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-rw-r--r--pkg/tcpip/header/checksum.go62
-rw-r--r--pkg/tcpip/header/checksum_test.go203
-rw-r--r--pkg/tcpip/header/interfaces.go38
-rw-r--r--pkg/tcpip/header/ipv4.go12
-rw-r--r--pkg/tcpip/header/tcp.go29
-rw-r--r--pkg/tcpip/header/udp.go29
6 files changed, 373 insertions, 0 deletions
diff --git a/pkg/tcpip/header/checksum.go b/pkg/tcpip/header/checksum.go
index 6aa9acfa8..e2c85e220 100644
--- a/pkg/tcpip/header/checksum.go
+++ b/pkg/tcpip/header/checksum.go
@@ -18,6 +18,7 @@ package header
import (
"encoding/binary"
+ "fmt"
"gvisor.dev/gvisor/pkg/tcpip"
"gvisor.dev/gvisor/pkg/tcpip/buffer"
@@ -234,3 +235,64 @@ func PseudoHeaderChecksum(protocol tcpip.TransportProtocolNumber, srcAddr tcpip.
return Checksum([]byte{0, uint8(protocol)}, xsum)
}
+
+// checksumUpdate2ByteAlignedUint16 updates a uint16 value in a calculated
+// checksum.
+//
+// The value MUST begin at a 2-byte boundary in the original buffer.
+func checksumUpdate2ByteAlignedUint16(xsum, old, new uint16) uint16 {
+ // As per RFC 1071 page 4,
+ // (4) Incremental Update
+ //
+ // ...
+ //
+ // To update the checksum, simply add the differences of the
+ // sixteen bit integers that have been changed. To see why this
+ // works, observe that every 16-bit integer has an additive inverse
+ // and that addition is associative. From this it follows that
+ // given the original value m, the new value m', and the old
+ // checksum C, the new checksum C' is:
+ //
+ // C' = C + (-m) + m' = C + (m' - m)
+ return ChecksumCombine(xsum, ChecksumCombine(new, ^old))
+}
+
+// checksumUpdate2ByteAlignedAddress updates an address in a calculated
+// checksum.
+//
+// The addresses must have the same length and must contain an even number
+// of bytes. The address MUST begin at a 2-byte boundary in the original buffer.
+func checksumUpdate2ByteAlignedAddress(xsum uint16, old, new tcpip.Address) uint16 {
+ const uint16Bytes = 2
+
+ if len(old) != len(new) {
+ panic(fmt.Sprintf("buffer lengths are different; old = %d, new = %d", len(old), len(new)))
+ }
+
+ if len(old)%uint16Bytes != 0 {
+ panic(fmt.Sprintf("buffer has an odd number of bytes; got = %d", len(old)))
+ }
+
+ // As per RFC 1071 page 4,
+ // (4) Incremental Update
+ //
+ // ...
+ //
+ // To update the checksum, simply add the differences of the
+ // sixteen bit integers that have been changed. To see why this
+ // works, observe that every 16-bit integer has an additive inverse
+ // and that addition is associative. From this it follows that
+ // given the original value m, the new value m', and the old
+ // checksum C, the new checksum C' is:
+ //
+ // C' = C + (-m) + m' = C + (m' - m)
+ for len(old) != 0 {
+ // Convert the 2 byte sequences to uint16 values then apply the increment
+ // update.
+ xsum = checksumUpdate2ByteAlignedUint16(xsum, (uint16(old[0])<<8)+uint16(old[1]), (uint16(new[0])<<8)+uint16(new[1]))
+ old = old[uint16Bytes:]
+ new = new[uint16Bytes:]
+ }
+
+ return xsum
+}
diff --git a/pkg/tcpip/header/checksum_test.go b/pkg/tcpip/header/checksum_test.go
index d267dabd0..3445511f4 100644
--- a/pkg/tcpip/header/checksum_test.go
+++ b/pkg/tcpip/header/checksum_test.go
@@ -23,6 +23,7 @@ import (
"sync"
"testing"
+ "gvisor.dev/gvisor/pkg/tcpip"
"gvisor.dev/gvisor/pkg/tcpip/buffer"
"gvisor.dev/gvisor/pkg/tcpip/header"
)
@@ -256,3 +257,205 @@ func TestICMPv6Checksum(t *testing.T) {
})
}, want, fmt.Sprintf("header: {% x} data {% x}", h, vv.ToView()))
}
+
+func randomAddress(size int) tcpip.Address {
