4 files changed, 272 insertions, 0 deletions
diff --git a/pkg/tcpip/header/BUILD b/pkg/tcpip/header/BUILD
index ca6cbe41a..144093c3a 100644
--- a/pkg/tcpip/header/BUILD
+++ b/pkg/tcpip/header/BUILD
@@ -11,6 +11,7 @@ go_library(
         "gue.go",
         "icmpv4.go",
         "icmpv6.go",
+        "igmp.go",
         "interfaces.go",
         "ipv4.go",
         "ipv6.go",
@@ -40,6 +41,7 @@ go_test(
     size = "small",
     srcs = [
         "checksum_test.go",
+        "igmp_test.go",
         "ipv6_test.go",
         "ipversion_test.go",
         "tcp_test.go",
diff --git a/pkg/tcpip/header/igmp.go b/pkg/tcpip/header/igmp.go
new file mode 100644
index 000000000..e0f5d46f4
--- /dev/null
+++ b/pkg/tcpip/header/igmp.go
@@ -0,0 +1,166 @@
+// 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 header
+
+import (
+	"encoding/binary"
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/tcpip"
+)
+
+// IGMP represents an IGMP header stored in a byte array.
+type IGMP []byte
+
+// IGMP implements `Transport`.
+var _ Transport = (*IGMP)(nil)
+
+const (
+	// IGMPMinimumSize is the minimum size of a valid IGMP packet in bytes,
+	// as per RFC 2236, Section 2, Page 2.
+	IGMPMinimumSize = 8
+
+	// IGMPQueryMinimumSize is the minimum size of a valid Membership Query
+	// Message in bytes, as per RFC 2236, Section 2, Page 2.
+	IGMPQueryMinimumSize = 8
+
+	// IGMPReportMinimumSize is the minimum size of a valid Report Message in
+	// bytes, as per RFC 2236, Section 2, Page 2.
+	IGMPReportMinimumSize = 8
+
+	// IGMPLeaveMessageMinimumSize is the minimum size of a valid Leave Message
+	// in bytes, as per RFC 2236, Section 2, Page 2.
+	IGMPLeaveMessageMinimumSize = 8
+
+	// IGMPTTL is the TTL for all IGMP messages, as per RFC 2236, Section 3, Page
+	// 3.
+	IGMPTTL = 1
+
+	// igmpTypeOffset defines the offset of the type field in an IGMP message.
+	igmpTypeOffset = 0
+
+	// igmpMaxRespTimeOffset defines the offset of the MaxRespTime field in an
+	// IGMP message.
+	igmpMaxRespTimeOffset = 1
+
+	// igmpChecksumOffset defines the offset of the checksum field in an IGMP
+	// message.
+	igmpChecksumOffset = 2
+
+	// igmpGroupAddressOffset defines the offset of the Group Address field in an
+	// IGMP message.
+	igmpGroupAddressOffset = 4
+
+	// IGMPProtocolNumber is IGMP's transport protocol number.
+	IGMPProtocolNumber tcpip.TransportProtocolNumber = 2
+)
+
+// IGMPType is the IGMP type field as per RFC 2236.
+type IGMPType byte
+
+// Values for the IGMP Type described in RFC 2236 Section 2.1, Page 2.
+// Descriptions below come from there.
+const (
+	// IGMPMembershipQuery indicates that the message type is Membership Query.
+	// "There are two sub-types of Membership Query messages:
+	// - General Query, used to learn which groups have members on an
+	//   attached network.
+	// - Group-Specific Query, used to learn if a particular group
+	//   has any members on an attached network.
+	// These two messages are differentiated by the Group Address, as
+	// described in section 1.4 ."
+	IGMPMembershipQuery IGMPType = 0x11
+	// IGMPv1MembershipReport indicates that the message is a Membership Report
+	// generated by a host using the IGMPv1 protocol: "an additional type of
+	// message, for backwards-compatibility with IGMPv1"
+	IGMPv1MembershipReport IGMPType = 0x12
+	// IGMPv2MembershipReport indicates that the Message type is a Membership
+	// Report generated by a host using the IGMPv2 protocol.
