Date:   Thu,  3 Jun 2021 14:14:21 +0400
From:   Dmitrii Banshchikov <me@...que.spb.ru>
To:     bpf@...r.kernel.org
Cc:     Dmitrii Banshchikov <me@...que.spb.ru>, ast@...nel.org,
        davem@...emloft.net, daniel@...earbox.net, andrii@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org,
        netdev@...r.kernel.org, rdna@...com
Subject: [PATCH bpf-next v1 06/10] bpfilter: Add struct target

struct target_ops defines polymorphic interface for targets. A target
consists of pointers to struct target_ops and struct xt_entry_target
which contains a payload for the target's type.

All target_ops are kept in a map by their name.

Signed-off-by: Dmitrii Banshchikov <me@...que.spb.ru>
---
 .clang-format                                 |   2 +-
 net/bpfilter/Makefile                         |   2 +-
 net/bpfilter/context.c                        |  36 +++++-
 net/bpfilter/context.h                        |   1 +
 net/bpfilter/target.c                         | 118 ++++++++++++++++++
 net/bpfilter/target.h                         |  49 ++++++++
 .../testing/selftests/bpf/bpfilter/.gitignore |   1 +
 tools/testing/selftests/bpf/bpfilter/Makefile |   7 +-
 .../selftests/bpf/bpfilter/bpfilter_util.h    |  31 +++++
 .../selftests/bpf/bpfilter/test_target.c      |  85 +++++++++++++
 10 files changed, 327 insertions(+), 5 deletions(-)
 create mode 100644 net/bpfilter/target.c
 create mode 100644 net/bpfilter/target.h
 create mode 100644 tools/testing/selftests/bpf/bpfilter/bpfilter_util.h
 create mode 100644 tools/testing/selftests/bpf/bpfilter/test_target.c

diff --git a/.clang-format b/.clang-format
index c24b147cac01..3212542df113 100644
--- a/.clang-format
+++ b/.clang-format
@@ -52,7 +52,7 @@ BreakConstructorInitializersBeforeComma: false
 #BreakConstructorInitializers: BeforeComma # Unknown to clang-format-4.0
 BreakAfterJavaFieldAnnotations: false
 BreakStringLiterals: false
-ColumnLimit: 80
+ColumnLimit: 100
 CommentPragmas: '^ IWYU pragma:'
 #CompactNamespaces: false # Unknown to clang-format-4.0
 ConstructorInitializerAllOnOneLineOrOnePerLine: false
diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile
index 59f2d35c1627..031c9dd40d2d 100644
--- a/net/bpfilter/Makefile
+++ b/net/bpfilter/Makefile
@@ -4,7 +4,7 @@
 #
 
 userprogs := bpfilter_umh
-bpfilter_umh-objs := main.o map-common.o match.o context.o
+bpfilter_umh-objs := main.o map-common.o context.o match.o target.o
 bpfilter_umh-objs += xt_udp.o
 userccflags += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi
 
diff --git a/net/bpfilter/context.c b/net/bpfilter/context.c
index 6b6203dd22a7..6e186399609e 100644
--- a/net/bpfilter/context.c
+++ b/net/bpfilter/context.c
@@ -12,6 +12,7 @@
 
 #include "map-common.h"
 #include "match.h"
+#include "target.h"
 
 static int init_match_ops_map(struct context *ctx)
 {
@@ -33,12 +34,45 @@ static int init_match_ops_map(struct context *ctx)
 	return 0;
 }
 
+static int init_target_ops_map(struct context *ctx)
+{
+	const struct target_ops *target_ops[] = { &standard_target_ops, &error_target_ops };
+	int i, err;
+
+	err = create_map(&ctx->target_ops_map, ARRAY_SIZE(target_ops));
+	if (err)
+		return err;
+
+	for (i = 0; i < ARRAY_SIZE(target_ops); ++i) {
+		const struct target_ops *t = target_ops[i];
+
+		err = map_insert(&ctx->target_ops_map, t->name, (void *)t);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
 int create_context(struct context *ctx)
 {
-	return init_match_ops_map(ctx);
+	int err;
+
+	err = init_match_ops_map(ctx);
+	if (err)
+		return err;
+
+	err = init_target_ops_map(ctx);
+	if (err) {
+		free_map(&ctx->match_ops_map);
+		return err;
+	}
+
+	return 0;
 }
 
 void free_context(struct context *ctx)
 {
 	free_map(&ctx->match_ops_map);
+	free_map(&ctx->target_ops_map);
 }
diff --git a/net/bpfilter/context.h b/net/bpfilter/context.h
index 60bb525843b0..ed268259adcc 100644
--- a/net/bpfilter/context.h
+++ b/net/bpfilter/context.h
@@ -15,6 +15,7 @@
 struct context {
 	FILE *log_file;
 	struct hsearch_data match_ops_map;
+	struct hsearch_data target_ops_map;
 };
 