+ s := make([]byte, size)
+ for i := 0; i < size; i++ {
+ s[i] = byte(rand.Uint32())
+ }
+ return tcpip.Address(s)
+}
+
+func TestChecksummableNetworkUpdateAddress(t *testing.T) {
+ tests := []struct {
+ name string
+ update func(header.IPv4, tcpip.Address)
+ }{
+ {
+ name: "SetSourceAddressWithChecksumUpdate",
+ update: header.IPv4.SetSourceAddressWithChecksumUpdate,
+ },
+ {
+ name: "SetDestinationAddressWithChecksumUpdate",
+ update: header.IPv4.SetDestinationAddressWithChecksumUpdate,
+ },
+ }
+
+ for _, test := range tests {
+ t.Run(test.name, func(t *testing.T) {
+ for i := 0; i < 1000; i++ {
+ var origBytes [header.IPv4MinimumSize]byte
+ header.IPv4(origBytes[:]).Encode(&header.IPv4Fields{
+ TOS: 1,
+ TotalLength: header.IPv4MinimumSize,
+ ID: 2,
+ Flags: 3,
+ FragmentOffset: 4,
+ TTL: 5,
+ Protocol: 6,
+ Checksum: 0,
+ SrcAddr: randomAddress(header.IPv4AddressSize),
+ DstAddr: randomAddress(header.IPv4AddressSize),
+ })
+
+ addr := randomAddress(header.IPv4AddressSize)
+
+ bytesCopy := origBytes
+ h := header.IPv4(bytesCopy[:])
+ origXSum := h.CalculateChecksum()
+ h.SetChecksum(^origXSum)
+
+ test.update(h, addr)
+ got := ^h.Checksum()
+ h.SetChecksum(0)
+ want := h.CalculateChecksum()
+ if got != want {
+ t.Errorf("got h.Checksum() = 0x%x, want = 0x%x; originalBytes = 0x%x, new addr = %s", got, want, origBytes, addr)
+ }
+ }
+ })
+ }
+}
+
+func TestChecksummableTransportUpdatePort(t *testing.T) {
+ // The fields in the pseudo header is not tested here so we just use 0.
+ const pseudoHeaderXSum = 0
+
+ tests := []struct {
+ name string
+ transportHdr func(_, _ uint16) (header.ChecksummableTransport, func(uint16) uint16)
+ proto tcpip.TransportProtocolNumber
+ }{
+ {
+ name: "TCP",
+ transportHdr: func(src, dst uint16) (header.ChecksummableTransport, func(uint16) uint16) {
+ h := header.TCP(make([]byte, header.TCPMinimumSize))
+ h.Encode(&header.TCPFields{
+ SrcPort: src,
+ DstPort: dst,
+ SeqNum: 1,
+ AckNum: 2,
+ DataOffset: header.TCPMinimumSize,
+ Flags: 3,
+ WindowSize: 4,
+ Checksum: 0,
+ UrgentPointer: 5,
+ })
+ h.SetChecksum(^h.CalculateChecksum(pseudoHeaderXSum))
+ return h, h.CalculateChecksum
+ },
+ proto: header.TCPProtocolNumber,
+ },
+ {
+ name: "UDP",
+ transportHdr: func(src, dst uint16) (header.ChecksummableTransport, func(uint16) uint16) {
+ h := header.UDP(make([]byte, header.UDPMinimumSize))
+ h.Encode(&header.UDPFields{
+ SrcPort: src,
+ DstPort: dst,
+ Length: 0,
+ Checksum: 0,
+ })
+ h.SetChecksum(^h.CalculateChecksum(pseudoHeaderXSum))
+ return h, h.CalculateChecksum
+ },
+ proto: header.UDPProtocolNumber,
+ },
+ }
+
+ for i := 0; i < 1000; i++ {
+ origSrcPort := uint16(rand.Uint32())
+ origDstPort := uint16(rand.Uint32())
+ newPort := uint16(rand.Uint32())
+
+ t.Run(fmt.Sprintf("OrigSrcPort=%d,OrigDstPort=%d,NewPort=%d", origSrcPort, origDstPort, newPort), func(*testing.T) {
+ for _, test := range tests {
+ t.Run(test.name, func(t *testing.T) {
+ for _, subTest := range []struct {
+ name string
+ update func(header.ChecksummableTransport)
+ }{
+ {
+ name: "Source port",
+ update: func(h header.ChecksummableTransport) { h.SetSourcePortWithChecksumUpdate(newPort) },
+ },
+ {
+ name: "Destination port",
+ update: func(h header.ChecksummableTransport) { h.SetDestinationPortWithChecksumUpdate(newPort) },
+ },
+ } {
+ t.Run(subTest.name, func(t *testing.T) {
+ h, calcXSum := test.transportHdr(origSrcPort, origDstPort)
+ subTest.update(h)
+ // TCP and UDP hold the 1s complement of the fully calculated
+ // checksum.
