196 lines
5.5 KiB
Go
196 lines
5.5 KiB
Go
// Copyright 2019 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// +build linux,amd64 linux,arm64
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package fdbased
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import (
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"encoding/binary"
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"syscall"
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"golang.org/x/sys/unix"
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"gvisor.dev/gvisor/pkg/tcpip"
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"gvisor.dev/gvisor/pkg/tcpip/buffer"
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"gvisor.dev/gvisor/pkg/tcpip/header"
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"gvisor.dev/gvisor/pkg/tcpip/link/rawfile"
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)
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const (
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tPacketAlignment = uintptr(16)
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tpStatusKernel = 0
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tpStatusUser = 1
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tpStatusCopy = 2
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tpStatusLosing = 4
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)
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// We overallocate the frame size to accommodate space for the
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// TPacketHdr+RawSockAddrLinkLayer+MAC header and any padding.
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//
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// Memory allocated for the ring buffer: tpBlockSize * tpBlockNR = 2 MiB
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//
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// NOTE:
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// Frames need to be aligned at 16 byte boundaries.
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// BlockSize needs to be page aligned.
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//
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// For details see PACKET_MMAP setting constraints in
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// https://www.kernel.org/doc/Documentation/networking/packet_mmap.txt
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const (
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tpFrameSize = 65536 + 128
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tpBlockSize = tpFrameSize * 32
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tpBlockNR = 1
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tpFrameNR = (tpBlockSize * tpBlockNR) / tpFrameSize
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)
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// tPacketAlign aligns the pointer v at a tPacketAlignment boundary. Direct
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// translation of the TPACKET_ALIGN macro in <linux/if_packet.h>.
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func tPacketAlign(v uintptr) uintptr {
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return (v + tPacketAlignment - 1) & uintptr(^(tPacketAlignment - 1))
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}
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// tPacketReq is the tpacket_req structure as described in
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// https://www.kernel.org/doc/Documentation/networking/packet_mmap.txt
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type tPacketReq struct {
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tpBlockSize uint32
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tpBlockNR uint32
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tpFrameSize uint32
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tpFrameNR uint32
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}
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// tPacketHdr is tpacket_hdr structure as described in <linux/if_packet.h>
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type tPacketHdr []byte
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const (
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tpStatusOffset = 0
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tpLenOffset = 8
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tpSnapLenOffset = 12
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tpMacOffset = 16
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tpNetOffset = 18
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tpSecOffset = 20
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tpUSecOffset = 24
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)
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func (t tPacketHdr) tpLen() uint32 {
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return binary.LittleEndian.Uint32(t[tpLenOffset:])
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}
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func (t tPacketHdr) tpSnapLen() uint32 {
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return binary.LittleEndian.Uint32(t[tpSnapLenOffset:])
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}
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func (t tPacketHdr) tpMac() uint16 {
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return binary.LittleEndian.Uint16(t[tpMacOffset:])
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}
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func (t tPacketHdr) tpNet() uint16 {
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return binary.LittleEndian.Uint16(t[tpNetOffset:])
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}
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func (t tPacketHdr) tpSec() uint32 {
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return binary.LittleEndian.Uint32(t[tpSecOffset:])
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}
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func (t tPacketHdr) tpUSec() uint32 {
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return binary.LittleEndian.Uint32(t[tpUSecOffset:])
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}
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func (t tPacketHdr) Payload() []byte {
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return t[uint32(t.tpMac()) : uint32(t.tpMac())+t.tpSnapLen()]
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}
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// packetMMapDispatcher uses PACKET_RX_RING's to read/dispatch inbound packets.
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// See: mmap_amd64_unsafe.go for implementation details.
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type packetMMapDispatcher struct {
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// fd is the file descriptor used to send and receive packets.
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fd int
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// e is the endpoint this dispatcher is attached to.
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e *endpoint
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// ringBuffer is only used when PacketMMap dispatcher is used and points
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// to the start of the mmapped PACKET_RX_RING buffer.
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ringBuffer []byte
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// ringOffset is the current offset into the ring buffer where the next
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// inbound packet will be placed by the kernel.
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ringOffset int
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}
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func (d *packetMMapDispatcher) readMMappedPacket() ([]byte, *tcpip.Error) {
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hdr := tPacketHdr(d.ringBuffer[d.ringOffset*tpFrameSize:])
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for hdr.tpStatus()&tpStatusUser == 0 {
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event := rawfile.PollEvent{
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FD: int32(d.fd),
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Events: unix.POLLIN | unix.POLLERR,
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}
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if _, errno := rawfile.BlockingPoll(&event, 1, nil); errno != 0 {
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if errno == syscall.EINTR {
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continue
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}
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return nil, rawfile.TranslateErrno(errno)
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}
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if hdr.tpStatus()&tpStatusCopy != 0 {
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// This frame is truncated so skip it after flipping the
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// buffer to the kernel.
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hdr.setTPStatus(tpStatusKernel)
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d.ringOffset = (d.ringOffset + 1) % tpFrameNR
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hdr = (tPacketHdr)(d.ringBuffer[d.ringOffset*tpFrameSize:])
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continue
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}
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}
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// Copy out the packet from the mmapped frame to a locally owned buffer.
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pkt := make([]byte, hdr.tpSnapLen())
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copy(pkt, hdr.Payload())
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// Release packet to kernel.
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hdr.setTPStatus(tpStatusKernel)
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d.ringOffset = (d.ringOffset + 1) % tpFrameNR
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return pkt, nil
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}
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// dispatch reads packets from an mmaped ring buffer and dispatches them to the
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// network stack.
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func (d *packetMMapDispatcher) dispatch() (bool, *tcpip.Error) {
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pkt, err := d.readMMappedPacket()
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if err != nil {
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return false, err
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}
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var (
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p tcpip.NetworkProtocolNumber
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remote, local tcpip.LinkAddress
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eth header.Ethernet
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)
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if d.e.hdrSize > 0 {
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eth = header.Ethernet(pkt)
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p = eth.Type()
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remote = eth.SourceAddress()
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local = eth.DestinationAddress()
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} else {
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// We don't get any indication of what the packet is, so try to guess
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// if it's an IPv4 or IPv6 packet.
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switch header.IPVersion(pkt) {
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case header.IPv4Version:
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p = header.IPv4ProtocolNumber
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case header.IPv6Version:
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p = header.IPv6ProtocolNumber
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default:
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return true, nil
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}
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}
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pkt = pkt[d.e.hdrSize:]
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d.e.dispatcher.DeliverNetworkPacket(d.e, remote, local, p, buffer.NewVectorisedView(len(pkt), []buffer.View{buffer.View(pkt)}), buffer.View(eth))
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return true, nil
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}
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