LinuxLists.cc - [PATCH bpf-next] bpf: add bpf_ct_lookup

2020-01-18 00:04:22

Subject: [PATCH bpf-next] bpf: add bpf_ct_lookup_{tcp,udp}() helpers

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.

Signed-off-by: Matthew Cover <[email protected]>
---
include/linux/bpf.h | 28 +++
include/uapi/linux/bpf.h | 111 ++++++++-
kernel/bpf/verifier.c | 105 +++++++-
net/core/filter.c | 277 +++++++++++++++++++++
scripts/bpf_helpers_doc.py | 4 +
tools/include/uapi/linux/bpf.h | 111 ++++++++-
tools/testing/selftests/bpf/test_verifier.c | 18 ++
.../testing/selftests/bpf/verifier/ref_tracking.c | 48 ++++
8 files changed, 694 insertions(+), 8 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 8e3b8f4..28d35c3 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 +1517,28 @@ enum bpf_text_poke_type {
int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
void *addr1, void *addr2);

+#if IS_BUILTIN(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
+bool bpf_nf_conn_is_valid_access(int off, int size, enum bpf_access_type type,
+ struct bpf_insn_access_aux *info)
+{
+ return false;
+}
+
+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/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 033d90a..12e16ad 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 is available only if the kernel was compiled with
+ * **CONFIG_NF_CONNTRACK=y** configuration option.
+ * 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 is available only if the kernel was compiled with
+ * **CONFIG_NF_CONNTRACK=y** configuration option.
+ * 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..39ba965 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_BUILTIN(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_BUILTIN(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_conntrack_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_BUILTIN(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_BUILTIN(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_BUILTIN(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/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..12e16ad 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 is available only if the kernel was compiled with
+ * **CONFIG_NF_CONNTRACK=y** configuration option.
+ * 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 is available only if the kernel was compiled with
+ * **CONFIG_NF_CONNTRACK=y** configuration option.
+ * 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/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 87eaa49..7569db2 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -294,6 +294,24 @@ static void bpf_fill_scale(struct bpf_test *self)
}
}

+/* BPF_CT_LOOKUP contains 13 instructions, if you need to fix up maps */
+#define BPF_CT_LOOKUP(func) \
+ /* struct bpf_nf_conntrack_tuple tuple = {} */ \
+ BPF_MOV64_IMM(BPF_REG_2, 0), \
+ BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_2, -8), \
+ BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -16), \
+ BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -24), \
+ BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -32), \
+ BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -40), \
+ BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -48), \
+ /* ct = func(ctx, &tuple, sizeof tuple, 0, 0) */ \
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), \
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -48), \
+ BPF_MOV64_IMM(BPF_REG_3, sizeof(struct bpf_nf_conntrack_tuple)),\
+ BPF_MOV64_IMM(BPF_REG_4, 0), \
+ BPF_MOV64_IMM(BPF_REG_5, 0), \
+ BPF_EMIT_CALL(BPF_FUNC_ ## func)
+
/* BPF_SK_LOOKUP contains 13 instructions, if you need to fix up maps */
#define BPF_SK_LOOKUP(func) \
/* struct bpf_sock_tuple tuple = {} */ \
diff --git a/tools/testing/selftests/bpf/verifier/ref_tracking.c b/tools/testing/selftests/bpf/verifier/ref_tracking.c
index 604b461..de5c550a 100644
--- a/tools/testing/selftests/bpf/verifier/ref_tracking.c
+++ b/tools/testing/selftests/bpf/verifier/ref_tracking.c
@@ -21,6 +21,17 @@
.result = REJECT,
},
{
+ "reference tracking: leak potential reference to nf_conn",
+ .insns = {
+ BPF_CT_LOOKUP(ct_lookup_tcp),
+ BPF_MOV64_REG(BPF_REG_6, BPF_REG_0), /* leak reference */
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_SCHED_CLS,
+ .errstr = "Unreleased reference",
+ .result = REJECT,
+},
+{
"reference tracking: leak potential reference on stack",
.insns = {
BPF_SK_LOOKUP(sk_lookup_tcp),
@@ -72,6 +83,17 @@
.result = REJECT,
},
{
+ "reference tracking: zero potential reference to nf_conn",
+ .insns = {
+ BPF_CT_LOOKUP(ct_lookup_tcp),
+ BPF_MOV64_IMM(BPF_REG_0, 0), /* leak reference */
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_SCHED_CLS,
+ .errstr = "Unreleased reference",
+ .result = REJECT,
+},
+{
"reference tracking: copy and zero potential references",
.insns = {
BPF_SK_LOOKUP(sk_lookup_tcp),
@@ -113,6 +135,20 @@
.result = REJECT,
},
{
+ "reference tracking: release reference to nf_conn without check",
+ .insns = {
+ BPF_CT_LOOKUP(ct_lookup_tcp),
+ /* reference in r0 may be NULL */
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+ BPF_MOV64_IMM(BPF_REG_2, 0),
+ BPF_EMIT_CALL(BPF_FUNC_ct_release),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_SCHED_CLS,
+ .errstr = "type=nf_conn_or_null expected=nf_conn",
+ .result = REJECT,
+},
+{
"reference tracking: release reference",
.insns = {
BPF_SK_LOOKUP(sk_lookup_tcp),
@@ -137,6 +173,18 @@
.result = ACCEPT,
},
{
+ "reference tracking: release reference to nf_conn",
+ .insns = {
+ BPF_CT_LOOKUP(ct_lookup_tcp),
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1),
+ BPF_EMIT_CALL(BPF_FUNC_ct_release),
+ BPF_EXIT_INSN(),
+ },
+ .prog_type = BPF_PROG_TYPE_SCHED_CLS,
+ .result = ACCEPT,
+},
+{
"reference tracking: release reference 2",
.insns = {
BPF_SK_LOOKUP(sk_lookup_tcp),
--
1.8.3.1

