Merge release-20200928.0-58-g99bf022c2 (automated)

1 files changed, 156 insertions, 4 deletions

diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index c8a3e0b34..73e50f8d6 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -16,7 +16,9 @@
 package ipv6
 
 import (
+	"encoding/binary"
 	"fmt"
+	"hash/fnv"
 	"sort"
 	"sync/atomic"
 
@@ -26,6 +28,7 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/header/parse"
 	"gvisor.dev/gvisor/pkg/tcpip/network/fragmentation"
+	"gvisor.dev/gvisor/pkg/tcpip/network/hash"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
 
@@ -40,6 +43,9 @@ const (
 	// DefaultTTL is the default hop limit for IPv6 Packets egressed by
 	// Netstack.
 	DefaultTTL = 64
+
+	// buckets for fragment identifiers
+	buckets = 2048
 )
 
 var _ stack.GroupAddressableEndpoint = (*endpoint)(nil)
@@ -376,7 +382,44 @@ func (e *endpoint) addIPHeader(r *stack.Route, pkt *stack.PacketBuffer, params s
 		SrcAddr:       r.LocalAddress,
 		DstAddr:       r.RemoteAddress,
 	})
-	pkt.NetworkProtocolNumber = header.IPv6ProtocolNumber
+	pkt.NetworkProtocolNumber = ProtocolNumber
+}
+
+func (e *endpoint) packetMustBeFragmented(pkt *stack.PacketBuffer, gso *stack.GSO) bool {
+	return pkt.Size() > int(e.linkEP.MTU()) && (gso == nil || gso.Type == stack.GSONone)
+}
+
+// handleFragments fragments pkt and calls the handler function on each
+// fragment. It returns the number of fragments handled and the number of
+// fragments left to be processed. The IP header must already be present in the
+// original packet. The mtu is the maximum size of the packets. The transport
+// header protocol number is required to avoid parsing the IPv6 extension
+// headers.
+func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, mtu uint32, pkt *stack.PacketBuffer, transProto tcpip.TransportProtocolNumber, handler func(*stack.PacketBuffer) *tcpip.Error) (int, int, *tcpip.Error) {
+	fragMTU := int(calculateFragmentInnerMTU(mtu, pkt))
+	if fragMTU < pkt.TransportHeader().View().Size() {
+		// As per RFC 8200 Section 4.5, the Transport Header is expected to be small
+		// enough to fit in the first fragment.
+		return 0, 1, tcpip.ErrMessageTooLong
+	}
+
+	pf := fragmentation.MakePacketFragmenter(pkt, fragMTU, calculateFragmentReserve(pkt))
+	id := atomic.AddUint32(&e.protocol.ids[hashRoute(r, e.protocol.hashIV)%buckets], 1)
+	networkHeader := header.IPv6(pkt.NetworkHeader().View())
+
+	var n int
+	for {
+		fragPkt, more := buildNextFragment(&pf, networkHeader, transProto, id)
+		if err := handler(fragPkt); err != nil {
+			return n, pf.RemainingFragmentCount() + 1, err
+		}
+		n++
+		if !more {
+			break
+		}
+	}
+
+	return n, 0, nil
 }
 
 // WritePacket writes a packet to the given destination address and protocol.
@@ -402,7 +445,7 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.Netw
 	// short circuits broadcasts before they are sent out to other hosts.
 	if pkt.NatDone {
 		netHeader := header.IPv6(pkt.NetworkHeader().View())
-		if ep, err := e.protocol.stack.FindNetworkEndpoint(header.IPv6ProtocolNumber, netHeader.DestinationAddress()); err == nil {
+		if ep, err := e.protocol.stack.FindNetworkEndpoint(ProtocolNumber, netHeader.DestinationAddress()); err == nil {
 			route := r.ReverseRoute(netHeader.SourceAddress(), netHeader.DestinationAddress())
 			ep.HandlePacket(&route, pkt)
 			return nil
@@ -423,15 +466,29 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.Netw
 		return nil
 	}
 
