Return
> + *             0 on success, or a negative error in case of failure.
>   */
>  #define __BPF_FUNC_MAPPER(FN)          \
>         FN(unspec),                     \
> @@ -3004,7 +3086,10 @@ struct bpf_stack_build_id {
>         FN(probe_read_user_str),        \
>         FN(probe_read_kernel_str),      \
>         FN(tcp_send_ack),               \
> -       FN(send_signal_thread),
> +       FN(send_signal_thread),         \
> +       FN(ct_lookup_tcp),              \
> +       FN(ct_lookup_udp),              \
> +       FN(ct_release),
>
>  /* integer value in 'imm' field of BPF_CALL instruction selects which helper
>   * function eBPF program intends to call
> @@ -3278,6 +3363,30 @@ struct bpf_sock_tuple {
>         };
>  };
>
> +struct bpf_nf_conn {
> +       __u32 cpu;
> +       __u32 mark;
> +       __u32 status;
> +       __u32 timeout;
> +};
> +
> +struct bpf_nf_conntrack_tuple {
> +       union {
> +               struct {
> +                       __be32 saddr;
> +                       __be32 daddr;
> +                       __be16 sport;
> +                       __be16 dport;
> +               } ipv4;
> +               struct {
> +                       __be32 saddr[4];
> +                       __be32 daddr[4];
> +                       __be16 sport;
> +                       __be16 dport;
> +               } ipv6;
> +       };
> +};
> +
>  struct bpf_xdp_sock {
>         __u32 queue_id;
>  };
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index ca17dccc..0ea0ee7 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -362,6 +362,11 @@ static const char *ltrim(const char *s)
>         env->prev_linfo = linfo;
>  }
>
> +static bool type_is_nf_ct_pointer(enum bpf_reg_type type)
> +{
> +       return type == PTR_TO_NF_CONN;
> +}
> +
>  static bool type_is_pkt_pointer(enum bpf_reg_type type)
>  {
>         return type == PTR_TO_PACKET ||
> @@ -381,7 +386,8 @@ static bool reg_type_may_be_null(enum bpf_reg_type type)
>         return type == PTR_TO_MAP_VALUE_OR_NULL ||
>                type == PTR_TO_SOCKET_OR_NULL ||
>                type == PTR_TO_SOCK_COMMON_OR_NULL ||
> -              type == PTR_TO_TCP_SOCK_OR_NULL;
> +              type == PTR_TO_TCP_SOCK_OR_NULL ||
> +              type == PTR_TO_NF_CONN_OR_NULL;
>  }
>
>  static bool reg_may_point_to_spin_lock(const struct bpf_reg_state *reg)
> @@ -395,12 +401,15 @@ static bool reg_type_may_be_refcounted_or_null(enum bpf_reg_type type)
>         return type == PTR_TO_SOCKET ||
>                 type == PTR_TO_SOCKET_OR_NULL ||
>                 type == PTR_TO_TCP_SOCK ||
> -               type == PTR_TO_TCP_SOCK_OR_NULL;
> +               type == PTR_TO_TCP_SOCK_OR_NULL ||
> +               type == PTR_TO_NF_CONN ||
> +               type == PTR_TO_NF_CONN_OR_NULL;
>  }
>
>  static bool arg_type_may_be_refcounted(enum bpf_arg_type type)
>  {
> -       return type == ARG_PTR_TO_SOCK_COMMON;
> +       return type == ARG_PTR_TO_SOCK_COMMON ||
> +               type == ARG_PTR_TO_NF_CONN;
>  }
>
>  /* Determine whether the function releases some resources allocated by another
> @@ -409,14 +418,17 @@ static bool arg_type_may_be_refcounted(enum bpf_arg_type type)
>   */
>  static bool is_release_function(enum bpf_func_id func_id)
>  {
> -       return func_id == BPF_FUNC_sk_release;
> +       return func_id == BPF_FUNC_sk_release ||
> +               func_id == BPF_FUNC_ct_release;
>  }
>
>  static bool is_acquire_function(enum bpf_func_id func_id)
>  {
>         return func_id == BPF_FUNC_sk_lookup_tcp ||
>                 func_id == BPF_FUNC_sk_lookup_udp ||
> -               func_id == BPF_FUNC_skc_lookup_tcp;
> +               func_id == BPF_FUNC_skc_lookup_tcp ||
> +               func_id == BPF_FUNC_ct_lookup_tcp ||
> +               func_id == BPF_FUNC_ct_lookup_udp;
>  }
>
>  static bool is_ptr_cast_function(enum bpf_func_id func_id)
