[PATCH bpf-next] samples/bpf: Fix sockex3 error: missing BPF prog type
From: Rong Tao
Date: Sat Nov 05 2022 - 02:54:45 EST
From: Rong Tao <rongtao@xxxxxxxx>
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@xxxxxxxx>
---
samples/bpf/sockex3_kern.c | 95 ++++++++++++++++++++++----------------
samples/bpf/sockex3_user.c | 23 ++++-----
2 files changed, 64 insertions(+), 54 deletions(-)
diff --git a/samples/bpf/sockex3_kern.c b/samples/bpf/sockex3_kern.c
index b363503357e5..26d916834865 100644
--- a/samples/bpf/sockex3_kern.c
+++ b/samples/bpf/sockex3_kern.c
@@ -17,47 +17,12 @@
#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;
- }
-}
+#define PROG_SOCKET_FILTER SEC("socket")
struct vlan_hdr {
__be16 h_vlan_TCI;
@@ -74,6 +39,8 @@ 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 +156,8 @@ static __always_inline void parse_ip_proto(struct __sk_buff *skb,
}
}
-PROG(PARSE_IP)(struct __sk_buff *skb)
+PROG_SOCKET_FILTER
+int bpf_func_ip(struct __sk_buff *skb)
{
struct globals *g = this_cpu_globals();
__u32 nhoff, verlen, ip_proto;
@@ -217,7 +185,8 @@ PROG(PARSE_IP)(struct __sk_buff *skb)
return 0;
}
-PROG(PARSE_IPV6)(struct __sk_buff *skb)
+PROG_SOCKET_FILTER
+int bpf_func_ipv6(struct __sk_buff *skb)
{
struct globals *g = this_cpu_globals();
__u32 nhoff, ip_proto;
@@ -240,7 +209,8 @@ PROG(PARSE_IPV6)(struct __sk_buff *skb)
return 0;
}
-PROG(PARSE_VLAN)(struct __sk_buff *skb)
+PROG_SOCKET_FILTER
+int bpf_func_vlan(struct __sk_buff *skb)
{
__u32 nhoff, proto;
@@ -256,7 +226,8 @@ PROG(PARSE_VLAN)(struct __sk_buff *skb)
return 0;
}
-PROG(PARSE_MPLS)(struct __sk_buff *skb)
+PROG_SOCKET_FILTER
+int bpf_func_mpls(struct __sk_buff *skb)
{
__u32 nhoff, label;
@@ -279,7 +250,49 @@ 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;
+ }
+}
+
+PROG_SOCKET_FILTER
int main_prog(struct __sk_buff *skb)
{
__u32 nhoff = ETH_HLEN;
diff --git a/samples/bpf/sockex3_user.c b/samples/bpf/sockex3_user.c
index cd6fa79df900..56044acbd25d 100644
--- a/samples/bpf/sockex3_user.c
+++ b/samples/bpf/sockex3_user.c
@@ -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");
--
2.31.1