Use different Ctty FDs based on the go version.

An upcoming change in Go 1.13 [1] changes the semantics of the SysProcAttr.Ctty
field. Prior to the change, the FD must be an FD in the child process's FD
table (aka "post-shuffle"). After the change, the FD must be an FD in the
current process's FD table (aka "pre-shuffle").

To be compatible with both versions this CL introduces a new boolean
"CttyFdIsPostShuffle" which indicates whether a pre- or post-shuffle FD should
be provided. We use build tags to chose the correct one.

1: https://go-review.googlesource.com/c/go/+/178919/
PiperOrigin-RevId: 255015303

3 files changed, 53 insertions, 1 deletions

diff --git a/runsc/console/BUILD b/runsc/console/BUILD
index 2d71cd371..b7d8f32ca 100644
--- a/runsc/console/BUILD
+++ b/runsc/console/BUILD
@@ -4,7 +4,11 @@ package(licenses = ["notice"])
 
 go_library(
     name = "console",
-    srcs = ["console.go"],
+    srcs = [
+        "console.go",
+        "ctty_1_12.go",
+        "ctty_1_13.go",
+    ],
     importpath = "gvisor.dev/gvisor/runsc/console",
     visibility = [
         "//runsc:__subpackages__",
diff --git a/runsc/console/ctty_1_12.go b/runsc/console/ctty_1_12.go
new file mode 100644
index 000000000..6e7a314a3
--- /dev/null
+++ b/runsc/console/ctty_1_12.go
@@ -0,0 +1,24 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build go1.12
+// +build !go1.13
+
+// TODO(b/133868570): Delete once Go 1.12 is no longer supported.
+
+package console
+
+// CttyFdIsPostShuffle indicates that in go1.12 and earlier, the
+// SysProcAttr.Ctty FD is determined "pre-shuffle" (not "post-shuffle").
+var CttyFdIsPostShuffle = false
diff --git a/runsc/console/ctty_1_13.go b/runsc/console/ctty_1_13.go
new file mode 100644
index 000000000..785d720e1
--- /dev/null
+++ b/runsc/console/ctty_1_13.go
@@ -0,0 +1,24 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build go1.13
+// +build !go1.14
+
+// TODO(b/133868570): Delete once Go 1.12 is no longer supported.
+
+package console
+
+// CttyFdIsPostShuffle indicates that in go1.13 and later, the SysProcAttr.Ctty
+// FD is determined "post-shuffle".
+var CttyFdIsPostShuffle = true