[PATCH bpf-next v3 7/9] bpf: offload: report device information for offloaded programs

[Jakub Kicinski]

Report to the user ifindex and namespace information of offloaded
programs.  If device has disappeared return -ENODEV.  Specify the
namespace using dev/inode combination.

CC: Eric W. Biederman <ebied...@xmission.com>
Signed-off-by: Jakub Kicinski <jakub.kicin...@netronome.com>
---
v3:
 - path_put() (Daniel);
 - move more of the logic to nsfs.c (Daniel).
v2:
 - take RTNL lock to grab a coherent snapshot of device state
   (ifindex vs name space) and avoid races with name space
   moves (based on Eric's comment on Kirill's patch to
   peernet2id_alloc()).
---
 include/linux/bpf.h            |  2 ++
 include/uapi/linux/bpf.h       |  3 +++
 kernel/bpf/offload.c           | 59 ++++++++++++++++++++++++++++++++++++++++++
 kernel/bpf/syscall.c           |  6 +++++
 tools/include/uapi/linux/bpf.h |  3 +++
 5 files changed, 73 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 9a916ab34299..7810ae57b357 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -531,6 +531,8 @@ 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/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index d01f1cb3cfc0..72b37fc3bc0c 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -921,6 +921,9 @@ struct bpf_prog_info {
        __u32 nr_map_ids;
        __aligned_u64 map_ids;
        char name[BPF_OBJ_NAME_LEN];
+       __u32 ifindex;
+       __u64 netns_dev;
+       __u64 netns_ino;
 } __attribute__((aligned(8)));
 
 struct bpf_map_info {
diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
index e4f1668a021c..040d4e0edf3f 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>
 #include <linux/rwsem.h>
 
@@ -176,6 +178,63 @@ int bpf_prog_offload_compile(struct bpf_prog *prog)
        return bpf_prog_offload_translate(prog);
 }
 
+struct ns_get_path_bpf_prog_args {
+       struct bpf_prog *prog;
+       struct bpf_prog_info *info;
+};
+
+static struct ns_common *bpf_prog_offload_info_fill_ns(void *private_data)
+{
+       struct ns_get_path_bpf_prog_args *args = private_data;
+       struct bpf_prog_aux *aux = args->prog->aux;
+       struct ns_common *ns;
+       struct net *net;
+
+       rtnl_lock();
+       down_read(&bpf_devs_lock);
+
+       if (aux->offload) {
+               args->info->ifindex = aux->offload->netdev->ifindex;
+               net = dev_net(aux->offload->netdev);
+               get_net(net);
+               ns = &net->ns;
+       } else {
+               args->info->ifindex = 0;
+               ns = NULL;
+       }
+
+       up_read(&bpf_devs_lock);
+       rtnl_unlock();
+
+       return ns;
+}
+
+int bpf_prog_offload_info_fill(struct bpf_prog_info *info,
+                              struct bpf_prog *prog)
+{
+       struct ns_get_path_bpf_prog_args args = {
+               .prog   = prog,
+               .info   = info,
+       };
+       struct inode *ns_inode;
+       struct path ns_path;
+       void *res;
+
+       res = ns_get_path_cb(&ns_path, bpf_prog_offload_info_fill_ns, &args);
+       if (IS_ERR(res)) {
+               if (!info->ifindex)
+                       return -ENODEV;
+               return PTR_ERR(res);
+       }
+
+       ns_inode = ns_path.dentry->d_inode;
+       info->netns_dev = new_encode_dev(ns_inode->i_sb->s_dev);
+       info->netns_ino = ns_inode->i_ino;
+       path_put(&ns_path);
+
+       return 0;
+}
+
 const struct bpf_prog_ops bpf_offload_prog_ops = {
 };
 
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 7d9f5b0f0e49..20444fd678d0 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1624,6 +1624,12 @@ 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 db1b0923a308..4e8c60acfa32 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -921,6 +921,9 @@ struct bpf_prog_info {
        __u32 nr_map_ids;
        __aligned_u64 map_ids;
        char name[BPF_OBJ_NAME_LEN];
+       __u32 ifindex;
+       __u64 netns_dev;
+       __u64 netns_ino;
 } __attribute__((aligned(8)));
 
 struct bpf_map_info {
-- 
2.15.1