[PATCH bpf-next 04/10] bpf: Implement link introspection for tc BPF link programs

[Daniel Borkmann <daniel@xxxxxxxxxxxxx>]

Implement tc BPF link specific show_fdinfo and link_info to emit ifindex,
attach location and priority.

Co-developed-by: Nikolay Aleksandrov <razor@xxxxxxxxxxxxx>
Signed-off-by: Nikolay Aleksandrov <razor@xxxxxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
---
 include/uapi/linux/bpf.h       |  5 +++++
 kernel/bpf/net.c               | 36 ++++++++++++++++++++++++++++++++++
 tools/include/uapi/linux/bpf.h |  5 +++++
 3 files changed, 46 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c006f561648e..f1b089170b78 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -6309,6 +6309,11 @@ struct bpf_link_info {
 		struct {
 			__u32 ifindex;
 		} xdp;
+		struct {
+			__u32 ifindex;
+			__u32 attach_type;
+			__u32 priority;
+		} tc;
 	};
 } __attribute__((aligned(8)));
 
diff --git a/kernel/bpf/net.c b/kernel/bpf/net.c
index c50bcf656b3f..a74b86bb60a9 100644
--- a/kernel/bpf/net.c
+++ b/kernel/bpf/net.c
@@ -357,10 +357,46 @@ static void xtc_link_dealloc(struct bpf_link *l)
 	kfree(link);
 }
 
+static void xtc_link_fdinfo(const struct bpf_link *l, struct seq_file *seq)
+{
+	struct bpf_tc_link *link = container_of(l, struct bpf_tc_link, link);
+	u32 ifindex = 0;
+
+	rtnl_lock();
+	if (link->dev)
+		ifindex = link->dev->ifindex;
+	rtnl_unlock();
+
+	seq_printf(seq, "ifindex:\t%u\n", ifindex);
+	seq_printf(seq, "attach_type:\t%u (%s)\n",
+		   link->location,
+		   link->location == BPF_NET_INGRESS ? "ingress" : "egress");
+	seq_printf(seq, "priority:\t%u\n", link->priority);
+}
+
+static int xtc_link_fill_info(const struct bpf_link *l,
+			      struct bpf_link_info *info)
+{
+	struct bpf_tc_link *link = container_of(l, struct bpf_tc_link, link);
+	u32 ifindex = 0;
+
+	rtnl_lock();
+	if (link->dev)
+		ifindex = link->dev->ifindex;
+	rtnl_unlock();
+
+	info->tc.ifindex = ifindex;
+	info->tc.attach_type = link->location;
+	info->tc.priority = link->priority;
+	return 0;
+}
+
 static const struct bpf_link_ops bpf_tc_link_lops = {
 	.release	= xtc_link_release,
 	.dealloc	= xtc_link_dealloc,
 	.update_prog	= xtc_link_update,
+	.show_fdinfo	= xtc_link_fdinfo,
+	.fill_link_info	= xtc_link_fill_info,
 };
 
 int xtc_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index c006f561648e..f1b089170b78 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -6309,6 +6309,11 @@ struct bpf_link_info {
 		struct {
 			__u32 ifindex;
 		} xdp;
+		struct {
+			__u32 ifindex;
+			__u32 attach_type;
+			__u32 priority;
+		} tc;
 	};
 } __attribute__((aligned(8)));
 
-- 
2.34.1