Merge branch 'Introduce bpf_ct_set_nat_info kfunc helper'

Lorenzo Bianconi says:

====================

Introduce bpf_ct_set_nat_info kfunc helper in order to set source and
destination nat addresses/ports in a new allocated ct entry not inserted
in the connection tracking table yet.
Introduce support for per-parameter trusted args.

Changes since v2:
- use int instead of a pointer for port in bpf_ct_set_nat_info signature
- modify KF_TRUSTED_ARGS definition in order to referenced pointer constraint
  just for PTR_TO_BTF_ID
- drop patch 2/4

Changes since v1:
- enable CONFIG_NF_NAT in tools/testing/selftests/bpf/config

Kumar Kartikeya Dwivedi (1):
  bpf: Tweak definition of KF_TRUSTED_ARGS
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Documentation/bpf/kfuncs.rst

@@ -137,14 +137,22 @@ KF_ACQUIRE and KF_RET_NULL flags.
 --------------------------
 
 The KF_TRUSTED_ARGS flag is used for kfuncs taking pointer arguments. It
-indicates that the all pointer arguments will always be refcounted, and have
-their offset set to 0. It can be used to enforce that a pointer to a refcounted
-object acquired from a kfunc or BPF helper is passed as an argument to this
-kfunc without any modifications (e.g. pointer arithmetic) such that it is
-trusted and points to the original object. This flag is often used for kfuncs
-that operate (change some property, perform some operation) on an object that
-was obtained using an acquire kfunc. Such kfuncs need an unchanged pointer to
-ensure the integrity of the operation being performed on the expected object.
+indicates that the all pointer arguments will always have a guaranteed lifetime,
+and pointers to kernel objects are always passed to helpers in their unmodified
+form (as obtained from acquire kfuncs).
+
+It can be used to enforce that a pointer to a refcounted object acquired from a
+kfunc or BPF helper is passed as an argument to this kfunc without any
+modifications (e.g. pointer arithmetic) such that it is trusted and points to
+the original object.
+
+Meanwhile, it is also allowed pass pointers to normal memory to such kfuncs,
+but those can have a non-zero offset.
+
+This flag is often used for kfuncs that operate (change some property, perform
+some operation) on an object that was obtained using an acquire kfunc. Such
+kfuncs need an unchanged pointer to ensure the integrity of the operation being
+performed on the expected object.
 
 2.4.6 KF_SLEEPABLE flag
 -----------------------

kernel/bpf/btf.c

@@ -6227,7 +6227,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 				    bool processing_call)
 {
 	enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
-	bool rel = false, kptr_get = false, trusted_arg = false;
+	bool rel = false, kptr_get = false, trusted_args = false;
 	bool sleepable = false;
 	struct bpf_verifier_log *log = &env->log;
 	u32 i, nargs, ref_id, ref_obj_id = 0;
@@ -6265,7 +6265,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 		/* Only kfunc can be release func */
 		rel = kfunc_meta->flags & KF_RELEASE;
 		kptr_get = kfunc_meta->flags & KF_KPTR_GET;
-		trusted_arg = kfunc_meta->flags & KF_TRUSTED_ARGS;
+		trusted_args = kfunc_meta->flags & KF_TRUSTED_ARGS;
 		sleepable = kfunc_meta->flags & KF_SLEEPABLE;
 	}
 
@@ -6276,6 +6276,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 		enum bpf_arg_type arg_type = ARG_DONTCARE;
 		u32 regno = i + 1;
 		struct bpf_reg_state *reg = &regs[regno];
+		bool obj_ptr = false;
 
 		t = btf_type_skip_modifiers(btf, args[i].type, NULL);
 		if (btf_type_is_scalar(t)) {
@@ -6323,10 +6324,17 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 			return -EINVAL;
 		}
 
+		/* These register types have special constraints wrt ref_obj_id
+		 * and offset checks. The rest of trusted args don't.
+		 */
+		obj_ptr = reg->type == PTR_TO_CTX || reg->type == PTR_TO_BTF_ID ||
+			  reg2btf_ids[base_type(reg->type)];
+
 		/* Check if argument must be a referenced pointer, args + i has
 		 * been verified to be a pointer (after skipping modifiers).
+		 * PTR_TO_CTX is ok without having non-zero ref_obj_id.
 		 */
-		if (is_kfunc && trusted_arg && !reg->ref_obj_id) {
+		if (is_kfunc && trusted_args && (obj_ptr && reg->type != PTR_TO_CTX) && !reg->ref_obj_id) {
 			bpf_log(log, "R%d must be referenced\n", regno);
 			return -EINVAL;
 		}
@@ -6335,7 +6343,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 		ref_tname = btf_name_by_offset(btf, ref_t->name_off);
 
