tests: add a simple proof of concept test for gnrc_sock + gnrc_neterr

tests/gnrc_sock_neterr/Makefile

@@ -0,0 +1,12 @@
+include ../Makefile.tests_common
+
+USEMODULE += auto_init_gnrc_netif
+USEMODULE += gnrc_ipv6_default
+USEMODULE += gnrc_neterr
+USEMODULE += gnrc_sock_udp
+USEMODULE += od
+USEMODULE += xtimer
+
+CFLAGS += -DGNRC_PKTBUF_SIZE=200
+
+include $(RIOTBASE)/Makefile.include

tests/gnrc_sock_neterr/Makefile.ci

@@ -0,0 +1,10 @@
+BOARD_INSUFFICIENT_MEMORY := \
+    arduino-duemilanove \
+    arduino-leonardo \
+    arduino-nano \
+    arduino-uno \
+    atmega328p \
+    nucleo-f031k6 \
+    nucleo-f042k6 \
+    stm32f030f4-demo \
+    #

tests/gnrc_sock_neterr/README.md

@@ -0,0 +1,11 @@
+This is a simple proof of concept test, that `gnrc_sock` with `gnrc_neterr`
+works as expected to report errors within the network stack up to the `sock`
+object.
+
+It just tests if the sock reports `-EHOSTUNREACH` when sending to an unreachable
+address. To confirm that this is indeed coming from the stack and not the `sock`
+wrapper you can do
+
+```
+git grep EHOSTUNREACH -- sys/net/gnrc/sock
+```

tests/gnrc_sock_neterr/main.c

@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2019 Freie Universität Berlin
+ *
+ * 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     tests
+ * @{
+ *
+ * @file
+ *
+ * @author      Martine Lenders <m.lenders@fu-berlin.de>
+ *
+ * @}
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include "msg.h"
+#include "net/sock/udp.h"
+
+#define TEST_PORT               (38664U)
+#define TEST_LINK_LOCAL_REMOTE  { 0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
+                                  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02 }
+#define TEST_GLOBAL_REMOTE      { 0x20, 0x01, 0x0d, 0xb8, 0x00, 0x00, 0x00, 0x00, \
+                                  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02 }
+#define TEST_PAYLOAD            { 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef }
+
+static const uint8_t _test_link_local_remote[] = TEST_LINK_LOCAL_REMOTE;
+static const uint8_t _test_global_remote[] = TEST_GLOBAL_REMOTE;
+static const uint8_t _test_payload[] = TEST_PAYLOAD;
+
+static msg_t _msg_queue[8U];
+static sock_udp_t _udp_sock;
+
+int _test_udp_send(sock_udp_ep_t *remote, char *errno_str, int exp_res) {
+
+    int res = sock_udp_send(&_udp_sock, _test_payload, sizeof(_test_payload),
+                        remote);
+    /* remote is not reachable or route does not exist, so it should return an
+     * error */
+    if (-res == exp_res) {
+        printf("SUCCESS: error code %s (%li == %i)\n",
+               errno_str, (long)(-res), exp_res);
+        return 0;
+    }
+    else {
+        printf("FAILURE: gnrc_udp_send() had an unexpected error code: %li\n",
+               (long int)res);
+        return 1;
+    }
+}
+
+int main(void)
+{
+    sock_udp_ep_t local = SOCK_IPV6_EP_ANY;
+    sock_udp_ep_t remote = SOCK_IPV6_EP_ANY;
+
+    local.port = TEST_PORT;
+    remote.port = TEST_PORT - 1;
+
+    msg_init_queue(_msg_queue, ARRAY_SIZE(_msg_queue));
+    sock_udp_create(&_udp_sock, &local, NULL, 0);
+
+    memcpy(remote.addr.ipv6, _test_link_local_remote,
+           sizeof(_test_link_local_remote));
+    /* With a 6LN this send may succeed, as according to RFC 6775 link-local
+     * addresses are assumed to be generated from the EUI-64, reversing the
+     * procedure of generating the address from EUI-64 for address resolution */
+    _test_udp_send(&remote, "EHOSTUNREACH", EHOSTUNREACH);
+    memcpy(remote.addr.ipv6, _test_global_remote,
+           sizeof(_test_global_remote));
+    _test_udp_send(&remote, "ENETUNREACH", ENETUNREACH);
+}
+
+/** @} */

tests/gnrc_sock_neterr/tests/01-run.py

@@ -0,0 +1,21 @@
+#!/usr/bin/env python3
+
+# Copyright (C) 2019 Freie Universität Berlin
+#
+# 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.
+
+import sys
+from testrunner import run
+
+
+def testfunc(child):
+    child.expect(r"SUCCESS: error code EHOSTUNREACH \((\d+) == (\d+)\)")
+    assert child.match.group(1) == child.match.group(2)
+    child.expect(r"SUCCESS: error code ENETUNREACH \((\d+) == (\d+)\)")
+    assert child.match.group(1) == child.match.group(2)
+
+
+if __name__ == "__main__":
+    sys.exit(run(testfunc))