[PATCH bpf-next v3 10/16] bpfilter: add target structure
From: Quentin Deslandes
Date: Fri Dec 23 2022 - 19:40:34 EST
Add target structure, containing a pointer to a target_ops structure and
a pointer to an xt_entry_target structure. The later containing the
payload for the target's type.
target_ops structure provides two operations:
- check: validates the target.
- gen_inline: generate the eBPF bytecode for the target.
All target_ops are kept in a map by their name.
Co-developed-by: Dmitrii Banshchikov <me@xxxxxxxxxxxxx>
Signed-off-by: Dmitrii Banshchikov <me@xxxxxxxxxxxxx>
Signed-off-by: Quentin Deslandes <qde@xxxxxxxx>
---
net/bpfilter/Makefile | 2 +-
net/bpfilter/context.c | 42 ++++
net/bpfilter/context.h | 1 +
net/bpfilter/target.c | 203 ++++++++++++++++++
net/bpfilter/target.h | 57 +++++
.../testing/selftests/bpf/bpfilter/.gitignore | 1 +
tools/testing/selftests/bpf/bpfilter/Makefile | 5 +-
.../selftests/bpf/bpfilter/bpfilter_util.h | 23 ++
.../selftests/bpf/bpfilter/test_target.c | 83 +++++++
9 files changed, 415 insertions(+), 2 deletions(-)
create mode 100644 net/bpfilter/target.c
create mode 100644 net/bpfilter/target.h
create mode 100644 tools/testing/selftests/bpf/bpfilter/test_target.c
diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile
index 345341a9ee30..7e642e0ae932 100644
--- a/net/bpfilter/Makefile
+++ b/net/bpfilter/Makefile
@@ -13,7 +13,7 @@ $(LIBBPF_A):
userprogs := bpfilter_umh
bpfilter_umh-objs := main.o logger.o map-common.o
bpfilter_umh-objs += context.o codegen.o
-bpfilter_umh-objs += match.o xt_udp.o
+bpfilter_umh-objs += match.o xt_udp.o target.o
bpfilter_umh-userldlibs := $(LIBBPF_A) -lelf -lz
userccflags += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi
diff --git a/net/bpfilter/context.c b/net/bpfilter/context.c
index f420fb8b6507..ac07b678baa7 100644
--- a/net/bpfilter/context.c
+++ b/net/bpfilter/context.c
@@ -15,6 +15,7 @@
#include "logger.h"
#include "map-common.h"
#include "match.h"
+#include "target.h"
static const struct match_ops *match_ops[] = { &xt_udp };
@@ -42,6 +43,35 @@ static int init_match_ops_map(struct context *ctx)
return 0;
}
+static const struct target_ops *target_ops[] = {
+ &standard_target_ops,
+ &error_target_ops
+};
+
+static int init_target_ops_map(struct context *ctx)
+{
+ int r;
+
+ r = create_map(&ctx->target_ops_map, ARRAY_SIZE(target_ops));
+ if (r) {
+ BFLOG_ERR("failed to create targets map: %s", STRERR(r));
+ return r;
+ }
+
+ for (int i = 0; i < ARRAY_SIZE(target_ops); ++i) {
+ const struct target_ops *t = target_ops[i];
+
+ r = map_upsert(&ctx->target_ops_map, t->name, (void *)t);
+ if (r) {
+ BFLOG_ERR("failed to upsert in targets map: %s",
+ STRERR(r));
+ return r;
+ }
+ }
+
+ return 0;
+}
+
int create_context(struct context *ctx)
{
int r;
@@ -52,10 +82,22 @@ int create_context(struct context *ctx)
return r;
}
+ r = init_target_ops_map(ctx);
+ if (r) {
+ BFLOG_ERR("failed to initialize targets map: %s", STRERR(r));
+ goto err_free_match_ops_map;
+ }
+
return 0;
+
+err_free_match_ops_map:
+ free_map(&ctx->match_ops_map);
+
+ return r;
}
void free_context(struct context *ctx)
{
+ free_map(&ctx->target_ops_map);
free_map(&ctx->match_ops_map);
}
diff --git a/net/bpfilter/context.h b/net/bpfilter/context.h
index e36aa8ebf57e..f9c34a9968b8 100644
--- a/net/bpfilter/context.h
+++ b/net/bpfilter/context.h
@@ -11,6 +11,7 @@
struct context {
struct hsearch_data match_ops_map;
+ struct hsearch_data target_ops_map;
};
int create_context(struct context *ctx);
diff --git a/net/bpfilter/target.c b/net/bpfilter/target.c
new file mode 100644
index 000000000000..a96ec7735c0e
--- /dev/null
+++ b/net/bpfilter/target.c
@@ -0,0 +1,203 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2021 Telegram FZ-LLC
+ * Copyright (c) 2022 Meta Platforms, Inc. and affiliates.
