From 7928ff6f0c5ce47b3a9a4e0773ca68a5df6d7c93 Mon Sep 17 00:00:00 2001
From: Kevin Krakauer <krakauer@google.com>
Date: Tue, 5 Sep 2023 09:53:50 -0700
Subject: [PATCH] tty: enable `TCSETSF`

While there is a difference between flavors of this ioctl (`TCSETS`,
`TCSETSF`, `TCSETSW`), in practice it seems not to matter. We should let
users call `TCSETSF` and can implement those differences if necessary.
---
 pkg/sentry/fsimpl/devpts/master.go  |  4 ++++
 pkg/sentry/fsimpl/devpts/replica.go |  4 ++++
 test/syscalls/linux/pty.cc          | 34 +++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+)

diff --git a/pkg/sentry/fsimpl/devpts/master.go b/pkg/sentry/fsimpl/devpts/master.go
index 62b651706..131875972 100644
--- a/pkg/sentry/fsimpl/devpts/master.go
+++ b/pkg/sentry/fsimpl/devpts/master.go
@@ -158,6 +158,10 @@ func (mfd *masterFileDescription) Ioctl(ctx context.Context, io usermem.IO, sysn
 	case linux.TCSETSW:
 		// TODO(b/29356795): This should drain the output queue first.
 		return mfd.t.ld.setTermios(t, args)
+	case linux.TCSETSF:
+		// TODO(b/29356795): This should drain the output queue and
+		// clear the input queue first.
+		return mfd.t.ld.setTermios(t, args)
 	case linux.TIOCGPTN:
 		nP := primitive.Uint32(mfd.t.n)
 		_, err := nP.CopyOut(t, args[2].Pointer())
diff --git a/pkg/sentry/fsimpl/devpts/replica.go b/pkg/sentry/fsimpl/devpts/replica.go
index 68614690f..67f9edccc 100644
--- a/pkg/sentry/fsimpl/devpts/replica.go
+++ b/pkg/sentry/fsimpl/devpts/replica.go
@@ -170,6 +170,10 @@ func (rfd *replicaFileDescription) Ioctl(ctx context.Context, io usermem.IO, sys
 	case linux.TCSETSW:
 		// TODO(b/29356795): This should drain the output queue first.
 		return rfd.inode.t.ld.setTermios(t, args)
+	case linux.TCSETSF:
+		// TODO(b/29356795): This should drain the output queue and
+		// clear the input queue first.
+		return rfd.inode.t.ld.setTermios(t, args)
 	case linux.TIOCGPTN:
 		nP := primitive.Uint32(rfd.inode.t.n)
 		_, err := nP.CopyOut(t, args[2].Pointer())
diff --git a/test/syscalls/linux/pty.cc b/test/syscalls/linux/pty.cc
index f2dc04440..bb34dc86e 100644
--- a/test/syscalls/linux/pty.cc
+++ b/test/syscalls/linux/pty.cc
@@ -777,6 +777,40 @@ TEST_F(PtyTest, TermiosONLCR) {
   ExpectFinished(replica_);
 }
 
+// ICRNL rewrites input \r to \n.
+TEST_F(PtyTest, TCSETSFTermiosICRNL) {
+  struct kernel_termios t = DefaultTermios();
+  t.c_iflag |= ICRNL;
+  t.c_lflag &= ~ICANON;  // for byte-by-byte reading.
+  ASSERT_THAT(ioctl(replica_.get(), TCSETSF, &t), SyscallSucceeds());
+
+  char c = '\r';
+  ASSERT_THAT(WriteFd(master_.get(), &c, 1), SyscallSucceedsWithValue(1));
+
+  ExpectReadable(replica_, 1, &c);
+  EXPECT_EQ(c, '\n');
+
+  ExpectFinished(replica_);
+}
+
+// ONLCR rewrites output \n to \r\n.
+TEST_F(PtyTest, TCSETSFTermiosONLCR) {
+  struct kernel_termios t = DefaultTermios();
+  t.c_oflag |= ONLCR;
+  t.c_lflag &= ~ICANON;  // for byte-by-byte reading.
+  ASSERT_THAT(ioctl(replica_.get(), TCSETSF, &t), SyscallSucceeds());
+
+  char c = '\n';
+  ASSERT_THAT(WriteFd(replica_.get(), &c, 1), SyscallSucceedsWithValue(1));
+
+  // Extra byte for NUL for EXPECT_STREQ.
+  char buf[3] = {};
+  ExpectReadable(master_, 2, buf);
+  EXPECT_STREQ(buf, "\r\n");
+
+  ExpectFinished(replica_);
+}
+
 TEST_F(PtyTest, TermiosIGNCR) {
   struct kernel_termios t = DefaultTermios();
   t.c_iflag |= IGNCR;