kernel: add MultiPath TCP diag kernel module

Add INET diag socket monitoring interface module for MultiPath TCP.
It allows using native Linux socket diagnostic tools such as 'ss' for
Multipath TCP connections.

Co-authored-by: Rodrigo B. de Sousa Martins <[email protected]>
Signed-off-by: sKy King <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/12884
Signed-off-by: Hauke Mehrtens <[email protected]>
Signed-off-by: Daniel Golle <[email protected]>

package/kernel/linux/modules/netsupport.mk

@@ -1494,6 +1494,23 @@ endef
 $(eval $(call KernelPackage,inet-diag))
 
 
+define KernelPackage/inet-mptcp-diag
+  SUBMENU:=$(NETWORK_SUPPORT_MENU)
+  TITLE:=INET diag support for MultiPath TCP
+  DEPENDS:=@KERNEL_MPTCP +kmod-inet-diag
+  KCONFIG:=CONFIG_INET_MPTCP_DIAG
+  FILES:=$(LINUX_DIR)/net/mptcp/mptcp_diag.ko
+  AUTOLOAD:=$(call AutoProbe,mptcp_diag)
+endef
+
+define KernelPackage/inet-mptcp-diag/description
+Support for INET (MultiPath TCP) socket monitoring interface used by
+native Linux tools such as ss.
+endef
+
+$(eval $(call KernelPackage,inet-mptcp-diag))
+
+
 define KernelPackage/xdp-sockets-diag
   SUBMENU:=$(NETWORK_SUPPORT_MENU)
   TITLE:=PF_XDP sockets monitoring interface support for ss utility