+ */
+
+#define _GNU_SOURCE
+
+#include "target.h"
+
+#include <linux/err.h>
+#include <linux/filter.h>
+#include <linux/list.h>
+#include <linux/netfilter/x_tables.h>
+
+#include <errno.h>
+#include <string.h>
+
+#include "codegen.h"
+#include "context.h"
+#include "logger.h"
+#include "map-common.h"
+
+static const struct target_ops *target_ops_map_find(struct hsearch_data *map,
+ const char *name)
+{
+ const size_t len = strnlen(name, BPFILTER_EXTENSION_MAXNAMELEN);
+
+ if (len < 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_ERR("unsupported verdict: %d", standard_target->verdict);
+
+ return -EINVAL;
+}
+
+static int standard_target_gen_inline(struct codegen *ctx,
+ const struct target *target)
+{
+ const struct bpfilter_ipt_standard_target *standard_target;
+ int r;
+
+ standard_target = (const struct bpfilter_ipt_standard_target *)target->ipt_target;
+
+ if (standard_target->verdict >= 0) {
+ struct codegen_subprog_desc *subprog;
+ struct codegen_fixup_desc *fixup;
+
+ subprog = malloc(sizeof(*subprog));
+ if (!subprog) {
+ BFLOG_ERR("out of memory");
+ return -ENOMEM;
+ }
+
+ INIT_LIST_HEAD(&subprog->list);
+ subprog->type = CODEGEN_SUBPROG_USER_CHAIN;
+ subprog->insn = 0;
+ subprog->offset = standard_target->verdict;
+
+ fixup = malloc(sizeof(*fixup));
+ if (!fixup) {
+ BFLOG_ERR("out of memory");
+ free(subprog);
+ return -ENOMEM;
+ }
+
+ INIT_LIST_HEAD(&fixup->list);
+ fixup->type = CODEGEN_FIXUP_JUMP_TO_CHAIN;
+ fixup->insn = ctx->len_cur;
+ fixup->offset = standard_target->verdict;
+
+ list_add_tail(&fixup->list, &ctx->fixup);
+
+ r = codegen_push_awaiting_subprog(ctx, subprog);
+ if (r) {
+ BFLOG_ERR("failed to push awaiting subprog: %s",
+ STRERR(r));
+ return r;
+ }
+
+ EMIT(ctx, BPF_JMP_IMM(BPF_JA, 0, 0, 0));
+
+ return 0;
+ }
+
+ if (standard_target->verdict == BPFILTER_RETURN) {
+ EMIT(ctx, BPF_EXIT_INSN());
+ return 0;
+ }
+
+ r = ctx->codegen_ops->emit_ret_code(ctx, convert_verdict(standard_target->verdict));
+ if (r) {
+ BFLOG_ERR("failed to emit return code: %s", STRERR(r));
+ return r;
+ }
+
+ EMIT(ctx, BPF_EXIT_INSN());
+
+ return 0;
+}
+
+const struct target_ops standard_target_ops = {
+ .name = "",
+ .revision = 0,
+ .size = sizeof(struct xt_standard_target),
+ .check = standard_target_check,
+ .gen_inline = standard_target_gen_inline,
+};
+
+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_ERR("failed to check error target: too long errorname");
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int error_target_gen_inline(struct codegen *ctx,
+ const struct target *target)
+{
+ return -EINVAL;
+}
+
+const struct target_ops error_target_ops = {
+ .name = "ERROR",
+ .revision = 0,
+ .size = sizeof(struct xt_error_target),
+ .check = error_target_check,
+ .gen_inline = error_target_gen_inline,
+};
+
+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 r;
+
+ if (strnlen(ipt_target->u.user.name, maxlen) == maxlen) {
+ BFLOG_ERR("cannot init target: too long target name '%s'",
+ ipt_target->u.user.name);
+ return -EINVAL;
+ }
+
+ found = target_ops_map_find(&ctx->target_ops_map,
+ ipt_target->u.user.name);
+ if (IS_ERR(found)) {
+ BFLOG_ERR("cannot find target by name '%s' in map",
+ 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_ERR("invalid target size: '%s'", ipt_target->u.user.name);
+ return -EINVAL;
+ }
+
+ r = found->check(ctx, ipt_target);
+ if (r)
+ return r;
+
+ 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..57bae658b6a2
--- /dev/null
+++ b/net/bpfilter/target.h
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2021 Telegram FZ-LLC
+ * Copyright (c) 2022 Meta Platforms, Inc. and affiliates.
