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-rw-r--r--pkg/tcpip/network/fragmentation/fragmentation.go78
-rw-r--r--pkg/tcpip/network/ipv4/ipv4.go168
-rw-r--r--pkg/tcpip/network/ipv6/ipv6.go160
3 files changed, 303 insertions, 103 deletions
diff --git a/pkg/tcpip/network/fragmentation/fragmentation.go b/pkg/tcpip/network/fragmentation/fragmentation.go
index e1909fab0..888ad62a3 100644
--- a/pkg/tcpip/network/fragmentation/fragmentation.go
+++ b/pkg/tcpip/network/fragmentation/fragmentation.go
@@ -13,7 +13,7 @@
// limitations under the License.
// Package fragmentation contains the implementation of IP fragmentation.
-// It is based on RFC 791 and RFC 815.
+// It is based on RFC 791, RFC 815 and RFC 8200.
package fragmentation
import (
@@ -25,6 +25,7 @@ import (
"gvisor.dev/gvisor/pkg/sync"
"gvisor.dev/gvisor/pkg/tcpip"
"gvisor.dev/gvisor/pkg/tcpip/buffer"
+ "gvisor.dev/gvisor/pkg/tcpip/stack"
)
const (
@@ -243,3 +244,78 @@ func (f *Fragmentation) releaseReassemblersLocked() {
f.release(r)
}
}
+
+// PacketFragmenter is the book-keeping struct for packet fragmentation.
+type PacketFragmenter struct {
+ transportHeader buffer.View
+ data buffer.VectorisedView
+ reserve int
+ innerMTU int
+ fragmentCount int
+ currentFragment int
+ fragmentOffset int
+}
+
+// MakePacketFragmenter prepares the struct needed for packet fragmentation.
+//
+// pkt is the packet to be fragmented.
+//
+// innerMTU is the maximum number of bytes of fragmentable data a fragment can
+// have.
+//
+// reserve is the number of bytes that should be reserved for the headers in
+// each generated fragment.
+func MakePacketFragmenter(pkt *stack.PacketBuffer, innerMTU int, reserve int) PacketFragmenter {
+ // As per RFC 8200 Section 4.5, some IPv6 extension headers should not be
+ // repeated in each fragment. However we do not currently support any header
+ // of that kind yet, so the following computation is valid for both IPv4 and
+ // IPv6.
+ // TODO(gvisor.dev/issue/3912): Once Authentication or ESP Headers are
+ // supported for outbound packets, the fragmentable data should not include
+ // these headers.
+ var fragmentableData buffer.VectorisedView
+ fragmentableData.AppendView(pkt.TransportHeader().View())
+ fragmentableData.Append(pkt.Data)
+ fragmentCount := (fragmentableData.Size() + innerMTU - 1) / innerMTU
+
+ return PacketFragmenter{
+ data: fragmentableData,
+ reserve: reserve,
+ innerMTU: innerMTU,
+ fragmentCount: fragmentCount,
+ }
+}
+
+// BuildNextFragment returns a packet with the payload of the next fragment,
+// along with the fragment's offset, the number of bytes copied and a boolean
+// indicating if there are more fragments left or not. If this function is
+// called again after it indicated that no more fragments were left, it will
+// panic.
+//
+// Note that the returned packet will not have its network and link headers
+// populated, but space for them will be reserved. The transport header will be
+// stored in the packet's data.
+func (pf *PacketFragmenter) BuildNextFragment() (*stack.PacketBuffer, int, int, bool) {
+ if pf.currentFragment >= pf.fragmentCount {
+ panic("BuildNextFragment should not be called again after the last fragment was returned")
+ }
+
+ fragPkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
+ ReserveHeaderBytes: pf.reserve,
+ })
+
+ // Copy data for the fragment.
+ copied := pf.data.ReadToVV(&fragPkt.Data, pf.innerMTU)
+
+ offset := pf.fragmentOffset
+ pf.fragmentOffset += copied
+ pf.currentFragment++
+ more := pf.currentFragment != pf.fragmentCount
+
+ return fragPkt, offset, copied, more
+}
+
+// RemainingFragmentCount returns the number of fragments left to be built.
+func (pf *PacketFragmenter) RemainingFragmentCount() int {
+ return pf.fragmentCount - pf.currentFragment
+}
diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index a2be64fb8..79c939129 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -190,99 +190,26 @@ func (e *endpoint) NetworkProtocolNumber() tcpip.NetworkProtocolNumber {
return e.protocol.Number()
}
-// writePacketFragments calls e.linkEP.WritePacket with each packet fragment to
-// write. It assumes that the IP header is already present in pkt.NetworkHeader.
-// pkt.TransportHeader may be set. mtu includes the IP header and options. This
-// does not support the DontFragment IP flag.
