rtnl_link: implement IFLA_PROTO_DOWN_REASON attribute decoding

IFLA_PROTO_DOWN_REASON is a nested attribute introduced by Linux commit
v5.9-rc1~133^2~77.

* src/xlat/rtnl_ifla_proto_down_reason_attrs.in: New file.
* src/rtnl_link.c: Include "xlat/rtnl_ifla_proto_down_reason_attrs.h".
(ifla_proto_down_reason_nla_decoders): New decoder table.
(decode_ifla_proto_down_reason): New function.
(ifinfomsg_nla_decoders) <[IFLA_PROTO_DOWN_REASON]>: New decoder,
calls decode_ifla_proto_down_reason.
* NEWS: Mention this.
* tests/nlattr_ifla_proto_down_reason.c: New file.
* tests/.gitignore: Add nlattr_ifla_proto_down_reason.
* tests/pure_executables.list: Likewise.
* tests/gen_tests.in (nlattr_ifla_proto_down_reason): New test.

7 files changed, 112 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 293fabcb2..c65d9dcf1 100644
--- a/NEWS
+++ b/NEWS
@@ -4,6 +4,7 @@ Noteworthy changes in release ?.?? (????-??-??)
 * Improvements
   * Implemented decoding of memfd_secret and quotactl_fd syscalls,
     introduced in Linux 5.14.
+  * Enhanced decoding of IFLA_* netlink attributes.
   * Updated lists of BPF_*, IORING_*, MADV_*, SCTP_*, and UFFD_* constants.
 
 * Bug fixes
diff --git a/src/rtnl_link.c b/src/rtnl_link.c
index 165d26bcb..2769ad917 100644
--- a/src/rtnl_link.c
+++ b/src/rtnl_link.c
@@ -30,6 +30,7 @@
 #include "xlat/rtnl_ifla_info_data_bridge_attrs.h"
 #include "xlat/rtnl_ifla_info_data_tun_attrs.h"
 #include "xlat/rtnl_ifla_port_attrs.h"
+#include "xlat/rtnl_ifla_proto_down_reason_attrs.h"
 #include "xlat/rtnl_ifla_vf_port_attrs.h"
 #include "xlat/rtnl_ifla_xdp_attached_mode.h"
 #include "xlat/rtnl_ifla_xdp_attrs.h"
@@ -926,6 +927,25 @@ decode_ifla_prop_list(struct tcb *const tcp,
 	return true;
 }
 
+static const nla_decoder_t ifla_proto_down_reason_nla_decoders[] = {
+	[IFLA_PROTO_DOWN_REASON_UNSPEC]	= NULL,
+	[IFLA_PROTO_DOWN_REASON_MASK]	= decode_nla_x32,
+	[IFLA_PROTO_DOWN_REASON_VALUE]	= decode_nla_x32,
+};
+
+static bool
+decode_ifla_proto_down_reason(struct tcb *const tcp,
+			      const kernel_ulong_t addr,
+			      const unsigned int len,
+			      const void *const opaque_data)
+{
+	decode_nlattr(tcp, addr, len, rtnl_ifla_proto_down_reason_attrs,
+		      "IFLA_PROTO_DOWN_REASON_???",
+		      ARRSZ_PAIR(ifla_proto_down_reason_nla_decoders),
+		      opaque_data);
+
+	return true;
+}
 
 static const nla_decoder_t ifinfomsg_nla_decoders[] = {
 	[IFLA_ADDRESS]		= decode_ifla_hwaddr,
@@ -982,6 +1002,7 @@ static const nla_decoder_t ifinfomsg_nla_decoders[] = {
 	[IFLA_PROP_LIST]	= decode_ifla_prop_list,
 	[IFLA_ALT_IFNAME]	= decode_nla_str,
 	[IFLA_PERM_ADDRESS]	= decode_ifla_hwaddr,
+	[IFLA_PROTO_DOWN_REASON]	= decode_ifla_proto_down_reason,
 };
 
