85 lines
2.8 KiB
Go
85 lines
2.8 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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"fmt"
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"sync/atomic"
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"syscall"
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"unsafe"
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"golang.org/x/sys/unix"
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)
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// tPacketHdrlen is the TPACKET_HDRLEN variable defined in <linux/if_packet.h>.
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var tPacketHdrlen = tPacketAlign(unsafe.Sizeof(tPacketHdr{}) + unsafe.Sizeof(syscall.RawSockaddrLinklayer{}))
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// tpStatus returns the frame status field.
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// The status is concurrently updated by the kernel as a result we must
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// use atomic operations to prevent races.
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func (t tPacketHdr) tpStatus() uint32 {
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hdr := unsafe.Pointer(&t[0])
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statusPtr := unsafe.Pointer(uintptr(hdr) + uintptr(tpStatusOffset))
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return atomic.LoadUint32((*uint32)(statusPtr))
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}
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// setTPStatus set's the frame status to the provided status.
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// The status is concurrently updated by the kernel as a result we must
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// use atomic operations to prevent races.
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func (t tPacketHdr) setTPStatus(status uint32) {
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hdr := unsafe.Pointer(&t[0])
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statusPtr := unsafe.Pointer(uintptr(hdr) + uintptr(tpStatusOffset))
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atomic.StoreUint32((*uint32)(statusPtr), status)
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}
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func newPacketMMapDispatcher(fd int, e *endpoint) (linkDispatcher, error) {
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d := &packetMMapDispatcher{
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fd: fd,
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e: e,
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}
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pageSize := unix.Getpagesize()
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if tpBlockSize%pageSize != 0 {
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return nil, fmt.Errorf("tpBlockSize: %d is not page aligned, pagesize: %d", tpBlockSize, pageSize)
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}
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tReq := tPacketReq{
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tpBlockSize: uint32(tpBlockSize),
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tpBlockNR: uint32(tpBlockNR),
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tpFrameSize: uint32(tpFrameSize),
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tpFrameNR: uint32(tpFrameNR),
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}
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// Setup PACKET_RX_RING.
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if err := setsockopt(d.fd, syscall.SOL_PACKET, syscall.PACKET_RX_RING, unsafe.Pointer(&tReq), unsafe.Sizeof(tReq)); err != nil {
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return nil, fmt.Errorf("failed to enable PACKET_RX_RING: %v", err)
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}
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// Let's mmap the blocks.
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sz := tpBlockSize * tpBlockNR
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buf, err := syscall.Mmap(d.fd, 0, sz, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED)
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if err != nil {
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return nil, fmt.Errorf("syscall.Mmap(...,0, %v, ...) failed = %v", sz, err)
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}
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d.ringBuffer = buf
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return d, nil
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}
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func setsockopt(fd, level, name int, val unsafe.Pointer, vallen uintptr) error {
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if _, _, errno := syscall.Syscall6(syscall.SYS_SETSOCKOPT, uintptr(fd), uintptr(level), uintptr(name), uintptr(val), vallen, 0); errno != 0 {
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return error(errno)
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}
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return nil
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}
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