> @@ -447,6 +459,8 @@ static bool is_ptr_cast_function(enum bpf_func_id func_id)
>         [PTR_TO_TP_BUFFER]      = "tp_buffer",
>         [PTR_TO_XDP_SOCK]       = "xdp_sock",
>         [PTR_TO_BTF_ID]         = "ptr_",
> +       [PTR_TO_NF_CONN]        = "nf_conn",
> +       [PTR_TO_NF_CONN_OR_NULL] = "nf_conn_or_null",
>  };
>
>  static char slot_type_char[] = {
> @@ -1913,6 +1927,8 @@ static bool is_spillable_regtype(enum bpf_reg_type type)
>         case PTR_TO_TCP_SOCK_OR_NULL:
>         case PTR_TO_XDP_SOCK:
>         case PTR_TO_BTF_ID:
> +       case PTR_TO_NF_CONN:
> +       case PTR_TO_NF_CONN_OR_NULL:
>                 return true;
>         default:
>                 return false;
> @@ -2440,6 +2456,35 @@ static int check_flow_keys_access(struct bpf_verifier_env *env, int off,
>         return 0;
>  }
>
> +static int check_nf_ct_access(struct bpf_verifier_env *env, int insn_idx,
> +                            u32 regno, int off, int size,
> +                            enum bpf_access_type t)
> +{
> +       struct bpf_reg_state *regs = cur_regs(env);
> +       struct bpf_reg_state *reg = &regs[regno];
> +       struct bpf_insn_access_aux info = {};
> +       bool valid;
> +
> +       switch (reg->type) {
> +       case PTR_TO_NF_CONN:
> +               valid = bpf_nf_conn_is_valid_access(off, size, t, &info);
> +               break;
> +       default:
> +               valid = false;
> +       }
> +
> +       if (valid) {
> +               env->insn_aux_data[insn_idx].ctx_field_size =
> +                       info.ctx_field_size;
> +               return 0;
> +       }
> +
> +       verbose(env, "R%d invalid %s access off=%d size=%d\n",
> +               regno, reg_type_str[reg->type], off, size);
> +
> +       return -EACCES;
> +}
> +
>  static int check_sock_access(struct bpf_verifier_env *env, int insn_idx,
>                              u32 regno, int off, int size,
>                              enum bpf_access_type t)
> @@ -2511,6 +2556,13 @@ static bool is_ctx_reg(struct bpf_verifier_env *env, int regno)
>         return reg->type == PTR_TO_CTX;
>  }
>
> +static bool is_nf_ct_reg(struct bpf_verifier_env *env, int regno)
> +{
> +       const struct bpf_reg_state *reg = reg_state(env, regno);
> +
> +       return type_is_nf_ct_pointer(reg->type);
> +}
> +
>  static bool is_sk_reg(struct bpf_verifier_env *env, int regno)
>  {
>         const struct bpf_reg_state *reg = reg_state(env, regno);
> @@ -2635,6 +2687,9 @@ static int check_ptr_alignment(struct bpf_verifier_env *env,
>         case PTR_TO_XDP_SOCK:
>                 pointer_desc = "xdp_sock ";
>                 break;
> +       case PTR_TO_NF_CONN:
> +               pointer_desc = "nf_conn ";
> +               break;
>         default:
>                 break;
>         }
> @@ -3050,6 +3105,15 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
>                 err = check_sock_access(env, insn_idx, regno, off, size, t);
>                 if (!err && value_regno >= 0)
>                         mark_reg_unknown(env, regs, value_regno);
> +       } else if (type_is_nf_ct_pointer(reg->type)) {
> +               if (t == BPF_WRITE) {
> +                       verbose(env, "R%d cannot write into %s\n",
> +                               regno, reg_type_str[reg->type]);
> +                       return -EACCES;
> +               }
> +               err = check_nf_ct_access(env, insn_idx, regno, off, size, t);
> +               if (!err && value_regno >= 0)
> +                       mark_reg_unknown(env, regs, value_regno);
>         } else if (reg->type == PTR_TO_TP_BUFFER) {
>                 err = check_tp_buffer_access(env, reg, regno, off, size);
>                 if (!err && t == BPF_READ && value_regno >= 0)
> @@ -3099,7 +3163,8 @@ static int check_xadd(struct bpf_verifier_env *env, int insn_idx, struct bpf_ins
