libbpf: add xdp program name support

In bpf program, only the program name is unique. Before this patch, if there
are multiple programs with the same section name, only the first program
will be attached. With program name support, users could specify the exact
program they want to attach.

Note this feature is only supported when iproute2 build with libbpf.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David Ahern <dsahern@kernel.org>

include/bpf_util.h

@@ -68,6 +68,7 @@ enum bpf_mode {
 struct bpf_cfg_in {
 	const char *object;
 	const char *section;
+	const char *prog_name;
 	const char *uds;
 	enum bpf_prog_type type;
 	enum bpf_mode mode;

ip/iplink.c

@@ -107,7 +107,11 @@ void iplink_usage(void)
 		"			 [ node_guid EUI64 ]\n"
 		"			 [ port_guid EUI64 ] ]\n"
 		"		[ { xdp | xdpgeneric | xdpdrv | xdpoffload } { off |\n"
+#ifdef HAVE_LIBBPF
+		"			  object FILE [ { section | program } NAME ] [ verbose ] |\n"
+#else
 		"			  object FILE [ section NAME ] [ verbose ] |\n"
+#endif
 		"			  pinned FILE } ]\n"
 		"		[ master DEVICE ][ vrf NAME ]\n"
 		"		[ nomaster ]\n"

lib/bpf_legacy.c

@@ -831,7 +831,7 @@ 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;
+	const char *file, *section, *uds_name, *prog_name;
 	bool verbose = false;
 	int i, ret, argc;
 	char **argv;
@@ -862,7 +862,7 @@ static int bpf_do_parse(struct bpf_cfg_in *cfg, const bool *opt_tbl)
 	}
 
 	NEXT_ARG();
-	file = section = uds_name = NULL;
+	file = section = uds_name = prog_name = NULL;
 	if (cfg->mode == EBPF_OBJECT || cfg->mode == EBPF_PINNED) {
 		file = *argv;
 		NEXT_ARG_FWD();
@@ -899,6 +899,12 @@ static int bpf_do_parse(struct bpf_cfg_in *cfg, const bool *opt_tbl)
 			NEXT_ARG_FWD();
 		}
 
+		if (argc > 0 && strcmp(*argv, "program") == 0) {
+			NEXT_ARG();
+			prog_name = *argv;
+			NEXT_ARG_FWD();
+		}
+
 		if (__bpf_prog_meta[cfg->type].may_uds_export) {
 			uds_name = getenv(BPF_ENV_UDS);
 			if (argc > 0 && !uds_name &&
@@ -936,6 +942,7 @@ static int bpf_do_parse(struct bpf_cfg_in *cfg, const bool *opt_tbl)
 	cfg->argc    = argc;
 	cfg->argv    = argv;
 	cfg->verbose = verbose;
+	cfg->prog_name = prog_name;
 
 	return ret;
 }

lib/bpf_libbpf.c

@@ -254,6 +254,22 @@ static bool bpf_map_is_offload_neutral(const struct bpf_map *map)
 	return bpf_map__type(map) == BPF_MAP_TYPE_PERF_EVENT_ARRAY;
 }
 
+static bool find_prog_to_attach(struct bpf_program *prog,
+				struct bpf_program *exist_prog,
+				const char *section, const char *prog_name)
+{
+	if (exist_prog)
+		return false;
+
+	/* We have default section name 'prog'. So do not check
+	 * section name if there already has program name.
+	 */
+	if (prog_name)
+		return !strcmp(bpf_program__name(prog), prog_name);
+	else
+		return !strcmp(get_bpf_program__section_name(prog), section);
+}
+
 static int load_bpf_object(struct bpf_cfg_in *cfg)
 {
 	struct bpf_program *p, *prog = NULL;
@@ -278,8 +294,9 @@ static int load_bpf_object(struct bpf_cfg_in *cfg)
 	}
 
 	bpf_object__for_each_program(p, obj) {
-		bool prog_to_attach = !prog && cfg->section &&
-			!strcmp(get_bpf_program__section_name(p), cfg->section);
+		bool prog_to_attach = find_prog_to_attach(p, prog,
+							  cfg->section,
+							  cfg->prog_name);
 
 		/* Only load the programs that will either be subsequently
 		 * attached or inserted into a tail call map */
@@ -304,7 +321,10 @@ static int load_bpf_object(struct bpf_cfg_in *cfg)
 	}
 
 	if (!prog) {
-		fprintf(stderr, "object file doesn't contain sec %s\n", cfg->section);
+		if (cfg->prog_name)
+			fprintf(stderr, "object file doesn't contain prog %s\n", cfg->prog_name);
+		else
+			fprintf(stderr, "object file doesn't contain sec %s\n", cfg->section);
 		return -ENOENT;
 	}
 

man/man8/ip-link.8.in

@@ -149,7 +149,7 @@ ip-link \- network device configuration
 .in +8
 .BR object
 .IR FILE
-.RB "[ " section
+.RB "[ { " section " | " program " } "
 .IR NAME " ]"
 .RB "[ " verbose " ] |"
 .br
@@ -2342,6 +2342,13 @@ to be passed with the
 .B object
 option.
 
+.BI program " NAME "
+- Specifies the BPF program name that need to be attached. When the program
+name is specified, the section name parameter will be ignored. This option
+only works when iproute2 build with
+.B libbpf
+support.
+
 .BI verbose
 - Act in verbose mode. For example, even in case of success, this will
 print the verifier log in case a program was loaded from a BPF ELF file.