 #define BFLOG_IMPL(ctx, level, fmt, ...)                                                           \
diff --git a/net/bpfilter/target.c b/net/bpfilter/target.c
new file mode 100644
index 000000000000..f87ef719ea4d
--- /dev/null
+++ b/net/bpfilter/target.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2021 Telegram FZ-LLC
+ */
+
+#define _GNU_SOURCE
+
+#include "target.h"
+
+#include <linux/err.h>
+#include <linux/netfilter/x_tables.h>
+
+#include <errno.h>
+#include <string.h>
+
+#include "context.h"
+#include "map-common.h"
+
+static const struct target_ops *target_ops_map_find(struct hsearch_data *map, const char *name)
+{
+	const size_t namelen = strnlen(name, BPFILTER_EXTENSION_MAXNAMELEN);
+
+	if (namelen < BPFILTER_EXTENSION_MAXNAMELEN)
+		return map_find(map, name);
+
+	return ERR_PTR(-EINVAL);
+}
+
+static int standard_target_check(struct context *ctx, const struct bpfilter_ipt_target *ipt_target)
+{
+	const struct bpfilter_ipt_standard_target *standard_target;
+
+	standard_target = (const struct bpfilter_ipt_standard_target *)ipt_target;
+
+	// Positive values of verdict denote a jump offset into a blob.
+	if (standard_target->verdict > 0)
+		return 0;
+
+	// Special values like ACCEPT, DROP, RETURN are encoded as negative values.
+	if (standard_target->verdict < 0) {
+		if (standard_target->verdict == BPFILTER_RETURN)
+			return 0;
+
+		switch (convert_verdict(standard_target->verdict)) {
+		case BPFILTER_NF_ACCEPT:
+		case BPFILTER_NF_DROP:
+		case BPFILTER_NF_QUEUE:
+			return 0;
+		}
+	}
+
+	BFLOG_DEBUG(ctx, "invalid verdict: %d\n", standard_target->verdict);
+
+	return -EINVAL;
+}
+
+const struct target_ops standard_target_ops = {
+	.name = "",
+	.revision = 0,
+	.size = sizeof(struct xt_standard_target),
+	.check = standard_target_check,
+};
+
+static int error_target_check(struct context *ctx, const struct bpfilter_ipt_target *ipt_target)
+{
+	const struct bpfilter_ipt_error_target *error_target;
+	size_t maxlen;
+
+	error_target = (const struct bpfilter_ipt_error_target *)&ipt_target;
+	maxlen = sizeof(error_target->error_name);
+	if (strnlen(error_target->error_name, maxlen) == maxlen) {
+		BFLOG_DEBUG(ctx, "cannot check error target: too long errorname\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+const struct target_ops error_target_ops = {
+	.name = "ERROR",
+	.revision = 0,
+	.size = sizeof(struct xt_error_target),
+	.check = error_target_check,
+};
+
+int init_target(struct context *ctx, const struct bpfilter_ipt_target *ipt_target,
+		struct target *target)
+{
+	const size_t maxlen = sizeof(ipt_target->u.user.name);
+	const struct target_ops *found;
+	int err;
+
+	if (strnlen(ipt_target->u.user.name, maxlen) == maxlen) {
+		BFLOG_DEBUG(ctx, "cannot init target: too long target name\n");
