1 files changed, 84 insertions, 0 deletions
diff --git a/pkg/tcpip/link/fdbased/mmap_unsafe.go b/pkg/tcpip/link/fdbased/mmap_unsafe.go
new file mode 100644
index 000000000..3894185ae
--- /dev/null
+++ b/pkg/tcpip/link/fdbased/mmap_unsafe.go
@@ -0,0 +1,84 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build linux,amd64 linux,arm64
+
+package fdbased
+
+import (
+	"fmt"
+	"sync/atomic"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+// tPacketHdrlen is the TPACKET_HDRLEN variable defined in <linux/if_packet.h>.
+var tPacketHdrlen = tPacketAlign(unsafe.Sizeof(tPacketHdr{}) + unsafe.Sizeof(syscall.RawSockaddrLinklayer{}))
+
+// 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 {
+	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) {
+	hdr := unsafe.Pointer(&t[0])
+	statusPtr := unsafe.Pointer(uintptr(hdr) + uintptr(tpStatusOffset))
+	atomic.StoreUint32((*uint32)(statusPtr), status)
+}
+
+func newPacketMMapDispatcher(fd int, e *endpoint) (linkDispatcher, error) {
+	d := &packetMMapDispatcher{
+		fd: fd,
+		e:  e,
+	}
+	pageSize := unix.Getpagesize()
+	if tpBlockSize%pageSize != 0 {
+		return nil, fmt.Errorf("tpBlockSize: %d is not page aligned, pagesize: %d", tpBlockSize, pageSize)
+	}
+	tReq := tPacketReq{
+		tpBlockSize: uint32(tpBlockSize),
+		tpBlockNR:   uint32(tpBlockNR),
+		tpFrameSize: uint32(tpFrameSize),
+		tpFrameNR:   uint32(tpFrameNR),
+	}
+	// Setup PACKET_RX_RING.
+	if err := setsockopt(d.fd, syscall.SOL_PACKET, syscall.PACKET_RX_RING, unsafe.Pointer(&tReq), unsafe.Sizeof(tReq)); err != nil {
+		return nil, fmt.Errorf("failed to enable PACKET_RX_RING: %v", err)
+	}
+	// Let's mmap the blocks.
+	sz := tpBlockSize * tpBlockNR
+	buf, err := syscall.Mmap(d.fd, 0, sz, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED)
+	if err != nil {
+		return nil, fmt.Errorf("syscall.Mmap(...,0, %v, ...) failed = %v", sz, err)
+	}
+	d.ringBuffer = buf
+	return d, nil
+}
+
+func setsockopt(fd, level, name int, val unsafe.Pointer, vallen uintptr) error {
+	if _, _, errno := syscall.Syscall6(syscall.SYS_SETSOCKOPT, uintptr(fd), uintptr(level), uintptr(name), uintptr(val), vallen, 0); errno != 0 {
+		return error(errno)
+	}
+
+	return nil
+}