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-rw-r--r--pkg/tcpip/header/ipv4.go7
-rw-r--r--pkg/tcpip/header/ipv6.go6
-rw-r--r--pkg/tcpip/network/fragmentation/fragmentation.go30
-rw-r--r--pkg/tcpip/network/ipv4/icmp.go7
-rw-r--r--pkg/tcpip/network/ipv4/ipv4.go82
-rw-r--r--pkg/tcpip/network/ipv6/icmp.go7
-rw-r--r--pkg/tcpip/network/ipv6/ipv6.go112
7 files changed, 158 insertions, 93 deletions
diff --git a/pkg/tcpip/header/ipv4.go b/pkg/tcpip/header/ipv4.go
index 4c6e4be64..ee307d163 100644
--- a/pkg/tcpip/header/ipv4.go
+++ b/pkg/tcpip/header/ipv4.go
@@ -148,6 +148,13 @@ const (
// packet that every IPv4 capable host must be able to
// process/reassemble.
IPv4MinimumProcessableDatagramSize = 576
+
+ // IPv4MinimumMTU is the minimum MTU required by IPv4, per RFC 791,
+ // section 3.2:
+ // Every internet module must be able to forward a datagram of 68 octets
+ // without further fragmentation. This is because an internet header may be
+ // up to 60 octets, and the minimum fragment is 8 octets.
+ IPv4MinimumMTU = 68
)
// Flags that may be set in an IPv4 packet.
diff --git a/pkg/tcpip/header/ipv6.go b/pkg/tcpip/header/ipv6.go
index c5d8a3456..09cb153b1 100644
--- a/pkg/tcpip/header/ipv6.go
+++ b/pkg/tcpip/header/ipv6.go
@@ -101,8 +101,10 @@ const (
// The address is ff02::2.
IPv6AllRoutersMulticastAddress tcpip.Address = "\xff\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02"
- // IPv6MinimumMTU is the minimum MTU required by IPv6, per RFC 2460,
- // section 5.
+ // IPv6MinimumMTU is the minimum MTU required by IPv6, per RFC 8200,
+ // section 5:
+ // IPv6 requires that every link in the Internet have an MTU of 1280 octets
+ // or greater. This is known as the IPv6 minimum link MTU.
IPv6MinimumMTU = 1280
// IPv6Loopback is the IPv6 Loopback address.
diff --git a/pkg/tcpip/network/fragmentation/fragmentation.go b/pkg/tcpip/network/fragmentation/fragmentation.go
index ed502a473..bb31ef61a 100644
--- a/pkg/tcpip/network/fragmentation/fragmentation.go
+++ b/pkg/tcpip/network/fragmentation/fragmentation.go
@@ -244,25 +244,25 @@ func (f *Fragmentation) releaseReassemblersLocked() {
// 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
+ transportHeader buffer.View
+ data buffer.VectorisedView
+ reserve int
+ fragmentPayloadLen 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
+// fragmentPayloadLen 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 {
+func MakePacketFragmenter(pkt *stack.PacketBuffer, fragmentPayloadLen uint32, 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
@@ -273,13 +273,13 @@ func MakePacketFragmenter(pkt *stack.PacketBuffer, innerMTU int, reserve int) Pa
var fragmentableData buffer.VectorisedView
fragmentableData.AppendView(pkt.TransportHeader().View())
fragmentableData.Append(pkt.Data)
- fragmentCount := (fragmentableData.Size() + innerMTU - 1) / innerMTU
+ fragmentCount := (uint32(fragmentableData.Size()) + fragmentPayloadLen - 1) / fragmentPayloadLen
return PacketFragmenter{
- data: fragmentableData,
- reserve: reserve,
- innerMTU: innerMTU,
- fragmentCount: fragmentCount,
+ data: fragmentableData,
+ reserve: reserve,
+ fragmentPayloadLen: int(fragmentPayloadLen),
+ fragmentCount: int(fragmentCount),
}
}
@@ -302,7 +302,7 @@ func (pf *PacketFragmenter) BuildNextFragment() (*stack.PacketBuffer, int, int,
})
// Copy data for the fragment.
