468 lines
14 KiB
Go
468 lines
14 KiB
Go
//go:build linux
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package transport
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"io"
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"syscall"
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"time"
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"omnisocketgo/cmd/internal/latencylog"
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"omnisocketgo/cmd/internal/protocol"
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)
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const (
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linuxTimestampControlBufferSize = 256 // 控制消息缓冲区。
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linuxTXTimestampWaitTimeout = 250 * time.Millisecond // 等待 TX 时间戳的上限。
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linuxTXTimestampPollInterval = time.Millisecond // 轮询 errqueue 的间隔。
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linuxDataPollInterval = time.Millisecond // 轮询普通收发的间隔。
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linuxSOTimestampingNew = 0x41
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linuxSCMTimestampingNew = linuxSOTimestampingNew
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linuxSOEEOriginTimestamping = 4 // timestamping errqueue 事件。
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linuxSCMTstampSnd = 0 // 对应 A_TX_SOFTWARE。
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linuxSCMTstampSched = 1 // 对应 A_TX_SCHED。
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linuxSOFTimestampingTXSoftware = 1 << 1 // 打开 TX software timestamp。
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linuxSOFTimestampingRXSoftware = 1 << 3 // 打开 RX software timestamp。
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linuxSOFTimestampingSoftware = 1 << 4 // software timestamp 总开关。
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linuxSOFTimestampingOptID = 1 << 7 // 给时间戳关联 ID。
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linuxSOFTimestampingTXSched = 1 << 8 // 打开 TX sched timestamp。
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linuxSOFTimestampingOptTSONLY = 1 << 11 // 只回时间戳。
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linuxSOFTimestampingOptIDTCP = 1 << 16 // 让 TCP 也带 timestamp ID。
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)
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// 拿到底层 fd，并打开 Linux timestamping。
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func (c *TCPConn) initLinuxTimestamping() error {
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sysConn, ok := c.conn.(interface {
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SyscallConn() (syscall.RawConn, error)
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})
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if !ok {
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return fmt.Errorf("transport: connection does not support SyscallConn")
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}
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rawConn, err := sysConn.SyscallConn()
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if err != nil || rawConn == nil {
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if err != nil {
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return fmt.Errorf("transport: get syscall conn: %w", err)
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}
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return fmt.Errorf("transport: missing syscall conn")
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}
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//socket是否可以成功打开 timestamping 取决于内核版本和配置，尝试多个 flag 组合直到成功或遇到非 EINVAL 错误。
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if err := enableLinuxTimestamping(rawConn); err != nil {
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return fmt.Errorf("transport: enable linux timestamping: %w", err)
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}
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//成功打开 timestamping 后，rawConn 就可以用来收 TX/RX 时间戳了。
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c.raw = rawConn
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return nil
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}
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// 给 socket开权限打开TX software timestamping。
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func enableLinuxTimestamping(rawConn syscall.RawConn) error {
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flagCandidates := []int{ //不同linux版本可能支持不同的 flag 组合，尝试多个组合直到成功。
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linuxSOFTimestampingTXSched |
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linuxSOFTimestampingTXSoftware |
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linuxSOFTimestampingRXSoftware |
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linuxSOFTimestampingSoftware |
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linuxSOFTimestampingOptID | //TCP 协议栈给每个时间戳生成一个序列号
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linuxSOFTimestampingOptIDTCP |
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linuxSOFTimestampingOptTSONLY,
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linuxSOFTimestampingTXSched |
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linuxSOFTimestampingTXSoftware |
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linuxSOFTimestampingRXSoftware |
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linuxSOFTimestampingSoftware |
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linuxSOFTimestampingOptID |
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linuxSOFTimestampingOptTSONLY,
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linuxSOFTimestampingTXSched |
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linuxSOFTimestampingTXSoftware |
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linuxSOFTimestampingRXSoftware |
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linuxSOFTimestampingSoftware |
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linuxSOFTimestampingOptTSONLY,
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}
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var lastErr error
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for _, flags := range flagCandidates { //尝试不同的 flag 组合，直到成功或遇到非 EINVAL 错误。
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// 内核根据 fd 找到对应的内存结构体（Socket 缓冲区）
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err := rawConn.Control(func(fd uintptr) { //Control 方法保证在回调里 fd 是有效的，可以安全地调用 syscall.SetsockoptInt。
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lastErr = syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, linuxSOTimestampingNew, flags)
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})
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if err != nil {
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return err
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}
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if lastErr == nil {
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return nil
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}
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if !errors.Is(lastErr, syscall.EINVAL) {
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return lastErr
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}
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}
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return lastErr
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}
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// sendMessageLinux 编码消息、写完整帧，再记录 TX 时间戳。
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func (c *TCPConn) sendMessageLinux(msg protocol.Message) error {
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payload, err := protocol.EncodeMessage(msg)
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if err != nil {
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return fmt.Errorf("protocol: encode message: %w", err)