+ */
+
+#ifndef NET_BPFILTER_TARGET_H
+#define NET_BPFILTER_TARGET_H
+
+#include "../../include/uapi/linux/bpfilter.h"
+
+#include <stdint.h>
+
+struct codegen;
+struct context;
+struct target;
+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);
+ int (*gen_inline)(struct codegen *ctx, const struct target *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 f84cc86493df..89912a44109f 100644
--- a/tools/testing/selftests/bpf/bpfilter/.gitignore
+++ b/tools/testing/selftests/bpf/bpfilter/.gitignore
@@ -3,3 +3,4 @@ tools/**
test_map
test_match
test_xt_udp
+test_target
diff --git a/tools/testing/selftests/bpf/bpfilter/Makefile b/tools/testing/selftests/bpf/bpfilter/Makefile
index 97f8d596de36..587951d14c0c 100644
--- a/tools/testing/selftests/bpf/bpfilter/Makefile
+++ b/tools/testing/selftests/bpf/bpfilter/Makefile
@@ -13,6 +13,7 @@ CFLAGS += -Wall -g -pthread -I$(TOOLSINCDIR) -I$(APIDIR) -I$(BPFILTERSRCDIR)
TEST_GEN_PROGS += test_map
TEST_GEN_PROGS += test_match
TEST_GEN_PROGS += test_xt_udp
+TEST_GEN_PROGS += test_target
KSFT_KHDR_INSTALL := 1
@@ -37,11 +38,13 @@ $(BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile) \
BPFILTER_MAP_SRCS := $(BPFILTERSRCDIR)/map-common.c
BPFILTER_CODEGEN_SRCS := $(BPFILTERSRCDIR)/codegen.c $(BPFOBJ) -lelf -lz
BPFILTER_MATCH_SRCS := $(BPFILTERSRCDIR)/match.c $(BPFILTERSRCDIR)/xt_udp.c
+BPFILTER_TARGET_SRCS := $(BPFILTERSRCDIR)/target.c
BPFILTER_COMMON_SRCS := $(BPFILTER_MAP_SRCS) $(BPFILTER_CODEGEN_SRCS)
BPFILTER_COMMON_SRCS += $(BPFILTERSRCDIR)/context.c $(BPFILTERSRCDIR)/logger.c
-BPFILTER_COMMON_SRCS += $(BPFILTER_MATCH_SRCS)
+BPFILTER_COMMON_SRCS += $(BPFILTER_MATCH_SRCS) $(BPFILTER_TARGET_SRCS)
$(OUTPUT)/test_map: test_map.c $(BPFILTER_MAP_SRCS)
$(OUTPUT)/test_match: test_match.c $(BPFILTER_COMMON_SRCS)
$(OUTPUT)/test_xt_udp: test_xt_udp.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
index 705fd1777a67..0d6a6bee5514 100644
--- a/tools/testing/selftests/bpf/bpfilter/bpfilter_util.h
+++ b/tools/testing/selftests/bpf/bpfilter/bpfilter_util.h
@@ -19,4 +19,27 @@ static inline void init_entry_match(struct xt_entry_match *match,
match->u.user.revision = revision;
}
+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..0ebe4b052a9b
--- /dev/null
+++ b/tools/testing/selftests/bpf/bpfilter/test_target.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define _GNU_SOURCE
+
+#include <linux/bpfilter.h>
+#include <linux/netfilter/x_tables.h>
+
+#include "../../kselftest_harness.h"
+
+#include "context.h"
+#include "logger.h"
+#include "target.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)
+{
+ logger_set_file(stderr);
+ ASSERT_EQ(0, create_context(&self->ctx));
+
+ 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)
+{
+ logger_set_file(stderr);
+ ASSERT_EQ(0, create_context(&self->ctx));
+
+ 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
--
2.38.1