Commit e5659e4e authored Nov 05, 2022 by Rong Tao Committed by Andrii Nakryiko Nov 07, 2022

samples/bpf: Fix sockex3 error: Missing BPF prog type



since commit 450b167f("libbpf: clean up SEC() handling"),
sec_def_matches() does not recognize "socket/xxx" as "socket", therefore,
the BPF program type is not recognized.

Instead of sockex3_user.c parsing section names to get the BPF program fd.
We use the program array map to assign a static index to each BPF program
(get inspired by selftests/bpf progs/test_prog_array_init.c).
Therefore, use SEC("socket") as section name instead of SEC("socket/xxx"),
so that the BPF program is parsed to SOCKET_FILTER type. The "missing BPF
prog type" problem is solved.

How to reproduce this error:
$ cd samples/bpf
$ sudo ./sockex3
libbpf: prog 'bpf_func_PARSE_IP': missing BPF prog type, check ELF section name 'socket/3'
libbpf: prog 'bpf_func_PARSE_IP': failed to load: -22
libbpf: failed to load object './sockex3_kern.o'
ERROR: loading BPF object file failed

Signed-off-by: Rong Tao <rongtao@cestc.cn>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/tencent_EBA3C18864069E42175946973C2ACBAF5408@qq.com

parent e8f50c4f

samples/bpf/sockex3_kern.c

+53 −42

Original line number	Diff line number	Diff line
		@@ -17,48 +17,11 @@
		#define IP_MF 0x2000
		#define IP_OFFSET 0x1FFF

		#define PROG(F) SEC("socket/"__stringify(F)) int bpf_func_##F

		struct {
		__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
		__uint(key_size, sizeof(u32));
		__uint(value_size, sizeof(u32));
		__uint(max_entries, 8);
		} jmp_table SEC(".maps");

		#define PARSE_VLAN 1
		#define PARSE_MPLS 2
		#define PARSE_IP 3
		#define PARSE_IPV6 4

		/* Protocol dispatch routine. It tail-calls next BPF program depending
		* on eth proto. Note, we could have used ...
		*
		* bpf_tail_call(skb, &jmp_table, proto);
		*
		* ... but it would need large prog_array and cannot be optimised given
		* the map key is not static.
		*/
		static inline void parse_eth_proto(struct __sk_buff *skb, u32 proto)
		{
		switch (proto) {
		case ETH_P_8021Q:
		case ETH_P_8021AD:
		bpf_tail_call(skb, &jmp_table, PARSE_VLAN);
		break;
		case ETH_P_MPLS_UC:
		case ETH_P_MPLS_MC:
		bpf_tail_call(skb, &jmp_table, PARSE_MPLS);
		break;
		case ETH_P_IP:
		bpf_tail_call(skb, &jmp_table, PARSE_IP);
		break;
		case ETH_P_IPV6:
		bpf_tail_call(skb, &jmp_table, PARSE_IPV6);
		break;
		}
		}

		struct vlan_hdr {
		__be16 h_vlan_TCI;
		__be16 h_vlan_encapsulated_proto;
		@@ -74,6 +37,8 @@ struct flow_key_record {
		__u32 ip_proto;
		};

		static inline void parse_eth_proto(struct __sk_buff *skb, u32 proto);

		static inline int ip_is_fragment(struct __sk_buff *ctx, __u64 nhoff)
		{
		return load_half(ctx, nhoff + offsetof(struct iphdr, frag_off))
		@@ -189,7 +154,8 @@ static __always_inline void parse_ip_proto(struct __sk_buff *skb,
		}
		}

		PROG(PARSE_IP)(struct __sk_buff *skb)
		SEC("socket")
		int bpf_func_ip(struct __sk_buff *skb)
		{
		struct globals *g = this_cpu_globals();
		__u32 nhoff, verlen, ip_proto;
		@@ -217,7 +183,8 @@ PROG(PARSE_IP)(struct __sk_buff *skb)
		return 0;
		}

		PROG(PARSE_IPV6)(struct __sk_buff *skb)
		SEC("socket")
		int bpf_func_ipv6(struct __sk_buff *skb)
		{
		struct globals *g = this_cpu_globals();
		__u32 nhoff, ip_proto;
		@@ -240,7 +207,8 @@ PROG(PARSE_IPV6)(struct __sk_buff *skb)
		return 0;
		}

