8000 esp32: Apply the LWIP active TCP socket limit. · micropython/micropython@a7d85e6 · GitHub
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esp32: Apply the LWIP active TCP socket limit.
This is a workaround for a bug in ESP-IDF where the configuration setting for maximum active TCP sockets (PCBs) is not applied. Fixes cases where a lot of short-lived TCP connections can cause: - Excessive memory usage (unbounded number of sockets in TIME-WAIT). - Much higher risk of stalled connections due to repeated port numbers. The maximum number of active TCP PCBs is reduced from 16 to 12 to further reduce this risk (trade-off against possibility of TIME-WAIT Assassination as described in RFC1337). This is not a watertight fix for the second point: a peer can still reuse a port number while a previous socket is in TIME-WAIT, and LWIP will reject that connection (in an RFC compliant way) causing the peer to stall. This work was funded through GitHub Sponsors. Signed-off-by: Angus Gratton <angus@redyak.com.au>
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‎ports/esp32/CMakeLists.txt

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@@ -74,5 +74,9 @@ list(APPEND EXTRA_COMPONENT_DIRS main_${IDF_TARGET})
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# Enable the panic handler wrapper
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idf_build_set_property(LINK_OPTIONS "-Wl,--wrap=esp_panic_handler" APPEND)
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# Patch LWIP memory pool allocators (see lwip_patch.c)
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idf_build_set_property(LINK_OPTIONS "-Wl,--wrap=memp_malloc" APPEND)
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idf_build_set_property(LINK_OPTIONS "-Wl,--wrap=memp_free" APPEND)
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# Define the project.
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project(micropython)

‎ports/esp32/boards/sdkconfig.base

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@@ -127,3 +127,7 @@ CONFIG_ETH_SPI_ETHERNET_DM9051=y
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# formatting in ROM instead and should override this, check
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# ESP_ROM_HAS_NEWLIB_NANO_FORMAT.
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CONFIG_NEWLIB_NANO_FORMAT=y
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# Further limit total sockets in TIME-WAIT when there are many short-lived
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# connections.
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CONFIG_LWIP_MAX_ACTIVE_TCP=12

‎ports/esp32/esp32_common.cmake

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@@ -77,6 +77,7 @@ list(APPEND MICROPY_SOURCE_PORT
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network_wlan.c
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mpnimbleport.c
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modsocket.c
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lwip_patch.c
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modesp.c
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esp32_nvs.c
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esp32_partition.c

‎ports/esp32/lwip_patch.c

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/*
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* This file is part of the MicroPython project, http://micropython.org/
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*
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* Development of the code in this file was sponsored by Microbric Pty Ltd
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* and Mnemote Pty Ltd
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2024 Angus Gratton
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "lwip/memp.h"
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// This is a link-time patch to enforce the limit of max active TCP PCBs. A
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// workaround for upstream issue https://github.com/espressif/esp-idf/issues/9670
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//
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// Without this limit the number of TCP PCBs in TIME-WAIT is unbounded, which can
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// have two problems on systems with a lot of short-lived TCP connections:
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//
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// - Higher memory usage.
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// - Increased chance of stalled TCP connections due to port reuse.
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static unsigned active_tcp_pcbs;
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void *__real_memp_malloc(memp_t type);
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void __real_memp_free(memp_t type, void *mem);
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void *__wrap_memp_malloc(memp_t type) {
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if (type != MEMP_TCP_PCB) {
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return __real_memp_malloc(type);
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}
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if (active_tcp_pcbs >= MEMP_NUM_TCP_PCB) {
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return NULL;
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}
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void *res = __real_memp_malloc(MEMP_TCP_PCB);
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if (res != NULL) {
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++active_tcp_pcbs;
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}
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return res;
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}
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void __wrap_memp_free(memp_t type, void *mem) {
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__real_memp_free(type, mem);
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if (type == MEMP_TCP_PCB && mem != NULL) {
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assert(active_tcp_pcbs);
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--active_tcp_pcbs;
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}
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}

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