Merge branch 'libbpf-fix-reuse-of-devmap'

Yureka Lilian says:

====================
libbpf: fix reuse of DEVMAP

changes in v3:

- instead of setting BPF_F_RDONLY_PROG on both sides, just
  clear BPF_F_RDONLY_PROG in map_info.map_flags as suggested
  by Andrii Nakryiko

- in the test, use ASSERT_* instead of CHECK
- shorten the test by using open_and_load from the skel
- in the test, drop NULL check before unloading/destroying bpf objs

- start the commit messages with "libbpf" and "selftests/bpf"
  respectively instead of just "bpf"

changes in v2:

- preserve compatibility with older kernels
- add a basic selftest covering the re-use of DEVMAP maps
====================

Link: https://patch.msgid.link/20250814180113.1245565-2-yuka@yuka.dev
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 8f5a81b672e1..fe4fc5438678 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -5093,6 +5093,16 @@ static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd)
 		return false;
 	}
 
+	/*
+	 * bpf_get_map_info_by_fd() for DEVMAP will always return flags with
+	 * BPF_F_RDONLY_PROG set, but it generally is not set at map creation time.
+	 * Thus, ignore the BPF_F_RDONLY_PROG flag in the flags returned from
+	 * bpf_get_map_info_by_fd() when checking for compatibility with an
+	 * existing DEVMAP.
+	 */
+	if (map->def.type == BPF_MAP_TYPE_DEVMAP || map->def.type == BPF_MAP_TYPE_DEVMAP_HASH)
+		map_info.map_flags &= ~BPF_F_RDONLY_PROG;
+
 	return (map_info.type == map->def.type &&
 		map_info.key_size == map->def.key_size &&
 		map_info.value_size == map->def.value_size &&