Signed-off-by: Matthew Cover <redacted>
---
 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