Add net:gethostname/0

Signed-off-by: Paul Guyot <pguyot@kallisys.net>

Author: pguyot

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added menuconfig option for enabling USE_USB_SERIAL, eg. serial over USB for certain ESP32-S2 boards etc.
 - Partial support for `erlang:fun_info/2`
 - Added support for `registered_name` in `erlang:process_info/2` and `Process.info/2`
+- Added `net:gethostname/0` on platforms with gethostname(3).
 
 ### Fixed
 - ESP32: improved sntp sync speed from a cold boot.

libs/estdlib/src/net.erl

@@ -20,7 +20,7 @@
 
 -module(net).
 
--export([getaddrinfo/1, getaddrinfo/2]).
+-export([getaddrinfo/1, getaddrinfo/2, gethostname/0]).
 
 %% nif call (so we can use guards at the API)
 -export([getaddrinfo_nif/2]).
@@ -78,3 +78,12 @@ getaddrinfo(Host, Service) when
 %% @hidden
 getaddrinfo_nif(_Host, _Service) ->
     erlang:nif_error(undefined).
+
+%%-----------------------------------------------------------------------------
+%% @returns The (usually short) name of the host.
+%% @doc     Get the hostname
+%% @end
+%%-----------------------------------------------------------------------------
+-spec gethostname() -> {ok, string()} | {error, any()}.
+gethostname() ->
+    erlang:nif_error(undefined).

src/libAtomVM/otp_net.c

@@ -26,6 +26,7 @@
 #include <nifs.h>
 #include <otp_net.h>
 #include <port.h>
+#include <posix_nifs.h>
 #include <term.h>
 
 #include <errno.h>
@@ -325,6 +326,38 @@ static term nif_net_getaddrinfo(Context *ctx, int argc, term argv[])
     return ret;
 }
 
+//
+// net:gethostname/0
+//
+#ifdef HAVE_GETHOSTNAME
+static term nif_net_gethostname(Context *ctx, int argc, term argv[])
+{
+    TRACE("nif_net_gethostname\n");
+    UNUSED(argc);
+    UNUSED(argv);
+
+    char buf[256];
+    int r = gethostname(buf, sizeof(buf));
+    if (UNLIKELY(r != 0)) {
+        if (UNLIKELY(memory_ensure_free_opt(ctx, TUPLE_SIZE(2), MEMORY_CAN_SHRINK) != MEMORY_GC_OK)) {
+            RAISE_ERROR(OUT_OF_MEMORY_ATOM);
+        }
+        return make_error_tuple(posix_errno_to_term(errno, ctx->global), ctx);
+    }
+
+    size_t len = strlen(buf);
+    if (UNLIKELY(memory_ensure_free_opt(ctx, TUPLE_SIZE(2) + LIST_SIZE(len, 1), MEMORY_CAN_SHRINK) != MEMORY_GC_OK)) {
+        RAISE_ERROR(OUT_OF_MEMORY_ATOM);
+    }
+
+    term result = term_alloc_tuple(2, &ctx->heap);
+    term_put_tuple_element(result, 0, OK_ATOM);
+    term_put_tuple_element(result, 1, interop_bytes_to_list(buf, len, &ctx->heap));
+
+    return result;
+}
+#endif
+
 //
 // Nifs
 //
@@ -333,6 +366,12 @@ static const struct Nif net_getaddrinfo_nif = {
     .base.type = NIFFunctionType,
     .nif_ptr = nif_net_getaddrinfo
 };
+#ifdef HAVE_GETHOSTNAME
+static const struct Nif net_gethostname_nif = {
+    .base.type = NIFFunctionType,
+    .nif_ptr = nif_net_gethostname
+};
+#endif
 