2020-01-18 11:40:26

by kernel test robot

[permalink] [raw]

Subject: Re: [PATCH bpf-next] bpf: add bpf_ct_lookup_{tcp,udp}() helpers

Hi Matthew,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on bpf-next/master]
[also build test ERROR on next-20200117]
[cannot apply to bpf/master net-next/master net/master linus/master sparc-next/master v5.5-rc6]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url: https://github.com/0day-ci/linux/commits/Matthew-Cover/bpf-add-bpf_ct_lookup_-tcp-udp-helpers/20200118-153032
base: https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: i386-alldefconfig (attached as .config)
compiler: gcc-7 (Debian 7.5.0-3) 7.5.0
reproduce:
# save the attached .config to linux build tree
make ARCH=i386

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <[email protected]>

All errors (new ones prefixed by >>):

ld: init/do_mounts.o: in function `bpf_nf_conn_is_valid_access':
>> do_mounts.c:(.text+0x70): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: init/do_mounts.o: in function `bpf_nf_conn_convert_ctx_access':
>> do_mounts.c:(.text+0x80): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: init/noinitramfs.o: in function `bpf_nf_conn_is_valid_access':
noinitramfs.c:(.text+0x0): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: init/noinitramfs.o: in function `bpf_nf_conn_convert_ctx_access':
noinitramfs.c:(.text+0x10): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/entry/common.o: in function `bpf_nf_conn_is_valid_access':
common.c:(.text+0x2b0): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/entry/common.o: in function `bpf_nf_conn_convert_ctx_access':
common.c:(.text+0x2c0): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/events/core.o: in function `bpf_nf_conn_is_valid_access':
core.c:(.text+0xbe0): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/events/core.o: in function `bpf_nf_conn_convert_ctx_access':
core.c:(.text+0xbf0): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/events/amd/core.o: in function `bpf_nf_conn_is_valid_access':
core.c:(.text+0x8f0): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/events/amd/core.o: in function `bpf_nf_conn_convert_ctx_access':
core.c:(.text+0x900): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/events/amd/uncore.o: in function `bpf_nf_conn_is_valid_access':
uncore.c:(.text+0x8d0): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/events/amd/uncore.o: in function `bpf_nf_conn_convert_ctx_access':
uncore.c:(.text+0x8e0): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/events/intel/core.o: in function `bpf_nf_conn_is_valid_access':
core.c:(.text+0x1d40): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/events/intel/core.o: in function `bpf_nf_conn_convert_ctx_access':
core.c:(.text+0x1d50): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/events/intel/bts.o: in function `bpf_nf_conn_is_valid_access':
bts.c:(.text+0x9c0): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/events/intel/bts.o: in function `bpf_nf_conn_convert_ctx_access':
bts.c:(.text+0x9d0): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/events/intel/ds.o: in function `bpf_nf_conn_is_valid_access':
ds.c:(.text+0x1920): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/events/intel/ds.o: in function `bpf_nf_conn_convert_ctx_access':
ds.c:(.text+0x1930): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/events/intel/knc.o: in function `bpf_nf_conn_is_valid_access':
knc.c:(.text+0x340): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/events/intel/knc.o: in function `bpf_nf_conn_convert_ctx_access':
knc.c:(.text+0x350): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/events/intel/lbr.o: in function `bpf_nf_conn_is_valid_access':
lbr.c:(.text+0x680): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/events/intel/lbr.o: in function `bpf_nf_conn_convert_ctx_access':
lbr.c:(.text+0x690): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/events/intel/p4.o: in function `bpf_nf_conn_is_valid_access':
p4.c:(.text+0x7d0): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/events/intel/p4.o: in function `bpf_nf_conn_convert_ctx_access':
p4.c:(.text+0x7e0): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/events/intel/p6.o: in function `bpf_nf_conn_is_valid_access':
