2 files changed, 97 insertions, 0 deletions
diff --git a/pkg/tcpip/network/hash/hash.go b/pkg/tcpip/network/hash/hash.go
new file mode 100644
index 000000000..0c91905dc
--- /dev/null
+++ b/pkg/tcpip/network/hash/hash.go
@@ -0,0 +1,93 @@
+// Copyright 2018 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 hash contains utility functions for hashing.
+package hash
+
+import (
+	"encoding/binary"
+
+	"gvisor.googlesource.com/gvisor/pkg/rand"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/header"
+)
+
+var hashIV = RandN32(1)[0]
+
+// RandN32 generates a slice of n cryptographic random 32-bit numbers.
+func RandN32(n int) []uint32 {
+	b := make([]byte, 4*n)
+	if _, err := rand.Read(b); err != nil {
+		panic("unable to get random numbers: " + err.Error())
+	}
+	r := make([]uint32, n)
+	for i := range r {
+		r[i] = binary.LittleEndian.Uint32(b[4*i : (4*i + 4)])
+	}
+	return r
+}
+
+// Hash3Words calculates the Jenkins hash of 3 32-bit words. This is adapted
+// from linux.
+func Hash3Words(a, b, c, initval uint32) uint32 {
+	const iv = 0xdeadbeef + (3 << 2)
+	initval += iv
+
+	a += initval
+	b += initval
+	c += initval
+
+	c ^= b
+	c -= rol32(b, 14)
+	a ^= c
+	a -= rol32(c, 11)
+	b ^= a
+	b -= rol32(a, 25)
+	c ^= b
+	c -= rol32(b, 16)
+	a ^= c
+	a -= rol32(c, 4)
+	b ^= a
+	b -= rol32(a, 14)
+	c ^= b
+	c -= rol32(b, 24)
+
+	return c
+}
+
+// IPv4FragmentHash computes the hash of the IPv4 fragment as suggested in RFC 791.
+func IPv4FragmentHash(h header.IPv4) uint32 {
+	x := uint32(h.ID())<<16 | uint32(h.Protocol())
+	t := h.SourceAddress()
+	y := uint32(t[0]) | uint32(t[1])<<8 | uint32(t[2])<<16 | uint32(t[3])<<24
+	t = h.DestinationAddress()
+	z := uint32(t[0]) | uint32(t[1])<<8 | uint32(t[2])<<16 | uint32(t[3])<<24
+	return Hash3Words(x, y, z, hashIV)
+}
+
+// IPv6FragmentHash computes the hash of the ipv6 fragment.
+// Unlike IPv4, the protocol is not used to compute the hash.
+// RFC 2640 (sec 4.5) is not very sharp on this aspect.
+// As a reference, also Linux ignores the protocol to compute
+// the hash (inet6_hash_frag).
+func IPv6FragmentHash(h header.IPv6, f header.IPv6Fragment) uint32 {
+	t := h.SourceAddress()
+	y := uint32(t[0]) | uint32(t[1])<<8 | uint32(t[2])<<16 | uint32(t[3])<<24
+	t = h.DestinationAddress()
+	z := uint32(t[0]) | uint32(t[1])<<8 | uint32(t[2])<<16 | uint32(t[3])<<24
+	return Hash3Words(f.ID(), y, z, hashIV)
+}
+
+func rol32(v, shift uint32) uint32 {
+	return (v << shift) | (v >> ((-shift) & 31))
+}
diff --git a/pkg/tcpip/network/hash/hash_state_autogen.go b/pkg/tcpip/network/hash/hash_state_autogen.go
new file mode 100755
index 000000000..a3bcd4b69
--- /dev/null
+++ b/pkg/tcpip/network/hash/hash_state_autogen.go
@@ -0,0 +1,4 @@
+// automatically generated by stateify.
+
+package hash
+