Make dedicated methods for data operations in PacketBuffer

One of the preparation to decouple underlying buffer implementation.
There are still some methods that tie to VectorisedView, and they will be
changed gradually in later CLs.

This CL also introduce a new ICMPv6ChecksumParams to replace long list of
parameters when calling ICMPv6Checksum, aiming to be more descriptive.

PiperOrigin-RevId: 360778149

1 files changed, 20 insertions, 33 deletions

diff --git a/pkg/tcpip/header/checksum.go b/pkg/tcpip/header/checksum.go
index 14a4b2b44..6aa9acfa8 100644
--- a/pkg/tcpip/header/checksum.go
+++ b/pkg/tcpip/header/checksum.go
@@ -186,42 +186,29 @@ func Checksum(buf []byte, initial uint16) uint16 {
 //
 // The initial checksum must have been computed on an even number of bytes.
 func ChecksumVV(vv buffer.VectorisedView, initial uint16) uint16 {
-	return ChecksumVVWithOffset(vv, initial, 0, vv.Size())
+	var c Checksumer
+	for _, v := range vv.Views() {
+		c.Add([]byte(v))
+	}
+	return ChecksumCombine(initial, c.Checksum())
 }
 
-// ChecksumVVWithOffset calculates the checksum (as defined in RFC 1071) of the
-// bytes in the given VectorizedView.
-//
-// The initial checksum must have been computed on an even number of bytes.
-func ChecksumVVWithOffset(vv buffer.VectorisedView, initial uint16, off int, size int) uint16 {
-	odd := false
-	sum := initial
-	for _, v := range vv.Views() {
-		if len(v) == 0 {
-			continue
-		}
-
-		if off >= len(v) {
-			off -= len(v)
-			continue
-		}
-		v = v[off:]
-
-		l := len(v)
-		if l > size {
-			l = size
-		}
-		v = v[:l]
-
-		sum, odd = unrolledCalculateChecksum(v, odd, uint32(sum))
-
-		size -= len(v)
-		if size == 0 {
-			break
-		}
-		off = 0
+// Checksumer calculates checksum defined in RFC 1071.
+type Checksumer struct {
+	sum uint16
+	odd bool
+}
+
+// Add adds b to checksum.
+func (c *Checksumer) Add(b []byte) {
+	if len(b) > 0 {
+		c.sum, c.odd = unrolledCalculateChecksum(b, c.odd, uint32(c.sum))
 	}
-	return sum
+}
+
+// Checksum returns the latest checksum value.
+func (c *Checksumer) Checksum() uint16 {
+	return c.sum
 }
 
 // ChecksumCombine combines the two uint16 to form their checksum. This is done