[llvm-branch-commits] [libc] f39930b - [libc] Fix sockatmark test (#210655)

[Pavel Labath via llvm-branch-commits]

Author: Pavel Labath
Date: 2026-08-31T14:18:40Z
New Revision: f39930bce62db6634f2098dde77c48c3885cd13e

URL: https://github.com/llvm/llvm-project/commit/f39930bce62db6634f2098dde77c48c3885cd13e
DIFF: https://github.com/llvm/llvm-project/commit/f39930bce62db6634f2098dde77c48c3885cd13e.diff

LOG: [libc] Fix sockatmark test (#210655)

When writing the test, I assumed that (linux) domain sockets do not
support OOB data, and that sockatmark returns 0, because it can never
read it.

In fact, as of 2021, linux does support OOB on domain sockets, but this
feature can be turned off at build time (CONFIG_AF_UNIX_OOB). In this
case (or in the case of older kernels), the kernel returns an error (and
the test fails).

Armed with this knowledge, I modify the test to test both "1" (OOB
present) and "0" (no OOB data) cases by actually sending OOB data into
the socket. I use the send call to determine the presence of OOB
support, and have the test skip itself if it is absent. OOB data only
makes sense on stream sockets, so change the socketpair type to that.

---------

Co-authored-by: Jeff Bailey <jbailey at raspberryginger.com>

Added: 
    

Modified: 
    libc/test/src/sys/socket/linux/CMakeLists.txt
    libc/test/src/sys/socket/linux/sockatmark_test.cpp

Removed: 
    


################################################################################
diff  --git a/libc/test/src/sys/socket/linux/CMakeLists.txt b/libc/test/src/sys/socket/linux/CMakeLists.txt
index 1f28b99601e61..f533e53c9069f 100644
--- a/libc/test/src/sys/socket/linux/CMakeLists.txt
+++ b/libc/test/src/sys/socket/linux/CMakeLists.txt
@@ -161,6 +161,7 @@ add_libc_unittest(
   DEPENDS
     libc.hdr.sys_socket_macros
     libc.src.errno.errno
+    libc.src.sys.socket.send
     libc.src.sys.socket.sockatmark
     libc.src.sys.socket.socketpair
     libc.src.unistd.close

diff  --git a/libc/test/src/sys/socket/linux/sockatmark_test.cpp b/libc/test/src/sys/socket/linux/sockatmark_test.cpp
index 249bd298f4832..25602dcf23407 100644
--- a/libc/test/src/sys/socket/linux/sockatmark_test.cpp
+++ b/libc/test/src/sys/socket/linux/sockatmark_test.cpp
@@ -11,31 +11,42 @@
 ///
 //===----------------------------------------------------------------------===//
 
-#include "hdr/sys_socket_macros.h" // For AF_UNIX and SOCK_DGRAM
+#include "hdr/sys_socket_macros.h" // For AF_UNIX and SOCK_STREAM
 #include "src/__support/CPP/scope.h"
+#include "src/sys/socket/send.h"
 #include "src/sys/socket/sockatmark.h"
 #include "src/sys/socket/socketpair.h"
 #include "src/unistd/close.h"
 #include "src/unistd/pipe.h"
 #include "test/UnitTest/ErrnoCheckingTest.h"
 #include "test/UnitTest/ErrnoSetterMatcher.h"
+#include "test/UnitTest/TestLogger.h"
 
 using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Fails;
 using LIBC_NAMESPACE::testing::ErrnoSetterMatcher::Succeeds;
 using LlvmLibcSockatmarkTest = LIBC_NAMESPACE::testing::ErrnoCheckingTest;
 using LIBC_NAMESPACE::cpp::scope_exit;
 
-TEST_F(LlvmLibcSockatmarkTest, SocketpairReturnsFalse) {
+TEST_F(LlvmLibcSockatmarkTest, Socketpair) {
   int sockpair[2] = {-1, -1};
-  ASSERT_THAT(LIBC_NAMESPACE::socketpair(AF_UNIX, SOCK_DGRAM, 0, sockpair),
+  ASSERT_THAT(LIBC_NAMESPACE::socketpair(AF_UNIX, SOCK_STREAM, 0, sockpair),
               Succeeds(0));
   scope_exit close_sockpair([&] {
     ASSERT_THAT(LIBC_NAMESPACE::close(sockpair[0]), Succeeds(0));
     ASSERT_THAT(LIBC_NAMESPACE::close(sockpair[1]), Succeeds(0));
   });
 
+  if (LIBC_NAMESPACE::send(sockpair[0], ".", 1, MSG_OOB) != 1) {
+    ASSERT_ERRNO_EQ(EOPNOTSUPP);
+    LIBC_NAMESPACE::testing::tlog << "No kernel support for AF_UNIX OOB\n";
+    ASSERT_THAT(LIBC_NAMESPACE::sockatmark(sockpair[0]), Fails(ENOTTY));
+    return;
+  }
+
+  // sockpair[1] has OOB data because we've sent it above. sockpair[0] does not
+  // because it's empty.
   ASSERT_THAT(LIBC_NAMESPACE::sockatmark(sockpair[0]), Succeeds(0));
-  ASSERT_THAT(LIBC_NAMESPACE::sockatmark(sockpair[1]), Succeeds(0));
+  ASSERT_THAT(LIBC_NAMESPACE::sockatmark(sockpair[1]), Succeeds(1));
 }
 
 TEST_F(LlvmLibcSockatmarkTest, InvalidFdFails) {