Merge branch 'selftests-bpf-use-local-types-for-kfunc-declarations'

Gregory Bell says:

====================
selftests/bpf: Use local types for kfunc declarations

The xdp_flowtable and test_tunnel_kern selftests were previously
rewritten to compile with CONFIG_NF_FLOW_TABLE=m and CONFIG_NET_FOU=m.
While the compilation issues were resolved, the tests fail at
runtime. In test_tunnel_kern.c, struct bpf_fou_encap___local is
defined with the correct fields but the kfunc declarations still
reference the forward-declared struct bpf_fou_encap. Similarly,
xdp_flowtable.c uses a forward-declared struct flow_offload_tuple_rhash
as the return type for bpf_xdp_flow_lookup(). Clang emits these forward
declarations as BTF FWD types, which fail to resolve against the
module-defined STRUCT types at run time:

libbpf: extern (func ksym) 'bpf_xdp_flow_lookup': func_proto [51] incompatible with nf_flow_table [128640]
libbpf: extern (func ksym) 'bpf_skb_get_fou_encap': func_proto [79] incompatible with fou [135045]

This patch updates both selftests to use ___local type suffixes
for kernel struct type, replacing the forward declarations.

struct flow_offload_tuple_rhash___local is defined without fields
because the test only uses the returned pointer for a null check.
This avoids needing to locally define its nested types,
struct rhash_head and struct flow_offload_tuple.

I understand that fixing selftests for specific config options is
generally not a priority, but since these tests were already
rewritten to support these configs, they should work correctly
with them.

Fixes: d17f9b370df6 ("selftests/bpf: Fix compilation failure when CONFIG_NET_FOU!=y")
Fixes: eeb23b54e447 ("selftests/bpf: fix compilation failure when CONFIG_NF_FLOW_TABLE=m")

Signed-off-by: Gregory Bell <grbell@redhat.com>

change log:
[0] https://lore.kernel.org/all/cover.1776280396.git.grbell@redhat.com/
- Add BPF_NO_KFUNC_PROTOTYPES macro to test_tunnel_kern.c so the test compiles
  when CONFIG_NET_FOU=y. Without it the function prototypes conflict with vmlinux.h
====================

Link: https://patch.msgid.link/20260417154122.2558890-1-grbell@redhat.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 11 insertions, 9 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_tunnel_kern.c b/tools/testing/selftests/bpf/progs/test_tunnel_kern.c
index 32127f1cd687..30f1de458669 100644
--- a/tools/testing/selftests/bpf/progs/test_tunnel_kern.c
+++ b/tools/testing/selftests/bpf/progs/test_tunnel_kern.c
@@ -6,6 +6,7 @@
  * modify it under the terms of version 2 of the GNU General Public
  * License as published by the Free Software Foundation.
  */
+#define BPF_NO_KFUNC_PROTOTYPES
 #include "vmlinux.h"
 #include <bpf/bpf_core_read.h>
 #include <bpf/bpf_helpers.h>
@@ -36,12 +37,10 @@ enum bpf_fou_encap_type___local {
 	FOU_BPF_ENCAP_GUE___local,
 };
 
-struct bpf_fou_encap;
-
 int bpf_skb_set_fou_encap(struct __sk_buff *skb_ctx,
-			  struct bpf_fou_encap *encap, int type) __ksym;
+			  struct bpf_fou_encap___local *encap, int type) __ksym;
 int bpf_skb_get_fou_encap(struct __sk_buff *skb_ctx,
-			  struct bpf_fou_encap *encap) __ksym;
+			  struct bpf_fou_encap___local *encap) __ksym;
 struct xfrm_state *
 bpf_xdp_get_xfrm_state(struct xdp_md *ctx, struct bpf_xfrm_state_opts *opts,
 		       u32 opts__sz) __ksym;
@@ -781,7 +780,7 @@ int ipip_gue_set_tunnel(struct __sk_buff *skb)
 	encap.sport = 0;
 	encap.dport = bpf_htons(5555);
 
-	ret = bpf_skb_set_fou_encap(skb, (struct bpf_fou_encap *)&encap,
+	ret = bpf_skb_set_fou_encap(skb, &encap,
 				    bpf_core_enum_value(enum bpf_fou_encap_type___local,
 							FOU_BPF_ENCAP_GUE___local));
 	if (ret < 0) {
@@ -820,7 +819,7 @@ int ipip_fou_set_tunnel(struct __sk_buff *skb)
 	encap.sport = 0;
 	encap.dport = bpf_htons(5555);
 
-	ret = bpf_skb_set_fou_encap(skb, (struct bpf_fou_encap *)&encap,
+	ret = bpf_skb_set_fou_encap(skb, &encap,
 				    FOU_BPF_ENCAP_FOU___local);
 	if (ret < 0) {
 		log_err(ret);
@@ -843,7 +842,7 @@ int ipip_encap_get_tunnel(struct __sk_buff *skb)
 		return TC_ACT_SHOT;
 	}
 
-	ret = bpf_skb_get_fou_encap(skb, (struct bpf_fou_encap *)&encap);
+	ret = bpf_skb_get_fou_encap(skb, &encap);
 	if (ret < 0) {
 		log_err(ret);
 		return TC_ACT_SHOT;
diff --git a/tools/testing/selftests/bpf/progs/xdp_flowtable.c b/tools/testing/selftests/bpf/progs/xdp_flowtable.c
index 7fdc7b23ee74..e67daa02749d 100644
--- a/tools/testing/selftests/bpf/progs/xdp_flowtable.c
+++ b/tools/testing/selftests/bpf/progs/xdp_flowtable.c
@@ -15,7 +15,10 @@ struct bpf_flowtable_opts___local {
 	s32 error;
 };
 
-struct flow_offload_tuple_rhash *
+struct flow_offload_tuple_rhash___local {
+};
+
+struct flow_offload_tuple_rhash___local *
 bpf_xdp_flow_lookup(struct xdp_md *, struct bpf_fib_lookup *,
 		    struct bpf_flowtable_opts___local *, u32) __ksym;
 
@@ -67,7 +70,7 @@ int xdp_flowtable_do_lookup(struct xdp_md *ctx)
 {
 	void *data_end = (void *)(long)ctx->data_end;
 	struct bpf_flowtable_opts___local opts = {};
-	struct flow_offload_tuple_rhash *tuplehash;
+	struct flow_offload_tuple_rhash___local *tuplehash;
 	struct bpf_fib_lookup tuple = {
 		.ifindex = ctx->ingress_ifindex,
 	};