1 files changed, 111 insertions, 2 deletions
diff --git a/test/syscalls/linux/socket_non_stream.cc b/test/syscalls/linux/socket_non_stream.cc
index d91c5ed39..c61817f14 100644
--- a/test/syscalls/linux/socket_non_stream.cc
+++ b/test/syscalls/linux/socket_non_stream.cc
@@ -113,7 +113,7 @@ TEST_P(NonStreamSocketPairTest, RecvmsgMsghdrFlagMsgTrunc) {
   EXPECT_EQ(0, memcmp(received_data, sent_data, sizeof(received_data)));
 
   // Check that msghdr flags were updated.
-  EXPECT_EQ(msg.msg_flags, MSG_TRUNC);
+  EXPECT_EQ(msg.msg_flags & MSG_TRUNC, MSG_TRUNC);
 }
 
 // Stream sockets allow data sent with multiple sends to be peeked at in a
@@ -193,7 +193,7 @@ TEST_P(NonStreamSocketPairTest, MsgTruncTruncationRecvmsgMsghdrFlagMsgTrunc) {
   EXPECT_EQ(0, memcmp(received_data, sent_data, sizeof(received_data)));
 
   // Check that msghdr flags were updated.
-  EXPECT_EQ(msg.msg_flags, MSG_TRUNC);
+  EXPECT_EQ(msg.msg_flags & MSG_TRUNC, MSG_TRUNC);
 }
 
 TEST_P(NonStreamSocketPairTest, MsgTruncSameSize) {
@@ -224,5 +224,114 @@ TEST_P(NonStreamSocketPairTest, MsgTruncNotFull) {
   EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
 }
 
+// This test tests reading from a socket with MSG_TRUNC and a zero length
+// receive buffer. The user should be able to get the message length.
+TEST_P(NonStreamSocketPairTest, RecvmsgMsgTruncZeroLen) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[10];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+  ASSERT_THAT(
+      RetryEINTR(send)(sockets->first_fd(), sent_data, sizeof(sent_data), 0),
+      SyscallSucceedsWithValue(sizeof(sent_data)));
+
+  // The receive buffer is of zero length.
+  char received_data[0] = {};
+
+  struct iovec iov;
+  iov.iov_base = received_data;
+  iov.iov_len = sizeof(received_data);
+  struct msghdr msg = {};
+  msg.msg_flags = -1;
+  msg.msg_iov = &iov;
+  msg.msg_iovlen = 1;
+
+  // The syscall succeeds returning the full size of the message on the socket.
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &msg, MSG_TRUNC),
+              SyscallSucceedsWithValue(sizeof(sent_data)));
+
+  // Check that MSG_TRUNC is set on msghdr flags.
+  EXPECT_EQ(msg.msg_flags & MSG_TRUNC, MSG_TRUNC);
+}
+
+// This test tests reading from a socket with MSG_TRUNC | MSG_PEEK and a zero
+// length receive buffer. The user should be able to get the message length
+// without reading data off the socket.
+TEST_P(NonStreamSocketPairTest, RecvmsgMsgTruncMsgPeekZeroLen) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  char sent_data[10];
+  RandomizeBuffer(sent_data, sizeof(sent_data));
+  ASSERT_THAT(
+      RetryEINTR(send)(sockets->first_fd(), sent_data, sizeof(sent_data), 0),
+      SyscallSucceedsWithValue(sizeof(sent_data)));
+
+  // The receive buffer is of zero length.
+  char peek_data[0] = {};
+
+  struct iovec peek_iov;
+  peek_iov.iov_base = peek_data;
+  peek_iov.iov_len = sizeof(peek_data);
+  struct msghdr peek_msg = {};
+  peek_msg.msg_flags = -1;
+  peek_msg.msg_iov = &peek_iov;
+  peek_msg.msg_iovlen = 1;
+
+  // The syscall succeeds returning the full size of the message on the socket.
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &peek_msg,
+                                  MSG_TRUNC | MSG_PEEK),
+              SyscallSucceedsWithValue(sizeof(sent_data)));
+
+  // Check that MSG_TRUNC is set on msghdr flags because the receive buffer is
+  // smaller than the message size.
+  EXPECT_EQ(peek_msg.msg_flags & MSG_TRUNC, MSG_TRUNC);
+
+  char received_data[sizeof(sent_data)] = {};
+
+  struct iovec received_iov;
+  received_iov.iov_base = received_data;
+  received_iov.iov_len = sizeof(received_data);
+  struct msghdr received_msg = {};
+  received_msg.msg_flags = -1;
+  received_msg.msg_iov = &received_iov;
+  received_msg.msg_iovlen = 1;
+
+  // Next we can read the actual data.
+  ASSERT_THAT(
+      RetryEINTR(recvmsg)(sockets->second_fd(), &received_msg, MSG_TRUNC),
+      SyscallSucceedsWithValue(sizeof(sent_data)));
+
+  EXPECT_EQ(0, memcmp(sent_data, received_data, sizeof(sent_data)));
+
+  // Check that MSG_TRUNC is not set on msghdr flags because we read the whole
+  // message.
+  EXPECT_EQ(received_msg.msg_flags & MSG_TRUNC, 0);
+}
+
+// This test tests reading from a socket with MSG_TRUNC | MSG_PEEK and a zero
+// length receive buffer and MSG_DONTWAIT. The user should be able to get an
+// EAGAIN or EWOULDBLOCK error response.
+TEST_P(NonStreamSocketPairTest, RecvmsgTruncPeekDontwaitZeroLen) {
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+
+  // NOTE: We don't send any data on the socket.
+
+  // The receive buffer is of zero length.
+  char peek_data[0] = {};
+
+  struct iovec peek_iov;
+  peek_iov.iov_base = peek_data;
+  peek_iov.iov_len = sizeof(peek_data);
+  struct msghdr peek_msg = {};
+  peek_msg.msg_flags = -1;
+  peek_msg.msg_iov = &peek_iov;
+  peek_msg.msg_iovlen = 1;
+
+  // recvmsg fails with EAGAIN because no data is available on the socket.
+  ASSERT_THAT(RetryEINTR(recvmsg)(sockets->second_fd(), &peek_msg,
+                                  MSG_TRUNC | MSG_PEEK | MSG_DONTWAIT),
+              SyscallFailsWithErrno(EAGAIN));
+}
+
 }  // namespace testing
 }  // namespace gvisor