WIP: packages: add ucode-mod-l2tp

packages/ucode-mod-l2tp/Makefile

@@ -0,0 +1,40 @@
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=ucode-mod-l2tp
+PKG_RELEASE:=0
+PKG_MAINTAINER:=Packet Please <[email protected]>
+
+include $(INCLUDE_DIR)/package.mk
+
+define Package/ucode-mod-l2tp
+  SECTION:=utils
+  CATEGORY:=Utilities
+  TITLE:=ucode l2tp module
+  DEPENDS:=+libucode +libubox +libnl-tiny
+  EXTRA_DEPENDS:=+kmod-l2tp
+endef
+
+define Package/ucode-mod-l2tp/description
+The l2tp module provides functionality for creating and configuring
+l2tp interfaces using the kernel generic netlink API.
+endef
+
+define Package/ucode-mod-l2tp/install
+	$(INSTALL_DIR) $(1)/usr/lib/ucode
+	$(CP) $(PKG_BUILD_DIR)/l2tp.so $(1)/usr/lib/ucode/
+endef
+
+define Build/Configure
+endef
+
+TARGET_CFLAGS += \
+	-D_GNU_SOURCE \
+	-I$(STAGING_DIR)/usr/include/libnl-tiny
+
+define Build/Compile
+	$(TARGET_CC) $(TARGET_CFLAGS) $(TARGET_LDFLAGS) $(FPIC) \
+		-Wall -ffunction-sections -Wl,--gc-sections -shared -Wl,--no-as-needed -lubox -lnl-tiny \
+		-o $(PKG_BUILD_DIR)/l2tp.so $(PKG_BUILD_DIR)/l2tp.c
+endef
+
+$(eval $(call BuildPackage,ucode-mod-l2tp))

packages/ucode-mod-l2tp/l2tp.c

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+
+static const uc_l2tp_nested_spec_t l2tp_tunnel_create_msg = {
+  .headsize = 0,
+  .nattrs = 5,
+  .attrs = {
+    { L2TP_ATTR_PROTO_VERSION, "proto_version", DT_, 0, NULL },
+    { L2TP_ATTR_CONN_ID, "conn_id", DT_, 0, NULL },
+    { L2TP_ATTR_PEER_CONN_ID, "peer_conn_id", DT_, 0, NULL },
+    { L2TP_ATTR_ENCAP_TYPE, "encap_type", DT_, 0, NULL },
+    { L2TP_ATTR_FD, "fd", DT_, 0, NULL },
+  }
+};
+
+static const uc_l2tp_nested_spec_t l2tp_tunnel_delete_msg = {
+  .headsize = 0,
+  .nattrs = 2,
+  .attrs = {
+    { L2TP_ATTR_CONN_ID, "conn_id", DT_, 0, NULL },
+    { L2TP_ATTR_SESSION_ID, "session_id", DT_, 0, NULL },
+  }
+};
+static const uc_l2tp_nested_spec_t l2tp_session_create_msg = {
+  .headsize = 0,
+  .nattrs = 5,
+  .attrs = {
+    { L2TP_ATTR_CONN_ID, "conn_id", DT_, 0, NULL },
+    { L2TP_ATTR_SESSION_ID, "session_id", DT_, 0, NULL },
+    { L2TP_ATTR_PEER_SESSION_ID, "peer_session_id", DT_, 0, NULL },
+    { L2TP_ATTR_PW_TYPE, "pw_type", DT_, 0, NULL },
+    { L2TP_ATTR_IFNAME, "ifname", DT_, 0, NULL },
+  }
+};
+static const uc_l2tp_nested_spec_t l2tp_session_delete_msg = {
+  .headsize = 0,
+  .nattrs = 1,
+  .attrs = {
+    { L2TP_ATTR_CONN_ID, "conn_id", DT_, 0, NULL },
+  }
+};
+static const uc_l2tp_nested_spec_t l2tp_session_set_mtu_msg = {
+  .headsize = 0,
+  .nattrs = 3,
+  .attrs = {
+    { L2TP_ATTR_CONN_ID, "conn_id", DT_, 0, NULL },
+    { L2TP_ATTR_SESSION_ID, "session_id", DT_, 0, NULL },
+    { L2TP_ATTR_MTU, "mtu", DT_, 0, NULL },
+  }
+};

