Re: [PATCH bpf-next v2] bpf: libbpf: retry map creation without the name

[Stanislav Fomichev]

On 11/20, Daniel Borkmann wrote:
> On 11/19/2018 11:49 PM, Stanislav Fomichev wrote:
> > 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 
> 
> Applied to bpf-next, thanks!
Great, thanks! It looks like there might be the same problem with the
program's name. I'll probably follow up with another patch soon.

Re: [PATCH bpf-next v2] bpf: libbpf: retry map creation without the name

[Daniel Borkmann]

On 11/19/2018 11:49 PM, Stanislav Fomichev wrote:
> 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 

Applied to bpf-next, thanks!

[PATCH bpf-next v2] bpf: libbpf: retry map creation without the name

[Stanislav Fomichev]

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 
---
 tools/lib/bpf/bpf.c | 11 ++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 03f9bcc4ef50..961e1b9fc592 100644
--- 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,
-- 
2.19.1.1215.g8438c0b245-goog