kcp: add package

KCP, a reliable ARQ protocol offering a TCP-like ordered stream over an
unreliable datagram transport. Built shared as libkcp with an imposed
soname, since upstream sets none.

Signed-off-by: Daniel Golle <redacted>

diff --git a/libs/kcp/Makefile b/libs/kcp/Makefile
new file mode 100644 (file)
index 0000000..63b1c23
--- /dev/null
+++ b/libs/kcp/Makefile
@@ -0,0 +1,63 @@
+#
+# Copyright (C) 2026 Daniel Golle <daniel@makrotopia.org>
+#
+# This is free software, licensed under the GNU General Public License v2.
+# See /LICENSE for more information.
+#
+
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=kcp
+PKG_VERSION:=2.1.1
+PKG_RELEASE:=1
+
+PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
+PKG_SOURCE_URL:=https://codeload.github.com/skywind3000/kcp/tar.gz/$(PKG_VERSION)?
+PKG_HASH:=54d3c80928d206529f67cba6f96f2c98007182b46e3112819b200d914f96e425
+
+PKG_MAINTAINER:=Daniel Golle <daniel@makrotopia.org>
+PKG_LICENSE:=MIT
+PKG_LICENSE_FILES:=LICENSE
+
+CMAKE_INSTALL:=1
+
+include $(INCLUDE_DIR)/package.mk
+include $(INCLUDE_DIR)/cmake.mk
+
+# Upstream honours BUILD_SHARED_LIBS but sets no VERSION/SOVERSION, so the
+# soname is imposed here (see Build/Prepare): a bare libkcp.so leaves no way
+# to express an ABI break. Upstream offers no ABI guarantee either way, so
+# treat 0 as a packaged ABI epoch and bump it if the ikcp_* surface changes.
+define Package/libkcp
+  SECTION:=libs
+  CATEGORY:=Libraries
+  TITLE:=KCP - A Fast and Reliable ARQ Protocol
+  URL:=https://github.com/skywind3000/kcp
+  ABI_VERSION:=0
+endef
+
+define Package/libkcp/description
+  KCP is a fast and reliable ARQ protocol implementing a TCP-like reliable
+  ordered stream on top of an unreliable datagram transport such as UDP,
+  trading about 10-20% more bandwidth for 30-40% lower latency than TCP.
+  It is a pure algorithm: the caller supplies the datagram in- and output.
+endef
+
+CMAKE_OPTIONS += \
+       -DBUILD_TESTING=OFF \
+       -DBUILD_SHARED_LIBS=ON
+
+# CMake sets the soname itself, so a linker flag cannot win; the target
+# property is the only thing it honours.
+define Build/Prepare
+       $(Build/Prepare/Default)
+       echo 'set_target_properties(kcp PROPERTIES VERSION $(PKG_VERSION) SOVERSION 0)' \
+               >> $(PKG_BUILD_DIR)/CMakeLists.txt
+endef
+
+define Package/libkcp/install
+       $(INSTALL_DIR) $(1)/usr/lib
+       $(CP) $(PKG_INSTALL_DIR)/usr/lib/libkcp.so.* $(1)/usr/lib/
+endef
+
+$(eval $(call BuildPackage,libkcp))