Use 1 fragmentation component per IP stack

This will help manage memory consumption by IP reassembly when
receiving IP fragments on multiple network endpoints. Previously,
each endpoint would cap memory consumption at 4MB, but with this
change, each IP stack will cap memory consumption at 4MB.

No behaviour changes.

PiperOrigin-RevId: 324913904

1 files changed, 25 insertions, 18 deletions

diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index d5f5d38f7..6c4f0ae3e 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -52,27 +52,25 @@ const (
 )
 
 type endpoint struct {
-	nicID         tcpip.NICID
-	id            stack.NetworkEndpointID
-	prefixLen     int
-	linkEP        stack.LinkEndpoint
-	dispatcher    stack.TransportDispatcher
-	fragmentation *fragmentation.Fragmentation
-	protocol      *protocol
-	stack         *stack.Stack
+	nicID      tcpip.NICID
+	id         stack.NetworkEndpointID
+	prefixLen  int
+	linkEP     stack.LinkEndpoint
+	dispatcher stack.TransportDispatcher
+	protocol   *protocol
+	stack      *stack.Stack
 }
 
 // NewEndpoint creates a new ipv4 endpoint.
 func (p *protocol) NewEndpoint(nicID tcpip.NICID, addrWithPrefix tcpip.AddressWithPrefix, linkAddrCache stack.LinkAddressCache, dispatcher stack.TransportDispatcher, linkEP stack.LinkEndpoint, st *stack.Stack) (stack.NetworkEndpoint, *tcpip.Error) {
 	e := &endpoint{
-		nicID:         nicID,
-		id:            stack.NetworkEndpointID{LocalAddress: addrWithPrefix.Address},
-		prefixLen:     addrWithPrefix.PrefixLen,
-		linkEP:        linkEP,
-		dispatcher:    dispatcher,
-		fragmentation: fragmentation.NewFragmentation(fragmentblockSize, fragmentation.HighFragThreshold, fragmentation.LowFragThreshold, fragmentation.DefaultReassembleTimeout),
-		protocol:      p,
-		stack:         st,
+		nicID:      nicID,
+		id:         stack.NetworkEndpointID{LocalAddress: addrWithPrefix.Address},
+		prefixLen:  addrWithPrefix.PrefixLen,
+		linkEP:     linkEP,
+		dispatcher: dispatcher,
+		protocol:   p,
+		stack:      st,
 	}
 
 	return e, nil
@@ -442,7 +440,9 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) {
 		}
 		var ready bool
 		var err error
-		pkt.Data, ready, err = e.fragmentation.Process(
+		pkt.Data, ready, err = e.protocol.fragmentation.Process(
+			// As per RFC 791 section 2.3, the identification value is unique
+			// for a source-destination pair and protocol.
 			fragmentation.FragmentID{
 				Source:      h.SourceAddress(),
 				Destination: h.DestinationAddress(),
@@ -484,6 +484,8 @@ type protocol struct {
 	// uint8 portion of it is meaningful and it must be accessed
 	// atomically.
 	defaultTTL uint32
+
+	fragmentation *fragmentation.Fragmentation
 }
 
 // Number returns the ipv4 protocol number.
@@ -605,5 +607,10 @@ func NewProtocol() stack.NetworkProtocol {
 	}
 	hashIV := r[buckets]
 
-	return &protocol{ids: ids, hashIV: hashIV, defaultTTL: DefaultTTL}
+	return &protocol{
+		ids:           ids,
+		hashIV:        hashIV,
+		defaultTTL:    DefaultTTL,
+		fragmentation: fragmentation.NewFragmentation(fragmentblockSize, fragmentation.HighFragThreshold, fragmentation.LowFragThreshold, fragmentation.DefaultReassembleTimeout),
+	}
 }