net: accept sufficient Ethernet address output buffers

tests/KernelFileSystemTests.cpp

@@ -135,6 +135,35 @@ void TestRandomDevices() {
   }
 }
 
+void TestFileDescriptorFlags() {
+  Loader::SymbolDatabase symbols;
+  Libs::InitLibKernel_1(&symbols);
+  const auto* symbol = symbols.Find(
+      {"8nY19bKoiZk", "Posix", 1, "libkernel", 1, 1, Loader::SymbolType::Func});
+  Check(symbol != nullptr, "POSIX fcntl export resolves");
+  const auto fcntl = reinterpret_cast<int (KYTY_SYSV_ABI *)(int, int, int)>(symbol->vaddr);
+  Check(fcntl(std::numeric_limits<int>::min(), 1, 0) == -1 &&
+            *Libs::Posix::GetErrorAddr() == Libs::Posix::POSIX_EBADF,
+        "invalid descriptor reports EBADF");
+  for (const auto* path : {"/dev/urandom", "/dev/random"}) {
+    const int fd = FileSystem::KernelOpen(path, 0, 0);
+    Check(fd >= 3, "open descriptor for flag checks");
+    Check(fcntl(fd, 1, 0) == 0 && fcntl(fd, 2, 1) == 0 && fcntl(fd, 1, 0) == 1,
+          "entropy descriptor retains close-on-exec flag");
+    Check(fcntl(fd, 2, 0) == 0 && fcntl(fd, 1, 0) == 0,
+          "close-on-exec flag can be cleared");
+    Check(fcntl(fd, -1, 0) == -1 && *Libs::Posix::GetErrorAddr() == Libs::Posix::POSIX_EINVAL,
+          "unsupported fcntl command reports EINVAL");
+    Check(FileSystem::KernelClose(fd) == OK, "close entropy source");
+    Check(fcntl(fd, 1, 0) == -1 && *Libs::Posix::GetErrorAddr() == Libs::Posix::POSIX_EBADF,
+          "closed descriptor reports EBADF");
+    const int cloexec_fd = FileSystem::KernelOpen(path, 0x00100000, 0);
+    Check(cloexec_fd >= 3 && fcntl(cloexec_fd, 1, 0) == 1,
+          "O_CLOEXEC sets the descriptor flag on open");
+    Check(FileSystem::KernelClose(cloexec_fd) == OK, "close flagged entropy source");
+  }
+}
+
 void TestSaveOpenVisibility() {
   constexpr char Path[] = "/savedata0/visible-save.dat";
   constexpr char Payload[] = "saved progress";
@@ -1132,6 +1161,38 @@ void CheckSocketReceiveBuffer(int reader, int writer) {
 }
 #endif
 
+void CheckEtherAddressFormatting() {
+  Loader::SymbolDatabase symbols;
+  Libs::LibNet::InitNet_1_Net(&symbols);
+  const auto *format_symbol = symbols.FindByNid("v6M4txecCuo", Loader::SymbolType::Func);
+  const auto *errno_symbol = symbols.FindByNid("HQOwnfMGipQ", Loader::SymbolType::Func);
+  Check(format_symbol && errno_symbol, "Ethernet formatting and errno exports resolve");
+  using Format = int (KYTY_SYSV_ABI *)(const Libs::Network::Net::NetEtherAddr *, char *, size_t);
+  using Errno = int *(KYTY_SYSV_ABI *)();
+  const auto format = reinterpret_cast<Format>(format_symbol->vaddr);
+  auto *net_errno = reinterpret_cast<Errno>(errno_symbol->vaddr)();
+  for (const auto address : {Libs::Network::Net::NetEtherAddr{},
+                             Libs::Network::Net::NetEtherAddr{{0x01, 0x23, 0x45, 0xab, 0xcd, 0xef}}}) {
+    const auto *expected = address.data[0] == 0 ? "00:00:00:00:00:00" : "01:23:45:ab:cd:ef";
+    for (const size_t size : {18u, 127u}) {
+      std::array<char, 128> text;
+      text.fill('!');
+      Check(format(&address, text.data(), size) == OK &&
+                std::strcmp(text.data(), expected) == 0 && text[18] == '!',
+            "Ethernet formatting accepts exact and larger buffers");
+    }
+  }
+  const Libs::Network::Net::NetEtherAddr address{};
+  std::array<char, 18> text;
+  text.fill('!');
+  Check(format(&address, text.data(), 17) == Libs::Network::NET_ERROR_EINVAL &&
+            *net_errno == Libs::Posix::POSIX_EINVAL &&
+            std::all_of(text.begin(), text.end(), [](char c) { return c == '!'; }) &&
+            format(nullptr, text.data(), text.size()) == Libs::Network::NET_ERROR_EINVAL &&
+            format(&address, nullptr, text.size()) == Libs::Network::NET_ERROR_EINVAL,
+        "Ethernet formatting rejects invalid arguments without writing output");
+}
+
 void CheckSocketWakeup() {
   namespace Net = Libs::Network::Net;
   Loader::SymbolDatabase symbols;
@@ -1413,6 +1474,7 @@ int main(int, char**) {
   TempDirectory temporary;
   FileSystem::Initialize();
   TestRandomDevices();
+  TestFileDescriptorFlags();
   CheckMountRoot(temporary.Path());
   CheckUnmappedPaths(temporary.Path());
   CheckArchiveMount(temporary.Path());
@@ -1427,6 +1489,7 @@ int main(int, char**) {
   CheckSaveRename(temporary.Path(), "replacement-save");
   FileSystem::Shutdown();
   CheckSocketWakeup();
+  CheckEtherAddressFormatting();
   TestNpWebApi2Memory();
   graphics.reset();
   subsystems.Destroy();