+	IGMPv2MembershipReport IGMPType = 0x16
+	// IGMPLeaveGroup indicates that the message type is a Leave Group
+	// notification message.
+	IGMPLeaveGroup IGMPType = 0x17
+)
+
+// Type is the IGMP type field.
+func (b IGMP) Type() IGMPType { return IGMPType(b[igmpTypeOffset]) }
+
+// SetType sets the IGMP type field.
+func (b IGMP) SetType(t IGMPType) { b[igmpTypeOffset] = byte(t) }
+
+// MaxRespTime gets the MaxRespTimeField. This is meaningful only in Membership
+// Query messages, in other cases it is set to 0 by the sender and ignored by
+// the receiver.
+func (b IGMP) MaxRespTime() byte { return b[igmpMaxRespTimeOffset] }
+
+// SetMaxRespTime sets the MaxRespTimeField.
+func (b IGMP) SetMaxRespTime(m byte) { b[igmpMaxRespTimeOffset] = m }
+
+// Checksum is the IGMP checksum field.
+func (b IGMP) Checksum() uint16 {
+	return binary.BigEndian.Uint16(b[igmpChecksumOffset:])
+}
+
+// SetChecksum sets the IGMP checksum field.
+func (b IGMP) SetChecksum(checksum uint16) {
+	binary.BigEndian.PutUint16(b[igmpChecksumOffset:], checksum)
+}
+
+// GroupAddress gets the Group Address field.
+func (b IGMP) GroupAddress() tcpip.Address {
+	return tcpip.Address(b[igmpGroupAddressOffset:][:IPv4AddressSize])
+}
+
+// SetGroupAddress sets the Group Address field.
+func (b IGMP) SetGroupAddress(address tcpip.Address) {
+	if n := copy(b[igmpGroupAddressOffset:], address); n != IPv4AddressSize {
+		panic(fmt.Sprintf("copied %d bytes, expected %d", n, IPv4AddressSize))
+	}
+}
+
+// SourcePort implements Transport.SourcePort.
+func (IGMP) SourcePort() uint16 {
+	return 0
+}
+
+// DestinationPort implements Transport.DestinationPort.
+func (IGMP) DestinationPort() uint16 {
+	return 0
+}
+
+// SetSourcePort implements Transport.SetSourcePort.
+func (IGMP) SetSourcePort(uint16) {
+}
+
+// SetDestinationPort implements Transport.SetDestinationPort.
+func (IGMP) SetDestinationPort(uint16) {
+}
+
+// Payload implements Transport.Payload.
+func (IGMP) Payload() []byte {
+	return nil
+}
+
+// IGMPCalculateChecksum calculates the IGMP checksum over the provided IGMP
+// header.
+func IGMPCalculateChecksum(h IGMP) uint16 {
+	// The header contains a checksum itself, set it aside to avoid checksumming
+	// the checksum and replace it afterwards.