- copied := pf.data.ReadToVV(&fragPkt.Data, pf.innerMTU)
+ copied := pf.data.ReadToVV(&fragPkt.Data, pf.fragmentPayloadLen)
offset := pf.fragmentOffset
pf.fragmentOffset += copied
diff --git a/pkg/tcpip/network/ipv4/icmp.go b/pkg/tcpip/network/ipv4/icmp.go
index 3407755ed..ac66403fa 100644
--- a/pkg/tcpip/network/ipv4/icmp.go
+++ b/pkg/tcpip/network/ipv4/icmp.go
@@ -182,8 +182,11 @@ func (e *endpoint) handleICMP(r *stack.Route, pkt *stack.PacketBuffer) {
e.handleControl(stack.ControlPortUnreachable, 0, pkt)
case header.ICMPv4FragmentationNeeded:
- mtu := uint32(h.MTU())
- e.handleControl(stack.ControlPacketTooBig, calculateMTU(mtu), pkt)
+ networkMTU, err := calculateNetworkMTU(uint32(h.MTU()), header.IPv4MinimumSize)
+ if err != nil {
+ networkMTU = 0
+ }
+ e.handleControl(stack.ControlPacketTooBig, networkMTU, pkt)
}
case header.ICMPv4SrcQuench:
diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index e7c58ae0a..41e548c85 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -176,7 +176,11 @@ func (e *endpoint) DefaultTTL() uint8 {
// MTU implements stack.NetworkEndpoint.MTU. It returns the link-layer MTU minus
// the network layer max header length.
func (e *endpoint) MTU() uint32 {
- return calculateMTU(e.nic.MTU())
+ networkMTU, err := calculateNetworkMTU(e.nic.MTU(), header.IPv4MinimumSize)
+ if err != nil {
+ return 0
+ }
+ return networkMTU
}
// MaxHeaderLength returns the maximum length needed by ipv4 headers (and
@@ -211,18 +215,15 @@ func (e *endpoint) addIPHeader(r *stack.Route, pkt *stack.PacketBuffer, params s
pkt.NetworkProtocolNumber = ProtocolNumber
}
-func (e *endpoint) packetMustBeFragmented(pkt *stack.PacketBuffer, gso *stack.GSO) bool {
- return (gso == nil || gso.Type == stack.GSONone) && pkt.Size() > int(e.nic.MTU())
-}
-
// 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.
-func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, mtu uint32, pkt *stack.PacketBuffer, handler func(*stack.PacketBuffer) *tcpip.Error) (int, int, *tcpip.Error) {
- fragMTU := int(calculateFragmentInnerMTU(mtu, pkt))
+// original packet.
+func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU uint32, pkt *stack.PacketBuffer, handler func(*stack.PacketBuffer) *tcpip.Error) (int, int, *tcpip.Error) {
+ // Round the MTU down to align to 8 bytes.
