Extract IGMPv2 core state machine

The IGMPv2 core state machine can be shared with MLDv1 since they are
almost identical, ignoring specific addresses, constants and packets.

Bug #4682, #4861

PiperOrigin-RevId: 344102615

2 files changed, 72 insertions, 177 deletions

diff --git a/pkg/tcpip/network/ipv4/BUILD b/pkg/tcpip/network/ipv4/BUILD
index 68b1ea1cd..32f53f217 100644
--- a/pkg/tcpip/network/ipv4/BUILD
+++ b/pkg/tcpip/network/ipv4/BUILD
@@ -18,6 +18,7 @@ go_library(
         "//pkg/tcpip/header/parse",
         "//pkg/tcpip/network/fragmentation",
         "//pkg/tcpip/network/hash",
+        "//pkg/tcpip/network/ip",
         "//pkg/tcpip/stack",
     ],
 )
diff --git a/pkg/tcpip/network/ipv4/igmp.go b/pkg/tcpip/network/ipv4/igmp.go
index 18fe2fd2f..c9bf117de 100644
--- a/pkg/tcpip/network/ipv4/igmp.go
+++ b/pkg/tcpip/network/ipv4/igmp.go
@@ -17,11 +17,13 @@ package ipv4
 import (
 	"fmt"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/network/ip"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
 
@@ -29,7 +31,7 @@ const (
 	// igmpV1PresentDefault is the initial state for igmpV1Present in the
 	// igmpState. As per RFC 2236 Page 9 says "No IGMPv1 Router Present ... is
 	// the initial state."
-	igmpV1PresentDefault = false
+	igmpV1PresentDefault = 0
 
 	// v1RouterPresentTimeout from RFC 2236 Section 8.11, Page 18
 	// See note on igmpState.igmpV1Present for more detail.
@@ -49,6 +51,8 @@ const (
 	UnsolicitedReportIntervalMax = 10 * time.Second
 )
 
+var _ ip.MulticastGroupProtocol = (*igmpState)(nil)
+
 // igmpState is the per-interface IGMP state.
 //
 // igmpState.init() MUST be called after creating an IGMP state.
@@ -56,22 +60,23 @@ type igmpState struct {
 	// The IPv4 endpoint this igmpState is for.
 	ep *endpoint
 
+	// igmpV1Present is for maintaining compatibility with IGMPv1 Routers, from
+	// RFC 2236 Section 4 Page 6: "The IGMPv1 router expects Version 1
+	// Membership Reports in response to its Queries, and will not pay
+	// attention to Version 2 Membership Reports.  Therefore, a state variable
+	// MUST be kept for each interface, describing whether the multicast
+	// Querier on that interface is running IGMPv1 or IGMPv2.  This variable
+	// MUST be based upon whether or not an IGMPv1 query was heard in the last
+	// [Version 1 Router Present Timeout] seconds".
+	//
+	// Must be accessed with atomic operations. Holds a value of 1 when true, 0
+	// when false.
+	igmpV1Present uint32
+
 	mu struct {
 		sync.RWMutex
 
-		// memberships contains the map of host groups to their state, timer, and
-		// flag info.
-		memberships map[tcpip.Address]membershipInfo
-
-		// igmpV1Present is for maintaining compatibility with IGMPv1 Routers, from
-		// RFC 2236 Section 4 Page 6: "The IGMPv1 router expects Version 1
-		// Membership Reports in response to its Queries, and will not pay
-		// attention to Version 2 Membership Reports.  Therefore, a state variable
-		// MUST be kept for each interface, describing whether the multicast
-		// Querier on that interface is running IGMPv1 or IGMPv2.  This variable
-		// MUST be based upon whether or not an IGMPv1 query was heard in the last
-		// [Version 1 Router Present Timeout] seconds"
-		igmpV1Present bool
+		genericMulticastProtocol ip.GenericMulticastProtocolState
 
 		// igmpV1Job is scheduled when this interface receives an IGMPv1 style
 		// message, upon expiration the igmpV1Present flag is cleared.
@@ -80,43 +85,26 @@ type igmpState struct {
 	}
 }
 
