sys/stdio_udp: add stdio over UDP

makefiles/dependency_resolution.inc.mk

@@ -80,4 +80,17 @@ else
                             "don't run this on public networks!$(COLOR_RESET)" 1>&2)
     endif
   endif
+
+  # Warn about STDIO UDP
+  ifneq (,$(filter stdio_udp,$(USEMODULE)))
+    ifneq (1,$(I_UNDERSTAND_THAT_STDIO_UDP_IS_INSECURE))
+      $(shell $(COLOR_ECHO) "$(COLOR_RED)stdio via UDP will be started automatically,"\
+                            "make sure you understand why this almost certainly"\
+                            "is a REALLY BAD idea before proceeding!$(COLOR_RESET)" 1>&2)
+      $(error I_UNDERSTAND_THAT_STDIO_UDP_IS_INSECURE must be set to 1 to proceed)
+    else
+      $(shell $(COLOR_ECHO) "$(COLOR_YELLOW)stdio via UDP will be started automatically,"\
+                            "don't run this on public networks!$(COLOR_RESET)" 1>&2)
+    endif
+  endif
 endif

makefiles/stdio.inc.mk

@@ -8,6 +8,7 @@ STDIO_MODULES = \
   stdio_rtt \
   stdio_semihosting \
   stdio_uart \
+  stdio_udp \
   stdio_telnet \
   stdio_tinyusb_cdc_acm \
   stdio_usb_serial_jtag \
@@ -75,6 +76,10 @@ ifneq (,$(filter stdio_telnet,$(USEMODULE)))
   USEMODULE += telnet
 endif
 
+ifneq (,$(filter stdio_udp,$(USEMODULE)))
+  USEMODULE += sock_udp
+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/stdio_udp/Makefile

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

sys/stdio_udp/doc.txt

@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2023 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    sys_stdio_udp   STDIO over UDP
+ * @ingroup     sys_stdio
+ * @brief       STDIO over UDP implementation
+ *
+ * This file implements STDIO via a UDP that can be used with e.g. netcat:
+ *
+ *      nc -u fe80::7837:fcff:fe7d:1aaf%tapbr0 2323
+ *
+ * It can be enabled with
+ *
+ *      USEMODULE += stdio_udp
+ *
+ * and will listen on `CONFIG_STDIO_UDP_PORT` for incoming connections.
+ *
+ * You will also have to set `I_UNDERSTAND_THAT_STDIO_UDP_IS_INSECURE = 1` to
+ * acknowledge that you will only use this for debugging in an isolated network.
+ *
+ * @warning     This is entirely unsecured, only use this for debugging in
+ *              an isolated network!
+ */

sys/stdio_udp/stdio_udp.c

@@ -0,0 +1,85 @@
+/*
+ * Copyright (C) 2023 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_stdio_udp
+ * @{
+ *
+ * @file
+ * @brief       STDIO over UDP implementation
+ *
+ * @author      Benjamin Valentin <benjamin.valentin@ml-pa.com>
+ *
+ * @}
+ */
+
+#include <errno.h>
+
+#include "macros/utils.h"
+#include "net/sock/udp.h"
+
+#ifndef CONFIG_STDIO_UDP_PORT
+#define CONFIG_STDIO_UDP_PORT       2323
+#endif
+
+#ifndef CONFIG_STDIO_UDP_RX_BUF_LEN
+#define CONFIG_STDIO_UDP_RX_BUF_LEN 64
+#endif
+
+static sock_udp_t sock;
+static sock_udp_ep_t remote;
+
+void stdio_init(void)
+{
+    const sock_udp_ep_t local = {
+        .family = AF_INET6,
+        .netif = SOCK_ADDR_ANY_NETIF,
+        .port = CONFIG_STDIO_UDP_PORT,
+    };
+
+    sock_udp_create(&sock, &local, NULL, 0);
+}
+
+ssize_t stdio_read(void* buffer, size_t count)
+{
+    static uint8_t rx_buf[CONFIG_STDIO_UDP_RX_BUF_LEN];
+    static uint8_t *pos;
+    static size_t left;
+
+    /* shell will only read one byte at a time, so we buffer the input */
+    if (left == 0) {
+        int res = sock_udp_recv(&sock, rx_buf, sizeof(rx_buf),
+                                SOCK_NO_TIMEOUT, &remote);
+        if (res > 0) {
+            left = res;
+            pos = rx_buf;
+        } else {
+            return res;
+        }
+    }
+
+    count = MIN(left, count);
+    memcpy(buffer, pos, count);
+
+    left -= count;
+    pos  += count;
+
+    return count;
+}
+
+ssize_t stdio_write(const void* buffer, size_t len)
+{
+    if (remote.port == 0) {
+        return -ENOTCONN;
+    }
+    if (len == 0) {
+        return 0;
+    }
+
+    return sock_udp_send(&sock, buffer, len, &remote);
+}