+ got := ^h.Checksum()
+ h.SetChecksum(0)
+
+ if want := calcXSum(pseudoHeaderXSum); got != want {
+ h, _ := test.transportHdr(origSrcPort, origDstPort)
+ t.Errorf("got Checksum() = 0x%x, want = 0x%x; originalBytes = %#v, new port = %d", got, want, h, newPort)
+ }
+ })
+ }
+ })
+ }
+ })
+ }
+}
+
+func TestChecksummableTransportUpdatePseudoHeaderAddress(t *testing.T) {
+ const addressSize = 6
+
+ tests := []struct {
+ name string
+ transportHdr func() header.ChecksummableTransport
+ proto tcpip.TransportProtocolNumber
+ }{
+ {
+ name: "TCP",
+ transportHdr: func() header.ChecksummableTransport { return header.TCP(make([]byte, header.TCPMinimumSize)) },
+ proto: header.TCPProtocolNumber,
+ },
+ {
+ name: "UDP",
+ transportHdr: func() header.ChecksummableTransport { return header.UDP(make([]byte, header.UDPMinimumSize)) },
+ proto: header.UDPProtocolNumber,
+ },
+ }
+
+ for i := 0; i < 1000; i++ {
+ permanent := randomAddress(addressSize)
+ old := randomAddress(addressSize)
+ new := randomAddress(addressSize)
+
+ t.Run(fmt.Sprintf("Permanent=%q,Old=%q,New=%q", permanent, old, new), func(t *testing.T) {
+ for _, test := range tests {
+ t.Run(test.name, func(t *testing.T) {
+ for _, fullChecksum := range []bool{true, false} {
+ t.Run(fmt.Sprintf("FullChecksum=%t", fullChecksum), func(t *testing.T) {
+ initialXSum := header.PseudoHeaderChecksum(test.proto, permanent, old, 0)
+ if fullChecksum {
+ // TCP and UDP hold the 1s complement of the fully calculated
+ // checksum.
+ initialXSum = ^initialXSum
+ }
+
+ h := test.transportHdr()
+ h.SetChecksum(initialXSum)
+ h.UpdateChecksumPseudoHeaderAddress(old, new, fullChecksum)
+
+ got := h.Checksum()
+ if fullChecksum {
+ got = ^got
+ }
+ if want := header.PseudoHeaderChecksum(test.proto, permanent, new, 0); got != want {
+ t.Errorf("got Checksum() = 0x%x, want = 0x%x; h = %#v", got, want, h)
+ }
+ })
+ }
+ })
+ }
+ })
+ }
+}
diff --git a/pkg/tcpip/header/interfaces.go b/pkg/tcpip/header/interfaces.go
index 861cbbb70..3a41adfc4 100644
--- a/pkg/tcpip/header/interfaces.go
+++ b/pkg/tcpip/header/interfaces.go
@@ -53,6 +53,31 @@ type Transport interface {
Payload() []byte
}
+// ChecksummableTransport is a Transport that supports checksumming.
+type ChecksummableTransport interface {
+ Transport
+
+ // SetSourcePortWithChecksumUpdate sets the source port and updates
+ // the checksum.
+ //
+ // The receiver's checksum must be a fully calculated checksum.
+ SetSourcePortWithChecksumUpdate(port uint16)
+
+ // SetDestinationPortWithChecksumUpdate sets the destination port and updates
+ // the checksum.
+ //
+ // The receiver's checksum must be a fully calculated checksum.
+ SetDestinationPortWithChecksumUpdate(port uint16)
+
+ // UpdateChecksumPseudoHeaderAddress updates the checksum to reflect an
+ // updated address in the pseudo header.
+ //
+ // If fullChecksum is true, the receiver's checksum field is assumed to hold a
+ // fully calculated checksum. Otherwise, it is assumed to hold a partially
+ // calculated checksum which only reflects the pseudo header.
+ UpdateChecksumPseudoHeaderAddress(old, new tcpip.Address, fullChecksum bool)
+}
+
// Network offers generic methods to query and/or update the fields of the
// header of a network protocol buffer.
type Network interface {
@@ -90,3 +115,16 @@ type Network interface {
// SetTOS sets the values of the "type of service" and "flow label" fields.
SetTOS(t uint8, l uint32)
}
+
+// ChecksummableNetwork is a Network that supports checksumming.
+type ChecksummableNetwork interface {
+ Network
+
+ // SetSourceAddressAndChecksum sets the source address and updates the
+ // checksum to reflect the new address.
+ SetSourceAddressWithChecksumUpdate(tcpip.Address)
+
+ // SetDestinationAddressAndChecksum sets the destination address and
+ // updates the checksum to reflect the new address.
+ SetDestinationAddressWithChecksumUpdate(tcpip.Address)
+}
diff --git a/pkg/tcpip/header/ipv4.go b/pkg/tcpip/header/ipv4.go
index e9abbb709..dcc549c7b 100644
--- a/pkg/tcpip/header/ipv4.go
+++ b/pkg/tcpip/header/ipv4.go
@@ -305,6 +305,18 @@ func (b IPv4) DestinationAddress() tcpip.Address {
return tcpip.Address(b[dstAddr : dstAddr+IPv4AddressSize])
}
+// SetSourceAddressWithChecksumUpdate implements ChecksummableNetwork.
