Don't modify a packet header when it can be used by other endpoints

Reported-by: syzbot+48c43f82fe7738fceae9@syzkaller.appspotmail.com
PiperOrigin-RevId: 348540796

1 files changed, 94 insertions, 0 deletions

diff --git a/pkg/tcpip/header/checksum_test.go b/pkg/tcpip/header/checksum_test.go
index 309403482..5ab20ee86 100644
--- a/pkg/tcpip/header/checksum_test.go
+++ b/pkg/tcpip/header/checksum_test.go
@@ -19,6 +19,7 @@ package header_test
 import (
 	"fmt"
 	"math/rand"
+	"sync"
 	"testing"
 
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
@@ -169,3 +170,96 @@ func BenchmarkChecksum(b *testing.B) {
 		}
 	}
 }
+
+func testICMPChecksum(t *testing.T, headerChecksum func() uint16, icmpChecksum func() uint16, want uint16, pktStr string) {
+	// icmpChecksum should not do any modifications of the header to
+	// calculate its checksum. Let's call it from a few go-routines and the
+	// race detector will trigger a warning if there are any concurrent
+	// read/write accesses.
+
+	const concurrency = 5
+	start := make(chan int)
+	ready := make(chan bool, concurrency)
+	var wg sync.WaitGroup
+	wg.Add(concurrency)
+	defer wg.Wait()
+
+	for i := 0; i < concurrency; i++ {
+		go func() {
+			defer wg.Done()
+
+			ready <- true
+			<-start
+
+			if got := headerChecksum(); want != got {
+				t.Errorf("new checksum for %s does not match old got: %x, want: %x", pktStr, got, want)
+			}
+			if got := icmpChecksum(); want != got {
+				t.Errorf("new checksum for %s does not match old got: %x, want: %x", pktStr, got, want)
+			}
+		}()
+	}
+	for i := 0; i < concurrency; i++ {
+		<-ready
+	}
+	close(start)
+}
+
+func TestICMPv4Checksum(t *testing.T) {
+	rnd := rand.New(rand.NewSource(42))
+
+	h := header.ICMPv4(make([]byte, header.ICMPv4MinimumSize))
+	if _, err := rnd.Read(h); err != nil {
+		t.Fatalf("rnd.Read failed: %v", err)
+	}
+	h.SetChecksum(0)
+
+	buf := make([]byte, 13)
+	if _, err := rnd.Read(buf); err != nil {
+		t.Fatalf("rnd.Read failed: %v", err)
+	}
+	vv := buffer.NewVectorisedView(len(buf), []buffer.View{
+		buffer.NewViewFromBytes(buf[:5]),
+		buffer.NewViewFromBytes(buf[5:]),
+	})
+
+	want := header.Checksum(vv.ToView(), 0)
+	want = ^header.Checksum(h, want)
+	h.SetChecksum(want)
+
+	testICMPChecksum(t, h.Checksum, func() uint16 {
+		return header.ICMPv4Checksum(h, vv)
+	}, want, fmt.Sprintf("header: {% x} data {% x}", h, vv.ToView()))
+}
+
+func TestICMPv6Checksum(t *testing.T) {
+	rnd := rand.New(rand.NewSource(42))
+
+	h := header.ICMPv6(make([]byte, header.ICMPv6MinimumSize))
+	if _, err := rnd.Read(h); err != nil {
+		t.Fatalf("rnd.Read failed: %v", err)
+	}
+	h.SetChecksum(0)
+
+	buf := make([]byte, 13)
+	if _, err := rnd.Read(buf); err != nil {
+		t.Fatalf("rnd.Read failed: %v", err)
+	}
+	vv := buffer.NewVectorisedView(len(buf), []buffer.View{
+		buffer.NewViewFromBytes(buf[:7]),
+		buffer.NewViewFromBytes(buf[7:10]),
+		buffer.NewViewFromBytes(buf[10:]),
+	})
+
+	dst := header.IPv6Loopback
+	src := header.IPv6Loopback
+
+	want := header.PseudoHeaderChecksum(header.ICMPv6ProtocolNumber, src, dst, uint16(len(h)+vv.Size()))
+	want = header.Checksum(vv.ToView(), want)
+	want = ^header.Checksum(h, want)
+	h.SetChecksum(want)
+
+	testICMPChecksum(t, h.Checksum, func() uint16 {
+		return header.ICMPv6Checksum(h, src, dst, vv)
+	}, want, fmt.Sprintf("header: {% x} data {% x}", h, vv.ToView()))
+}