		PROG(PARSE_VLAN)(struct __sk_buff *skb)
		SEC("socket")
		int bpf_func_vlan(struct __sk_buff *skb)
		{
		__u32 nhoff, proto;

		@@ -256,7 +224,8 @@ PROG(PARSE_VLAN)(struct __sk_buff *skb)
		return 0;
		}

		PROG(PARSE_MPLS)(struct __sk_buff *skb)
		SEC("socket")
		int bpf_func_mpls(struct __sk_buff *skb)
		{
		__u32 nhoff, label;

		@@ -279,7 +248,49 @@ PROG(PARSE_MPLS)(struct __sk_buff *skb)
		return 0;
		}

		SEC("socket/0")
		struct {
		__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
		__uint(key_size, sizeof(u32));
		__uint(max_entries, 8);
		__array(values, u32 (void *));
		} prog_array_init SEC(".maps") = {
		.values = {
		[PARSE_VLAN] = (void *)&bpf_func_vlan,
		[PARSE_IP] = (void *)&bpf_func_ip,
		[PARSE_IPV6] = (void *)&bpf_func_ipv6,
		[PARSE_MPLS] = (void *)&bpf_func_mpls,
		},
		};

		/* Protocol dispatch routine. It tail-calls next BPF program depending
		* on eth proto. Note, we could have used ...
		*
		* bpf_tail_call(skb, &prog_array_init, proto);
		*
		* ... but it would need large prog_array and cannot be optimised given
		* the map key is not static.
		*/
		static inline void parse_eth_proto(struct __sk_buff *skb, u32 proto)
		{
		switch (proto) {
		case ETH_P_8021Q:
		case ETH_P_8021AD:
		bpf_tail_call(skb, &prog_array_init, PARSE_VLAN);
		break;
		case ETH_P_MPLS_UC:
		case ETH_P_MPLS_MC:
		bpf_tail_call(skb, &prog_array_init, PARSE_MPLS);
		break;
		case ETH_P_IP:
		bpf_tail_call(skb, &prog_array_init, PARSE_IP);
		break;
		case ETH_P_IPV6:
		bpf_tail_call(skb, &prog_array_init, PARSE_IPV6);
		break;
		}
		}

		SEC("socket")
		int main_prog(struct __sk_buff *skb)
		{
		__u32 nhoff = ETH_HLEN;

samples/bpf/sockex3_user.c

+10 −13

Original line number	Diff line number	Diff line
		@@ -24,10 +24,9 @@ struct pair {

		int main(int argc, char **argv)
		{
		int i, sock, key, fd, main_prog_fd, jmp_table_fd, hash_map_fd;
		int i, sock, fd, main_prog_fd, hash_map_fd;
		struct bpf_program *prog;
		struct bpf_object *obj;
		const char *section;
		char filename[256];
		FILE *f;

		@@ -45,26 +44,24 @@ int main(int argc, char **argv)
		goto cleanup;
		}

		jmp_table_fd = bpf_object__find_map_fd_by_name(obj, "jmp_table");
		hash_map_fd = bpf_object__find_map_fd_by_name(obj, "hash_map");
		if (jmp_table_fd < 0 \|\| hash_map_fd < 0) {
		if (hash_map_fd < 0) {
		fprintf(stderr, "ERROR: finding a map in obj file failed\n");
		goto cleanup;
		}

		/* find BPF main program */
		main_prog_fd = 0;
		bpf_object__for_each_program(prog, obj) {
		fd = bpf_program__fd(prog);

		section = bpf_program__section_name(prog);
		if (sscanf(section, "socket/%d", &key) != 1) {
		fprintf(stderr, "ERROR: finding prog failed\n");
		goto cleanup;
		if (!strcmp(bpf_program__name(prog), "main_prog"))
		main_prog_fd = fd;
		}

		if (key == 0)
		main_prog_fd = fd;
		else
		bpf_map_update_elem(jmp_table_fd, &key, &fd, BPF_ANY);
		if (main_prog_fd == 0) {
		fprintf(stderr, "ERROR: can't find main_prog\n");
		goto cleanup;
		}

		sock = open_raw_sock("lo");