From 2747030ec7453219c09b34f773b7d2ba6a7fc552 Mon Sep 17 00:00:00 2001
From: Tamir Duberstein <tamird@google.com>
Date: Mon, 14 Sep 2020 15:19:50 -0700
Subject: Store multicast memberships in a set

This is simpler and more performant.

PiperOrigin-RevId: 331639978
---
 pkg/tcpip/transport/udp/endpoint.go       | 39 ++++++++++++-------------------
 pkg/tcpip/transport/udp/endpoint_state.go |  2 +-
 2 files changed, 16 insertions(+), 25 deletions(-)

diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index 2828b2c01..b572c39db 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -139,7 +139,7 @@ type endpoint struct {
 
 	// multicastMemberships that need to be remvoed when the endpoint is
 	// closed. Protected by the mu mutex.
-	multicastMemberships []multicastMembership
+	multicastMemberships map[multicastMembership]struct{}
 
 	// effectiveNetProtos contains the network protocols actually in use. In
 	// most cases it will only contain "netProto", but in cases like IPv6
@@ -182,12 +182,13 @@ func newEndpoint(s *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQue
 		// TTL=1.
 		//
 		// Linux defaults to TTL=1.
-		multicastTTL:  1,
-		multicastLoop: true,
-		rcvBufSizeMax: 32 * 1024,
-		sndBufSizeMax: 32 * 1024,
-		state:         StateInitial,
-		uniqueID:      s.UniqueID(),
+		multicastTTL:         1,
+		multicastLoop:        true,
+		rcvBufSizeMax:        32 * 1024,
+		sndBufSizeMax:        32 * 1024,
+		multicastMemberships: make(map[multicastMembership]struct{}),
+		state:                StateInitial,
+		uniqueID:             s.UniqueID(),
 	}
 
 	// Override with stack defaults.
@@ -237,10 +238,10 @@ func (e *endpoint) Close() {
 		e.boundPortFlags = ports.Flags{}
 	}
 
-	for _, mem := range e.multicastMemberships {
+	for mem := range e.multicastMemberships {
 		e.stack.LeaveGroup(e.NetProto, mem.nicID, mem.multicastAddr)
 	}
-	e.multicastMemberships = nil
+	e.multicastMemberships = make(map[multicastMembership]struct{})
 
 	// Close the receive list and drain it.
 	e.rcvMu.Lock()
@@ -752,17 +753,15 @@ func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
 		e.mu.Lock()
 		defer e.mu.Unlock()
 
-		for _, mem := range e.multicastMemberships {
-			if mem == memToInsert {
-				return tcpip.ErrPortInUse
-			}
+		if _, ok := e.multicastMemberships[memToInsert]; ok {
+			return tcpip.ErrPortInUse
 		}
 
 		if err := e.stack.JoinGroup(e.NetProto, nicID, v.MulticastAddr); err != nil {
 			return err
 		}
 
-		e.multicastMemberships = append(e.multicastMemberships, memToInsert)
+		e.multicastMemberships[memToInsert] = struct{}{}
 
 	case *tcpip.RemoveMembershipOption:
 		if !header.IsV4MulticastAddress(v.MulticastAddr) && !header.IsV6MulticastAddress(v.MulticastAddr) {
@@ -786,18 +785,11 @@ func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
 		}
 
 		memToRemove := multicastMembership{nicID: nicID, multicastAddr: v.MulticastAddr}
-		memToRemoveIndex := -1
 
 		e.mu.Lock()
 		defer e.mu.Unlock()
 
-		for i, mem := range e.multicastMemberships {
-			if mem == memToRemove {
-				memToRemoveIndex = i
-				break
-			}
-		}
-		if memToRemoveIndex == -1 {
+		if _, ok := e.multicastMemberships[memToRemove]; !ok {
 			return tcpip.ErrBadLocalAddress
 		}
 
@@ -805,8 +797,7 @@ func (e *endpoint) SetSockOpt(opt tcpip.SettableSocketOption) *tcpip.Error {
 			return err
 		}
 
-		e.multicastMemberships[memToRemoveIndex] = e.multicastMemberships[len(e.multicastMemberships)-1]
-		e.multicastMemberships = e.multicastMemberships[:len(e.multicastMemberships)-1]
+		delete(e.multicastMemberships, memToRemove)
 
 	case *tcpip.BindToDeviceOption:
 		id := tcpip.NICID(*v)
diff --git a/pkg/tcpip/transport/udp/endpoint_state.go b/pkg/tcpip/transport/udp/endpoint_state.go
index 851e6b635..858c99a45 100644
--- a/pkg/tcpip/transport/udp/endpoint_state.go
+++ b/pkg/tcpip/transport/udp/endpoint_state.go
@@ -92,7 +92,7 @@ func (e *endpoint) Resume(s *stack.Stack) {
 
 	e.stack = s
 
-	for _, m := range e.multicastMemberships {
+	for m := range e.multicastMemberships {
 		if err := e.stack.JoinGroup(e.NetProto, m.nicID, m.multicastAddr); err != nil {
 			panic(err)
 		}
-- 
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