 		/* Trusted args have the same offset checks as release arguments */
-		if (trusted_arg || (rel && reg->ref_obj_id))
+		if ((trusted_args && obj_ptr) || (rel && reg->ref_obj_id))
 			arg_type |= OBJ_RELEASE;
 		ret = check_func_arg_reg_off(env, reg, regno, arg_type);
 		if (ret < 0)
@@ -6435,7 +6443,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 							   reg_ref_t->name_off);
 			if (!btf_struct_ids_match(log, reg_btf, reg_ref_id,
 						  reg->off, btf, ref_id,
-						  trusted_arg || (rel && reg->ref_obj_id))) {
+						  trusted_args || (rel && reg->ref_obj_id))) {
 				bpf_log(log, "kernel function %s args#%d expected pointer to %s %s but R%d has a pointer to %s %s\n",
 					func_name, i,
 					btf_type_str(ref_t), ref_tname,

net/netfilter/nf_conntrack_bpf.c

@@ -17,6 +17,7 @@
 #include <net/netfilter/nf_conntrack.h>
 #include <net/netfilter/nf_conntrack_bpf.h>
 #include <net/netfilter/nf_conntrack_core.h>
+#include <net/netfilter/nf_nat.h>
 
 /* bpf_ct_opts - Options for CT lookup helpers
  *
@@ -137,7 +138,6 @@ __bpf_nf_ct_alloc_entry(struct net *net, struct bpf_sock_tuple *bpf_tuple,
 
 	memset(&ct->proto, 0, sizeof(ct->proto));
 	__nf_ct_set_timeout(ct, timeout * HZ);
-	ct->status |= IPS_CONFIRMED;
 
 out:
 	if (opts->netns_id >= 0)
@@ -390,6 +390,7 @@ struct nf_conn *bpf_ct_insert_entry(struct nf_conn___init *nfct_i)
 	struct nf_conn *nfct = (struct nf_conn *)nfct_i;
 	int err;
 
+	nfct->status |= IPS_CONFIRMED;
 	err = nf_conntrack_hash_check_insert(nfct);
 	if (err < 0) {
 		nf_conntrack_free(nfct);
@@ -475,6 +476,49 @@ int bpf_ct_change_status(struct nf_conn *nfct, u32 status)
 	return nf_ct_change_status_common(nfct, status);
 }
 
+/* bpf_ct_set_nat_info - Set source or destination nat address
+ *
+ * Set source or destination nat address of the newly allocated
+ * nf_conn before insertion. This must be invoked for referenced
+ * PTR_TO_BTF_ID to nf_conn___init.
+ *
+ * Parameters:
+ * @nfct	- Pointer to referenced nf_conn object, obtained using
+ *		  bpf_xdp_ct_alloc or bpf_skb_ct_alloc.
+ * @addr	- Nat source/destination address
+ * @port	- Nat source/destination port. Non-positive values are
+ *		  interpreted as select a random port.
+ * @manip	- NF_NAT_MANIP_SRC or NF_NAT_MANIP_DST
+ */
+int bpf_ct_set_nat_info(struct nf_conn___init *nfct,
+			union nf_inet_addr *addr, int port,
+			enum nf_nat_manip_type manip)
+{
+#if ((IS_MODULE(CONFIG_NF_NAT) && IS_MODULE(CONFIG_NF_CONNTRACK)) || \
+     IS_BUILTIN(CONFIG_NF_NAT))
+	struct nf_conn *ct = (struct nf_conn *)nfct;
+	u16 proto = nf_ct_l3num(ct);
+	struct nf_nat_range2 range;
+
+	if (proto != NFPROTO_IPV4 && proto != NFPROTO_IPV6)
+		return -EINVAL;
+
+	memset(&range, 0, sizeof(struct nf_nat_range2));
+	range.flags = NF_NAT_RANGE_MAP_IPS;
+	range.min_addr = *addr;
+	range.max_addr = range.min_addr;
+	if (port > 0) {
+		range.flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
+		range.min_proto.all = cpu_to_be16(port);
+		range.max_proto.all = range.min_proto.all;
+	}
+
+	return nf_nat_setup_info(ct, &range, manip) == NF_DROP ? -ENOMEM : 0;
+#else
+	return -EOPNOTSUPP;
+#endif
+}
+
 __diag_pop()
 
 BTF_SET8_START(nf_ct_kfunc_set)
@@ -488,6 +532,7 @@ BTF_ID_FLAGS(func, bpf_ct_set_timeout, KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_ct_change_timeout, KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_ct_set_status, KF_TRUSTED_ARGS)
 BTF_ID_FLAGS(func, bpf_ct_change_status, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_ct_set_nat_info, KF_TRUSTED_ARGS)
 BTF_SET8_END(nf_ct_kfunc_set)
 
 static const struct btf_kfunc_id_set nf_conntrack_kfunc_set = {

tools/testing/selftests/bpf/config

@@ -63,6 +63,7 @@ CONFIG_NF_CONNTRACK=y
 CONFIG_NF_CONNTRACK_MARK=y
 CONFIG_NF_DEFRAG_IPV4=y
 CONFIG_NF_DEFRAG_IPV6=y
+CONFIG_NF_NAT=y
 CONFIG_RC_CORE=y
 CONFIG_SECURITY=y
 CONFIG_SECURITYFS=y

tools/testing/selftests/bpf/prog_tests/bpf_nf.c

@@ -27,6 +27,9 @@ enum {
 };
 
