Change registerData that must be bytesData to explicit bytesData with…

…in ops.

Change resulted from realization that it is currently unnecessary and extra to
store all bytesData within operations generically. If this is needed in the
future, we can change it then, but for now, a more direct and as-necessary
implementation is preferred.

PiperOrigin-RevId: 673908276

pkg/tcpip/nftables/nftables.go

@@ -605,9 +605,9 @@ func (op immediate) evaluate(regs *registerSet, pkt *stack.PacketBuffer) {
 // if the comparison is false.
 // Note: comparison operations are not supported for the verdict register.
 type comparison struct {
-	data registerData // Data to compare the source register to.
-	sreg uint8        // Number of the source register.
-	cop  cmpOp        // Comparison operator.
+	data bytesData // Data to compare the source register to.
+	sreg uint8     // Number of the source register.
+	cop  cmpOp     // Comparison operator.
 }
 
 // cmpOp is the comparison operator for a Comparison operation.
@@ -666,19 +666,16 @@ func newComparison(sreg uint8, op int, data []byte) (*comparison, error) {
 // data and breaks from the rule if the comparison is false.
 func (op comparison) evaluate(regs *registerSet, pkt *stack.PacketBuffer) {
 	// Gets the data to compare to.
-	bytesData, ok := op.data.(bytesData)
-	if !ok {
-		panic("comparison operation data is not BytesData")
-	}
+	data := op.data.data
 	// Gets the data from the source register.
 	regBuf := getRegisterBuffer(regs, op.sreg)
 
 	// Compares bytes from left to right for all bytes in the comparison data.
 	dif := 0
-	for i := 0; i < len(bytesData.data) && dif == 0; i++ {
-		if regBuf[i] < bytesData.data[i] {
+	for i := 0; i < len(data) && dif == 0; i++ {
+		if regBuf[i] < data[i] {
 			dif = -1
-		} else if regBuf[i] > bytesData.data[i] {
+		} else if regBuf[i] > data[i] {
 			dif = 1
 		}
 	}
@@ -991,13 +988,13 @@ func (bop bitwiseOp) String() string {
 // a given register, storing the result in a destination register.
 // Note: bitwise operations are not supported for the verdict register.
 type bitwise struct {
-	sreg  uint8        // Number of the source register.
-	dreg  uint8        // Number of the destination register.
-	bop   bitwiseOp    // Bitwise operator to use.
-	blen  uint8        // Number of bytes to apply bitwise operation to.
-	mask  registerData // Mask to apply bitwise & for boolean operations (before ^).
-	xor   registerData // Xor to apply bitwise ^ for boolean operations (after &).
-	shift uint32       // Shift to apply bitwise <</>> for non-boolean operations.
+	sreg  uint8     // Number of the source register.
+	dreg  uint8     // Number of the destination register.
+	bop   bitwiseOp // Bitwise operator to use.
+	blen  uint8     // Number of bytes to apply bitwise operation to.
+	mask  bytesData // Mask to apply bitwise & for boolean operations (before ^).
+	xor   bytesData // Xor to apply bitwise ^ for boolean operations (after &).
+	shift uint32    // Shift to apply bitwise <</>> for non-boolean operations.
 
 	// Note: Technically, the linux kernel has defined bool, lshift, and rshift
 	// as the 3 types of bitwise operations. However, we have not been able to
@@ -1122,15 +1119,7 @@ func (op bitwise) evaluate(regs *registerSet, pkt *stack.PacketBuffer) {
 	dregBuf := getRegisterBuffer(regs, op.dreg)[:op.blen]
 
 	if op.bop == linux.NFT_BITWISE_BOOL {
-		mask, ok := op.mask.(bytesData)
-		if !ok {
-			panic("bitwise bool mask data is not BytesData")
-		}
-		xor, ok := op.xor.(bytesData)
-		if !ok {
-			panic("bitwise bool xor data is not BytesData")
-		}
-		evaluateBitwiseBool(sregBuf, dregBuf, mask.data, xor.data)
+		evaluateBitwiseBool(sregBuf, dregBuf, op.mask.data, op.xor.data)
 		return
 	} else {
 		if op.bop == linux.NFT_BITWISE_LSHIFT {
@@ -1188,7 +1177,7 @@ type verdictData struct {
 }
 
 // newVerdictData creates a registerData for a verdict.
-func newVerdictData(verdict Verdict) registerData { return verdictData{data: verdict} }
+func newVerdictData(verdict Verdict) verdictData { return verdictData{data: verdict} }
 
 // String returns a string representation of the verdict data.
 func (rd verdictData) String() string {
@@ -1229,7 +1218,7 @@ type bytesData struct {
 }
 
 // newBytesData creates a registerData for <= 16 bytes of data.
-func newBytesData(bytes []byte) registerData {
+func newBytesData(bytes []byte) bytesData {
 	if len(bytes) == 0 {
 		panic("bytes data cannot be empty")
 	}