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

since commit 450b167fb9be("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
This commit is contained in:
Rong Tao 2022-11-05 14:48:00 +08:00 committed by Andrii Nakryiko
parent e8f50c4f0c
commit e5659e4e19
2 changed files with 63 additions and 55 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

95
samples/bpf/sockex3_kern.c
View File

@ -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;

23
samples/bpf/sockex3_user.c
View File

@ -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 (key == 0)
if (!strcmp(bpf_program__name(prog), "main_prog"))
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");