Perform IGMPv2 when joining IPv4 multicast groups

Added headers, stats, checksum parsing capabilities from RFC 2236 describing
IGMPv2.

IGMPv2 state machine is implemented for each condition, sending and receiving
IGMP Membership Reports and Leave Group messages with backwards compatibility
with IGMPv1 routers.

Test:
* Implemented igmp header parser and checksum calculator in header/igmp_test.go
* ipv4/igmp_test.go tests incoming and outgoing IGMP messages and pathways.
* Added unit test coverage for IGMPv2 RFC behavior + IGMPv1 backwards
   compatibility in ipv4/igmp_test.go.

Fixes #4682

PiperOrigin-RevId: 343408809

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.