-// membershipInfo holds the IGMPv2 state for a particular multicast address.
-type membershipInfo struct {
-	// state contains the current IGMP state for this member.
-	state hostState
-
-	// lastToSendReport is true if this was "the last host to send a report from
-	// this group."
-	// RFC 2236, Section 6, Page 9. This is used to track whether or not there
-	// are other hosts on this subnet that belong to this group - RFC 2236
-	// Section 3, Page 5.
-	lastToSendReport bool
-
-	// delayedReportJob is used to delay sending responses to IGMP messages in
-	// order to reduce duplicate reports from multiple hosts on the interface.
-	// Must not be nil.
-	delayedReportJob *tcpip.Job
+// SendReport implements ip.MulticastGroupProtocol.
+func (igmp *igmpState) SendReport(groupAddress tcpip.Address) *tcpip.Error {
+	igmpType := header.IGMPv2MembershipReport
+	if igmp.v1Present() {
+		igmpType = header.IGMPv1MembershipReport
+	}
+	return igmp.writePacket(groupAddress, groupAddress, igmpType)
 }
 
-type hostState int
-
-// From RFC 2236, Section 6, Page 7.
-const (
-	// "'Non-Member' state, when the host does not belong to the group on
-	// the interface.  This is the initial state for all memberships on
-	// all network interfaces; it requires no storage in the host."
-	_ hostState = iota
-
-	// delayingMember is the "'Delaying Member' state, when the host belongs to
-	// the group on the interface and has a report delay timer running for that
-	// membership."
-	delayingMember
-
-	// idleMember is the "Idle Member" state, when the host belongs to the group
-	// on the interface and does not have a report delay timer running for that
-	// membership.
-	idleMember
-)
+// SendLeave implements ip.MulticastGroupProtocol.
+func (igmp *igmpState) SendLeave(groupAddress tcpip.Address) *tcpip.Error {
+	// As per RFC 2236 Section 6, Page 8: "If the interface state says the
+	// Querier is running IGMPv1, this action SHOULD be skipped. If the flag
+	// saying we were the last host to report is cleared, this action MAY be
+	// skipped."
+	if igmp.v1Present() {
+		return nil
+	}
+	return igmp.writePacket(header.IPv4AllRoutersGroup, groupAddress, header.IGMPLeaveGroup)
+}
 
 // init sets up an igmpState struct, and is required to be called before using
 // a new igmpState.
@@ -124,10 +112,10 @@ func (igmp *igmpState) init(ep *endpoint) {
 	igmp.mu.Lock()
 	defer igmp.mu.Unlock()
 	igmp.ep = ep
-	igmp.mu.memberships = make(map[tcpip.Address]membershipInfo)
-	igmp.mu.igmpV1Present = igmpV1PresentDefault
+	igmp.mu.genericMulticastProtocol.Init(ep.protocol.stack.Rand(), ep.protocol.stack.Clock(), igmp, UnsolicitedReportIntervalMax)
+	igmp.igmpV1Present = igmpV1PresentDefault
 	igmp.mu.igmpV1Job = igmp.ep.protocol.stack.NewJob(&igmp.mu, func() {
-		igmp.mu.igmpV1Present = false
+		igmp.setV1Present(false)
 	})
 }
 
@@ -188,6 +176,18 @@ func (igmp *igmpState) handleIGMP(pkt *stack.PacketBuffer) {
 	}
 }
 
+func (igmp *igmpState) v1Present() bool {
+	return atomic.LoadUint32(&igmp.igmpV1Present) == 1
+}
+
+func (igmp *igmpState) setV1Present(v bool) {
+	if v {
+		atomic.StoreUint32(&igmp.igmpV1Present, 1)
+	} else {
+		atomic.StoreUint32(&igmp.igmpV1Present, 0)
+	}
+}
+
 func (igmp *igmpState) handleMembershipQuery(groupAddress tcpip.Address, maxRespTime time.Duration) {
 	igmp.mu.Lock()
 	defer igmp.mu.Unlock()
@@ -198,56 +198,22 @@ func (igmp *igmpState) handleMembershipQuery(groupAddress tcpip.Address, maxResp
 	if maxRespTime == 0 {
 		igmp.mu.igmpV1Job.Cancel()
 		igmp.mu.igmpV1Job.Schedule(v1RouterPresentTimeout)
-		igmp.mu.igmpV1Present = true
+		igmp.setV1Present(true)
 		maxRespTime = v1MaxRespTime
 	}
 