 #define TIMEOUT_MS		3000
+#define IPS_STATUS_MASK		(IPS_CONFIRMED | IPS_SEEN_REPLY | \
+				 IPS_SRC_NAT_DONE | IPS_DST_NAT_DONE | \
+				 IPS_SRC_NAT | IPS_DST_NAT)
 
 static int connect_to_server(int srv_fd)
 {
@@ -114,10 +117,11 @@ static void test_bpf_nf_ct(int mode)
 	ASSERT_GT(skel->bss->test_delta_timeout, 8, "Test for min ct timeout update");
 	ASSERT_LE(skel->bss->test_delta_timeout, 10, "Test for max ct timeout update");
 	ASSERT_EQ(skel->bss->test_insert_lookup_mark, 77, "Test for insert and lookup mark value");
-	ASSERT_EQ(skel->bss->test_status, IPS_CONFIRMED | IPS_SEEN_REPLY,
-		  "Test for ct status update ");
+	ASSERT_EQ(skel->bss->test_status, IPS_STATUS_MASK, "Test for ct status update ");
 	ASSERT_EQ(skel->data->test_exist_lookup, 0, "Test existing connection lookup");
 	ASSERT_EQ(skel->bss->test_exist_lookup_mark, 43, "Test existing connection lookup ctmark");
+	ASSERT_EQ(skel->data->test_snat_addr, 0, "Test for source natting");
+	ASSERT_EQ(skel->data->test_dnat_addr, 0, "Test for destination natting");
 end:
 	if (srv_client_fd != -1)
 		close(srv_client_fd);

tools/testing/selftests/bpf/progs/test_bpf_nf.c

 // SPDX-License-Identifier: GPL-2.0
 #include <vmlinux.h>
 #include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
 
 #define EAFNOSUPPORT 97
 #define EPROTO 71
@@ -24,6 +25,8 @@ int test_succ_lookup = -ENOENT;
 u32 test_delta_timeout = 0;
 u32 test_status = 0;
 u32 test_insert_lookup_mark = 0;
+int test_snat_addr = -EINVAL;
+int test_dnat_addr = -EINVAL;
 __be32 saddr = 0;
 __be16 sport = 0;
 __be32 daddr = 0;
@@ -54,6 +57,8 @@ void bpf_ct_set_timeout(struct nf_conn *, u32) __ksym;
 int bpf_ct_change_timeout(struct nf_conn *, u32) __ksym;
 int bpf_ct_set_status(struct nf_conn *, u32) __ksym;
 int bpf_ct_change_status(struct nf_conn *, u32) __ksym;
+int bpf_ct_set_nat_info(struct nf_conn *, union nf_inet_addr *,
+			int port, enum nf_nat_manip_type) __ksym;
 
 static __always_inline void
 nf_ct_test(struct nf_conn *(*lookup_fn)(void *, struct bpf_sock_tuple *, u32,
@@ -141,11 +146,22 @@ nf_ct_test(struct nf_conn *(*lookup_fn)(void *, struct bpf_sock_tuple *, u32,
 	ct = alloc_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4), &opts_def,
 		      sizeof(opts_def));
 	if (ct) {
+		__u16 sport = bpf_get_prandom_u32();
+		__u16 dport = bpf_get_prandom_u32();
+		union nf_inet_addr saddr = {};
+		union nf_inet_addr daddr = {};
 		struct nf_conn *ct_ins;
 
 		bpf_ct_set_timeout(ct, 10000);
 		ct->mark = 77;
 
+		/* snat */
+		saddr.ip = bpf_get_prandom_u32();
+		bpf_ct_set_nat_info(ct, &saddr, sport, NF_NAT_MANIP_SRC);
+		/* dnat */
+		daddr.ip = bpf_get_prandom_u32();
+		bpf_ct_set_nat_info(ct, &daddr, dport, NF_NAT_MANIP_DST);
+
 		ct_ins = bpf_ct_insert_entry(ct);
 		if (ct_ins) {
 			struct nf_conn *ct_lk;
@@ -153,6 +169,17 @@ nf_ct_test(struct nf_conn *(*lookup_fn)(void *, struct bpf_sock_tuple *, u32,
 			ct_lk = lookup_fn(ctx, &bpf_tuple, sizeof(bpf_tuple.ipv4),
 					  &opts_def, sizeof(opts_def));
 			if (ct_lk) {
+				struct nf_conntrack_tuple *tuple;
+
+				/* check snat and dnat addresses */
+				tuple = &ct_lk->tuplehash[IP_CT_DIR_REPLY].tuple;
+				if (tuple->dst.u3.ip == saddr.ip &&
+				    tuple->dst.u.all == bpf_htons(sport))
+					test_snat_addr = 0;
+				if (tuple->src.u3.ip == daddr.ip &&
+				    tuple->src.u.all == bpf_htons(dport))
+					test_dnat_addr = 0;
+
 				/* update ct entry timeout */
 				bpf_ct_change_timeout(ct_lk, 10000);
 				test_delta_timeout = ct_lk->timeout - bpf_jiffies64();