>         if (is_ctx_reg(env, insn->dst_reg) ||
>             is_pkt_reg(env, insn->dst_reg) ||
>             is_flow_key_reg(env, insn->dst_reg) ||
> -           is_sk_reg(env, insn->dst_reg)) {
> +           is_sk_reg(env, insn->dst_reg) ||
> +           is_nf_ct_reg(env, insn->dst_reg)) {
>                 verbose(env, "BPF_XADD stores into R%d %s is not allowed\n",
>                         insn->dst_reg,
>                         reg_type_str[reg_state(env, insn->dst_reg)->type]);
> @@ -3501,6 +3566,19 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
>                                 regno);
>                         return -EACCES;
>                 }
> +       } else if (arg_type == ARG_PTR_TO_NF_CONN) {
> +               expected_type = PTR_TO_NF_CONN;
> +               if (!type_is_nf_ct_pointer(type))
> +                       goto err_type;
> +               if (reg->ref_obj_id) {
> +                       if (meta->ref_obj_id) {
> +                               verbose(env, "verifier internal error: more than one arg with ref_obj_id R%d %u %u\n",
> +                                       regno, reg->ref_obj_id,
> +                                       meta->ref_obj_id);
> +                               return -EFAULT;
> +                       }
> +                       meta->ref_obj_id = reg->ref_obj_id;
> +               }
>         } else if (arg_type == ARG_PTR_TO_SPIN_LOCK) {
>                 if (meta->func_id == BPF_FUNC_spin_lock) {
>                         if (process_spin_lock(env, regno, true))
> @@ -4368,6 +4446,10 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
>                 mark_reg_known_zero(env, regs, BPF_REG_0);
>                 regs[BPF_REG_0].type = PTR_TO_TCP_SOCK_OR_NULL;
>                 regs[BPF_REG_0].id = ++env->id_gen;
> +       } else if (fn->ret_type == RET_PTR_TO_NF_CONN_OR_NULL) {
> +               mark_reg_known_zero(env, regs, BPF_REG_0);
> +               regs[BPF_REG_0].type = PTR_TO_NF_CONN_OR_NULL;
> +               regs[BPF_REG_0].id = ++env->id_gen;
>         } else {
>                 verbose(env, "unknown return type %d of func %s#%d\n",
>                         fn->ret_type, func_id_name(func_id), func_id);
> @@ -4649,6 +4731,8 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
>         case PTR_TO_TCP_SOCK:
>         case PTR_TO_TCP_SOCK_OR_NULL:
>         case PTR_TO_XDP_SOCK:
> +       case PTR_TO_NF_CONN:
> +       case PTR_TO_NF_CONN_OR_NULL:
>                 verbose(env, "R%d pointer arithmetic on %s prohibited\n",
>                         dst, reg_type_str[ptr_reg->type]);
>                 return -EACCES;
> @@ -5915,6 +5999,8 @@ static void mark_ptr_or_null_reg(struct bpf_func_state *state,
>                         reg->type = PTR_TO_SOCK_COMMON;
>                 } else if (reg->type == PTR_TO_TCP_SOCK_OR_NULL) {
>                         reg->type = PTR_TO_TCP_SOCK;
> +               } else if (reg->type == PTR_TO_NF_CONN_OR_NULL) {
> +                       reg->type = PTR_TO_NF_CONN;
>                 }
>                 if (is_null) {
>                         /* We don't need id and ref_obj_id from this point
> @@ -7232,6 +7318,8 @@ static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur,
>         case PTR_TO_TCP_SOCK:
>         case PTR_TO_TCP_SOCK_OR_NULL:
>         case PTR_TO_XDP_SOCK:
> +       case PTR_TO_NF_CONN:
> +       case PTR_TO_NF_CONN_OR_NULL:
>                 /* Only valid matches are exact, which memcmp() above
>                  * would have accepted
>                  */
> @@ -7760,6 +7848,8 @@ static bool reg_type_mismatch_ok(enum bpf_reg_type type)
>         case PTR_TO_TCP_SOCK_OR_NULL:
>         case PTR_TO_XDP_SOCK:
>         case PTR_TO_BTF_ID:
> +       case PTR_TO_NF_CONN:
> +       case PTR_TO_NF_CONN_OR_NULL:
>                 return false;