+	if e.packetMustBeFragmented(pkt, gso) {
+		sent, remain, err := e.handleFragments(r, gso, e.linkEP.MTU(), pkt, params.Protocol, func(fragPkt *stack.PacketBuffer) *tcpip.Error {
+			// TODO(gvisor.dev/issue/3884): Evaluate whether we want to send each
+			// fragment one by one using WritePacket() (current strategy) or if we
+			// want to create a PacketBufferList from the fragments and feed it to
+			// WritePackets(). It'll be faster but cost more memory.
+			return e.linkEP.WritePacket(r, gso, ProtocolNumber, fragPkt)
+		})
+		r.Stats().IP.PacketsSent.IncrementBy(uint64(sent))
+		r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(remain))
+		return err
+	}
+
 	if err := e.linkEP.WritePacket(r, gso, ProtocolNumber, pkt); err != nil {
 		r.Stats().IP.OutgoingPacketErrors.Increment()
 		return err
 	}
+
 	r.Stats().IP.PacketsSent.Increment()
 	return nil
 }
 
-// WritePackets implements stack.LinkEndpoint.WritePackets.
+// WritePackets implements stack.NetworkEndpoint.WritePackets.
 func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, *tcpip.Error) {
 	if r.Loop&stack.PacketLoop != 0 {
 		panic("not implemented")
@@ -442,6 +499,23 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 
 	for pb := pkts.Front(); pb != nil; pb = pb.Next() {
 		e.addIPHeader(r, pb, params)
+		if e.packetMustBeFragmented(pb, gso) {
+			current := pb
+			_, _, err := e.handleFragments(r, gso, e.linkEP.MTU(), pb, params.Protocol, func(fragPkt *stack.PacketBuffer) *tcpip.Error {
+				// Modify the packet list in place with the new fragments.
+				pkts.InsertAfter(current, fragPkt)
+				current = current.Next()
+				return nil
+			})
+			if err != nil {
+				r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(pkts.Len()))
+				return 0, err
+			}
+			// The fragmented packet can be released. The rest of the packets can be
+			// processed.
+			pkts.Remove(pb)
+			pb = current
+		}
 	}
 
 	// iptables filtering. All packets that reach here are locally
@@ -470,7 +544,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 		}
 		if _, ok := natPkts[pkt]; ok {
 			netHeader := header.IPv6(pkt.NetworkHeader().View())
-			if ep, err := e.protocol.stack.FindNetworkEndpoint(header.IPv6ProtocolNumber, netHeader.DestinationAddress()); err == nil {
+			if ep, err := e.protocol.stack.FindNetworkEndpoint(ProtocolNumber, netHeader.DestinationAddress()); err == nil {
 				src := netHeader.SourceAddress()
 				dst := netHeader.DestinationAddress()
 				route := r.ReverseRoute(src, dst)
@@ -1155,6 +1229,9 @@ type protocol struct {
 		eps map[*endpoint]struct{}
 	}
 
+	ids    []uint32
+	hashIV uint32
+
 	// defaultTTL is the current default TTL for the protocol. Only the
 	// uint8 portion of it is meaningful.
 	//
@@ -1376,10 +1453,15 @@ type Options struct {
 func NewProtocolWithOptions(opts Options) stack.NetworkProtocolFactory {
 	opts.NDPConfigs.validate()
 
+	ids := hash.RandN32(buckets)
+	hashIV := hash.RandN32(1)[0]
+
 	return func(s *stack.Stack) stack.NetworkProtocol {
 		p := &protocol{
 			stack:         s,
 			fragmentation: fragmentation.NewFragmentation(header.IPv6FragmentExtHdrFragmentOffsetBytesPerUnit, fragmentation.HighFragThreshold, fragmentation.LowFragThreshold, fragmentation.DefaultReassembleTimeout, s.Clock()),
+			ids:           ids,
+			hashIV:        hashIV,
 