+		return -EINVAL;
+	}
+
+	found = target_ops_map_find(&ctx->target_ops_map, ipt_target->u.user.name);
+	if (IS_ERR(found)) {
+		BFLOG_DEBUG(ctx, "cannot find target by name: '%s'\n", ipt_target->u.user.name);
+		return PTR_ERR(found);
+	}
+
+	if (found->size != ipt_target->u.target_size ||
+	    found->revision != ipt_target->u.user.revision) {
+		BFLOG_DEBUG(ctx, "invalid target: '%s'\n", ipt_target->u.user.name);
+		return -EINVAL;
+	}
+
+	err = found->check(ctx, ipt_target);
+	if (err)
+		return err;
+
+	target->target_ops = found;
+	target->ipt_target = ipt_target;
+
+	return 0;
+}
diff --git a/net/bpfilter/target.h b/net/bpfilter/target.h
new file mode 100644
index 000000000000..e27816d73cc2
--- /dev/null
+++ b/net/bpfilter/target.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2021 Telegram FZ-LLC
+ */
+
+#ifndef NET_BPFILTER_TARGET_H
+#define NET_BPFILTER_TARGET_H
+
+#include "../../include/uapi/linux/bpfilter.h"
+
+#include <stdint.h>
+
+struct context;
+struct target_ops_map;
+
+struct target_ops {
+	char name[BPFILTER_EXTENSION_MAXNAMELEN];
+	uint8_t revision;
+	uint16_t size;
+	int (*check)(struct context *ctx, const struct bpfilter_ipt_target *ipt_target);
+};
+
+struct target {
+	const struct target_ops *target_ops;
+	const struct bpfilter_ipt_target *ipt_target;
+};
+
+extern const struct target_ops standard_target_ops;
+extern const struct target_ops error_target_ops;
+
+/* Restore verdict's special value(ACCEPT, DROP, etc.) from its negative representation. */
+static inline int convert_verdict(int verdict)
+{
+	return -verdict - 1;
+}
+
+static inline int standard_target_verdict(const struct bpfilter_ipt_target *ipt_target)
+{
+	const struct bpfilter_ipt_standard_target *standard_target;
+
+	standard_target = (const struct bpfilter_ipt_standard_target *)ipt_target;
+
+	return standard_target->verdict;
+}
+
+int init_target(struct context *ctx, const struct bpfilter_ipt_target *ipt_target,
+		struct target *target);
+
+#endif // NET_BPFILTER_TARGET_H
diff --git a/tools/testing/selftests/bpf/bpfilter/.gitignore b/tools/testing/selftests/bpf/bpfilter/.gitignore
index 9250411fa7aa..7e077f506af1 100644
--- a/tools/testing/selftests/bpf/bpfilter/.gitignore
+++ b/tools/testing/selftests/bpf/bpfilter/.gitignore
@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0-only
 test_map
 test_match
+test_target
diff --git a/tools/testing/selftests/bpf/bpfilter/Makefile b/tools/testing/selftests/bpf/bpfilter/Makefile
index 0ef156cdb198..a11775e8b5af 100644
--- a/tools/testing/selftests/bpf/bpfilter/Makefile
+++ b/tools/testing/selftests/bpf/bpfilter/Makefile
@@ -10,15 +10,18 @@ CFLAGS += -Wall -g -pthread -I$(TOOLSINCDIR) -I$(APIDIR) -I$(BPFILTERSRCDIR)
 