>         default:
>                 return true;
> @@ -8867,6 +8957,9 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
>                                 return -EINVAL;
>                         }
>                         continue;
> +               case PTR_TO_NF_CONN:
> +                       convert_ctx_access = bpf_nf_conn_convert_ctx_access;
> +                       break;
>                 default:
>                         continue;
>                 }
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 17de674..80319d3 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -74,6 +74,12 @@
>  #include <net/ipv6_stubs.h>
>  #include <net/bpf_sk_storage.h>
>
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
> +#include <net/netfilter/nf_conntrack_tuple.h>
> +#include <net/netfilter/nf_conntrack_core.h>
> +#include <net/netfilter/nf_conntrack.h>
> +#endif
> +
>  /**
>   *     sk_filter_trim_cap - run a packet through a socket filter
>   *     @sk: sock associated with &sk_buff
> @@ -5122,6 +5128,253 @@ static void bpf_update_srh_state(struct sk_buff *skb)
>  };
>  #endif /* CONFIG_IPV6_SEG6_BPF */
>
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
> +bool bpf_nf_conn_is_valid_access(int off, int size, enum bpf_access_type type,
> +                                struct bpf_insn_access_aux *info)
> +{
> +       if (off < 0 || off >= offsetofend(struct bpf_nf_conn,
> +                                         timeout))
> +               return false;
> +
> +       if (off % size != 0)
> +               return false;
> +
> +       return size == sizeof(__u32);
> +}
> +
> +u32 bpf_nf_conn_convert_ctx_access(enum bpf_access_type type,
> +                                  const struct bpf_insn *si,
> +                                  struct bpf_insn *insn_buf,
> +                                  struct bpf_prog *prog, u32 *target_size)
> +{
> +       struct bpf_insn *insn = insn_buf;
> +
> +       switch (si->off) {
> +       case offsetof(struct bpf_nf_conn, cpu):
> +               BUILD_BUG_ON(FIELD_SIZEOF(struct nf_conn, cpu) != 2);
> +
> +               *insn++ = BPF_LDX_MEM(BPF_H, si->dst_reg, si->src_reg,
> +                                     offsetof(struct nf_conn, cpu));
> +
> +               break;
> +
> +       case offsetof(struct bpf_nf_conn, mark):
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK_MARK)
> +               BUILD_BUG_ON(FIELD_SIZEOF(struct nf_conn, mark) != 4);
> +
> +               *insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->src_reg,
> +                                     offsetof(struct nf_conn, mark));
> +#else
> +               *target_size = 4;
> +               *insn++ = BPF_MOV64_IMM(si->dst_reg, 0);
> +#endif
> +               break;
> +
> +       case offsetof(struct bpf_nf_conn, status):
> +               BUILD_BUG_ON(FIELD_SIZEOF(struct nf_conn, status) < 4 ||
> +                            __IPS_MAX_BIT > 32);
> +
> +               *insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->src_reg,
> +                                     offsetof(struct nf_conn, status));
> +
> +               break;
> +
> +       case offsetof(struct bpf_nf_conn, timeout):
> +               BUILD_BUG_ON(FIELD_SIZEOF(struct nf_conn, timeout) != 4);
> +
> +               *insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->src_reg,
> +                                     offsetof(struct nf_conn, timeout));
> +
> +               break;
> +       }
> +
> +       return insn - insn_buf;
> +}
> +
> +static struct nf_conn *
> +ct_lookup(struct net *net, struct bpf_nf_conntrack_tuple *tuple,
> +         u8 family, u8 proto)
> +{
> +       struct nf_conntrack_tuple_hash *hash;
> +       struct nf_conntrack_tuple tup;
> +       struct nf_conn *ct = NULL;
> +
> +       memset(&tup, 0, sizeof(tup));
> +
> +       tup.dst.protonum = proto;