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}
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//编码后的消息 payload 前面加 4 字节长度，构成完整帧。
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frame := make([]byte, 4+len(payload))
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binary.BigEndian.PutUint32(frame[:4], uint32(len(payload)))
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copy(frame[4:], payload)
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if err := c.writeFrameLinux(frame); err != nil {
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return fmt.Errorf("protocol: write frame: %w", err)
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}
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//记录发送延时日志
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c.logTXTimestampEvents(msg)
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return nil
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}
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// writeFrameLinux 用 sendmsg 写完整帧。
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func (c *TCPConn) writeFrameLinux(frame []byte) error {
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written := 0
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for written < len(frame) {
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n, err := c.sendmsgDataOnce(frame[written:])
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switch {
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case err == nil:
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if n <= 0 {
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return io.ErrShortWrite
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}
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written += n
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case isWouldBlock(err):
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time.Sleep(linuxDataPollInterval)
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default:
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return err
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}
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}
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return nil
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}
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// 把 A_TX_SCHED / A_TX_SOFTWARE 写入日志。(发送过程中）
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func (c *TCPConn) logTXTimestampEvents(msg protocol.Message) {
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timestamps := c.collectTXTimestampEvents()
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if ts, ok := timestamps[latencylog.EventATXSched]; ok {
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latencylog.LogMessageEventAt(c.logger, c.nodeRole, c.nodeID, latencylog.EventATXSched, ts, msg)
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}
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if ts, ok := timestamps[latencylog.EventATXSoftware]; ok {
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latencylog.LogMessageEventAt(c.logger, c.nodeRole, c.nodeID, latencylog.EventATXSoftware, ts, msg)
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}
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}
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// 在 errqueue 里等两类 TX 时间戳。
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func (c *TCPConn) collectTXTimestampEvents() map[string]int64 {
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timestamps := make(map[string]int64, 2)
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//设置合理等待上限
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deadline := time.Now().Add(linuxTXTimestampWaitTimeout)
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//轮询 errqueue 直到拿到两类时间戳，或超时，或遇到非 EAGAIN 错误。
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for len(timestamps) < 2 && time.Now().Before(deadline) {
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eventName, ts, err := c.recvTXTimestampOnce()
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if err != nil {
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if isWouldBlock(err) {
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time.Sleep(linuxTXTimestampPollInterval)
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continue
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}
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break
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}
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if eventName == "" || ts <= 0 {
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continue
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}
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if _, exists := timestamps[eventName]; !exists {
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timestamps[eventName] = ts
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}
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}
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return timestamps
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}
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// recvTXTimestampOnce 从 errqueue 读一次时间戳事件。
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func (c *TCPConn) recvTXTimestampOnce() (string, int64, error) {
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var (
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eventName string // 事件名，例如 A_TX_SCHED 或 A_TX_SOFTWARE。
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tsUnixNS int64 // 时间戳的 UnixNano 表示。
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opErr error
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)
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err := c.raw.Control(func(fd uintptr) {
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//设置足够大的 oob buffer 来接收控制消息，调用 recvmsg 从 errqueue 读一条消息。
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oob := make([]byte, linuxTimestampControlBufferSize)
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//recvmsg 的 flags 里必须带 MSG_ERRQUEUE，才能从 errqueue 里读消息，非阻塞模式下如果没有消息可读会返回 EAGAIN。
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_, oobn, _, _, recvErr := syscall.Recvmsg(int(fd), nil, oob, syscall.MSG_ERRQUEUE|syscall.MSG_DONTWAIT)
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if recvErr != nil {
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opErr = recvErr
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return
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}
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//解析控制消息，看看是不是我们关心的 TX 时间戳事件，如果是就拿到事件名和时间戳。
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eventName, tsUnixNS = parseTXTimestampControlMessages(oob[:oobn])
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})
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if err != nil {
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return "", 0, err
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}
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if opErr != nil {
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return "", 0, opErr
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}
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return eventName, tsUnixNS, nil //如果成功拿到时间戳事件，eventName 会是 A_TX_SCHED 或 A_TX_SOFTWARE 之一，tsUnixNS 是对应的时间戳；如果没有拿到事件或时间戳无效，eventName 会是空字符串，tsUnixNS 会是 0。
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}
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// 把底层时间戳映射成日志事件名。
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func parseTXTimestampControlMessages(oob []byte) (string, int64) {
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if len(oob) == 0 {
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return "", 0
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}
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//解析控制消息，看看是不是我们关心的 TX 时间戳事件，如果是就拿到事件名和时间戳。
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controlMessages, err := syscall.ParseSocketControlMessage(oob)
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if err != nil {
