refactor(lwip): Added on/off switch for LwIP stack

* This switch allows applications to replace lwip with a different
  IP stack or just make it build if it is a dependency but not
  actually needed.

components/esp-tls/CMakeLists.txt

@@ -35,7 +35,7 @@ set_property(TARGET ${lwip} APPEND PROPERTY LINK_INTERFACE_MULTIPLICITY 5)
 else()
     # Check if LWIP in the build for linux target to adapt esp-tls compatibility layer
     idf_build_get_property(build_components BUILD_COMPONENTS)
-    if("lwip" IN_LIST build_components)
+    if(CONFIG_LWIP_ENABLE)
         target_compile_definitions(${COMPONENT_LIB} PRIVATE ESP_TLS_WITH_LWIP=1)
     endif()
 endif()

components/lwip/CMakeLists.txt

@@ -1,10 +1,12 @@
 idf_build_get_property(target IDF_TARGET)
-if(NOT ${target} STREQUAL "linux")
+
+if(CONFIG_LWIP_ENABLE)
+    if(NOT ${target} STREQUAL "linux")
         # ESP platform targets share the same port folder
         set(target esp32xx)
-endif()
+    endif()
 
-set(include_dirs
+    set(include_dirs
         include
         include/apps
         include/apps/sntp
@@ -16,7 +18,7 @@ set(include_dirs
         port/${target}/include/sys
         )
 
-set(srcs
+    set(srcs
         "apps/sntp/sntp.c"
         "lwip/src/api/api_lib.c"
         "lwip/src/api/api_msg.c"
@@ -100,7 +102,7 @@ set(srcs
         "port/sockets_ext.c"
         "port/freertos/sys_arch.c")
 
-if(CONFIG_LWIP_PPP_SUPPORT)
+    if(CONFIG_LWIP_PPP_SUPPORT)
         list(APPEND srcs
             "lwip/src/netif/ppp/auth.c"
             "lwip/src/netif/ppp/ccp.c"
@@ -132,35 +134,39 @@ if(CONFIG_LWIP_PPP_SUPPORT)
             "lwip/src/netif/ppp/polarssl/md4.c"
             "lwip/src/netif/ppp/polarssl/md5.c"
             "lwip/src/netif/ppp/polarssl/sha1.c")
-endif()
+    endif()
 
-if(NOT ${target} STREQUAL "linux")
+    if(NOT ${target} STREQUAL "linux")
         # Support for vfs and linker fragments only for target builds
-    set(priv_requires vfs)
         set(linker_fragments linker.lf)
         if(CONFIG_VFS_SUPPORT_IO)
             list(APPEND srcs "port/${target}/vfs_lwip.c")
         else()
             list(APPEND srcs "port/${target}/no_vfs_syscalls.c")
         endif()
-else()
+    else()
         # This wraps some posix IO functions to conditionally pass control to lwip
         list(APPEND srcs "port/${target}/vfs_lwip.c")
-endif()
+    endif()
 
-if(CONFIG_LWIP_ICMP)
+    if(CONFIG_LWIP_ICMP)
         list(APPEND srcs
             "apps/ping/esp_ping.c"
             "apps/ping/ping.c"
             "apps/ping/ping_sock.c")
-endif()
+    endif()
 
-if(CONFIG_LWIP_DHCPS)
+    if(CONFIG_LWIP_DHCPS)
         list(APPEND srcs "apps/dhcpserver/dhcpserver.c")
-endif()
+    endif()
 
-if(CONFIG_LWIP_DHCP_RESTORE_LAST_IP)
+    if(CONFIG_LWIP_DHCP_RESTORE_LAST_IP)
         list(APPEND srcs "port/esp32xx/netif/dhcp_state.c")
+    endif()
+endif() # CONFIG_LWIP_ENABLE
+
+if(NOT ${target} STREQUAL "linux")
+    set(priv_requires vfs)
 endif()
 
 idf_component_register(SRCS "${srcs}"
@@ -168,43 +174,44 @@ idf_component_register(SRCS "${srcs}"
                     LDFRAGMENTS   ${linker_fragments}
                     PRIV_REQUIRES ${priv_requires})
 
-# lots of LWIP source files evaluate macros that check address of stack variables
+if(CONFIG_LWIP_ENABLE)
-target_compile_options(${COMPONENT_LIB} PRIVATE -Wno-address)
+    # lots of LWIP source files evaluate macros that check address of stack variables
-target_compile_definitions(${COMPONENT_LIB} PRIVATE ESP_LWIP_COMPONENT_BUILD)
+    target_compile_options(${COMPONENT_LIB} PRIVATE -Wno-address)
+    target_compile_definitions(${COMPONENT_LIB} PRIVATE ESP_LWIP_COMPONENT_BUILD)
 
