1 files changed, 30 insertions, 8 deletions

diff --git a/pkg/tcpip/link/fdbased/mmap_amd64_unsafe.go b/pkg/tcpip/link/fdbased/mmap_amd64_unsafe.go
index e49cf9f61..e5ac7996d 100644
--- a/pkg/tcpip/link/fdbased/mmap_amd64_unsafe.go
+++ b/pkg/tcpip/link/fdbased/mmap_amd64_unsafe.go
@@ -19,6 +19,7 @@ package fdbased
 import (
 	"encoding/binary"
 	"fmt"
+	"sync/atomic"
 	"syscall"
 	"unsafe"
 
@@ -42,7 +43,12 @@ const (
 //
 // Memory allocated for the ring buffer: tpBlockSize * tpBlockNR = 2 MiB
 //
-// NOTE: Frames need to be aligned at 16 byte boundaries.
+// NOTE:
+//   Frames need to be aligned at 16 byte boundaries.
+//   BlockSize needs to be page aligned.
+//
+//   For details see PACKET_MMAP setting constraints in
+//   https://www.kernel.org/doc/Documentation/networking/packet_mmap.txt
 const (
 	tpFrameSize = 65536 + 128
 	tpBlockSize = tpFrameSize * 32
@@ -81,12 +87,22 @@ const (
 	tpUSecOffset    = 24
 )
 
+// tpStatus returns the frame status field.
+// The status is concurrently updated by the kernel as a result we must
+// use atomic operations to prevent races.
 func (t tPacketHdr) tpStatus() uint32 {
-	return binary.LittleEndian.Uint32(t[tpStatusOffset:])
+	hdr := unsafe.Pointer(&t[0])
+	statusPtr := unsafe.Pointer(uintptr(hdr) + uintptr(tpStatusOffset))
+	return atomic.LoadUint32((*uint32)(statusPtr))
 }
 
+// setTPStatus set's the frame status to the provided status.
+// The status is concurrently updated by the kernel as a result we must
+// use atomic operations to prevent races.
 func (t tPacketHdr) setTPStatus(status uint32) {
-	binary.LittleEndian.PutUint32(t[tpStatusOffset:], status)
+	hdr := unsafe.Pointer(&t[0])
+	statusPtr := unsafe.Pointer(uintptr(hdr) + uintptr(tpStatusOffset))
+	atomic.StoreUint32((*uint32)(statusPtr), status)
 }
 
 func (t tPacketHdr) tpLen() uint32 {
@@ -118,6 +134,10 @@ func (t tPacketHdr) Payload() []byte {
 }
 
 func (e *endpoint) setupPacketRXRing() error {
+	pageSize := unix.Getpagesize()
+	if tpBlockSize%pageSize != 0 {
+		return fmt.Errorf("tpBlockSize: %d is not page aligned, pagesize: %d", tpBlockSize, pageSize)
+	}
 	tReq := tPacketReq{
 		tpBlockSize: uint32(tpBlockSize),
 		tpBlockNR:   uint32(tpBlockNR),
@@ -139,8 +159,8 @@ func (e *endpoint) setupPacketRXRing() error {
 }
 
 func (e *endpoint) readMMappedPacket() ([]byte, *tcpip.Error) {
-	hdr := (tPacketHdr)(e.ringBuffer[0+e.ringOffset*tpFrameSize:])
-	for (hdr.tpStatus() & tpStatusUser) == 0 {
+	hdr := (tPacketHdr)(e.ringBuffer[e.ringOffset*tpFrameSize:])
+	for hdr.tpStatus()&tpStatusUser == 0 {
 		event := rawfile.PollEvent{
 			FD:     int32(e.fd),
 			Events: unix.POLLIN | unix.POLLERR,
@@ -153,9 +173,11 @@ func (e *endpoint) readMMappedPacket() ([]byte, *tcpip.Error) {
 			return nil, rawfile.TranslateErrno(errno)
 		}
 		if hdr.tpStatus()&tpStatusCopy != 0 {
-			continue
-		}
-		if hdr.tpStatus()&tpStatusLosing != 0 {
+			// This frame is truncated so skip it after flipping the
+			// buffer to the kernel.
+			hdr.setTPStatus(tpStatusKernel)
+			e.ringOffset = (e.ringOffset + 1) % tpFrameNR
+			hdr = (tPacketHdr)(e.ringBuffer[e.ringOffset*tpFrameSize:])
 			continue
 		}
 	}