sys/net/application_layer: add telnet server module

makefiles/pseudomodules.inc.mk

@@ -151,6 +151,7 @@ PSEUDOMODULES += stdin
 PSEUDOMODULES += stdio_cdc_acm
 PSEUDOMODULES += stdio_ethos
 PSEUDOMODULES += stdio_uart_rx
+PSEUDOMODULES += stdio_telnet
 PSEUDOMODULES += stm32_eth
 PSEUDOMODULES += stm32_eth_auto
 PSEUDOMODULES += stm32_eth_link_up

makefiles/stdio.inc.mk

@@ -6,6 +6,7 @@ STDIO_MODULES = \
   stdio_rtt \
   stdio_semihosting \
   stdio_uart \
+  stdio_telnet \
   #
 
 ifneq (,$(filter newlib picolibc,$(USEMODULE)))
@@ -49,6 +50,11 @@ ifneq (,$(filter stdio_semihosting,$(USEMODULE)))
   FEATURES_REQUIRED_ANY += cpu_core_cortexm|arch_riscv
 endif
 
+ifneq (,$(filter stdio_telnet,$(USEMODULE)))
+  DEFAULT_MODULE += auto_init_telnet
+  USEMODULE += telnet
+endif
+
 # enable stdout buffering for modules that benefit from sending out buffers in larger chunks
 ifneq (,$(filter picolibc,$(USEMODULE)))
   ifneq (,$(filter stdio_cdc_acm stdio_ethos slipdev_stdio stdio_semihosting,$(USEMODULE)))

sys/Makefile

@@ -8,6 +8,9 @@ endif
 ifneq (,$(filter cipher_modes,$(USEMODULE)))
   DIRS += crypto/modes
 endif
+ifneq (,$(filter telnet,$(USEMODULE)))
+  DIRS += net/application_layer/telnet
+endif
 ifneq (,$(filter constfs,$(USEMODULE)))
   DIRS += fs/constfs
 endif

sys/Makefile.dep

@@ -314,6 +314,11 @@ ifneq (,$(filter sema_inv,$(USEMODULE)))
   USEMODULE += atomic_utils
 endif
 
+ifneq (,$(filter telnet,$(USEMODULE)))
+  USEMODULE += pipe
+  USEMODULE += sock_tcp
+endif
+
 ifneq (,$(filter luid,$(USEMODULE)))
   FEATURES_OPTIONAL += periph_cpuid
 endif

sys/auto_init/auto_init.c

@@ -279,6 +279,12 @@ void auto_init(void)
         gnrc_dhcpv6_client_simple_pd_init();
     }
 
+    if (IS_USED(MODULE_AUTO_INIT_TELNET)) {
+        LOG_DEBUG("auto_init TELNET server\n");
+        extern void telnet_server_start(void);
+        telnet_server_start();
+    }
+
     if (IS_USED(MODULE_AUTO_INIT_MULTIMEDIA)) {
         LOG_DEBUG("auto_init MULTIMEDIA\n");
         if (IS_USED(MODULE_DFPLAYER)) {

sys/include/net/telnet.h

@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2021 ML!PA Consulting GmbH
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @defgroup    net_telnet basic Telnet server implementation
+ * @ingroup     net_ipv6
+ * @brief       Telnet server functions
+ * @{
+ *
+ * @file
+ * @brief   Telnet server ([RFC 855](https://tools.ietf.org/html/rfc855)) implementation
+ * @note    This implementation only supports a single client
+ *
+ * @author  Benjamin Valentin <[email protected]>
+ */
+#ifndef NET_TELNET_H
+#define NET_TELNET_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   The port for the Telnet server to listen on
+ */
+#ifndef TELNET_PORT
+#define TELNET_PORT (23)
+#endif
+
+/**
+ * @brief   Start the Telnet server thread
+ *
+ * @return  0 on success, error otherwise
+ */
+int telnet_server_start(void);
+
+/**
+ * @brief   Write data to the telnet client
+ *
+ * @params[in] buffer   The buffer to send to the client
+ * @params[in] len      The length of the buffer
+ *
+ * @return  0 on success, error otherwise
+ */
+int telnet_server_write(const void* buffer, size_t len);
+
+/**
+ * @brief   Read data from the telnet client, will block until data is available.
+ *
+ * @params[out] buffer   The buffer to write data from the client
+ * @params[in]  count    Number of bytes to read
+ *
+ * @return  number of bytes read, error otherwise
+ */
+int telnet_server_read(void* buffer, size_t count);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* NET_TELNET_H */
+/** @} */

sys/net/application_layer/telnet/Makefile

@@ -0,0 +1 @@
+include $(RIOTBASE)/Makefile.base

sys/net/application_layer/telnet/stdio_telnet.c

@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2021 ML!PA Consulting GmbH
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     sys
+ * @{
+ *
+ * @file
+ * @brief       STDIO over Telnet implementation
+ *
+ * This file implements STDIO via a Telnet server with fallback UART output
+ *
+ * @author      Benjamin Valentin <[email protected]>
+ *
+ * @}
+ */
+
+#include <errno.h>
+
+#include "board.h"
+#include "kernel_defines.h"
+#include "net/telnet.h"
+#if IS_USED(MODULE_PERIPH_UART)
+#include "stdio_uart.h"
+#include "periph/uart.h"
+#endif
+#if IS_USED(MODULE_VFS)
+#include "vfs.h"
+#endif
+
+#define ENABLE_DEBUG 0
+#include "debug.h"
+
+static inline void _init_fallback(void)
+{
+#if defined(STDIO_UART_DEV) && IS_USED(MODULE_PERIPH_UART)
+    uart_init(STDIO_UART_DEV, STDIO_UART_BAUDRATE, NULL, NULL);
+#endif
+}
+
+static inline int _write_fallback(const void* buffer, size_t len)
+{
+#if defined(STDIO_UART_DEV) && IS_USED(MODULE_PERIPH_UART)
+    uart_write(STDIO_UART_DEV, buffer, len);
+#else
+    (void)buffer;
+#endif
+
+    return len;
+}
+
+void stdio_init(void)
+{
+    _init_fallback();
+
+#if IS_USED(MODULE_VFS)
+    vfs_bind_stdio();
+#endif
+}
+
+ssize_t stdio_read(void* buffer, size_t count)
+{
+    return telnet_server_read(buffer, count);
+}
+
+ssize_t stdio_write(const void* buffer, size_t len)
+{
+    int res = telnet_server_write(buffer, len);
+    if (res != -ENOTCONN) {
+        return res;
+    }
+
+    return _write_fallback(buffer, len);
+}