+func (b IPv4) SetSourceAddressWithChecksumUpdate(new tcpip.Address) {
+ b.SetChecksum(^checksumUpdate2ByteAlignedAddress(^b.Checksum(), b.SourceAddress(), new))
+ b.SetSourceAddress(new)
+}
+
+// SetDestinationAddressWithChecksumUpdate implements ChecksummableNetwork.
+func (b IPv4) SetDestinationAddressWithChecksumUpdate(new tcpip.Address) {
+ b.SetChecksum(^checksumUpdate2ByteAlignedAddress(^b.Checksum(), b.DestinationAddress(), new))
+ b.SetDestinationAddress(new)
+}
+
// padIPv4OptionsLength returns the total length for IPv4 options of length l
// after applying padding according to RFC 791:
// The internet header padding is used to ensure that the internet
diff --git a/pkg/tcpip/header/tcp.go b/pkg/tcpip/header/tcp.go
index 8dabe3354..a75e51a28 100644
--- a/pkg/tcpip/header/tcp.go
+++ b/pkg/tcpip/header/tcp.go
@@ -390,6 +390,35 @@ func (b TCP) EncodePartial(partialChecksum, length uint16, seqnum, acknum uint32
b.SetChecksum(^checksum)
}
+// SetSourcePortWithChecksumUpdate implements ChecksummableTransport.
+func (b TCP) SetSourcePortWithChecksumUpdate(new uint16) {
+ old := b.SourcePort()
+ b.SetSourcePort(new)
+ b.SetChecksum(^checksumUpdate2ByteAlignedUint16(^b.Checksum(), old, new))
+}
+
+// SetDestinationPortWithChecksumUpdate implements ChecksummableTransport.
+func (b TCP) SetDestinationPortWithChecksumUpdate(new uint16) {
+ old := b.DestinationPort()
+ b.SetDestinationPort(new)
+ b.SetChecksum(^checksumUpdate2ByteAlignedUint16(^b.Checksum(), old, new))
+}
+
+// UpdateChecksumPseudoHeaderAddress implements ChecksummableTransport.
+func (b TCP) UpdateChecksumPseudoHeaderAddress(old, new tcpip.Address, fullChecksum bool) {
+ xsum := b.Checksum()
+ if fullChecksum {
+ xsum = ^xsum
+ }
+
+ xsum = checksumUpdate2ByteAlignedAddress(xsum, old, new)
+ if fullChecksum {
+ xsum = ^xsum
+ }
+
+ b.SetChecksum(xsum)
+}
+
// ParseSynOptions parses the options received in a SYN segment and returns the
// relevant ones. opts should point to the option part of the TCP header.
func ParseSynOptions(opts []byte, isAck bool) TCPSynOptions {
diff --git a/pkg/tcpip/header/udp.go b/pkg/tcpip/header/udp.go
index ae9d167ff..f69d53314 100644
--- a/pkg/tcpip/header/udp.go
+++ b/pkg/tcpip/header/udp.go
@@ -130,3 +130,32 @@ func (b UDP) Encode(u *UDPFields) {
binary.BigEndian.PutUint16(b[udpLength:], u.Length)
binary.BigEndian.PutUint16(b[udpChecksum:], u.Checksum)
}
+
+// SetSourcePortWithChecksumUpdate implements ChecksummableTransport.
+func (b UDP) SetSourcePortWithChecksumUpdate(new uint16) {
+ old := b.SourcePort()
+ b.SetSourcePort(new)
+ b.SetChecksum(^checksumUpdate2ByteAlignedUint16(^b.Checksum(), old, new))
+}
+
+// SetDestinationPortWithChecksumUpdate implements ChecksummableTransport.
+func (b UDP) SetDestinationPortWithChecksumUpdate(new uint16) {
+ old := b.DestinationPort()
+ b.SetDestinationPort(new)
+ b.SetChecksum(^checksumUpdate2ByteAlignedUint16(^b.Checksum(), old, new))
+}
+
+// UpdateChecksumPseudoHeaderAddress implements ChecksummableTransport.
+func (b UDP) UpdateChecksumPseudoHeaderAddress(old, new tcpip.Address, fullChecksum bool) {
+ xsum := b.Checksum()
+ if fullChecksum {
+ xsum = ^xsum
+ }
+
+ xsum = checksumUpdate2ByteAlignedAddress(xsum, old, new)
+ if fullChecksum {
+ xsum = ^xsum
+ }
+
+ b.SetChecksum(xsum)
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-27 01:54:25 +0000