netlink_inet_diag: implement INET_DIAG_MD5SIG attribute decoding

* linux/inet_diag.h (INET_DIAG_MD5SIG): New enum entity.
(TCP_MD5SIG_MAXKEYLEN): New macro.
(struct tcp_diag_md5sig): New type definition.
* netlink_inet_diag.c (decode_tcp_md5sig): New function.
(inet_diag_msg_nla_decoders) <[INET_DIAG_MD5SIG]>: New attribute,
decoded by decode_tcp_md5sig.
* xlat/inet_diag_attrs.in (INET_DIAG_MD5SIG): New constant.
* xlat/inet_diag_extended_flags.in (1<<(INET_DIAG_MD5SIG-1)): New flag.

linux/inet_diag.h

@@ -109,6 +109,7 @@ enum {
 	INET_DIAG_MARK,
 	INET_DIAG_BBRINFO,
 	INET_DIAG_CLASS_ID,
+	INET_DIAG_MD5SIG,
 };
 
 /* INET_DIAG_MEM */
@@ -145,4 +146,15 @@ struct tcp_bbr_info {
 	uint32_t bbr_cwnd_gain;
 };
 
+/* INET_DIAG_MD5SIG */
+#define TCP_MD5SIG_MAXKEYLEN   80
+
+struct tcp_diag_md5sig {
+	uint8_t  tcpm_family;
+	uint8_t  tcpm_prefixlen;
+	uint16_t tcpm_keylen;
+	uint32_t tcpm_addr[4]; /* big endian */
+	uint8_t  tcpm_key[TCP_MD5SIG_MAXKEYLEN];
+};
+
 #endif /* !STRACE_LINUX_INET_DIAG_H */

netlink_inet_diag.c

@@ -370,6 +370,51 @@ decode_tcp_bbr_info(struct tcb *const tcp,
 	return true;
 }
 
+static bool
+decode_tcp_md5sig(struct tcb *const tcp,
+		  const kernel_ulong_t addr,
+		  const unsigned int len,
+		  const void *const opaque_data)
+{
+	struct tcp_diag_md5sig sig;
+
+	if (len < sizeof(sig))
+		return false;
+
+	kernel_ulong_t l = len;
+	kernel_ulong_t a = addr;
+
+	for (; len >= sizeof(sig); l -= sizeof(sig), a += sizeof(sig)) {
+		if (a != addr)
+			tprints(", ");
+
+		if (umove(tcp, a, &sig)) {
+			tprints("/* ");
+			printaddr(a);
+			tprints(" */");
+
+			return true;
+		}
+
+		PRINT_FIELD_XVAL("{", sig, tcpm_family, addrfams, "AF_???");
+		PRINT_FIELD_U(", ", sig, tcpm_prefixlen);
+		PRINT_FIELD_U(", ", sig, tcpm_keylen);
+		PRINT_FIELD_INET_ADDR(", ", sig, tcpm_addr, sig.tcpm_family);
+		tprints(", ");
+		print_quoted_string((char *) sig.tcpm_key,
+				    MIN(sizeof(sig.tcpm_key), sig.tcpm_keylen),
+				    QUOTE_FORCE_HEX);
+		tprints("}");
+	}
+
+	if (l) {
+		tprints(",");
+		tprintf_comment("%" PRI_klu " bytes of unexpected data", l);
+	}
+
+	return true;
+}
+
 static const nla_decoder_t inet_diag_msg_nla_decoders[] = {
 	[INET_DIAG_MEMINFO]	= decode_inet_diag_meminfo,
 	[INET_DIAG_INFO]	= NULL,			/* unimplemented */
@@ -387,7 +432,8 @@ static const nla_decoder_t inet_diag_msg_nla_decoders[] = {
 	[INET_DIAG_PAD]		= NULL,
 	[INET_DIAG_MARK]	= decode_nla_u32,
 	[INET_DIAG_BBRINFO]	= decode_tcp_bbr_info,
-	[INET_DIAG_CLASS_ID]	= decode_nla_u32
+	[INET_DIAG_CLASS_ID]	= decode_nla_u32,
+	[INET_DIAG_MD5SIG]	= decode_tcp_md5sig,
 };
 
 DECL_NETLINK_DIAG_DECODER(decode_inet_diag_msg)

xlat/inet_diag_attrs.in

@@ -17,3 +17,4 @@ INET_DIAG_PAD
 INET_DIAG_MARK
 INET_DIAG_BBRINFO
 INET_DIAG_CLASS_ID
+INET_DIAG_MD5SIG

xlat/inet_diag_extended_flags.in

@@ -16,3 +16,4 @@
 1<<(INET_DIAG_MARK-1)
 1<<(INET_DIAG_BBRINFO-1)
 1<<(INET_DIAG_CLASS_ID-1)
+1<<(INET_DIAG_MD5SIG-1)