packages/ucode-mod-l2tp/notes.md

@@ -0,0 +1,107 @@
+
+# ucode-mod-l2tp
+
+## tunneldigger
+
+context_process()
+
+context_process_control_packet()
+
+context_setup_tunnel()
+L2TP_CMD_TUNNEL_CREATE {
+  L2TP_ATTR_CONN_ID => ctx.tunnel_id
+  L2TP_ATTR_PEER_CONN_ID => peer_tunnel_id
+  L2TP_ATTR_PROTO_VERSION => 3
+  L2TP_ATTR_ENCAP_TYPE => L2TP_ENCAPTYPE_UDP
+  L2TP_ATTR_FD => ctx.fd
+}
+L2TP_CMD_SESSION_CREATE {
+  L2TP_ATTR_CONN_ID => ctx.tunnel_id
+  L2TP_ATTR_SESSION_ID => 1 or ctx.tunnel_id
+  L2TP_ATTR_PEER_SESSION_ID =>  1 or peer_tunnel_id
+  L2TP_ATTR_PW_TYPE => L2TP_PWTYPE_ETH
+  L2TP_ATTR_IFNAME => ctx.tunnel_iface
+}
+
+context_session_set_mtu()
+L2TP_CMD_SESSION_MODIFY {
+  L2TP_ATTR_CONN_ID => ctx.tunnel_id
+  L2TP_ATTR_SESSION_ID => 1
+  L2TP_ATTR_MTU => mtu
+}
+
+context_delete_tunnel()
+L2TP_CMD_SESSION_DELETE {
+  L2TP_ATTR_CONN_ID => ctx.tunnel_id
+  L2TP_ATTR_SESSION_ID => 1
+}
+L2TP_CMD_TUNNEL_DELETE {
+  L2TP_ATTR_CONN_ID => ctx.tunnel_id
+}
+
+packet headers, ctrl types, state machine:
+```
+// L2TP data header overhead for calculating tunnel MTU; takes
+// the following headers into account:
+//
+//   20 bytes (IP header)
+//    8 bytes (UDP header)
+//    4 bytes (L2TPv3 Session ID)
+//    4 bytes (L2TPv3 Cookie)
+//    4 bytes (L2TPv3 Pseudowire CE)
+//   14 bytes (Ethernet)
+//
+#define L2TP_TUN_OVERHEAD 54
+
+enum l2tp_ctrl_type {
+  // Unreliable messages (0x00 - 0x7F).
+  CONTROL_TYPE_COOKIE    = 0x01,
+  CONTROL_TYPE_PREPARE   = 0x02,
+  CONTROL_TYPE_ERROR     = 0x03,
+  CONTROL_TYPE_TUNNEL    = 0x04,
+  CONTROL_TYPE_KEEPALIVE = 0x05,
+  CONTROL_TYPE_PMTUD     = 0x06,
+  CONTROL_TYPE_PMTUD_ACK = 0x07,
+  CONTROL_TYPE_REL_ACK   = 0x08,
+  CONTROL_TYPE_PMTU_NTFY = 0x09,
+  CONTROL_TYPE_USAGE     = 0x0A,
+  // Reliable messages (0x80 - 0xFF).
+  CONTROL_TYPE_LIMIT     = 0x80,
+};
+
+/* The state machine looks as follows:
+   STATE_REINIT (initial state)
+   When the FD is successfully initialized:
+   -> STATE_RESOLVING
+   When DNS resolving succeeds:
+   -> STATE_GET_USAGE (sending a usage and a cookie request every 2s)
+   when we receive usage information or a cookie
+   -> STATE_STANBDY
+
+   Now broker selection is performed; for the selected broker the main loop changes the state so
+   that we go on:
+   -> STATE_GET_COOKIE (sending a cookie request every 2s)
+   when we receive the cookie
+   -> STATE_GET_TUNNEL
+   when we receive the tunnel information
+   -> STATE_KEEPALIVE
+   when the connection fails
+   -> STATE_FAILED
+
+   In case of an error, we transition to STATE_REINIT (if it happens early) or STATE_FAILED
+   (if it happens when we are already >= STATE_GET_COOKIE).  The main loop restarts everything
+   once the selected broker enters STATE_FAILED.
+   For broken brokers, the main loop sets the state to STATE_FAILED to make sure that
+   they do not do anything.
+*/
+enum l2tp_ctrl_state {
+  STATE_REINIT,
+  STATE_RESOLVING,
+  STATE_GET_USAGE,
+  STATE_STANBDY,
+  STATE_GET_COOKIE,
+  STATE_GET_TUNNEL,
+  STATE_KEEPALIVE,
+  STATE_FAILED,
+};
+```