netdev - [RFC PATCH iproute2] Add ability to specify eBPF pin path

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Date: Wed, 3 May 2023 13:33:49 -0400
From: Max Tottenham <mtottenh@...mai.com>
To: <netdev@...r.kernel.org>
CC: <johunt@...mai.com>, Max Tottenham <mtottenh@...mai.com>
Subject: [RFC PATCH iproute2] Add ability to specify eBPF pin path

---
 include/bpf_util.h |  1 +
 lib/bpf_legacy.c   | 11 +++++++++--
 lib/bpf_libbpf.c   | 16 +++++++++-------
 tc/f_bpf.c         |  4 +++-
 4 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/include/bpf_util.h b/include/bpf_util.h
index 6a5f8ec6..e7ad643b 100644
--- a/include/bpf_util.h
+++ b/include/bpf_util.h
@@ -70,6 +70,7 @@ struct bpf_cfg_in {
 	const char *section;
 	const char *prog_name;
 	const char *uds;
+	const char *pin_path;
 	enum bpf_prog_type type;
 	enum bpf_mode mode;
 	__u32 ifindex;
diff --git a/lib/bpf_legacy.c b/lib/bpf_legacy.c
index 8ac64235..18b2760c 100644
--- a/lib/bpf_legacy.c
+++ b/lib/bpf_legacy.c
@@ -827,7 +827,7 @@ static int bpf_obj_pinned(const char *pathname, enum bpf_prog_type type)
 
 static int bpf_do_parse(struct bpf_cfg_in *cfg, const bool *opt_tbl)
 {
-	const char *file, *section, *uds_name, *prog_name;
+	const char *file, *section, *uds_name, *prog_name, *pin_path;
 	bool verbose = false;
 	int i, ret, argc;
 	char **argv;
@@ -858,7 +858,7 @@ static int bpf_do_parse(struct bpf_cfg_in *cfg, const bool *opt_tbl)
 	}
 
 	NEXT_ARG();
-	file = section = uds_name = prog_name = NULL;
+	file = section = uds_name = prog_name = pin_path = NULL;
 	if (cfg->mode == EBPF_OBJECT || cfg->mode == EBPF_PINNED) {
 		file = *argv;
 		NEXT_ARG_FWD();
@@ -901,6 +901,12 @@ static int bpf_do_parse(struct bpf_cfg_in *cfg, const bool *opt_tbl)
 			NEXT_ARG_FWD();
 		}
 
+		if (argc > 0 && strcmp(*argv, "pin_path") == 0) {
+			NEXT_ARG();
+			pin_path = *argv;
+			NEXT_ARG_FWD();
+		}
+
 		if (__bpf_prog_meta[cfg->type].may_uds_export) {
 			uds_name = getenv(BPF_ENV_UDS);
 			if (argc > 0 && !uds_name &&
@@ -939,6 +945,7 @@ static int bpf_do_parse(struct bpf_cfg_in *cfg, const bool *opt_tbl)
 	cfg->argv    = argv;
 	cfg->verbose = verbose;
 	cfg->prog_name = prog_name;
+	cfg->pin_path = pin_path;
 
 	return ret;
 }
diff --git a/lib/bpf_libbpf.c b/lib/bpf_libbpf.c
index e1c211a1..6c4e18f7 100644
--- a/lib/bpf_libbpf.c
+++ b/lib/bpf_libbpf.c
@@ -226,7 +226,7 @@ static int handle_legacy_maps(struct bpf_object *obj)
 
 	bpf_object__for_each_map(map, obj) {
 		map_name = bpf_map__name(map);
-
+		fprintf(stderr, "Processing map: %s\n", map_name);
 		ret = handle_legacy_map_in_map(obj, map, map_name);
 		if (ret)
 			return ret;
@@ -277,16 +277,18 @@ static int load_bpf_object(struct bpf_cfg_in *cfg)
 	char root_path[PATH_MAX];
 	struct bpf_map *map;
 	int prog_fd, ret = 0;
-
-	ret = iproute2_get_root_path(root_path, PATH_MAX);
-	if (ret)
-		return ret;
-
+	if (cfg->pin_path) {
+		strncpy(root_path , cfg->pin_path, PATH_MAX);
+	} else {
+		ret = iproute2_get_root_path(root_path, PATH_MAX);
+		if (ret)
+			return ret;
+	}
 	DECLARE_LIBBPF_OPTS(bpf_object_open_opts, open_opts,
 			.relaxed_maps = true,
 			.pin_root_path = root_path,
 	);
-
+	fprintf(stderr, "About to bpf_object__open_file()\n");
 	obj = bpf_object__open_file(cfg->object, &open_opts);
 	if (libbpf_get_error(obj)) {
 		fprintf(stderr, "ERROR: opening BPF object file failed\n");
diff --git a/tc/f_bpf.c b/tc/f_bpf.c
index a6d4875f..4eb3e817 100644
--- a/tc/f_bpf.c
+++ b/tc/f_bpf.c
@@ -28,7 +28,7 @@ static void explain(void)
 		"\n"
 		"eBPF use case:\n"
 		" object-file FILE [ section CLS_NAME ] [ export UDS_FILE ]"
-		" [ verbose ] [ direct-action ] [ skip_hw | skip_sw ]\n"
+		" [ verbose ] [ direct-action ] [ skip_hw | skip_sw ] [pin_path PATH]\n"
 		" object-pinned FILE [ direct-action ] [ skip_hw | skip_sw ]\n"
 		"\n"
 		"Common remaining options:\n"
@@ -48,6 +48,8 @@ static void explain(void)
 		"Where UDS_FILE points to a unix domain socket file in order\n"
 		"to hand off control of all created eBPF maps to an agent.\n"
 		"\n"
+		"Where PATH points to a path under bpffs where all eBPF maps will be pinned.\n"
+		"\n"
 		"ACTION_SPEC := ... look at individual actions\n"
 		"NOTE: CLASSID is parsed as hexadecimal input.\n",
 		bpf_prog_to_default_section(bpf_type));
-- 
2.25.1