> +       tup.src.l3num = family;
> +
> +       if (family == AF_INET) {
> +               tup.src.u3.ip = tuple->ipv4.saddr;
> +               tup.dst.u3.ip = tuple->ipv4.daddr;
> +               tup.src.u.tcp.port = tuple->ipv4.sport;
> +               tup.dst.u.tcp.port = tuple->ipv4.dport;
> +#if IS_ENABLED(CONFIG_IPV6)
> +       } else {
> +               memcpy(tup.src.u3.ip6, tuple->ipv6.saddr, sizeof(tup.src.u3.ip6));
> +               memcpy(tup.dst.u3.ip6, tuple->ipv6.daddr, sizeof(tup.dst.u3.ip6));
> +               tup.src.u.tcp.port = tuple->ipv6.sport;
> +               tup.dst.u.tcp.port = tuple->ipv6.dport;
> +#endif
> +       }
> +
> +       hash = nf_ct_find_get(net, &nf_ct_zone_dflt, &tup);
> +       if (!hash)
> +               goto out;
> +       ct = nf_ct_tuplehash_to_ctrack(hash);
> +
> +out:
> +       return ct;
> +}
> +
> +static struct nf_conn *
> +__bpf_ct_lookup(struct sk_buff *skb, struct bpf_nf_conntrack_tuple *tuple, u32 len,
> +               struct net *caller_net, u8 proto, u64 netns_id, u64 flags)
> +{
> +       struct nf_conn *ct = NULL;
> +       u8 family = AF_UNSPEC;
> +       struct net *net;
> +
> +       if (len == sizeof(tuple->ipv4))
> +               family = AF_INET;
> +       else if (len == sizeof(tuple->ipv6))
> +               family = AF_INET6;
> +       else
> +               goto out;
> +
> +       if (unlikely(family == AF_UNSPEC || flags ||
> +                    !((s32)netns_id < 0 || netns_id <= S32_MAX)))
> +               goto out;
> +
> +       if ((s32)netns_id < 0) {
> +               net = caller_net;
> +               ct = ct_lookup(net, tuple, family, proto);
> +       } else {
> +               net = get_net_ns_by_id(caller_net, netns_id);
> +               if (unlikely(!net))
> +                       goto out;
> +               ct = ct_lookup(net, tuple, family, proto);
> +               put_net(net);
> +       }
> +
> +out:
> +       return ct;
> +}
> +
> +static struct nf_conn *
> +bpf_ct_lookup(struct sk_buff *skb, struct bpf_nf_conntrack_tuple *tuple, u32 len,
> +             u8 proto, u64 netns_id, u64 flags)
> +{
> +       struct net *caller_net;
> +
> +       if (skb->dev) {
> +               caller_net = dev_net(skb->dev);
> +       } else {
> +               caller_net = sock_net(skb->sk);
> +       }
> +
> +       return __bpf_ct_lookup(skb, tuple, len, caller_net, proto,
> +                              netns_id, flags);
> +}
> +
> +BPF_CALL_5(bpf_ct_lookup_tcp, struct sk_buff *, skb,
> +          struct bpf_nf_conntrack_tuple *, tuple, u32, len, u64, netns_id,
> +          u64, flags)
> +{
> +       return (unsigned long)bpf_ct_lookup(skb, tuple, len, IPPROTO_TCP,
> +                                            netns_id, flags);
> +}
> +
> +static const struct bpf_func_proto bpf_ct_lookup_tcp_proto = {
> +       .func           = bpf_ct_lookup_tcp,
> +       .gpl_only       = true,
> +       .pkt_access     = true,
> +       .ret_type       = RET_PTR_TO_NF_CONN_OR_NULL,
> +       .arg1_type      = ARG_PTR_TO_CTX,
> +       .arg2_type      = ARG_PTR_TO_MEM,
> +       .arg3_type      = ARG_CONST_SIZE,
> +       .arg4_type      = ARG_ANYTHING,
> +       .arg5_type      = ARG_ANYTHING,
> +};
> +
> +BPF_CALL_5(bpf_xdp_ct_lookup_tcp, struct xdp_buff *, ctx,
> +          struct bpf_nf_conntrack_tuple *, tuple, u32, len, u32, netns_id,
> +          u64, flags)
> +{
> +       struct net *caller_net = dev_net(ctx->rxq->dev);
> +
> +       return (unsigned long)__bpf_ct_lookup(NULL, tuple, len, caller_net,
> +                                             IPPROTO_TCP, netns_id, flags);
> +}
> +
> +static const struct bpf_func_proto bpf_xdp_ct_lookup_tcp_proto = {
> +       .func           = bpf_xdp_ct_lookup_tcp,
> +       .gpl_only       = true,
> +       .pkt_access     = true,
> +       .ret_type       = RET_PTR_TO_NF_CONN_OR_NULL,