-func (e *endpoint) writePacketFragments(r *stack.Route, gso *stack.GSO, mtu int, pkt *stack.PacketBuffer) *tcpip.Error {
- // This packet is too big, it needs to be fragmented.
- ip := header.IPv4(pkt.NetworkHeader().View())
- flags := ip.Flags()
-
- // Update mtu to take into account the header, which will exist in all
- // fragments anyway.
- innerMTU := mtu - int(ip.HeaderLength())
-
- // Round the MTU down to align to 8 bytes. Then calculate the number of
- // fragments. Calculate fragment sizes as in RFC791.
- innerMTU &^= 7
- n := (int(ip.PayloadLength()) + innerMTU - 1) / innerMTU
-
- outerMTU := innerMTU + int(ip.HeaderLength())
- offset := ip.FragmentOffset()
-
- // Keep the length reserved for link-layer, we need to create fragments with
- // the same reserved length.
- reservedForLink := pkt.AvailableHeaderBytes()
-
- // Destroy the packet, pull all payloads out for fragmentation.
- transHeader, data := pkt.TransportHeader().View(), pkt.Data
-
- // Where possible, the first fragment that is sent has the same
- // number of bytes reserved for header as the input packet. The link-layer
- // endpoint may depend on this for looking at, eg, L4 headers.
- transFitsFirst := len(transHeader) <= innerMTU
-
- for i := 0; i < n; i++ {
- reserve := reservedForLink + int(ip.HeaderLength())
- if i == 0 && transFitsFirst {
- // Reserve for transport header if it's going to be put in the first
- // fragment.
- reserve += len(transHeader)
- }
- fragPkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
- ReserveHeaderBytes: reserve,
- })
- fragPkt.NetworkProtocolNumber = header.IPv4ProtocolNumber
-
- // Copy data for the fragment.
- avail := innerMTU
-
- if n := len(transHeader); n > 0 {
- if n > avail {
- n = avail
- }
- if i == 0 && transFitsFirst {
- copy(fragPkt.TransportHeader().Push(n), transHeader)
- } else {
- fragPkt.Data.AppendView(transHeader[:n:n])
- }
- transHeader = transHeader[n:]
- avail -= n
- }
-
- if avail > 0 {
- n := data.Size()
- if n > avail {
- n = avail
- }
- data.ReadToVV(&fragPkt.Data, n)
- avail -= n
- }
-
- copied := uint16(innerMTU - avail)
-
- // Set lengths in header and calculate checksum.
- h := header.IPv4(fragPkt.NetworkHeader().Push(len(ip)))
- copy(h, ip)
- if i != n-1 {
- h.SetTotalLength(uint16(outerMTU))
- h.SetFlagsFragmentOffset(flags|header.IPv4FlagMoreFragments, offset)
- } else {
- h.SetTotalLength(uint16(h.HeaderLength()) + copied)
- h.SetFlagsFragmentOffset(flags, offset)
- }
- h.SetChecksum(0)
- h.SetChecksum(^h.CalculateChecksum())
- offset += copied
-
- // Send out the fragment.
+// writePacketFragments fragments pkt and writes the results on the link
+// endpoint. The IP header must already present in the original packet. The mtu
+// is the maximum size of the packets.
+func (e *endpoint) writePacketFragments(r *stack.Route, gso *stack.GSO, mtu uint32, pkt *stack.PacketBuffer) *tcpip.Error {
+ networkHeader := header.IPv4(pkt.NetworkHeader().View())
+ fragMTU := int(calculateFragmentInnerMTU(mtu, pkt))
+ pf := fragmentation.MakePacketFragmenter(pkt, fragMTU, pkt.AvailableHeaderBytes()+len(networkHeader))
+
+ for {
+ fragPkt, more := buildNextFragment(&pf, networkHeader)
if err := e.linkEP.WritePacket(r, gso, ProtocolNumber, fragPkt); err != nil {
- r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(n - i))
+ r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(pf.RemainingFragmentCount() + 1))
return err
}
r.Stats().IP.PacketsSent.Increment()
+ if !more {
+ break
+ }
}
+
return nil
}
@@ -304,7 +231,7 @@ func (e *endpoint) addIPHeader(r *stack.Route, pkt *stack.PacketBuffer, params s
DstAddr: r.RemoteAddress,
})
ip.SetChecksum(^ip.CalculateChecksum())
- pkt.NetworkProtocolNumber = header.IPv4ProtocolNumber
+ pkt.NetworkProtocolNumber = ProtocolNumber
}
// WritePacket writes a packet to the given destination address and protocol.
