bpf: report offload info to user space

Extend struct bpf_prog_info to contain information about program
being bound to a device.  Since the netdev may get destroyed while
program still exists we need a flag to indicate the program is
loaded for a device, even if the device is gone.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/bpf.h

@@ -506,6 +506,7 @@ static inline int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu,
 
 int bpf_prog_offload_compile(struct bpf_prog *prog);
 void bpf_prog_offload_destroy(struct bpf_prog *prog);
+u32 bpf_prog_offload_ifindex(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);

include/uapi/linux/bpf.h

@@ -895,6 +895,10 @@ enum sk_action {
 
 #define BPF_TAG_SIZE	8
 
+enum bpf_prog_status {
+	BPF_PROG_STATUS_DEV_BOUND	= (1 << 0),
+};
+
 struct bpf_prog_info {
 	__u32 type;
 	__u32 id;
@@ -908,6 +912,8 @@ struct bpf_prog_info {
 	__u32 nr_map_ids;
 	__aligned_u64 map_ids;
 	char name[BPF_OBJ_NAME_LEN];
+	__u32 ifindex;
+	__u32 status;
 } __attribute__((aligned(8)));
 
 struct bpf_map_info {

kernel/bpf/offload.c

@@ -144,6 +144,18 @@ int bpf_prog_offload_compile(struct bpf_prog *prog)
 	return bpf_prog_offload_translate(prog);
 }
 
+u32 bpf_prog_offload_ifindex(struct bpf_prog *prog)
+{
+	struct bpf_dev_offload *offload = prog->aux->offload;
+	u32 ifindex;
+
+	rtnl_lock();
+	ifindex = offload->netdev ? offload->netdev->ifindex : 0;
+	rtnl_unlock();
+
+	return ifindex;
+}
+
 const struct bpf_prog_ops bpf_offload_prog_ops = {
 };
 

kernel/bpf/syscall.c

@@ -1592,6 +1592,11 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog,
 			return -EFAULT;
 	}
 
+	if (bpf_prog_is_dev_bound(prog->aux)) {
+		info.status |= BPF_PROG_STATUS_DEV_BOUND;
+		info.ifindex = bpf_prog_offload_ifindex(prog);
+	}
+
 done:
 	if (copy_to_user(uinfo, &info, info_len) ||
 	    put_user(info_len, &uattr->info.info_len))