+ fragmentPayloadSize := networkMTU &^ 7
networkHeader := header.IPv4(pkt.NetworkHeader().View())
- pf := fragmentation.MakePacketFragmenter(pkt, fragMTU, pkt.AvailableHeaderBytes()+len(networkHeader))
+ pf := fragmentation.MakePacketFragmenter(pkt, fragmentPayloadSize, pkt.AvailableHeaderBytes()+len(networkHeader))
var n int
for {
@@ -280,8 +281,14 @@ func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.Packet
return nil
}
- if e.packetMustBeFragmented(pkt, gso) {
- sent, remain, err := e.handleFragments(r, gso, e.nic.MTU(), pkt, func(fragPkt *stack.PacketBuffer) *tcpip.Error {
+ networkMTU, err := calculateNetworkMTU(e.nic.MTU(), uint32(pkt.NetworkHeader().View().Size()))
+ if err != nil {
+ r.Stats().IP.OutgoingPacketErrors.Increment()
+ return err
+ }
+
+ if packetMustBeFragmented(pkt, networkMTU, gso) {
+ sent, remain, err := e.handleFragments(r, gso, networkMTU, pkt, 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
@@ -292,6 +299,7 @@ func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.Packet
r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(remain))
return err
}
+
if err := e.nic.WritePacket(r, gso, ProtocolNumber, pkt); err != nil {
r.Stats().IP.OutgoingPacketErrors.Increment()
return err
@@ -311,17 +319,23 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
e.addIPHeader(r, pkt, params)
- if e.packetMustBeFragmented(pkt, gso) {
+ networkMTU, err := calculateNetworkMTU(e.nic.MTU(), uint32(pkt.NetworkHeader().View().Size()))
+ if err != nil {
+ r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(pkts.Len()))
+ return 0, err
+ }
+
+ if packetMustBeFragmented(pkt, networkMTU, gso) {
// Keep track of the packet that is about to be fragmented so it can be
// removed once the fragmentation is done.
originalPkt := pkt
- if _, _, err := e.handleFragments(r, gso, e.nic.MTU(), pkt, func(fragPkt *stack.PacketBuffer) *tcpip.Error {
+ if _, _, err := e.handleFragments(r, gso, networkMTU, pkt, func(fragPkt *stack.PacketBuffer) *tcpip.Error {
// Modify the packet list in place with the new fragments.
pkts.InsertAfter(pkt, fragPkt)
pkt = fragPkt
return nil
}); err != nil {
- panic(fmt.Sprintf("e.handleFragments(_, _, %d, _, _) = %s", e.nic.MTU(), err))
+ panic(fmt.Sprintf("e.handleFragments(_, _, %d, _, _) = %s", networkMTU, err))
}
// Remove the packet that was just fragmented and process the rest.
pkts.Remove(originalPkt)
@@ -778,26 +792,32 @@ func (p *protocol) SetForwarding(v bool) {
}
}
-// calculateMTU calculates the network-layer payload MTU based on the link-layer
-// payload mtu.
-func calculateMTU(mtu uint32) uint32 {
- if mtu > MaxTotalSize {
- mtu = MaxTotalSize
+// calculateNetworkMTU calculates the network-layer payload MTU based on the
+// link-layer payload mtu.
+func calculateNetworkMTU(linkMTU, networkHeaderSize uint32) (uint32, *tcpip.Error) {
+ if linkMTU < header.IPv4MinimumMTU {
+ return 0, tcpip.ErrInvalidEndpointState
}
- 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
+ // As per RFC 791 section 3.1, an IPv4 header cannot exceed 60 bytes in
+ // length:
+ // The maximal internet header is 60 octets, and a typical internet header
+ // is 20 octets, allowing a margin for headers of higher level protocols.
+ if networkHeaderSize > header.IPv4MaximumHeaderSize {
+ return 0, tcpip.ErrMalformedHeader
}
- mtu -= uint32(pkt.NetworkHeader().View().Size())
- // Round the MTU down to align to 8 bytes.
- mtu &^= 7
- return mtu
+
+ networkMTU := linkMTU
+ if networkMTU > MaxTotalSize {
+ networkMTU = MaxTotalSize
+ }
+
+ return networkMTU - uint32(networkHeaderSize), nil
+}
+
+func packetMustBeFragmented(pkt *stack.PacketBuffer, networkMTU uint32, gso *stack.GSO) bool {
+ payload := pkt.TransportHeader().View().Size() + pkt.Data.Size()
+ return (gso == nil || gso.Type == stack.GSONone) && uint32(payload) > networkMTU
}
// addressToUint32 translates an IPv4 address into its little endian uint32
diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go
index ead6bedcb..40908ddaa 100644
--- a/pkg/tcpip/network/ipv6/icmp.go
+++ b/pkg/tcpip/network/ipv6/icmp.go
@@ -170,8 +170,11 @@ func (e *endpoint) handleICMP(r *stack.Route, pkt *stack.PacketBuffer, hasFragme
return
}
pkt.Data.TrimFront(header.ICMPv6PacketTooBigMinimumSize)
- mtu := header.ICMPv6(hdr).MTU()
- e.handleControl(stack.ControlPacketTooBig, calculateMTU(mtu), pkt)
+ networkMTU, err := calculateNetworkMTU(header.ICMPv6(hdr).MTU(), header.IPv6MinimumSize)
+ if err != nil {
+ networkMTU = 0
+ }
+ e.handleControl(stack.ControlPacketTooBig, networkMTU, pkt)
case header.ICMPv6DstUnreachable:
received.DstUnreachable.Increment()
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index 9670696c7..3c2578343 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -46,7 +46,7 @@ const (
// ProtocolNumber is the ipv6 protocol number.