@@ -330,7 +257,7 @@ 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.IPv4(pkt.NetworkHeader().View())
- ep, err := e.protocol.stack.FindNetworkEndpoint(header.IPv4ProtocolNumber, netHeader.DestinationAddress())
+ ep, err := e.protocol.stack.FindNetworkEndpoint(ProtocolNumber, netHeader.DestinationAddress())
if err == nil {
route := r.ReverseRoute(netHeader.SourceAddress(), netHeader.DestinationAddress())
ep.HandlePacket(&route, pkt)
@@ -347,7 +274,7 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.Netw
return nil
}
if pkt.Size() > int(e.linkEP.MTU()) && (gso == nil || gso.Type == stack.GSONone) {
- return e.writePacketFragments(r, gso, int(e.linkEP.MTU()), pkt)
+ return e.writePacketFragments(r, gso, e.linkEP.MTU(), pkt)
}
if err := e.linkEP.WritePacket(r, gso, ProtocolNumber, pkt); err != nil {
r.Stats().IP.OutgoingPacketErrors.Increment()
@@ -397,7 +324,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
}
if _, ok := natPkts[pkt]; ok {
netHeader := header.IPv4(pkt.NetworkHeader().View())
- if ep, err := e.protocol.stack.FindNetworkEndpoint(header.IPv4ProtocolNumber, 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)
@@ -809,14 +736,36 @@ func calculateMTU(mtu uint32) uint32 {
return mtu - header.IPv4MinimumSize
}
+// 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 {
+ if mtu > MaxTotalSize {
+ mtu = MaxTotalSize
+ }
+ mtu -= uint32(pkt.NetworkHeader().View().Size())
+ // Round the MTU down to align to 8 bytes.
+ mtu &^= 7
+ return mtu
+}
+
+// addressToUint32 translates an IPv4 address into its little endian uint32
+// representation.
+//
+// This function does the same thing as binary.LittleEndian.Uint32 but operates
+// on a tcpip.Address (a string) without the need to convert it to a byte slice,
+// which would cause an allocation.
+func addressToUint32(addr tcpip.Address) uint32 {
+ _ = addr[3] // bounds check hint to compiler
+ return uint32(addr[0]) | uint32(addr[1])<<8 | uint32(addr[2])<<16 | uint32(addr[3])<<24
+}
+
// hashRoute calculates a hash value for the given route. It uses the source &
-// destination address, the transport protocol number, and a random initial
-// value (generated once on initialization) to generate the hash.
+// destination address, the transport protocol number and a 32-bit number to
+// generate the hash.
func hashRoute(r *stack.Route, protocol tcpip.TransportProtocolNumber, hashIV uint32) uint32 {
- t := r.LocalAddress
- a := uint32(t[0]) | uint32(t[1])<<8 | uint32(t[2])<<16 | uint32(t[3])<<24
- t = r.RemoteAddress
- b := uint32(t[0]) | uint32(t[1])<<8 | uint32(t[2])<<16 | uint32(t[3])<<24
+ a := addressToUint32(r.LocalAddress)
+ b := addressToUint32(r.RemoteAddress)
return hash.Hash3Words(a, b, uint32(protocol), hashIV)
}
@@ -839,3 +788,26 @@ func NewProtocol(s *stack.Stack) stack.NetworkProtocol {
fragmentation: fragmentation.NewFragmentation(fragmentblockSize, fragmentation.HighFragThreshold, fragmentation.LowFragThreshold, fragmentation.DefaultReassembleTimeout, s.Clock()),
}
}
+
+func buildNextFragment(pf *fragmentation.PacketFragmenter, originalIPHeader header.IPv4) (*stack.PacketBuffer, bool) {
+ fragPkt, offset, copied, more := pf.BuildNextFragment()
+ fragPkt.NetworkProtocolNumber = ProtocolNumber
+
+ originalIPHeaderLength := len(originalIPHeader)
+ nextFragIPHeader := header.IPv4(fragPkt.NetworkHeader().Push(originalIPHeaderLength))
+
+ if copied := copy(nextFragIPHeader, originalIPHeader); copied != len(originalIPHeader) {
+ panic(fmt.Sprintf("wrong number of bytes copied into fragmentIPHeaders: got = %d, want = %d", copied, originalIPHeaderLength))
+ }
+
+ flags := originalIPHeader.Flags()
+ if more {
+ flags |= header.IPv4FlagMoreFragments
+ }
+ nextFragIPHeader.SetFlagsFragmentOffset(flags, uint16(offset))
+ nextFragIPHeader.SetTotalLength(uint16(nextFragIPHeader.HeaderLength()) + uint16(copied))
+ nextFragIPHeader.SetChecksum(0)
+ nextFragIPHeader.SetChecksum(^nextFragIPHeader.CalculateChecksum())
+
+ return fragPkt, more
+}
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
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-02 23:06:45 +0000