 			ndpDisp:              opts.NDPDisp,
 			ndpConfigs:           opts.NDPConfigs,
@@ -1397,3 +1479,73 @@ func NewProtocolWithOptions(opts Options) stack.NetworkProtocolFactory {
 func NewProtocol(s *stack.Stack) stack.NetworkProtocol {
 	return NewProtocolWithOptions(Options{})(s)
 }
+
+// calculateFragmentInnerMTU calculates the maximum number of bytes of
+// fragmentable data a fragment can have, based on the link layer mtu and pkt's
+// network header size.
+func calculateFragmentInnerMTU(mtu uint32, pkt *stack.PacketBuffer) uint32 {
+	// TODO(gvisor.dev/issue/3912): Once the Authentication or ESP Headers are
+	// supported for outbound packets, their length should not affect the fragment
+	// MTU because they should only be transmitted once.
+	mtu -= uint32(pkt.NetworkHeader().View().Size())
+	mtu -= header.IPv6FragmentHeaderSize
+	// Round the MTU down to align to 8 bytes.
+	mtu &^= 7
+	if mtu <= maxPayloadSize {
+		return mtu
+	}
+	return maxPayloadSize
+}
+
+func calculateFragmentReserve(pkt *stack.PacketBuffer) int {
+	return pkt.AvailableHeaderBytes() + pkt.NetworkHeader().View().Size() + header.IPv6FragmentHeaderSize
+}
+
+// hashRoute calculates a hash value for the given route. It uses the source &
+// destination address and 32-bit number to generate the hash.
+func hashRoute(r *stack.Route, hashIV uint32) uint32 {
+	// The FNV-1a was chosen because it is a fast hashing algorithm, and
+	// cryptographic properties are not needed here.
+	h := fnv.New32a()
+	if _, err := h.Write([]byte(r.LocalAddress)); err != nil {
+		panic(fmt.Sprintf("Hash.Write: %s, but Hash' implementation of Write is not expected to ever return an error", err))
+	}
+
+	if _, err := h.Write([]byte(r.RemoteAddress)); err != nil {
+		panic(fmt.Sprintf("Hash.Write: %s, but Hash' implementation of Write is not expected to ever return an error", err))
+	}
+
+	s := make([]byte, 4)
+	binary.LittleEndian.PutUint32(s, hashIV)
+	if _, err := h.Write(s); err != nil {
+		panic(fmt.Sprintf("Hash.Write: %s, but Hash' implementation of Write is not expected ever to return an error", err))
+	}
+
+	return h.Sum32()
+}
+
+func buildNextFragment(pf *fragmentation.PacketFragmenter, originalIPHeaders header.IPv6, transportProto tcpip.TransportProtocolNumber, id uint32) (*stack.PacketBuffer, bool) {
+	fragPkt, offset, copied, more := pf.BuildNextFragment()
+	fragPkt.NetworkProtocolNumber = ProtocolNumber
+
+	originalIPHeadersLength := len(originalIPHeaders)
+	fragmentIPHeadersLength := originalIPHeadersLength + header.IPv6FragmentHeaderSize
+	fragmentIPHeaders := header.IPv6(fragPkt.NetworkHeader().Push(fragmentIPHeadersLength))
+
+	// Copy the IPv6 header and any extension headers already populated.
+	if copied := copy(fragmentIPHeaders, originalIPHeaders); copied != originalIPHeadersLength {
+		panic(fmt.Sprintf("wrong number of bytes copied into fragmentIPHeaders: got %d, want %d", copied, originalIPHeadersLength))
+	}
+	fragmentIPHeaders.SetNextHeader(header.IPv6FragmentHeader)
+	fragmentIPHeaders.SetPayloadLength(uint16(copied + fragmentIPHeadersLength - header.IPv6MinimumSize))
+
+	fragmentHeader := header.IPv6Fragment(fragmentIPHeaders[originalIPHeadersLength:])
+	fragmentHeader.Encode(&header.IPv6FragmentFields{
+		M:              more,
+		FragmentOffset: uint16(offset / header.IPv6FragmentExtHdrFragmentOffsetBytesPerUnit),
+		Identification: id,
+		NextHeader:     uint8(transportProto),
+	})
+
+	return fragPkt, more
+}