[PATCH bpf-next v2 1/2] bpf: add bpf_ct_lookup_{tcp,udp}() helpers

From: Matthew Cover
Date: Tue Jan 21 2020 - 15:20:59 EST

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)

Signed-off-by: Matthew Cover <matthew.cover@xxxxxxxxxxxxx>
---
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