ProtocolNumber = header.IPv6ProtocolNumber
- // maxTotalSize is maximum size that can be encoded in the 16-bit
+ // maxPayloadSize is the maximum size that can be encoded in the 16-bit
// PayloadLength field of the ipv6 header.
maxPayloadSize = 0xffff
@@ -363,7 +363,11 @@ func (e *endpoint) DefaultTTL() uint8 {
// MTU implements stack.NetworkEndpoint.MTU. It returns the link-layer MTU minus
// the network layer max header length.
func (e *endpoint) MTU() uint32 {
- return calculateMTU(e.nic.MTU())
+ networkMTU, err := calculateNetworkMTU(e.nic.MTU(), header.IPv6MinimumSize)
+ if err != nil {
+ return 0
+ }
+ return networkMTU
}
// MaxHeaderLength returns the maximum length needed by ipv6 headers (and
@@ -386,27 +390,40 @@ func (e *endpoint) addIPHeader(r *stack.Route, pkt *stack.PacketBuffer, params s
pkt.NetworkProtocolNumber = ProtocolNumber
}
-func (e *endpoint) packetMustBeFragmented(pkt *stack.PacketBuffer, gso *stack.GSO) bool {
- return (gso == nil || gso.Type == stack.GSONone) && pkt.Size() > int(e.nic.MTU())
+func packetMustBeFragmented(pkt *stack.PacketBuffer, networkMTU uint32, gso *stack.GSO) bool {
+ payload := pkt.TransportHeader().View().Size() + pkt.Data.Size()
+ return (gso == nil || gso.Type == stack.GSONone) && uint32(payload) > networkMTU
}
// 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() {
+// original packet. The transport header protocol number is required to avoid
+// parsing the IPv6 extension headers.
+func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU uint32, pkt *stack.PacketBuffer, transProto tcpip.TransportProtocolNumber, handler func(*stack.PacketBuffer) *tcpip.Error) (int, int, *tcpip.Error) {
+ networkHeader := header.IPv6(pkt.NetworkHeader().View())
+
+ // TODO(gvisor.dev/issue/3912): Once the Authentication or ESP Headers are
+ // supported for outbound packets, their length should not affect the fragment
+ // maximum payload length because they should only be transmitted once.
+ fragmentPayloadLen := (networkMTU - header.IPv6FragmentHeaderSize) &^ 7
+ if fragmentPayloadLen < header.IPv6FragmentExtHdrFragmentOffsetBytesPerUnit {
+ // We need at least 8 bytes of space left for the fragmentable part because
+ // the fragment payload must obviously be non-zero and must be a multiple
+ // of 8 as per RFC 8200 section 4.5:
+ // Each complete fragment, except possibly the last ("rightmost") one, is
+ // an integer multiple of 8 octets long.
