[RFC] bpf: offload: report device information for offloaded programs

[Jakub Kicinski]

Report to the user ifindex and namespace information of offloaded
programs.  Always set dev_bound to true if program was loaded for
a device which has been since removed.  Specify the namespace
using dev/inode combination.

Signed-off-by: Jakub Kicinski <jakub.kicinski@xxxxxxxxxxxxx>
Reviewed-by: Simon Horman <simon.horman@xxxxxxxxxxxxx>
Reviewed-by: Quentin Monnet <quentin.monnet@xxxxxxxxxxxxx>
---
 fs/nsfs.c                      |  2 +-
 include/linux/bpf.h            |  2 ++
 include/linux/proc_ns.h        |  1 +
 include/uapi/linux/bpf.h       |  5 +++++
 kernel/bpf/offload.c           | 34 ++++++++++++++++++++++++++++++++++
 kernel/bpf/syscall.c           |  6 ++++++
 tools/include/uapi/linux/bpf.h |  5 +++++
 7 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/fs/nsfs.c b/fs/nsfs.c
index ef243e14b6eb..d2b89372544a 100644
--- a/fs/nsfs.c
+++ b/fs/nsfs.c
@@ -51,7 +51,7 @@ static void nsfs_evict(struct inode *inode)
 	ns->ops->put(ns);
 }
 
-static void *__ns_get_path(struct path *path, struct ns_common *ns)
+void *__ns_get_path(struct path *path, struct ns_common *ns)
 {
 	struct vfsmount *mnt = nsfs_mnt;
 	struct dentry *dentry;
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index e55e4255a210..fc7ab26e10bf 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -516,6 +516,8 @@ static inline struct bpf_prog *bpf_prog_get_type(u32 ufd,
 
 int bpf_prog_offload_compile(struct bpf_prog *prog);
 void bpf_prog_offload_destroy(struct bpf_prog *prog);
+int bpf_prog_offload_info_fill(struct bpf_prog_info *info,
+			       struct bpf_prog *prog);
 
 #if defined(CONFIG_NET) && defined(CONFIG_BPF_SYSCALL)
 int bpf_prog_offload_init(struct bpf_prog *prog, union bpf_attr *attr);
diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h
index 2ff18c9840a7..1733359cf713 100644
--- a/include/linux/proc_ns.h
+++ b/include/linux/proc_ns.h
@@ -76,6 +76,7 @@ static inline int ns_alloc_inum(struct ns_common *ns)
 
 extern struct file *proc_ns_fget(int fd);
 #define get_proc_ns(inode) ((struct ns_common *)(inode)->i_private)
+extern void *__ns_get_path(struct path *path, struct ns_common *ns);
 extern void *ns_get_path(struct path *path, struct task_struct *task,
 			const struct proc_ns_operations *ns_ops);
 
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 4c223ab30293..3183674496a2 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -910,6 +910,11 @@ struct bpf_prog_info {
 	__u32 nr_map_ids;
 	__aligned_u64 map_ids;
 	char name[BPF_OBJ_NAME_LEN];
+	__u32 dev_bound:1;
+	__u32 reserved:31;
+	__u32 ifindex;
+	__u64 ns_dev;
+	__u64 ns_inode;
 } __attribute__((aligned(8)));
 
 struct bpf_map_info {
diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
index 8455b89d1bbf..da98349c647d 100644
--- a/kernel/bpf/offload.c
+++ b/kernel/bpf/offload.c
@@ -16,9 +16,11 @@
 #include <linux/bpf.h>
 #include <linux/bpf_verifier.h>
 #include <linux/bug.h>
+#include <linux/kdev_t.h>
 #include <linux/list.h>
 #include <linux/netdevice.h>
 #include <linux/printk.h>
+#include <linux/proc_ns.h>
 #include <linux/rtnetlink.h>
 
 /* protected by RTNL */
@@ -164,6 +166,38 @@ int bpf_prog_offload_compile(struct bpf_prog *prog)
 	return bpf_prog_offload_translate(prog);
 }
 
+int bpf_prog_offload_info_fill(struct bpf_prog_info *info,
+			       struct bpf_prog *prog)
+{
+	struct bpf_dev_offload *offload = prog->aux->offload;
+	struct inode *ns_inode;
+	struct path ns_path;
+	struct net *net;
+	int ret = 0;
+	void *ptr;
+
+	info->dev_bound = 1;
+
+	rtnl_lock();
+	if (!offload->netdev)
+		goto out;
+
+	net = dev_net(offload->netdev);
+	get_net(net); /* __ns_get_path() drops the reference */
+	ptr = __ns_get_path(&ns_path, &net->ns);
+	ret = PTR_ERR_OR_ZERO(ptr);
+	if (ret)
+		goto out;
+	ns_inode = ns_path.dentry->d_inode;
+
+	info->ns_dev = new_encode_dev(ns_inode->i_sb->s_dev);
+	info->ns_inode = ns_inode->i_ino;
+	info->ifindex = offload->netdev->ifindex;
+out:
+	rtnl_unlock();
+	return ret;
+}
+
 const struct bpf_prog_ops bpf_offload_prog_ops = {
 };
 
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 2c4cfeaa8d5e..101ee3a3e80e 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1616,6 +1616,12 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog,
 			return -EFAULT;
 	}
 
+	if (bpf_prog_is_dev_bound(prog->aux)) {
+		err = bpf_prog_offload_info_fill(&info, prog);
+		if (err)
+			return err;
+	}
+
 done:
 	if (copy_to_user(uinfo, &info, info_len) ||
 	    put_user(info_len, &uattr->info.info_len))
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 4c223ab30293..3183674496a2 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -910,6 +910,11 @@ struct bpf_prog_info {
 	__u32 nr_map_ids;
 	__aligned_u64 map_ids;
 	char name[BPF_OBJ_NAME_LEN];
+	__u32 dev_bound:1;
+	__u32 reserved:31;
+	__u32 ifindex;
+	__u64 ns_dev;
+	__u64 ns_inode;
 } __attribute__((aligned(8)));
 
 struct bpf_map_info {
-- 
2.14.1