Add sanity check on return values from Write

io.Writer.Write requires err to be non-nil if n < len(v).

We could allow this but it will be irreversible if users depend on this
behavior.

Ported the test that discovered this.

PiperOrigin-RevId: 352065946

1 files changed, 4 insertions, 0 deletions

diff --git a/pkg/tcpip/buffer/view.go b/pkg/tcpip/buffer/view.go
index 5dd1b1b6b..09d3dac66 100644
--- a/pkg/tcpip/buffer/view.go
+++ b/pkg/tcpip/buffer/view.go
@@ -17,6 +17,7 @@ package buffer
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 )
 
@@ -167,6 +168,9 @@ func (vv *VectorisedView) ReadTo(dst io.Writer, count int, peek bool) (int, erro
 		if err != nil {
 			break
 		}
+		if n != len(v) {
+			panic(fmt.Sprintf("io.Writer.Write succeeded with incomplete write: %d != %d", n, len(v)))
+		}
 	}
 	if !peek {
 		vv.TrimFront(done)