-	// IPv4Any is the General Query Address.
-	if groupAddress == header.IPv4Any {
-		for membershipAddress, info := range igmp.mu.memberships {
-			igmp.setDelayTimerForAddressRLocked(membershipAddress, &info, maxRespTime)
-			igmp.mu.memberships[membershipAddress] = info
-		}
-	} else if info, ok := igmp.mu.memberships[groupAddress]; ok {
-		igmp.setDelayTimerForAddressRLocked(groupAddress, &info, maxRespTime)
-		igmp.mu.memberships[groupAddress] = info
-	}
-}
-
-// setDelayTimerForAddressRLocked modifies the passed info only and does not
-// modify IGMP state directly.
-//
-// Precondition: igmp.mu MUST be read locked.
-func (igmp *igmpState) setDelayTimerForAddressRLocked(groupAddress tcpip.Address, info *membershipInfo, maxRespTime time.Duration) {
-	if info.state == delayingMember {
-		// As per RFC 2236 Section 3, page 3: "If a timer for the group is already
-		// running, it is reset to the random value only if the requested Max
-		// Response Time is less than the remaining value of the running timer.
-		// TODO: Reset the timer if time remaining is greater than maxRespTime.
-		return
-	}
-	info.state = delayingMember
-	info.delayedReportJob.Cancel()
-	info.delayedReportJob.Schedule(igmp.calculateDelayTimerDuration(maxRespTime))
+	igmp.mu.genericMulticastProtocol.HandleQuery(groupAddress, maxRespTime)
 }
 
 func (igmp *igmpState) handleMembershipReport(groupAddress tcpip.Address) {
 	igmp.mu.Lock()
 	defer igmp.mu.Unlock()
-
-	// As per RFC 2236 Section 3, pages 3-4: "If the host receives another host's
-	// Report (version 1 or 2) while it has a timer running, it stops its timer
-	// for the specified group and does not send a Report"
-	if info, ok := igmp.mu.memberships[groupAddress]; ok {
-		info.delayedReportJob.Cancel()
-		info.lastToSendReport = false
-		igmp.mu.memberships[groupAddress] = info
-	}
+	igmp.mu.genericMulticastProtocol.HandleReport(groupAddress)
 }
 
 // writePacket assembles and sends an IGMP packet with the provided fields,
 // incrementing the provided stat counter on success.
-func (igmp *igmpState) writePacket(destAddress tcpip.Address, groupAddress tcpip.Address, igmpType header.IGMPType) {
+func (igmp *igmpState) writePacket(destAddress tcpip.Address, groupAddress tcpip.Address, igmpType header.IGMPType) *tcpip.Error {
 	igmpData := header.IGMP(buffer.NewView(header.IGMPReportMinimumSize))
 	igmpData.SetType(igmpType)
 	igmpData.SetGroupAddress(groupAddress)
@@ -275,56 +241,19 @@ func (igmp *igmpState) writePacket(destAddress tcpip.Address, groupAddress tcpip
 	sent := igmp.ep.protocol.stack.Stats().IGMP.PacketsSent
 	if err := igmp.ep.nic.WritePacketToRemote(header.EthernetAddressFromMulticastIPv4Address(destAddress), nil /* gso */, header.IPv4ProtocolNumber, pkt); err != nil {
 		sent.Dropped.Increment()
-	} else {
-		switch igmpType {
-		case header.IGMPv1MembershipReport:
-			sent.V1MembershipReport.Increment()
-		case header.IGMPv2MembershipReport:
-			sent.V2MembershipReport.Increment()
-		case header.IGMPLeaveGroup:
-			sent.LeaveGroup.Increment()
-		default:
-			panic(fmt.Sprintf("unrecognized igmp type = %d", igmpType))
-		}
+		return err
 	}
-}
-
-// sendReport sends a Host Membership Report in response to a query or after
-// this host joins a new group on this interface.
-//
-// Precondition: igmp.mu MUST be locked.
-func (igmp *igmpState) sendReportLocked(groupAddress tcpip.Address) {
-	igmpType := header.IGMPv2MembershipReport
-	if igmp.mu.igmpV1Present {
-		igmpType = header.IGMPv1MembershipReport
-	}
-	igmp.writePacket(groupAddress, groupAddress, igmpType)
-
-	// Update the state of the membership for this group. If the group no longer
-	// exists, do nothing since this report must have been a race with a remove
-	// or is in the process of being added.
-	info, ok := igmp.mu.memberships[groupAddress]
-	if !ok {
-		return
-	}
-	info.state = idleMember
-	info.lastToSendReport = true
-	igmp.mu.memberships[groupAddress] = info
-}
-
-// sendLeave sends a Leave Group report to the IPv4 All Routers Group.
-//
-// Precondition: igmp.mu MUST be read locked.
-func (igmp *igmpState) sendLeaveRLocked(groupAddress tcpip.Address) {
-	// As per RFC 2236 Section 6, Page 8: "If the interface state says the
-	// Querier is running IGMPv1, this action SHOULD be skipped. If the flag
-	// saying we were the last host to report is cleared, this action MAY be
-	// skipped."
-	if igmp.mu.igmpV1Present || !igmp.mu.memberships[groupAddress].lastToSendReport {
-		return
+	switch igmpType {
+	case header.IGMPv1MembershipReport:
+		sent.V1MembershipReport.Increment()
+	case header.IGMPv2MembershipReport:
+		sent.V2MembershipReport.Increment()
+	case header.IGMPLeaveGroup:
+		sent.LeaveGroup.Increment()
+	default:
+		panic(fmt.Sprintf("unrecognized igmp type = %d", igmpType))
 	}
-
-	igmp.writePacket(header.IPv4AllRoutersGroup, groupAddress, header.IGMPLeaveGroup)
+	return nil
 }
 