> +       .arg1_type      = ARG_PTR_TO_CTX,
> +       .arg2_type      = ARG_PTR_TO_MEM,
> +       .arg3_type      = ARG_CONST_SIZE,
> +       .arg4_type      = ARG_ANYTHING,
> +       .arg5_type      = ARG_ANYTHING,
> +};
> +
> +BPF_CALL_5(bpf_ct_lookup_udp, struct sk_buff *, skb,
> +          struct bpf_nf_conntrack_tuple *, tuple, u32, len, u64, netns_id,
> +          u64, flags)
> +{
> +       return (unsigned long)bpf_ct_lookup(skb, tuple, len, IPPROTO_UDP,
> +                                            netns_id, flags);
> +}
> +
> +static const struct bpf_func_proto bpf_ct_lookup_udp_proto = {
> +       .func           = bpf_ct_lookup_udp,
> +       .gpl_only       = true,
> +       .pkt_access     = true,
> +       .ret_type       = RET_PTR_TO_NF_CONN_OR_NULL,
> +       .arg1_type      = ARG_PTR_TO_CTX,
> +       .arg2_type      = ARG_PTR_TO_MEM,
> +       .arg3_type      = ARG_CONST_SIZE,
> +       .arg4_type      = ARG_ANYTHING,
> +       .arg5_type      = ARG_ANYTHING,
> +};
> +
> +BPF_CALL_5(bpf_xdp_ct_lookup_udp, struct xdp_buff *, ctx,
> +          struct bpf_nf_conntrack_tuple *, tuple, u32, len, u32, netns_id,
> +          u64, flags)
> +{
> +       struct net *caller_net = dev_net(ctx->rxq->dev);
> +
> +       return (unsigned long)__bpf_ct_lookup(NULL, tuple, len, caller_net,
> +                                             IPPROTO_UDP, netns_id, flags);
> +}
> +
> +static const struct bpf_func_proto bpf_xdp_ct_lookup_udp_proto = {
> +       .func           = bpf_xdp_ct_lookup_udp,
> +       .gpl_only       = true,
> +       .pkt_access     = true,
> +       .ret_type       = RET_PTR_TO_NF_CONN_OR_NULL,
> +       .arg1_type      = ARG_PTR_TO_CTX,
> +       .arg2_type      = ARG_PTR_TO_MEM,
> +       .arg3_type      = ARG_CONST_SIZE,
> +       .arg4_type      = ARG_ANYTHING,
> +       .arg5_type      = ARG_ANYTHING,
> +};
> +
> +BPF_CALL_1(bpf_ct_release, struct nf_conn *, ct)
> +{
> +       nf_conntrack_put(&ct->ct_general);
> +       return 0;
> +}
> +
> +static const struct bpf_func_proto bpf_ct_release_proto = {
> +       .func           = bpf_ct_release,
> +       .gpl_only       = true,
> +       .ret_type       = RET_INTEGER,
> +       .arg1_type      = ARG_PTR_TO_NF_CONN,
> +};
> +#endif
> +
>  #ifdef CONFIG_INET
>  static struct sock *sk_lookup(struct net *net, struct bpf_sock_tuple *tuple,
>                               int dif, int sdif, u8 family, u8 proto)
> @@ -6139,6 +6392,14 @@ bool bpf_helper_changes_pkt_data(void *func)
>         case BPF_FUNC_tcp_gen_syncookie:
>                 return &bpf_tcp_gen_syncookie_proto;
>  #endif
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
> +       case BPF_FUNC_ct_lookup_tcp:
> +               return &bpf_ct_lookup_tcp_proto;
> +       case BPF_FUNC_ct_lookup_udp:
> +               return &bpf_ct_lookup_udp_proto;
> +       case BPF_FUNC_ct_release:
> +               return &bpf_ct_release_proto;
> +#endif
>         default:
>                 return bpf_base_func_proto(func_id);
>         }
> @@ -6180,6 +6441,14 @@ bool bpf_helper_changes_pkt_data(void *func)
>         case BPF_FUNC_tcp_gen_syncookie:
>                 return &bpf_tcp_gen_syncookie_proto;
>  #endif
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
> +       case BPF_FUNC_ct_lookup_tcp:
> +               return &bpf_xdp_ct_lookup_tcp_proto;
> +       case BPF_FUNC_ct_lookup_udp:
> +               return &bpf_xdp_ct_lookup_udp_proto;
> +       case BPF_FUNC_ct_release:
> +               return &bpf_ct_release_proto;
> +#endif
>         default:
>                 return bpf_base_func_proto(func_id);
>         }
> @@ -6284,6 +6553,14 @@ bool bpf_helper_changes_pkt_data(void *func)
>         case BPF_FUNC_skc_lookup_tcp:
>                 return &bpf_skc_lookup_tcp_proto;
>  #endif
> +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