-set_source_files_properties(
+    set_source_files_properties(
         lwip/src/netif/ppp/pppos.c
         PROPERTIES COMPILE_FLAGS
         -Wno-type-limits
         )
-# "comparison is always false due to limited range of data type" warning
+    # "comparison is always false due to limited range of data type" warning
-# when setting CONFIG_LWIP_TCP_WND_DEFAULT to 65535
+    # when setting CONFIG_LWIP_TCP_WND_DEFAULT to 65535
-set_source_files_properties(
+    set_source_files_properties(
         lwip/src/core/tcp.c
         PROPERTIES COMPILE_FLAGS
         -Wno-type-limits
-)
+    )
 
-# ignore some declaration mismatches
+    # ignore some declaration mismatches
-set_source_files_properties(
+    set_source_files_properties(
         lwip/src/netif/ppp/chap_ms.c
         PROPERTIES COMPILE_FLAGS
         -Wno-array-parameter
-)
+    )
 
-if(CONFIG_OPENTHREAD_ENABLED)
+    if(CONFIG_OPENTHREAD_ENABLED)
         idf_component_optional_requires(PRIVATE openthread)
-endif()
+    endif()
 
-if(CONFIG_ETH_ENABLED)
+    if(CONFIG_ETH_ENABLED)
         idf_component_optional_requires(PRIVATE esp_eth)
-endif()
+    endif()
 
-if(CONFIG_LWIP_DHCP_RESTORE_LAST_IP)
+    if(CONFIG_LWIP_DHCP_RESTORE_LAST_IP)
         idf_component_optional_requires(PRIVATE nvs_flash)
-endif()
+    endif()
 
-if(${target} STREQUAL "linux")
+    if(${target} STREQUAL "linux")
         set(THREADS_PREFER_PTHREAD_FLAG ON)
         find_package(Threads REQUIRED)
         target_link_libraries(${COMPONENT_LIB} PRIVATE Threads::Threads)
@@ -217,4 +224,5 @@ if(${target} STREQUAL "linux")
                     target_link_libraries(${COMPONENT_LIB} INTERFACE "-Wl,--wrap=${wrap}")
                     target_link_libraries(${COMPONENT_LIB} INTERFACE "-u __wrap_${wrap}")
         endforeach()
+    endif()
 endif()

components/lwip/Kconfig

@@ -1,4 +1,15 @@
 menu "LWIP"
+    config LWIP_ENABLE
+        bool "Enable LwIP stack"
+        default y if !IDF_TARGET_LINUX
+        default n if IDF_TARGET_LINUX
+        help
+            Builds normally if selected. Excludes LwIP from build if unselected, even if it is a
+            dependency of a component or application.
+            Some applications can switch their IP stacks, e.g., when switching between chip
+            and Linux targets (LwIP stack vs. Linux IP stack). Since the LwIP dependency cannot
+            easily be excluded based on a Kconfig option, it has to be a dependency in all cases.
+            This switch allows the LwIP stack to be built selectively, even if it is a dependency.
 
     config LWIP_LOCAL_HOSTNAME
         string "Local netif hostname"

components/mbedtls/CMakeLists.txt

@@ -134,8 +134,7 @@ endif()
 
 # net_sockets.c should only be compiled if BSD socket functions are available.
 # Do this by checking if lwip component is included into the build.
-idf_build_get_property(build_components BUILD_COMPONENTS)
+if(CONFIG_LWIP_ENABLE)
-if(lwip IN_LIST build_components)
     list(APPEND mbedtls_target_sources "${COMPONENT_DIR}/port/net_sockets.c")
     idf_component_get_property(lwip_lib lwip COMPONENT_LIB)
     target_link_libraries(${COMPONENT_LIB} ${linkage_type} ${lwip_lib})

examples/protocols/sockets/udp_client/sdkconfig.ci.linux

@@ -1,3 +1,4 @@
 CONFIG_IDF_TARGET="linux"
 CONFIG_EXAMPLE_IPV4_ADDR="127.0.0.1"
 CONFIG_EXAMPLE_CONNECT_LWIP_TAPIF=n
+CONFIG_LWIP_ENABLE=y

examples/protocols/sockets/udp_client/sdkconfig.defaults.linux

@@ -0,0 +1 @@
+CONFIG_LWIP_ENABLE=y