+	existingXsum := h.Checksum()
+	h.SetChecksum(0)
+	xsum := ^Checksum(h, 0)
+	h.SetChecksum(existingXsum)
+	return xsum
+}
diff --git a/pkg/tcpip/header/igmp_test.go b/pkg/tcpip/header/igmp_test.go
new file mode 100644
index 000000000..66e872880
--- /dev/null
+++ b/pkg/tcpip/header/igmp_test.go
@@ -0,0 +1,101 @@
+// 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 header_test
+
+import (
+	"testing"
+
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+)
+
+// TestIGMPHeader tests the functions within header.igmp
+func TestIGMPHeader(t *testing.T) {
+	b := []byte{
+		0x11,       // IGMP Type, Membership Query
+		0xF0,       // Maximum Response Time
+		0xC0, 0xC0, // Checksum
+		0x01, 0x02, 0x03, 0x04, // Group Address
+	}
+
+	igmpHeader := header.IGMP(b)
+
+	if got, want := igmpHeader.Type(), header.IGMPMembershipQuery; got != want {
+		t.Errorf("got igmpHeader.Type() = %x, want = %x", got, want)
+	}
+
+	if got, want := igmpHeader.MaxRespTime(), byte(0xF0); got != want {
+		t.Errorf("got igmpHeader.MaxRespTime() = %x, want = %x", got, want)
+	}
+
+	if got, want := igmpHeader.Checksum(), uint16(0xC0C0); got != want {
+		t.Errorf("got igmpHeader.Checksum() = %x, want = %x", got, want)
+	}
+
+	if got, want := igmpHeader.GroupAddress(), tcpip.Address("\x01\x02\x03\x04"); got != want {
+		t.Errorf("got igmpHeader.GroupAddress() = %s, want = %s", got, want)
+	}
+
+	igmpType := header.IGMPv2MembershipReport
+	igmpHeader.SetType(igmpType)
+	if got := igmpHeader.Type(); got != igmpType {
+		t.Errorf("got igmpHeader.Type() = %x, want = %x", got, igmpType)
+	}
+	if got := header.IGMPType(b[0]); got != igmpType {
+		t.Errorf("got IGMPtype in backing buffer = %x, want %x", got, igmpType)
+	}
+
+	respTime := byte(0x02)
+	igmpHeader.SetMaxRespTime(respTime)
+	if got := igmpHeader.MaxRespTime(); got != respTime {
+		t.Errorf("got igmpHeader.MaxRespTime() = %x, want = %x", got, respTime)
+	}
+
+	checksum := uint16(0x0102)
+	igmpHeader.SetChecksum(checksum)
+	if got := igmpHeader.Checksum(); got != checksum {
+		t.Errorf("got igmpHeader.Checksum() = %x, want = %x", got, checksum)
+	}
+
+	groupAddress := tcpip.Address("\x04\x03\x02\x01")
+	igmpHeader.SetGroupAddress(groupAddress)
+	if got := igmpHeader.GroupAddress(); got != groupAddress {
+		t.Errorf("got igmpHeader.GroupAddress() = %s, want = %s", got, groupAddress)
+	}
+}
+
+// TestIGMPChecksum ensures that the checksum calculator produces the expected
+// checksum.
+func TestIGMPChecksum(t *testing.T) {
+	b := []byte{
+		0x11,       // IGMP Type, Membership Query
+		0xF0,       // Maximum Response Time
+		0xC0, 0xC0, // Checksum
+		0x01, 0x02, 0x03, 0x04, // Group Address
+	}
+
+	igmpHeader := header.IGMP(b)
+
+	// Calculate the initial checksum after setting the checksum temporarily to 0
+	// to avoid checksumming the checksum.
+	initialChecksum := igmpHeader.Checksum()
+	igmpHeader.SetChecksum(0)
+	checksum := ^header.Checksum(b, 0)
+	igmpHeader.SetChecksum(initialChecksum)
+
+	if got := header.IGMPCalculateChecksum(igmpHeader); got != checksum {
+		t.Errorf("got IGMPCalculateChecksum = %x, want %x", got, checksum)
+	}
+}
diff --git a/pkg/tcpip/header/ipv4.go b/pkg/tcpip/header/ipv4.go
index 91fe7b6a5..5fddd2af6 100644
--- a/pkg/tcpip/header/ipv4.go
+++ b/pkg/tcpip/header/ipv4.go
@@ -157,6 +157,9 @@ const (
 	// IPv4Any is the non-routable IPv4 "any" meta address.
 	IPv4Any tcpip.Address = "\x00\x00\x00\x00"
 
+	// IPv4AllRoutersGroup is a multicast address for all routers.
+	IPv4AllRoutersGroup tcpip.Address = "\xe0\x00\x00\x02"
+
 	// IPv4MinimumProcessableDatagramSize is the minimum size of an IP
 	// packet that every IPv4 capable host must be able to
 	// process/reassemble.