bpf: libbpf: retry map creation without the name

Since commit 88cda1c9da02 ("bpf: libbpf: Provide basic API support
to specify BPF obj name"), libbpf unconditionally sets bpf_attr->name
for maps. Pre v4.14 kernels don't know about map names and return an
error about unexpected non-zero data. Retry sys_bpf without a map
name to cover older kernels.

v2 changes:
* check for errno == EINVAL as suggested by Daniel Borkmann

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 03f9bcc4ef501776520256e248600bb12e03f18c..961e1b9fc5927637d708d4679ee421ec046b517d 100644 (file)
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -69,6 +69,7 @@ int bpf_create_map_xattr(const struct bpf_create_map_attr *create_attr)
 {
        __u32 name_len = create_attr->name ? strlen(create_attr->name) : 0;
        union bpf_attr attr;
+       int ret;
 
        memset(&attr, '\0', sizeof(attr));
 
@@ -86,7 +87,15 @@ int bpf_create_map_xattr(const struct bpf_create_map_attr *create_attr)
        attr.map_ifindex = create_attr->map_ifindex;
        attr.inner_map_fd = create_attr->inner_map_fd;
 
-       return sys_bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
+       ret = sys_bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
+       if (ret < 0 && errno == EINVAL && create_attr->name) {
+               /* Retry the same syscall, but without the name.
+                * Pre v4.14 kernels don't support map names.
+                */
+               memset(attr.map_name, 0, sizeof(attr.map_name));
+               return sys_bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
+       }
+       return ret;
 }
 
 int bpf_create_map_node(enum bpf_map_type map_type, const char *name,