p6.c:(.text+0x170): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/events/intel/p6.o: in function `bpf_nf_conn_convert_ctx_access':
p6.c:(.text+0x180): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/events/intel/pt.o: in function `bpf_nf_conn_is_valid_access':
pt.c:(.text+0x1a70): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/events/intel/pt.o: in function `bpf_nf_conn_convert_ctx_access':
pt.c:(.text+0x1a80): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/kernel/process_32.o: in function `bpf_nf_conn_is_valid_access':
process_32.c:(.text+0x0): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/kernel/process_32.o: in function `bpf_nf_conn_convert_ctx_access':
process_32.c:(.text+0x10): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/kernel/signal.o: in function `bpf_nf_conn_is_valid_access':
signal.c:(.text+0x270): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/kernel/signal.o: in function `bpf_nf_conn_convert_ctx_access':
signal.c:(.text+0x280): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/kernel/ioport.o: in function `bpf_nf_conn_is_valid_access':
ioport.c:(.text+0x40): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/kernel/ioport.o: in function `bpf_nf_conn_convert_ctx_access':
ioport.c:(.text+0x50): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/kernel/ldt.o: in function `bpf_nf_conn_is_valid_access':
ldt.c:(.text+0x4c0): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/kernel/ldt.o: in function `bpf_nf_conn_convert_ctx_access':
ldt.c:(.text+0x4d0): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/kernel/setup.o: in function `bpf_nf_conn_is_valid_access':
setup.c:(.text+0x60): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/kernel/setup.o: in function `bpf_nf_conn_convert_ctx_access':
setup.c:(.text+0x70): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/kernel/e820.o: in function `bpf_nf_conn_is_valid_access':
e820.c:(.text+0x0): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/kernel/e820.o: in function `bpf_nf_conn_convert_ctx_access':
e820.c:(.text+0x10): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/kernel/hw_breakpoint.o: in function `bpf_nf_conn_is_valid_access':
hw_breakpoint.c:(.text+0x0): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/kernel/hw_breakpoint.o: in function `bpf_nf_conn_convert_ctx_access':
hw_breakpoint.c:(.text+0x10): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/kernel/process.o: in function `bpf_nf_conn_is_valid_access':
process.c:(.text+0xe0): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/kernel/process.o: in function `bpf_nf_conn_convert_ctx_access':
process.c:(.text+0xf0): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/kernel/ptrace.o: in function `bpf_nf_conn_is_valid_access':
ptrace.c:(.text+0x690): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/kernel/ptrace.o: in function `bpf_nf_conn_convert_ctx_access':
ptrace.c:(.text+0x6a0): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/kernel/tls.o: in function `bpf_nf_conn_is_valid_access':
tls.c:(.text+0x2b0): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/kernel/tls.o: in function `bpf_nf_conn_convert_ctx_access':
tls.c:(.text+0x2c0): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/kernel/cpu/umwait.o: in function `bpf_nf_conn_is_valid_access':
umwait.c:(.text+0x210): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/kernel/cpu/umwait.o: in function `bpf_nf_conn_convert_ctx_access':
umwait.c:(.text+0x220): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here
ld: arch/x86/kernel/reboot.o: in function `bpf_nf_conn_is_valid_access':
reboot.c:(.text+0xb0): multiple definition of `bpf_nf_conn_is_valid_access'; init/main.o:main.c:(.text+0x80): first defined here
ld: arch/x86/kernel/reboot.o: in function `bpf_nf_conn_convert_ctx_access':
reboot.c:(.text+0xc0): multiple definition of `bpf_nf_conn_convert_ctx_access'; init/main.o:main.c:(.text+0x90): first defined here

---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/hyperkitty/list/[email protected] Intel Corporation

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2020-01-18 12:03:07

On Tue, Jan 21, 2020 at 12:36 PM Matt Cover <[email protected]> wrote:
>
> On Tue, Jan 21, 2020 at 1:20 PM Matthew Cover <[email protected]> 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.