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return "", 0
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}
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var (
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tsUnixNS int64 //时间戳的 UnixNano 表示。
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tsKind uint32 //extended err里，告诉我们这个时间戳是 sched 还是 software。
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hasTS bool // 是否拿到时间戳了。
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hasKind bool // 是否拿到时间戳类型了。
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)
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//一个 recvmsg 可能会收到多个控制消息，循环找我们关心的时间戳事件，拿到时间戳和事件类型。
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for _, controlMessage := range controlMessages {
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switch {
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case controlMessage.Header.Level == syscall.SOL_SOCKET && controlMessage.Header.Type == linuxSCMTimestampingNew:
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if ts := parseSCMTimestampingData(controlMessage.Data); ts > 0 {
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tsUnixNS = ts
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hasTS = true
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}
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case isSocketExtendedErr(controlMessage): //判断时间戳是否进入了errqueue，
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if info, ok := parseSocketExtendedErrInfo(controlMessage.Data); ok {
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tsKind = info //时间戳类型被内核放在 extended err 的附加信息里，解析出来。
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hasKind = true
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}
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}
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}
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if !hasTS || !hasKind {
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return "", 0
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}
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switch tsKind { //把内核的时间戳类型映射成日志事件名。（记录时只关心 sched 和 software 两类时间戳）
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case linuxSCMTstampSched:
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return latencylog.EventATXSched, tsUnixNS
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case linuxSCMTstampSnd:
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return latencylog.EventATXSoftware, tsUnixNS
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default:
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return "", 0
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}
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}
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// 判断控制消息是否来自 socket extended err。
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// 内核产生的时间戳并不会混合在普通的数据流里，而是被包装成一种特殊的“错误消息”丢进 Error Queue。
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func isSocketExtendedErr(controlMessage syscall.SocketControlMessage) bool {
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switch {
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case controlMessage.Header.Level == syscall.SOL_IP && controlMessage.Header.Type == syscall.IP_RECVERR:
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return true
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case controlMessage.Header.Level == syscall.SOL_IPV6 && controlMessage.Header.Type == syscall.IPV6_RECVERR:
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return true
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default:
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return false
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}
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}
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// 从 socket extended err 的数据里取 origin timestamping 信息。
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func parseSocketExtendedErrInfo(data []byte) (uint32, bool) {
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if len(data) < 16 {
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return 0, false
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}
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if data[4] != linuxSOEEOriginTimestamping {
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return 0, false
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}
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return binary.NativeEndian.Uint32(data[8:12]), true
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}
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// 读一条完整消息，并记录 B_RX_SOFTWARE。
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func (c *TCPConn) receiveMessageLinux() (protocol.Message, error) {
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payload, rxTimestamp, err := c.readFrameLinux()
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if err != nil {
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return protocol.Message{}, fmt.Errorf("protocol: read frame: %w", err)
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}
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msg, err := protocol.DecodeMessage(payload)
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if err != nil {
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return protocol.Message{}, fmt.Errorf("protocol: decode message: %w", err)
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}
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if rxTimestamp > 0 {
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latencylog.LogMessageEventAt(c.logger, c.nodeRole, c.nodeID, latencylog.EventBRXSoftware, rxTimestamp, msg)
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}
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return msg, nil
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}
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// readFrameLinux 先读 4 字节长度，再读整条 payload。
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func (c *TCPConn) readFrameLinux() ([]byte, int64, error) {
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var frameHeader [4]byte
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rxTimestamp, err := c.readFullLinux(frameHeader[:])
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if err != nil {
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return nil, rxTimestamp, err
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}
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size := binary.BigEndian.Uint32(frameHeader[:])
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switch {
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case size == 0:
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return nil, rxTimestamp, protocol.ErrInvalidFrameLength
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case size > protocol.MaxFrameSize:
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return nil, rxTimestamp, protocol.ErrFrameTooLarge
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}
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payload := make([]byte, int(size))
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bodyTimestamp, err := c.readFullLinux(payload)
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if rxTimestamp == 0 {
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rxTimestamp = bodyTimestamp
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}
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if err != nil {
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return nil, rxTimestamp, err
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}
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return payload, rxTimestamp, nil
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}
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// 读满 buf，并保留首个 RX_SOFTWARE（返回进入tcp协议栈的时间戳）。
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func (c *TCPConn) readFullLinux(buf []byte) (int64, error) {
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if len(buf) == 0 {