> +       case BPF_FUNC_ct_lookup_tcp:
> +               return &bpf_ct_lookup_tcp_proto;
> +       case BPF_FUNC_ct_lookup_udp:
> +               return &bpf_ct_lookup_udp_proto;
> +       case BPF_FUNC_ct_release:
> +               return &bpf_ct_release_proto;
> +#endif
>         default:
>                 return bpf_base_func_proto(func_id);
>         }
> diff --git a/net/netfilter/core.c b/net/netfilter/core.c
> index 78f046e..855c6b0 100644
> --- a/net/netfilter/core.c
> +++ b/net/netfilter/core.c
> @@ -617,6 +617,22 @@ bool nf_ct_get_tuple_skb(struct nf_conntrack_tuple *dst_tuple,
>  }
>  EXPORT_SYMBOL(nf_ct_get_tuple_skb);
>
> +struct nf_conntrack_tuple_hash *
> +nf_ct_find_get(struct net *net, const struct nf_conntrack_zone *zone,
> +              const struct nf_conntrack_tuple *tuple)
> +{
> +       struct nf_ct_hook *ct_hook;
> +       struct nf_conntrack_tuple_hash *ret = NULL;
> +
> +       rcu_read_lock();
> +       ct_hook = rcu_dereference(nf_ct_hook);
> +       if (ct_hook)
> +               ret = ct_hook->find_get(net, zone, tuple);
> +       rcu_read_unlock();
> +       return ret;
> +}
> +EXPORT_SYMBOL_GPL(nf_ct_find_get);
> +
>  /* Built-in default zone used e.g. by modules. */
>  const struct nf_conntrack_zone nf_ct_zone_dflt = {
>         .id     = NF_CT_DEFAULT_ZONE_ID,
> diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
> index f4c4b46..a44df88 100644
> --- a/net/netfilter/nf_conntrack_core.c
> +++ b/net/netfilter/nf_conntrack_core.c
> @@ -2484,6 +2484,7 @@ int nf_conntrack_init_start(void)
>         .update         = nf_conntrack_update,
>         .destroy        = destroy_conntrack,
>         .get_tuple_skb  = nf_conntrack_get_tuple_skb,
> +       .find_get       = nf_conntrack_find_get,
>  };
>
>  void nf_conntrack_init_end(void)
> diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py
> index 90baf7d..26f0c2a 100755
> --- a/scripts/bpf_helpers_doc.py
> +++ b/scripts/bpf_helpers_doc.py
> @@ -398,6 +398,8 @@ class PrinterHelpers(Printer):
>
>      type_fwds = [
>              'struct bpf_fib_lookup',
> +            'struct bpf_nf_conn',
> +            'struct bpf_nf_conntrack_tuple',
>              'struct bpf_perf_event_data',
>              'struct bpf_perf_event_value',
>              'struct bpf_sock',
> @@ -433,6 +435,8 @@ class PrinterHelpers(Printer):
>              '__wsum',
>
>              'struct bpf_fib_lookup',
> +            'struct bpf_nf_conn',
> +            'struct bpf_nf_conntrack_tuple',
>              'struct bpf_perf_event_data',
>              'struct bpf_perf_event_value',
>              'struct bpf_sock',
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 033d90a..85c4b3f 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -2885,6 +2885,88 @@ struct bpf_stack_build_id {
>   *             **-EPERM** if no permission to send the *sig*.
>   *
>   *             **-EAGAIN** if bpf program can try again.
> + *
> + * struct bpf_nf_conn *bpf_ct_lookup_tcp(void *ctx, struct bpf_nf_conntrack_tuple *tuple, u32 tuple_size, u64 netns, u64 flags)
> + *     Description
> + *             Look for TCP nf_conntrack entry matching *tuple*, optionally in
> + *             a child network namespace *netns*. The return value must be
> + *             checked, and if non-**NULL**, released via
> + *             **bpf_ct_release**\ ().
> + *
> + *             The *ctx* should point to the context of the program, such as
> + *             the skb or xdp_md (depending on the hook in use). This is used
> + *             to determine the base network namespace for the lookup.
> + *
> + *             *tuple_size* must be one of:
> + *
> + *             **sizeof**\ (*tuple*\ **->ipv4**)
> + *                     Look for an IPv4 nf_conn.
> + *             **sizeof**\ (*tuple*\ **->ipv6**)
> + *                     Look for an IPv6 nf_conn.