 // joinGroup handles adding a new group to the membership map, setting up the
@@ -336,28 +265,11 @@ func (igmp *igmpState) sendLeaveRLocked(groupAddress tcpip.Address) {
 func (igmp *igmpState) joinGroup(groupAddress tcpip.Address) *tcpip.Error {
 	igmp.mu.Lock()
 	defer igmp.mu.Unlock()
-	if _, ok := igmp.mu.memberships[groupAddress]; ok {
-		// The group already exists in the membership map.
-		return tcpip.ErrDuplicateAddress
-	}
 
-	info := membershipInfo{
-		// There isn't a Job scheduled currently, so it's just idle.
-		state: idleMember,
-		// Joining a group immediately sends a report.
-		lastToSendReport: true,
-		delayedReportJob: igmp.ep.protocol.stack.NewJob(&igmp.mu, func() {
-			igmp.sendReportLocked(groupAddress)
-		}),
+	// JoinGroup returns false if we have already joined the group.
+	if !igmp.mu.genericMulticastProtocol.JoinGroup(groupAddress) {
+		return tcpip.ErrDuplicateAddress
 	}
-
-	// As per RFC 2236 Section 3, Page 5: "When a host joins a multicast group,
-	// it should immediately transmit an unsolicited Version 2 Membership Report
-	// for that group" ... "it is recommended that it be repeated"
-	igmp.sendReportLocked(groupAddress)
-	igmp.setDelayTimerForAddressRLocked(groupAddress, &info, UnsolicitedReportIntervalMax)
-	igmp.mu.memberships[groupAddress] = info
-
 	return nil
 }
 
@@ -370,23 +282,5 @@ func (igmp *igmpState) joinGroup(groupAddress tcpip.Address) *tcpip.Error {
 func (igmp *igmpState) leaveGroup(groupAddress tcpip.Address) {
 	igmp.mu.Lock()
 	defer igmp.mu.Unlock()
-	info, ok := igmp.mu.memberships[groupAddress]
-	if !ok {
-		return
-	}
-
-	// Clean up the state of the group before sending the leave message and
-	// removing it from the map.
-	info.delayedReportJob.Cancel()
-	info.state = idleMember
-	igmp.mu.memberships[groupAddress] = info
-
-	igmp.sendLeaveRLocked(groupAddress)
-	delete(igmp.mu.memberships, groupAddress)
-}
-
-// RFC 2236 Section 3, Page 3: The response time is set to a "random value...
-// selected from the range (0, Max Response Time]".
-func (igmp *igmpState) calculateDelayTimerDuration(maxRespTime time.Duration) time.Duration {
-	return time.Duration(igmp.ep.protocol.stack.Rand().Int63n(int64(maxRespTime)))
+	igmp.mu.genericMulticastProtocol.LeaveGroup(groupAddress)
 }