From c8eeedcc1d6b1ee25532ae630a7efd7aa4656bdc Mon Sep 17 00:00:00 2001
From: Bhasker Hariharan <bhaskerh@google.com>
Date: Tue, 24 Mar 2020 15:33:16 -0700
Subject: Add support for setting TCP segment hash.

This allows the link layer endpoints to consistenly hash a TCP
segment to a single underlying queue in case a link layer endpoint
does support multiple underlying queues.

Updates #231

PiperOrigin-RevId: 302760664
---
 pkg/tcpip/stack/rand.go | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 pkg/tcpip/stack/rand.go

(limited to 'pkg/tcpip/stack/rand.go')

diff --git a/pkg/tcpip/stack/rand.go b/pkg/tcpip/stack/rand.go
new file mode 100644
index 000000000..421fb5c15
--- /dev/null
+++ b/pkg/tcpip/stack/rand.go
@@ -0,0 +1,40 @@
+// Copyright 2020 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 stack
+
+import (
+	mathrand "math/rand"
+
+	"gvisor.dev/gvisor/pkg/sync"
+)
+
+// lockedRandomSource provides a threadsafe rand.Source.
+type lockedRandomSource struct {
+	mu  sync.Mutex
+	src mathrand.Source
+}
+
+func (r *lockedRandomSource) Int63() (n int64) {
+	r.mu.Lock()
+	n = r.src.Int63()
+	r.mu.Unlock()
+	return n
+}
+
+func (r *lockedRandomSource) Seed(seed int64) {
+	r.mu.Lock()
+	r.src.Seed(seed)
+	r.mu.Unlock()
+}
-- 
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