I think there's an important distinction between accessing sockets and
accessing the connection tracker: Sockets are inherently tied to local
processes. They consume resources regardless of what kind of fancy
networking behaviour you desire out of the stack. Connection-tracking
on the other hand only consumes resources if you enable features that
explicitly require that functionality. This raises some interesting
questions.

The kernel disables nf_conntrack by default to alleviate the costs
associated with it[0]. In the case of this proposal, the BPF program
itself is trying to use nf_conntrack, so does that mean that the
kernel should auto-enable nf_conntrack hooks for the current namespace
(or all namespaces, given that the helper provides access into other
namespaces as well) whenever a BPF program is loaded that uses this
helper?

Related side note: What if you wanted to migitate the performance
penalty of turning on nf_conntrack by programmatically choosing
whether to populate the ct table? Do we then need to define an
interface that allows a BPF program to tell nf_conntrack whether or
not to track a given connection?

More importantly, nf_conntrack has a particular view in mind of what a
connection is and the metadata that can be associated with a
connection. On the other hand, one of the big pulls for building
networking functionality in BPF is to allow flexibility. Over time,
more complex use cases will arise that demand additional metadata to
be stored with their connections. Cilium's connection tracking entries
provides a glimpse of this[1]. I'm sure that the OVS-BPF project would
have similar demands. Longer term, do we encourage such projects to
migrate to this implementation, proposing metadata extensions that are
programmable from BPF?

Taking the metadata question further, there is not only the metadata
that arbitrary BPF programs wish to associate with nf_conntrack. There
is also the various extensions that nf_conntrack itself has which
could be interesting for users that depend on that state. Would we
draw a line before providing access into those aspects of nf_conntrack
from BPF?

Beyond metadata, there is the question of write access to
nf_conntrack. Presumably if a read helper like this is added to the
BPF API, it is only balanced to also add create, update and delete
operations? No doubt if someone wants to build NAT or firewall
functionality in BPF using nf_conntrack, they will want this. Does
this take us on the track of eventually exporting the entire
nf_conntrack module (or even nf_nat) internal kernel APIs as external
BPF API?

If the BPF API is going to provide a connection tracker, I feel that
it should aim to solve connection tracking for various potential
users. This takes us from not just what this patch does, but to the
full vision of where this API goes with a connection tracker
implementation that could be reused by e.g. OVS-BPF or Cilium. At this
point, I'm not convinced why such an implementation should exist in
the BPF API rather than as a common library that can be forked and
tweaked for anyone's uses.

What do you see as the split of responsibility between BPF and other
subsystems long-term for your use case that motivates relying upon
nf_conntrack always running?

[0] https://github.com/torvalds/linux/commit/4d3a57f23dec59f0a2362e63540b2d01b37afe0a
[1] https://github.com/cilium/cilium/blob/v1.6.5/bpf/lib/common.h#L510

2020-01-24 21:47:49

by Matthew Cover

[permalink] [raw]

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

On Fri, Jan 24, 2020 at 12:11 PM Joe Stringer <[email protected]> wrote:

Joe, thank you for taking the time to respond. And thank you for your
efforts on the sk helpers; I both use them and borrowed heavily from
them in coding this submission.

>
> On Tue, Jan 21, 2020 at 12:36 PM Matt Cover <[email protected]> wrote:
> >
> > On Tue, Jan 21, 2020 at 1:20 PM Matthew Cover <[email protected]> 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.
>
> I think there's an important distinction between accessing sockets and
> accessing the connection tracker: Sockets are inherently tied to local
> processes. They consume resources regardless of what kind of fancy
> networking behaviour you desire out of the stack. Connection-tracking
> on the other hand only consumes resources if you enable features that
> explicitly require that functionality. This raises some interesting
> questions.

Sockets require local config to exist; a service must be listening.
nf_conntrack entries require local config to exist. To me, this is
not so different.

In addition to the nf_conntrack helpers, I'm hoping to add helpers for
lookups to the ipvs connection table via ip_vs_conn_in_get(). From my
perspective, this is again similar. The connection is locally
known/owned, but there is no socket. The state lives elsewhere in the
kernel, but already exists.

