[PATCH v4 bpf-next 6/9] bpf: implement BPF XDP link-specific introspection APIs

[Andrii Nakryiko <andriin@xxxxxx>]

Implement XDP link-specific show_fdinfo and link_info to emit ifindex.

Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
---
 include/uapi/linux/bpf.h |  3 +++
 net/core/dev.c           | 31 +++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 1da0c2984e7f..27bd1c8b0041 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4062,6 +4062,9 @@ struct bpf_link_info {
 			__u32 netns_ino;
 			__u32 attach_type;
 		} netns;
+		struct {
+			__u32 ifindex;
+		} xdp;
 	};
 } __attribute__((aligned(8)));
 
diff --git a/net/core/dev.c b/net/core/dev.c
index 44264eff7f1c..9859dae7d4dc 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8996,6 +8996,35 @@ static void bpf_xdp_link_dealloc(struct bpf_link *link)
 	kfree(xdp_link);
 }
 
+static void bpf_xdp_link_show_fdinfo(const struct bpf_link *link,
+				     struct seq_file *seq)
+{
+	struct bpf_xdp_link *xdp_link = container_of(link, struct bpf_xdp_link, link);
+	u32 ifindex = 0;
+
+	rtnl_lock();
+	if (xdp_link->dev)
+		ifindex = xdp_link->dev->ifindex;
+	rtnl_unlock();
+
+	seq_printf(seq, "ifindex:\t%u\n", ifindex);
+}
+
+static int bpf_xdp_link_fill_link_info(const struct bpf_link *link,
+				       struct bpf_link_info *info)
+{
+	struct bpf_xdp_link *xdp_link = container_of(link, struct bpf_xdp_link, link);
+	u32 ifindex = 0;
+
+	rtnl_lock();
+	if (xdp_link->dev)
+		ifindex = xdp_link->dev->ifindex;
+	rtnl_unlock();
+
+	info->xdp.ifindex = ifindex;
+	return 0;
+}
+
 static int bpf_xdp_link_update(struct bpf_link *link, struct bpf_prog *new_prog,
 			       struct bpf_prog *old_prog)
 {
@@ -9041,6 +9070,8 @@ static int bpf_xdp_link_update(struct bpf_link *link, struct bpf_prog *new_prog,
 static const struct bpf_link_ops bpf_xdp_link_lops = {
 	.release = bpf_xdp_link_release,
 	.dealloc = bpf_xdp_link_dealloc,
+	.show_fdinfo = bpf_xdp_link_show_fdinfo,
+	.fill_link_info = bpf_xdp_link_fill_link_info,
 	.update_prog = bpf_xdp_link_update,
 };
 
-- 
2.24.1