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// 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.
//go:build (linux && amd64) || (linux && arm64)
// +build linux,amd64 linux,arm64
package fdbased
import (
"encoding/binary"
"fmt"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/buffer"
"gvisor.dev/gvisor/pkg/rawfile"
"gvisor.dev/gvisor/pkg/tcpip"
"gvisor.dev/gvisor/pkg/tcpip/header"
"gvisor.dev/gvisor/pkg/tcpip/link/stopfd"
"gvisor.dev/gvisor/pkg/tcpip/stack"
)
const (
tPacketAlignment = uintptr(16)
tpStatusKernel = 0
tpStatusUser = 1
tpStatusCopy = 2
tpStatusLosing = 4
)
// We overallocate the frame size to accommodate space for the
// TPacketHdr+RawSockAddrLinkLayer+MAC header and any padding.
//
// Memory allocated for the ring buffer: tpBlockSize * tpBlockNR = 2 MiB
//
// 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
tpBlockNR = 1
tpFrameNR = (tpBlockSize * tpBlockNR) / tpFrameSize
)
// tPacketAlign aligns the pointer v at a tPacketAlignment boundary. Direct
// translation of the TPACKET_ALIGN macro in <linux/if_packet.h>.
func tPacketAlign(v uintptr) uintptr {
return (v + tPacketAlignment - 1) & uintptr(^(tPacketAlignment - 1))
}
// tPacketReq is the tpacket_req structure as described in
// https://www.kernel.org/doc/Documentation/networking/packet_mmap.txt
type tPacketReq struct {
tpBlockSize uint32
tpBlockNR uint32
tpFrameSize uint32
tpFrameNR uint32
}
// tPacketHdr is tpacket_hdr structure as described in <linux/if_packet.h>
type tPacketHdr []byte
const (
tpStatusOffset = 0
tpLenOffset = 8
tpSnapLenOffset = 12
tpMacOffset = 16
tpNetOffset = 18
tpSecOffset = 20
tpUSecOffset = 24
)
func (t tPacketHdr) tpLen() uint32 {
return binary.LittleEndian.Uint32(t[tpLenOffset:])
}
func (t tPacketHdr) tpSnapLen() uint32 {
return binary.LittleEndian.Uint32(t[tpSnapLenOffset:])
}
func (t tPacketHdr) tpMac() uint16 {
return binary.LittleEndian.Uint16(t[tpMacOffset:])
}
func (t tPacketHdr) tpNet() uint16 {
return binary.LittleEndian.Uint16(t[tpNetOffset:])
}
func (t tPacketHdr) tpSec() uint32 {
return binary.LittleEndian.Uint32(t[tpSecOffset:])
}
func (t tPacketHdr) tpUSec() uint32 {
return binary.LittleEndian.Uint32(t[tpUSecOffset:])
}
func (t tPacketHdr) Payload() []byte {
return t[uint32(t.tpMac()) : uint32(t.tpMac())+t.tpSnapLen()]
}
// packetMMapDispatcher uses PACKET_RX_RING's to read/dispatch inbound packets.
// See: mmap_amd64_unsafe.go for implementation details.
type packetMMapDispatcher struct {
stopfd.StopFD
// fd is the file descriptor used to send and receive packets.
fd int
// e is the endpoint this dispatcher is attached to.
e *endpoint
// ringBuffer is only used when PacketMMap dispatcher is used and points
// to the start of the mmapped PACKET_RX_RING buffer.
ringBuffer []byte
// ringOffset is the current offset into the ring buffer where the next
// inbound packet will be placed by the kernel.
ringOffset int
// mgr is the processor goroutine manager.
mgr *processorManager
}
func (d *packetMMapDispatcher) release() {
d.mgr.close()
}
func (d *packetMMapDispatcher) readMMappedPackets() (stack.PacketBufferList, bool, tcpip.Error) {
var pkts stack.PacketBufferList
hdr := tPacketHdr(d.ringBuffer[d.ringOffset*tpFrameSize:])
for hdr.tpStatus()&tpStatusUser == 0 {
stopped, errno := rawfile.BlockingPollUntilStopped(d.EFD, d.fd, unix.POLLIN|unix.POLLERR)
if errno != 0 {
if errno == unix.EINTR {
continue
}
return pkts, stopped, tcpip.TranslateErrno(errno)
}
if stopped {
return pkts, true, nil
}
if hdr.tpStatus()&tpStatusCopy != 0 {
// This frame is truncated so skip it after flipping the
// buffer to the kernel.
hdr.setTPStatus(tpStatusKernel)
d.ringOffset = (d.ringOffset + 1) % tpFrameNR
hdr = (tPacketHdr)(d.ringBuffer[d.ringOffset*tpFrameSize:])
continue
}
}
for hdr.tpStatus()&tpStatusUser == 1 {
// Copy out the packet from the mmapped frame to a locally owned buffer.
pkts.PushBack(stack.NewPacketBuffer(stack.PacketBufferOptions{
Payload: buffer.MakeWithView(buffer.NewViewWithData(hdr.Payload())),
}))
// Release packet to kernel.
hdr.setTPStatus(tpStatusKernel)
d.ringOffset = (d.ringOffset + 1) % tpFrameNR
hdr = tPacketHdr(d.ringBuffer[d.ringOffset*tpFrameSize:])
}
return pkts, false, nil
}
// dispatch reads packets from an mmaped ring buffer and dispatches them to the
// network stack.
func (d *packetMMapDispatcher) dispatch() (bool, tcpip.Error) {
pkts, stopped, err := d.readMMappedPackets()
defer pkts.Reset()
if err != nil || stopped {
return false, err
}
for _, pkt := range pkts.AsSlice() {
if d.e.hdrSize > 0 {
hdr, ok := pkt.LinkHeader().Consume(d.e.hdrSize)
if !ok {
panic(fmt.Sprintf("LinkHeader().Consume(%d) must succeed", d.e.hdrSize))
}
pkt.NetworkProtocolNumber = header.Ethernet(hdr).Type()
}
d.mgr.queuePacket(pkt, d.e.hdrSize > 0)
}
if pkts.Len() > 0 {
d.mgr.wakeReady()
}
return true, nil
}
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