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return 0, nil
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}
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var (
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offset int
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firstRXTime int64
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)
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for offset < len(buf) {
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n, rxTimestamp, err := c.recvmsgLinux(buf[offset:])
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if firstRXTime == 0 && rxTimestamp > 0 {
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firstRXTime = rxTimestamp
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}
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if err != nil {
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if errors.Is(err, io.EOF) && offset > 0 {
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return firstRXTime, io.ErrUnexpectedEOF
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}
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return firstRXTime, err
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}
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offset += n
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}
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return firstRXTime, nil
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}
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// recvmsgLinux 用 recvmsg 同时读取数据和控制消息。
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func (c *TCPConn) recvmsgLinux(buf []byte) (int, int64, error) {
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for {
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n, rxTimeNS, err := c.recvmsgDataOnce(buf)
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switch {
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case err == nil:
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if n == 0 {
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return 0, 0, io.EOF
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}
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return n, rxTimeNS, nil
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case isWouldBlock(err):
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time.Sleep(linuxDataPollInterval)
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default:
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return 0, 0, err
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}
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}
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}
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// 从控制消息里取 RX_SOFTWARE。
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func parseRXTimestampControlMessages(oob []byte) int64 {
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if len(oob) == 0 {
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return 0
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}
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controlMessages, err := syscall.ParseSocketControlMessage(oob)
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if err != nil {
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return 0
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}
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for _, controlMessage := range controlMessages {
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if controlMessage.Header.Level != syscall.SOL_SOCKET || controlMessage.Header.Type != linuxSCMTimestampingNew {
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continue
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}
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if ts := parseSCMTimestampingData(controlMessage.Data); ts > 0 {
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return ts
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}
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}
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return 0
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}
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// 取第一个非零 timespec。
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func parseSCMTimestampingData(data []byte) int64 {
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const timespec64Size = 16
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for offset := 0; offset+timespec64Size <= len(data); offset += timespec64Size {
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sec := int64(binary.NativeEndian.Uint64(data[offset : offset+8]))
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nsec := int64(binary.NativeEndian.Uint64(data[offset+8 : offset+16]))
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if sec == 0 && nsec == 0 {
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continue
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}
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return sec*int64(time.Second) + nsec
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}
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return 0
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}
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// 判断错误是否是 EAGAIN 或 EWOULDBLOCK。
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func isWouldBlock(err error) bool {
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return errors.Is(err, syscall.EAGAIN) || errors.Is(err, syscall.EWOULDBLOCK)
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}
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func (c *TCPConn) sendmsgDataOnce(buf []byte) (int, error) {
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var (
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n int
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opErr error
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)
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err := c.raw.Control(func(fd uintptr) {
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n, opErr = syscall.SendmsgN(int(fd), buf, nil, nil, 0)
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})
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if err != nil {
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return 0, err
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}
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return n, opErr
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}
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func (c *TCPConn) recvmsgDataOnce(buf []byte) (int, int64, error) {
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var (
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n int
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rxTimeNS int64
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opErr error
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)
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err := c.raw.Control(func(fd uintptr) {
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oob := make([]byte, linuxTimestampControlBufferSize)
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readN, oobN, _, _, recvErr := syscall.Recvmsg(int(fd), buf, oob, 0)
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if recvErr != nil {
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opErr = recvErr
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return
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}
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n = readN
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rxTimeNS = parseRXTimestampControlMessages(oob[:oobN])
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})
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if err != nil {
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return 0, 0, err
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}
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return n, rxTimeNS, opErr
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}
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