 TEST_GEN_PROGS += test_map
 TEST_GEN_PROGS += test_match
+TEST_GEN_PROGS += test_target
 
 KSFT_KHDR_INSTALL := 1
 
 include ../../lib.mk
 
 BPFILTER_MATCH_SRCS := $(BPFILTERSRCDIR)/match.c $(BPFILTERSRCDIR)/xt_udp.c
+BPFILTER_TARGET_SRCS := $(BPFILTERSRCDIR)/target.c
 
 BPFILTER_COMMON_SRCS := $(BPFILTERSRCDIR)/map-common.c $(BPFILTERSRCDIR)/context.c
-BPFILTER_COMMON_SRCS += $(BPFILTER_MATCH_SRCS)
+BPFILTER_COMMON_SRCS += $(BPFILTER_MATCH_SRCS) $(BPFILTER_TARGET_SRCS)
 
 $(OUTPUT)/test_map: test_map.c $(BPFILTERSRCDIR)/map-common.c
-$(OUTPUT)/test_match: test_match.c $(BPFILTER_COMMON_SRCS) $(BPFILTER_MATCH_SRCS)
+$(OUTPUT)/test_match: test_match.c $(BPFILTER_COMMON_SRCS)
+$(OUTPUT)/test_target: test_target.c $(BPFILTER_COMMON_SRCS)
diff --git a/tools/testing/selftests/bpf/bpfilter/bpfilter_util.h b/tools/testing/selftests/bpf/bpfilter/bpfilter_util.h
new file mode 100644
index 000000000000..d82ff86f280e
--- /dev/null
+++ b/tools/testing/selftests/bpf/bpfilter/bpfilter_util.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef BPFILTER_UTIL_H
+#define BPFILTER_UTIL_H
+
+#include <linux/bpfilter.h>
+#include <linux/netfilter/x_tables.h>
+
+#include <stdio.h>
+
+static inline void init_standard_target(struct xt_standard_target *ipt_target, int revision,
+					int verdict)
+{
+	snprintf(ipt_target->target.u.user.name, sizeof(ipt_target->target.u.user.name), "%s",
+		 BPFILTER_STANDARD_TARGET);
+	ipt_target->target.u.user.revision = revision;
+	ipt_target->target.u.user.target_size = sizeof(*ipt_target);
+	ipt_target->verdict = verdict;
+}
+
+static inline void init_error_target(struct xt_error_target *ipt_target, int revision,
+				     const char *error_name)
+{
+	snprintf(ipt_target->target.u.user.name, sizeof(ipt_target->target.u.user.name), "%s",
+		 BPFILTER_ERROR_TARGET);
+	ipt_target->target.u.user.revision = revision;
+	ipt_target->target.u.user.target_size = sizeof(*ipt_target);
+	snprintf(ipt_target->errorname, sizeof(ipt_target->errorname), "%s", error_name);
+}
+
+#endif // BPFILTER_UTIL_H
diff --git a/tools/testing/selftests/bpf/bpfilter/test_target.c b/tools/testing/selftests/bpf/bpfilter/test_target.c
new file mode 100644
index 000000000000..6765497b53c4
--- /dev/null
+++ b/tools/testing/selftests/bpf/bpfilter/test_target.c
@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define _GNU_SOURCE
+
+#include "context.h"
+#include "target.h"
+
+#include <linux/bpfilter.h>
+#include <linux/err.h>
+
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter_ipv4/ip_tables.h>
+
+#include "../../kselftest_harness.h"
+
+#include "bpfilter_util.h"
+
+FIXTURE(test_standard_target)
+{
+	struct context ctx;
+	struct xt_standard_target ipt_target;
+	struct target target;
+};
+
+FIXTURE_VARIANT(test_standard_target)
+{
+	int verdict;
+};
+
+FIXTURE_VARIANT_ADD(test_standard_target, accept) {
+	.verdict = -BPFILTER_NF_ACCEPT - 1,
+};
+
+FIXTURE_VARIANT_ADD(test_standard_target, drop) {
+	.verdict = -BPFILTER_NF_DROP - 1,
+};
+
+FIXTURE_SETUP(test_standard_target)
+{
+	ASSERT_EQ(0, create_context(&self->ctx));
+	self->ctx.log_file = stderr;
+
+	memset(&self->ipt_target, 0, sizeof(self->ipt_target));
+	init_standard_target(&self->ipt_target, 0, variant->verdict);
+}
+
+FIXTURE_TEARDOWN(test_standard_target)
+{
+	free_context(&self->ctx);
+}
+
+TEST_F(test_standard_target, init)
+{
+	ASSERT_EQ(0, init_target(&self->ctx, (const struct bpfilter_ipt_target *)&self->ipt_target,
+				 &self->target));
+}
+
+FIXTURE(test_error_target)
+{
+	struct context ctx;
+	struct xt_error_target ipt_target;
+	struct target target;
+};
+
+FIXTURE_SETUP(test_error_target)
+{
+	ASSERT_EQ(0, create_context(&self->ctx));
+	self->ctx.log_file = stderr;
+
+	memset(&self->ipt_target, 0, sizeof(self->ipt_target));
+	init_error_target(&self->ipt_target, 0, "x");
+}
+
+FIXTURE_TEARDOWN(test_error_target)
+{
+	free_context(&self->ctx);
+}
+
+TEST_F(test_error_target, init)
+{
+	ASSERT_EQ(0, init_target(&self->ctx, (const struct bpfilter_ipt_target *)&self->ipt_target,
+				 &self->target));
+}
+
+TEST_HARNESS_MAIN
-- 
2.25.1

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