netstack: Refactor tcpip.Endpoint.Read

Read now takes a destination io.Writer, count, options. Keeping the method name
Read, in contrast to the Write method.

This enables:
* direct transfer of views under VV
* zero copy

It also eliminates the need for sentry to keep a slice of view because
userspace had requested a read that is smaller than the view returned, removing
the complexity there.

Read/Peek/ReadPacket are now consolidated together and some duplicate code is
removed.

PiperOrigin-RevId: 350636322

1 files changed, 12 insertions, 0 deletions

diff --git a/pkg/tcpip/checker/checker.go b/pkg/tcpip/checker/checker.go
index 91971b687..0ac2000ca 100644
--- a/pkg/tcpip/checker/checker.go
+++ b/pkg/tcpip/checker/checker.go
@@ -1603,3 +1603,15 @@ func IPv6RouterAlert(want header.IPv6RouterAlertValue) IPv6ExtHdrOptionChecker {
 		}
 	}
 }
+
+// IgnoreCmpPath returns a cmp.Option that ignores listed field paths.
+func IgnoreCmpPath(paths ...string) cmp.Option {
+	ignores := map[string]struct{}{}
+	for _, path := range paths {
+		ignores[path] = struct{}{}
+	}
+	return cmp.FilterPath(func(path cmp.Path) bool {
+		_, ok := ignores[path.String()]
+		return ok
+	}, cmp.Ignore())
+}