[v2,2/2] tools: bpftool: add net detach command to detach XDP on interface

["Daniel T. Lee" <danieltimlee@gmail.com>]

By this commit, using `bpftool net detach`, the attached XDP prog can
be detached. Detaching the BPF prog will be done through libbpf
'bpf_set_link_xdp_fd' with the progfd set to -1.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
---
Changes in v2:
  - command 'unload' changed to 'detach' for the consistency

 tools/bpf/bpftool/net.c | 55 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 54 insertions(+), 1 deletion(-)

diff --git a/tools/bpf/bpftool/net.c b/tools/bpf/bpftool/net.c
index f3b57660b303..2ae9a613b05c 100644
--- a/tools/bpf/bpftool/net.c
+++ b/tools/bpf/bpftool/net.c
@@ -281,6 +281,31 @@ static int parse_attach_args(int argc, char **argv, int *progfd,
 	return 0;
 }
 
+static int parse_detach_args(int argc, char **argv,
+			     enum net_attach_type *attach_type, int *ifindex)
+{
+	if (!REQ_ARGS(2))
+		return -EINVAL;
+
+	*attach_type = parse_attach_type(*argv);
+	if (*attach_type == __MAX_NET_ATTACH_TYPE) {
+		p_err("invalid net attach/detach type");
+		return -EINVAL;
+	}
+
+	NEXT_ARG();
+	if (!REQ_ARGS(1))
+		return -EINVAL;
+
+	*ifindex = if_nametoindex(*argv);
+	if (!*ifindex) {
+		p_err("Invalid ifname");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int do_attach_detach_xdp(int *progfd, enum net_attach_type *attach_type,
 				int *ifindex)
 {
@@ -323,6 +348,31 @@ static int do_attach(int argc, char **argv)
 	return 0;
 }
 
+static int do_detach(int argc, char **argv)
+{
+	enum net_attach_type attach_type;
+	int err, progfd, ifindex;
+
+	err = parse_detach_args(argc, argv, &attach_type, &ifindex);
+	if (err)
+		return err;
+
+	/* to detach xdp prog */
+	progfd = -1;
+	if (is_prefix("xdp", attach_type_strings[attach_type]))
+		err = do_attach_detach_xdp(&progfd, &attach_type, &ifindex);
+
+	if (err < 0) {
+		p_err("link set %s failed", attach_type_strings[attach_type]);
+		return -1;
+	}
+
+	if (json_output)
+		jsonw_null(json_wtr);
+
+	return 0;
+}
+
 static int do_show(int argc, char **argv)
 {
 	struct bpf_attach_info attach_info = {};
@@ -406,6 +456,7 @@ static int do_help(int argc, char **argv)
 	fprintf(stderr,
 		"Usage: %s %s { show | list } [dev <devname>]\n"
 		"       %s %s attach PROG LOAD_TYPE <devname>\n"
+		"       %s %s detach LOAD_TYPE <devname>\n"
 		"       %s %s help\n"
 		"\n"
 		"       " HELP_SPEC_PROGRAM "\n"
@@ -415,7 +466,8 @@ static int do_help(int argc, char **argv)
 		"      to dump program attachments. For program types\n"
 		"      sk_{filter,skb,msg,reuseport} and lwt/seg6, please\n"
 		"      consult iproute2.\n",
-		bin_name, argv[-2], bin_name, argv[-2], bin_name, argv[-2]);
+		bin_name, argv[-2], bin_name, argv[-2], bin_name, argv[-2],
+		bin_name, argv[-2]);
 
 	return 0;
 }
@@ -424,6 +476,7 @@ static const struct cmd cmds[] = {
 	{ "show",	do_show },
 	{ "list",	do_show },
 	{ "attach",	do_attach },
+	{ "detach",	do_detach },
 	{ "help",	do_help },
 	{ 0 }
 };
-- 
2.20.1