Fix IPv4 ICMP echo handler to copy options

The IPv4 RFCs are specific (though obtuse) that an echo response
packet needs to contain all the options from the echo request,
much as if it been routed back to the sender, though apparently
with a new TTL. They suggest copying the incoming packet header
to achieve this so that is what this patch does.

PiperOrigin-RevId: 335559176

1 files changed, 13 insertions, 5 deletions

diff --git a/pkg/tcpip/buffer/view.go b/pkg/tcpip/buffer/view.go
index ea0c5413d..8db70a700 100644
--- a/pkg/tcpip/buffer/view.go
+++ b/pkg/tcpip/buffer/view.go
@@ -84,8 +84,8 @@ type VectorisedView struct {
 	size  int
 }
 
-// NewVectorisedView creates a new vectorised view from an already-allocated slice
-// of View and sets its size.
+// NewVectorisedView creates a new vectorised view from an already-allocated
+// slice of View and sets its size.
 func NewVectorisedView(size int, views []View) VectorisedView {
 	return VectorisedView{views: views, size: size}
 }
@@ -170,8 +170,9 @@ func (vv *VectorisedView) CapLength(length int) {
 }
 
 // Clone returns a clone of this VectorisedView.
-// If the buffer argument is large enough to contain all the Views of this VectorisedView,
-// the method will avoid allocations and use the buffer to store the Views of the clone.
+// If the buffer argument is large enough to contain all the Views of this
+// VectorisedView, the method will avoid allocations and use the buffer to
+// store the Views of the clone.
 func (vv *VectorisedView) Clone(buffer []View) VectorisedView {
 	return VectorisedView{views: append(buffer[:0], vv.views...), size: vv.size}
 }
@@ -209,7 +210,8 @@ func (vv *VectorisedView) PullUp(count int) (View, bool) {
 	return newFirst, true
 }
 
-// Size returns the size in bytes of the entire content stored in the vectorised view.
+// Size returns the size in bytes of the entire content stored in the
+// vectorised view.
 func (vv *VectorisedView) Size() int {
 	return vv.size
 }
@@ -222,6 +224,12 @@ func (vv *VectorisedView) ToView() View {
 	if len(vv.views) == 1 {
 		return vv.views[0]
 	}
+	return vv.ToOwnedView()
+}
+
+// ToOwnedView returns a single view containing the content of the vectorised
+// view that vv does not own.
+func (vv *VectorisedView) ToOwnedView() View {
 	u := make([]byte, 0, vv.size)
 	for _, v := range vv.views {
 		u = append(u, v...)