> + *
> + *             If the *netns* is a negative signed 32-bit integer, then the
> + *             nf_conn lookup table in the netns associated with the *ctx* will
> + *             will be used. For the TC hooks, this is the netns of the device
> + *             in the skb. For XDP hooks, this is the netns of the device in
> + *             the xdp_md. If *netns* is any other signed 32-bit value greater
> + *             than or equal to zero then it specifies the ID of the netns
> + *             relative to the netns associated with the *ctx*. *netns* values
> + *             beyond the range of 32-bit integers are reserved for future
> + *             use.
> + *
> + *             All values for *flags* are reserved for future usage, and must
> + *             be left at zero.
> + *
> + *             This helper will always return NULL if the kernel was compiled
> + *             without **CONFIG_NF_CONNTRACK**.
> + *     Return
> + *             Pointer to **struct bpf_nf_conn**, or **NULL** in case of
> + *             failure.
> + *
> + * struct bpf_nf_conn *bpf_ct_lookup_udp(void *ctx, struct bpf_nf_conntrack_tuple *tuple, u32 tuple_size, u64 netns, u64 flags)
> + *     Description
> + *             Look for UDP nf_conntrack entry matching *tuple*, optionally in
> + *             a child network namespace *netns*. The return value must be
> + *             checked, and if non-**NULL**, released via
> + *             **bpf_ct_release**\ ().
> + *
> + *             The *ctx* should point to the context of the program, such as
> + *             the skb or xdp_md (depending on the hook in use). This is used
> + *             to determine the base network namespace for the lookup.
> + *
> + *             *tuple_size* must be one of:
> + *
> + *             **sizeof**\ (*tuple*\ **->ipv4**)
> + *                     Look for an IPv4 nf_conn.
> + *             **sizeof**\ (*tuple*\ **->ipv6**)
> + *                     Look for an IPv6 nf_conn.
> + *
> + *             If the *netns* is a negative signed 32-bit integer, then the
> + *             nf_conn lookup table in the netns associated with the *ctx* will
> + *             will be used. For the TC hooks, this is the netns of the device
> + *             in the skb. For XDP hooks, this is the netns of the device in
> + *             the xdp_md. If *netns* is any other signed 32-bit value greater
> + *             than or equal to zero then it specifies the ID of the netns
> + *             relative to the netns associated with the *ctx*. *netns* values
> + *             beyond the range of 32-bit integers are reserved for future
> + *             use.
> + *
> + *             All values for *flags* are reserved for future usage, and must
> + *             be left at zero.
> + *
> + *             This helper will always return NULL if the kernel was compiled
> + *             without **CONFIG_NF_CONNTRACK**.
> + *     Return
> + *             Pointer to **struct bpf_nf_conn**, or **NULL** in case of
> + *             failure.
> + *
> + * int bpf_ct_release(struct bpf_nf_conn *ct)
> + *     Description
> + *             Release the reference held by *ct*. *ct* must be a
> + *             non-**NULL** pointer that was returned from
> + *             **bpf_ct_lookup_xxx**\ ().
> + *     Return
> + *             0 on success, or a negative error in case of failure.
>   */
>  #define __BPF_FUNC_MAPPER(FN)          \
>         FN(unspec),                     \
> @@ -3004,7 +3086,10 @@ struct bpf_stack_build_id {
>         FN(probe_read_user_str),        \
>         FN(probe_read_kernel_str),      \
>         FN(tcp_send_ack),               \
> -       FN(send_signal_thread),
> +       FN(send_signal_thread),         \
> +       FN(ct_lookup_tcp),              \
> +       FN(ct_lookup_udp),              \
> +       FN(ct_release),
>
>  /* integer value in 'imm' field of BPF_CALL instruction selects which helper
>   * function eBPF program intends to call
> @@ -3278,6 +3363,30 @@ struct bpf_sock_tuple {
>         };
>  };
>
> +struct bpf_nf_conn {
> +       __u32 cpu;
> +       __u32 mark;
> +       __u32 status;
> +       __u32 timeout;
> +};
> +
> +struct bpf_nf_conntrack_tuple {
> +       union {
> +               struct {
> +                       __be32 saddr;
> +                       __be32 daddr;
> +                       __be16 sport;
> +                       __be16 dport;
> +               } ipv4;
> +               struct {
> +                       __be32 saddr[4];
> +                       __be32 daddr[4];
> +                       __be16 sport;
> +                       __be16 dport;
> +               } ipv6;
> +       };
> +};
> +
>  struct bpf_xdp_sock {
>         __u32 queue_id;
>  };
> --
> 1.8.3.1
>