net: ping6: Add ping6 command

Implement ping6 command to ping hosts using IPv6. It works the same way as
an ordinary ping command. There is no ICMP request so it is not possible
to ping our host. This patch adds options in Kconfig and Makefile to
build ping6 command.

Series-changes: 3
- Added structures and functions descriptions
- Added to ping6_receive() return value instead of void

Series-changes: 4
- Fixed structures and functions description style

Signed-off-by: Viacheslav Mitrofanov <v.v.mitrofanov@yadro.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

cmd/Kconfig

@@ -1847,6 +1847,13 @@ config CMD_PING
 	help
 	  Send ICMP ECHO_REQUEST to network host
 
+config CMD_PING6
+	bool "ping6"
+	depends on IPV6
+	default y if (CMD_PING && IPV6)
+	help
+	  Send ICMPv6 ECHO_REQUEST to network host
+
 config CMD_CDP
 	bool "cdp"
 	help

cmd/net.c

@@ -403,6 +403,32 @@ U_BOOT_CMD(
 );
 #endif
 
+#if IS_ENABLED(CONFIG_CMD_PING6)
+int do_ping6(struct cmd_tbl *cmdtp, int flag, int argc, char * const argv[])
+{
+	if (string_to_ip6(argv[1], strlen(argv[1]), &net_ping_ip6))
+		return CMD_RET_USAGE;
+
+	use_ip6 = true;
+	if (net_loop(PING6) < 0) {
+		use_ip6 = false;
+		printf("ping6 failed; host %pI6c is not alive\n",
+		       &net_ping_ip6);
+		return 1;
+	}
+
+	use_ip6 = false;
+	printf("host %pI6c is alive\n", &net_ping_ip6);
+	return 0;
+}
+
+U_BOOT_CMD(
+	ping6,  2,      1,      do_ping6,
+	"send ICMPv6 ECHO_REQUEST to network host",
+	"pingAddress"
+);
+#endif /* CONFIG_CMD_PING6 */
+
 #if defined(CONFIG_CMD_CDP)
 
 static void cdp_update_env(void)