inet_diag: implement INET_DIAG_SOCKOPT attribute decoding

* src/netlink_inet_diag.c (decode_diag_sockopt): New function.
(OPT_PRINT_FIELD_U): New macro.
(inet_diag_msg_nla_decoders) <[INET_DIAG_SOCKOPT]>: New entry
with the value of decode_diag_sockopt.
* tests/nlattr_inet_diag_msg.c: Add checks.
* NEWS: Mention it.

3 files changed, 108 insertions, 1 deletions

diff --git a/NEWS b/NEWS
index b546164c1..9829d98a3 100644
--- a/NEWS
+++ b/NEWS
@@ -10,7 +10,8 @@ Noteworthy changes in release ?.?? (????-??-??)
   * Implemented printing of Unix socket sun_path field's SELinux context.
   * Improved decoding of INET_DIAG_MD5SIG, INET_DIAG_PROTOCOL,
     INET_DIAG_REQ_PROTOCOL, INET_DIAG_SHUTDOWN, INET_DIAG_SK_BPF_STORAGES,
-    and INET_DIAG_ULP_INFO NETLINK_SOCK_DIAG netlink attributes.
+    INET_DIAG_SOCKOPT, and INET_DIAG_ULP_INFO NETLINK_SOCK_DIAG netlink
+    attributes.
   * Updated the list of NET_IPV4_CONF_* constants.
   * Updated lists of ioctl commands from Linux 5.19.
 
diff --git a/src/netlink_inet_diag.c b/src/netlink_inet_diag.c
index 93ae94ad5..2cc3f24e2 100644
--- a/src/netlink_inet_diag.c
+++ b/src/netlink_inet_diag.c
@@ -667,6 +667,80 @@ decode_diag_bpf_storages(struct tcb *const tcp,
 	return true;
 }
 
+static bool
+decode_diag_sockopt(struct tcb *const tcp,
+		    const kernel_ulong_t addr,
+		    const unsigned int len,
+		    const void *const opaque_data)
+{
+	/*
+	 * The own version of struct inet_diag_sockopt here since
+	 * there is no trivial way to detect new bit fields and, as a result,
+	 * shrinkage of the "unused" field.
+	 */
+	struct inet_diag_sockopt {
+		uint8_t	recverr			:1,
+			is_icsk			:1,
+			freebind		:1,
+			hdrincl			:1,
+			mc_loop			:1,
+			transparent		:1,
+			mc_all			:1,
+			nodefrag		:1;
+		uint8_t	bind_address_no_port	:1,
+			recverr_rfc4884		:1,
+			defer_connect		:1,
+			unused			:5;
+	} sockopt;
+
+	if (len < sizeof(sockopt))
+		return false;
+	if (umove_or_printaddr(tcp, addr, &sockopt))
+		return true;
+
+	void (*delim_f)(void) = tprint_struct_begin;
+
+#define OPT_PRINT_FIELD_U(where_, field_)				\
+	do {								\
+		if (!abbrev(tcp) || ((where_).field_)) {		\
+			delim_f();					\
+			delim_f = tprint_struct_next;			\
+			PRINT_FIELD_U_CAST((where_), field_, uint8_t);	\
+		}							\
+	} while (0)
+
+	OPT_PRINT_FIELD_U(sockopt, recverr);
+	OPT_PRINT_FIELD_U(sockopt, is_icsk);
+	OPT_PRINT_FIELD_U(sockopt, freebind);
+	OPT_PRINT_FIELD_U(sockopt, hdrincl);
+	OPT_PRINT_FIELD_U(sockopt, mc_loop);
+	OPT_PRINT_FIELD_U(sockopt, transparent);
+	OPT_PRINT_FIELD_U(sockopt, mc_all);
+	OPT_PRINT_FIELD_U(sockopt, nodefrag);
+	OPT_PRINT_FIELD_U(sockopt, bind_address_no_port);
+	OPT_PRINT_FIELD_U(sockopt, recverr_rfc4884);
+	OPT_PRINT_FIELD_U(sockopt, defer_connect);
+
+	if (!abbrev(tcp) || sockopt.unused) {
+		delim_f();
+		delim_f = tprint_struct_next;
+		PRINT_FIELD_X_CAST(sockopt, unused, uint8_t);
+		tprints_comment("bits 3..8");
+	}
+
+	if (delim_f == tprint_struct_begin)
+		tprint_struct_begin();
+
+	tprint_struct_end();
+
+#undef OPT_PRINT_FIELD_U
+
+	print_nonzero_bytes(tcp, tprint_array_next, addr, sizeof(sockopt),
+			    MIN(len, get_pagesize()), QUOTE_FORCE_HEX);
+
+	return true;
+}
+
 static const nla_decoder_t inet_diag_msg_nla_decoders[] = {
 	[INET_DIAG_MEMINFO]		= decode_inet_diag_meminfo,
 	[INET_DIAG_INFO]		= NULL,		/* unimplemented */
@@ -689,6 +763,7 @@ static const nla_decoder_t inet_diag_msg_nla_decoders[] = {
 	[INET_DIAG_ULP_INFO]		= decode_diag_ulp_info,
 	[INET_DIAG_SK_BPF_STORAGES]	= decode_diag_bpf_storages,
 	[INET_DIAG_CGROUP_ID]		= decode_nla_u64,
+	[INET_DIAG_SOCKOPT]		= decode_diag_sockopt,
 };
 
 DECL_NETLINK_DIAG_DECODER(decode_inet_diag_msg)
diff --git a/tests/nlattr_inet_diag_msg.c b/tests/nlattr_inet_diag_msg.c
index 792f60d28..e178e763b 100644
--- a/tests/nlattr_inet_diag_msg.c
+++ b/tests/nlattr_inet_diag_msg.c
@@ -782,6 +782,37 @@ main(void)
 				    printf("%s", bpfst_vals[i].str));
 	}
 
+	/* INET_DIAG_SOCKOPT */
+	static const struct {
+		ssize_t sz;
+		const char *val;
+		const char *str;
+	} sockopts[] = {
+		{ 1, "\xbe", "\"\\xbe\"" },
+		{ 2, "\x00\x00", "{}" },
+		{ 2, BE_LE("\xca\xa0", "\x53\x05"),
+		  "{recverr=1, is_icsk=1, mc_loop=1, mc_all=1"
+		  ", bind_address_no_port=1, defer_connect=1}" },
+		{ 3, BE_LE("\x1e\xad", "\x78\xb5"),
+		  "{hdrincl=1, mc_loop=1, transparent=1, mc_all=1"
+		  ", bind_address_no_port=1, defer_connect=1"
+		  ", unused=0x16 /* bits 3..8 */}" },
+		{ 4, "\xff\xff\x00\xff",
+		  "{recverr=1, is_icsk=1, freebind=1, hdrincl=1, mc_loop=1"
+		  ", transparent=1, mc_all=1, nodefrag=1"
+		  ", bind_address_no_port=1, recverr_rfc4884=1, defer_connect=1"
+		  ", unused=0x1f /* bits 3..8 */}"
+		  ", /* bytes 2..3 */ \"\\x00\\xff\"" },
+	};
+
+	for (size_t i = 0; i < ARRAY_SIZE(sockopts); i++) {
+		TEST_NLATTR(fd, nlh0, hdrlen,
+			    init_inet_diag_msg, print_inet_diag_msg,
+			    INET_DIAG_SOCKOPT,
+			    sockopts[i].sz, sockopts[i].val, sockopts[i].sz,
+			    printf("%s", sockopts[i].str));
+	}
+
 	puts("+++ exited with 0 +++");
 	return 0;
 }