 DECL_NETLINK_ROUTE_DECODER(decode_ifinfomsg)
diff --git a/src/xlat/rtnl_ifla_proto_down_reason_attrs.in b/src/xlat/rtnl_ifla_proto_down_reason_attrs.in
new file mode 100644
index 000000000..4b5469b8d
--- /dev/null
+++ b/src/xlat/rtnl_ifla_proto_down_reason_attrs.in
@@ -0,0 +1,5 @@
+#unconditional
+#value_indexed
+IFLA_PROTO_DOWN_REASON_UNSPEC
+IFLA_PROTO_DOWN_REASON_MASK
+IFLA_PROTO_DOWN_REASON_VALUE
diff --git a/tests/.gitignore b/tests/.gitignore
index abf5eb767..abed1b4fd 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -522,6 +522,7 @@ nlattr_ifla_af_spec
 nlattr_ifla_brport
 nlattr_ifla_linkinfo
 nlattr_ifla_port
+nlattr_ifla_proto_down_reason
 nlattr_ifla_xdp
 nlattr_ifla_xdp-y
 nlattr_inet_diag_msg
diff --git a/tests/gen_tests.in b/tests/gen_tests.in
index 60fce6a34..0442749c8 100644
--- a/tests/gen_tests.in
+++ b/tests/gen_tests.in
@@ -497,6 +497,7 @@ nlattr_ifla_af_spec		+netlink_sock_diag.test
 nlattr_ifla_brport		+netlink_sock_diag.test
 nlattr_ifla_linkinfo		+netlink_sock_diag.test
 nlattr_ifla_port		+netlink_sock_diag.test
+nlattr_ifla_proto_down_reason	+netlink_sock_diag.test
 nlattr_ifla_xdp			+netlink_sock_diag.test
 nlattr_ifla_xdp-y		+netlink_sock_diag.test -y; exec 9</dev/full
 nlattr_inet_diag_msg		+netlink_sock_diag.test
diff --git a/tests/nlattr_ifla_proto_down_reason.c b/tests/nlattr_ifla_proto_down_reason.c
new file mode 100644
index 000000000..94d72ded1
--- /dev/null
+++ b/tests/nlattr_ifla_proto_down_reason.c
@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2017 JingPiao Chen <chenjingpiao@gmail.com>
+ * Copyright (c) 2017-2021 The strace developers.
+ * All rights reserved.
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "tests.h"
+
+#include <stdio.h>
+#include "test_nlattr.h"
+#include <linux/if.h>
+#include <linux/if_arp.h>
+#include <linux/if_link.h>
+#include <linux/rtnetlink.h>
+
+#define XLAT_MACROS_ONLY
+# include "xlat/rtnl_ifla_proto_down_reason_attrs.h"
+#undef XLAT_MACROS_ONLY
+
+#define IFLA_ATTR IFLA_PROTO_DOWN_REASON
+#include "nlattr_ifla.h"
+
+int
+main(void)
+{
+	skip_if_unavailable("/proc/self/fd/");
+
+	const union {
+		uint8_t  bytes[4];
+		uint32_t num;
+	} num = { .num=0xabacdbcd };
+	const int fd = create_nl_socket(NETLINK_ROUTE);
+	void *nlh0 = midtail_alloc(NLMSG_SPACE(hdrlen),
+				   NLA_HDRLEN + sizeof(num));
+
+	static char pattern[4096];
+	fill_memory_ex(pattern, sizeof(pattern), 'a', 'z' - 'a' + 1);
+
+	static const struct {
+		uint8_t val;
+		const char *str;
+	} inv_attrs[] = {
+		{ ARG_STR(IFLA_PROTO_DOWN_REASON_UNSPEC) },
+		{ ARG_STR(0x3)  " /* IFLA_PROTO_DOWN_REASON_??? */" },
+		{ ARG_STR(0xfe) " /* IFLA_PROTO_DOWN_REASON_??? */" },
+	};
+
+	for (size_t i = 0; i < ARRAY_SIZE(inv_attrs); i++) {
+		TEST_NESTED_NLATTR_OBJECT_EX_(fd, nlh0, hdrlen,
+					      init_ifinfomsg, print_ifinfomsg,
+					      inv_attrs[i].val,
+					      inv_attrs[i].str,
+					      pattern, num,
+					      print_quoted_hex, 1,
+					      printf("\"\\x%x\\x%x\\x%x\\x%x\"",
+						     num.bytes[0], num.bytes[1],
+						     num.bytes[2], num.bytes[3])
+					      );
+	}
+
+	static const struct {
+		uint32_t val;
+		const char *str;
+	} attrs[] = {
+		{ ARG_STR(IFLA_PROTO_DOWN_REASON_MASK) },
+		{ ARG_STR(IFLA_PROTO_DOWN_REASON_VALUE) },
+	};
+
+	for (size_t i = 0; i < ARRAY_SIZE(attrs); i++) {
+		TEST_NESTED_NLATTR_OBJECT_EX_(fd, nlh0, hdrlen,
+					      init_ifinfomsg, print_ifinfomsg,
+					      attrs[i].val, attrs[i].str,
+					      pattern, num,
+					      print_quoted_hex, 1,
+					      printf("%#x", num.num));
+	}
+
+	puts("+++ exited with 0 +++");
+	return 0;
+}
diff --git a/tests/pure_executables.list b/tests/pure_executables.list
index 892d87fc5..c940251ce 100755
--- a/tests/pure_executables.list
+++ b/tests/pure_executables.list
@@ -386,6 +386,7 @@ nlattr_ifla_af_spec
 nlattr_ifla_brport
 nlattr_ifla_linkinfo
 nlattr_ifla_port
+nlattr_ifla_proto_down_reason
 nlattr_ifla_xdp
 nlattr_inet_diag_msg
 nlattr_inet_diag_req_compat