There is no need to pay the memory cost for native bpf ct in these
cases (i.e. when nf_conntrack is already in use or when the flow
traverses ipvs rather than terminating at a socket).

>
> The kernel disables nf_conntrack by default to alleviate the costs
> associated with it[0]. In the case of this proposal, the BPF program
> itself is trying to use nf_conntrack, so does that mean that the
> kernel should auto-enable nf_conntrack hooks for the current namespace
> (or all namespaces, given that the helper provides access into other
> namespaces as well) whenever a BPF program is loaded that uses this
> helper?

I see no reason to auto-enable nf_conntrack. When nf_conntrack is
not present, unloaded, or not configured the helpers return NULL.
This is similar to the sk helpers when no service is listening on
<daddr>:<dport>.

>
> Related side note: What if you wanted to migitate the performance
> penalty of turning on nf_conntrack by programmatically choosing
> whether to populate the ct table? Do we then need to define an
> interface that allows a BPF program to tell nf_conntrack whether or
> not to track a given connection?

This certainly could be of interest for certain use cases. Adding
such functionality is neither included nor precluded by this
submission.

Writing to an existing nf_conn could be added to this helper in the
future. Then, as an example, an XDP program could populate ct->mark
and a restore mark rule could be used to apply the mark to the skb.
This is conceptually similar to the XDP/tc interaction example.

https://github.com/xdp-project/xdp-tutorial/tree/master/advanced01-xdp-tc-interact

Adding new entries would be another helper if desired. Again, there
is nothing I see in this submission to preclude the addition of such
a helper, it simply isn't part of my current use case.

>
> More importantly, nf_conntrack has a particular view in mind of what a
> connection is and the metadata that can be associated with a
> connection. On the other hand, one of the big pulls for building
> networking functionality in BPF is to allow flexibility. Over time,
> more complex use cases will arise that demand additional metadata to
> be stored with their connections. Cilium's connection tracking entries
> provides a glimpse of this[1]. I'm sure that the OVS-BPF project would
> have similar demands. Longer term, do we encourage such projects to
> migrate to this implementation, proposing metadata extensions that are
> programmable from BPF?

Presumably, such a push would require a helper to add new ct entries
which I see as beyond the scope of this submission. However, I would
imagine that, as long as a metadata extensions approach wasn't overly
cumbersome to use, the performance of the two ct solutions would be
the deciding factor.

>
> Taking the metadata question further, there is not only the metadata
> that arbitrary BPF programs wish to associate with nf_conntrack. There
> is also the various extensions that nf_conntrack itself has which
> could be interesting for users that depend on that state. Would we
> draw a line before providing access into those aspects of nf_conntrack
> from BPF?

I'm planning to add a bpf_tcp_nf_conn() helper which gives access to
members of ip_ct_tcp. This is similar to bpf_tcp_sock() in my mind.
Are these the types of extensions you mean?

>
> Beyond metadata, there is the question of write access to
> nf_conntrack. Presumably if a read helper like this is added to the
> BPF API, it is only balanced to also add create, update and delete
> operations? No doubt if someone wants to build NAT or firewall
> functionality in BPF using nf_conntrack, they will want this. Does
> this take us on the track of eventually exporting the entire
> nf_conntrack module (or even nf_nat) internal kernel APIs as external
> BPF API?

I touched on create and update above. Delete, like create, would
almost certainly be a separate helper. This submission is not
intended to put us on that track. I do not believe it hinders an
effort such as that either. Are you worried that adding nf_conn to
bpf is a slippery slope?

>
> If the BPF API is going to provide a connection tracker, I feel that
> it should aim to solve connection tracking for various potential
> users. This takes us from not just what this patch does, but to the
> full vision of where this API goes with a connection tracker
> implementation that could be reused by e.g. OVS-BPF or Cilium. At this
> point, I'm not convinced why such an implementation should exist in
> the BPF API rather than as a common library that can be forked and
> tweaked for anyone's uses.
>
> What do you see as the split of responsibility between BPF and other
> subsystems long-term for your use case that motivates relying upon
> nf_conntrack always running?

I do not see this as relying on nf_conntrack always running; I see
it as not always relying that flow/connection ownership is determined
by socket presence/state. Sockets, nf_conns, and ip_vs_conns are all
of interest for different workloads.

>
> [0] https://github.com/torvalds/linux/commit/4d3a57f23dec59f0a2362e63540b2d01b37afe0a
> [1] https://github.com/cilium/cilium/blob/v1.6.5/bpf/lib/common.h#L510