Add abi definitions for POSIX message queues.

Updates #136

pkg/abi/linux/BUILD

@@ -41,6 +41,7 @@ go_library(
         "linux.go",
         "membarrier.go",
         "mm.go",
+        "mqueue.go",
         "msgqueue.go",
         "netdevice.go",
         "netfilter.go",

pkg/abi/linux/mqueue.go

@@ -0,0 +1,55 @@
+// Copyright 2021 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.
+
+package linux
+
+// Default values for POSIX message queues. Source:
+// include/linux/ipc_namespace.h
+const (
+	DFLT_QUEUESMAX       = 256
+	MIN_MSGMAX           = 1
+	DFLT_MSG        uint = 10
+	DFLT_MSGMAX          = 10
+	HARD_MSGMAX          = 65536
+	MIN_MSGSIZEMAX       = 128
+	DFLT_MSGSIZE    uint = 8192
+	DFLT_MSGSIZEMAX      = 8192
+	HARD_MSGSIZEMAX      = (16 * 1024 * 1024)
+)
+
+// Maximum values for a message queue. Source: include/uapi/linux/mqueue.h
+const (
+	MQ_PRIO_MAX  = 32768
+	MQ_BYTES_MAX = 819200
+)
+
+// Codes used by mq_notify. Source: include/uapi/linux/mqueue.h
+const (
+	NOTIFY_NONE    = 0
+	NOTIFY_WOKENUP = 1
+	NOTIFY_REMOVED = 2
+
+	NOTIFY_COOKIE_LEN = 32
+)
+
+// MqAttr is equivelant to struct mq_attr. Source: include/uapi/linux/mqueue.h
+//
+// +marshal
+type MqAttr struct {
+	MqFlags   int64    // Message queue flags.
+	MqMaxmsg  int64    // Maximum number of messages.
+	MqMsgsize int64    // Maximum message size.
+	MqCurmsgs int64    // Number of messages currently queued.
+	_         [4]int64 // Ignored for input, zeroed for output.
+}