 //
 // Entrypoints
@@ -346,6 +385,12 @@ const struct Nif *otp_net_nif_get_nif(const char *nifname)
             TRACE("Resolved platform nif %s ...\n", nifname);
             return &net_getaddrinfo_nif;
         }
+#ifdef HAVE_GETHOSTNAME
+        if (strcmp("gethostname/0", rest) == 0) {
+            TRACE("Resolved platform nif %s ...\n", nifname);
+            return &net_gethostname_nif;
+        }
+#endif
     }
     return NULL;
 }

src/platforms/esp32/components/avm_sys/CMakeLists.txt

@@ -70,6 +70,10 @@ set(CMAKE_REQUIRED_INCLUDES ${CMAKE_REQUIRED_INCLUDES} ${soc_target_include_dir}
 include(CheckSymbolExists)
 include(CheckCSourceCompiles)
 
+# Both don't exist in ESP32 at the moment
+define_if_function_exists(libAtomVM${PLATFORM_LIB_SUFFIX} getservbyname "netdb.h" PRIVATE HAVE_SERVBYNAME)
+define_if_function_exists(libAtomVM${PLATFORM_LIB_SUFFIX} gethostname "unistd.h" PRIVATE HAVE_GETHOSTNAME)
+
 if ("${pthread_srcs}" MATCHES pthread_rwlock.c)
 set(HAVE_PTHREAD_RWLOCK YES)
 message(STATUS "pthread component includes pthread_rwlock.c, assuming it is available")

src/platforms/generic_unix/lib/CMakeLists.txt

@@ -58,6 +58,7 @@ endif()
 include(DefineIfExists)
 define_if_function_exists(libAtomVM${PLATFORM_LIB_SUFFIX} signal "signal.h" PRIVATE HAVE_SIGNAL)
 define_if_function_exists(libAtomVM${PLATFORM_LIB_SUFFIX} getservbyname "netdb.h" PRIVATE HAVE_SERVBYNAME)
+define_if_function_exists(libAtomVM${PLATFORM_LIB_SUFFIX} gethostname "unistd.h" PRIVATE HAVE_GETHOSTNAME)
 
 target_link_libraries(libAtomVM${PLATFORM_LIB_SUFFIX} PUBLIC libAtomVM)
 include_directories(${CMAKE_SOURCE_DIR}/src/platforms/generic_unix/lib)

src/platforms/rp2/src/lib/CMakeLists.txt

@@ -102,6 +102,11 @@ if (PICO_CYW43_SUPPORTED)
             otp_net_lwip_raw.h)
     target_link_libraries(libAtomVM${PLATFORM_LIB_SUFFIX} PUBLIC pico_cyw43_arch_lwip_threadsafe_background pico_lwip_sntp INTERFACE pan_lwip_dhserver)
     target_link_options(libAtomVM${PLATFORM_LIB_SUFFIX} PUBLIC "SHELL:-Wl,-u -Wl,networkregister_port_driver -Wl,-u -Wl,otp_socket_nif -Wl,-u -Wl,otp_net_nif -Wl,-u -Wl,otp_ssl_nif")
+
+    include(CheckSymbolExists)
+
+    define_if_function_exists(libAtomVM${PLATFORM_LIB_SUFFIX} getservbyname "netdb.h" PRIVATE HAVE_SERVBYNAME)
+    define_if_function_exists(libAtomVM${PLATFORM_LIB_SUFFIX} gethostname "unistd.h" PRIVATE HAVE_GETHOSTNAME)
 endif()
 
 target_link_options(libAtomVM${PLATFORM_LIB_SUFFIX} PUBLIC "SHELL:-Wl,-u -Wl,gpio_nif -Wl,-u -Wl,otp_crypto_nif")

tests/libs/estdlib/test_net.erl

@@ -25,6 +25,7 @@
 test() ->
     ok = test_getaddrinfo(),
     ok = test_getaddrinfo2(),
+    ok = test_gethostname(),
     ok.
 
 test_getaddrinfo() ->
@@ -141,3 +142,7 @@ get_addr(AddrInfo) ->
         _ ->
             maps:get(addr, maps:get(address, AddrInfo))
     end.
+
+test_gethostname() ->
+    {ok, [_ | _]} = net:gethostname(),
+    ok.