+ return 0, 1, tcpip.ErrMessageTooLong
+ }
+
+ if fragmentPayloadLen < uint32(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))
+ pf := fragmentation.MakePacketFragmenter(pkt, fragmentPayloadLen, 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 {
@@ -468,8 +485,14 @@ func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.Packet
return nil
}
- if e.packetMustBeFragmented(pkt, gso) {
- sent, remain, err := e.handleFragments(r, gso, e.nic.MTU(), pkt, protocol, func(fragPkt *stack.PacketBuffer) *tcpip.Error {
+ networkMTU, err := calculateNetworkMTU(e.nic.MTU(), uint32(pkt.NetworkHeader().View().Size()))
+ if err != nil {
+ r.Stats().IP.OutgoingPacketErrors.Increment()
+ return err
+ }
+
+ if packetMustBeFragmented(pkt, networkMTU, gso) {
+ sent, remain, err := e.handleFragments(r, gso, networkMTU, pkt, 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
@@ -499,13 +522,20 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
return pkts.Len(), nil
}
+ linkMTU := e.nic.MTU()
for pb := pkts.Front(); pb != nil; pb = pb.Next() {
e.addIPHeader(r, pb, params)
- if e.packetMustBeFragmented(pb, gso) {
+
+ networkMTU, err := calculateNetworkMTU(linkMTU, uint32(pb.NetworkHeader().View().Size()))
+ if err != nil {
+ r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(pkts.Len()))
+ return 0, err
+ }
+ if packetMustBeFragmented(pb, networkMTU, gso) {
// Keep track of the packet that is about to be fragmented so it can be
// removed once the fragmentation is done.
originalPkt := pb
- if _, _, err := e.handleFragments(r, gso, e.nic.MTU(), pb, params.Protocol, func(fragPkt *stack.PacketBuffer) *tcpip.Error {
+ if _, _, err := e.handleFragments(r, gso, networkMTU, pb, params.Protocol, func(fragPkt *stack.PacketBuffer) *tcpip.Error {
// Modify the packet list in place with the new fragments.
pkts.InsertAfter(pb, fragPkt)
pb = fragPkt
@@ -569,7 +599,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
return n + len(dropped), nil
}
-// WriteHeaderIncludedPacker implements stack.NetworkEndpoint.
+// WriteHeaderIncludedPacket implements stack.NetworkEndpoint.
func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBuffer) *tcpip.Error {
// The packet already has an IP header, but there are a few required checks.
h, ok := pkt.Data.PullUp(header.IPv6MinimumSize)
@@ -1427,14 +1457,31 @@ func (p *protocol) SetForwarding(v bool) {
}
}
-// calculateMTU calculates the network-layer payload MTU based on the link-layer
-// payload mtu.
-func calculateMTU(mtu uint32) uint32 {
- mtu -= header.IPv6MinimumSize
- if mtu <= maxPayloadSize {
- return mtu
+// calculateNetworkMTU calculates the network-layer payload MTU based on the
+// link-layer payload MTU and the length of every IPv6 header.
+// Note that this is different than the Payload Length field of the IPv6 header,
+// which includes the length of the extension headers.
+func calculateNetworkMTU(linkMTU, networkHeadersLen uint32) (uint32, *tcpip.Error) {
+ if linkMTU < header.IPv6MinimumMTU {
+ return 0, tcpip.ErrInvalidEndpointState
+ }
+
+ // As per RFC 7112 section 5, we should discard packets if their IPv6 header
+ // is bigger than 1280 bytes (ie, the minimum link MTU) since we do not
+ // support PMTU discovery:
+ // Hosts that do not discover the Path MTU MUST limit the IPv6 Header Chain
+ // length to 1280 bytes. Limiting the IPv6 Header Chain length to 1280
+ // bytes ensures that the header chain length does not exceed the IPv6
+ // minimum MTU.
+ if networkHeadersLen > header.IPv6MinimumMTU {
+ return 0, tcpip.ErrMalformedHeader
}
- return maxPayloadSize
+
+ networkMTU := linkMTU - uint32(networkHeadersLen)
+ if networkMTU > maxPayloadSize {
+ networkMTU = maxPayloadSize
+ }
+ return networkMTU, nil
}
// Options holds options to configure a new protocol.
@@ -1509,23 +1556,6 @@ 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
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-17 01:28:29 +0000