analysis: split TCP retransmissions into forward and return, and show both on the line cards

tcp.retrans.up counts retransmitted segments sent by the dialing side, tcp.retrans.down those sent by the listening side. The cards show RTT as a round trip (⇄) with forward (→) and return (←) rows for QUIC loss and TCP retransmission.

backend/src/MoShiro.Backend.Analysis/Metrics/MetricRegistry.cs

@@ -12,7 +12,7 @@ public static class MetricRegistry
     [
         LinkMetrics.Rtt, LinkMetrics.LossUp, LinkMetrics.LossDown, LinkMetrics.LossTotal,
         LinkMetrics.JitterUp, LinkMetrics.JitterDown, LinkMetrics.LossRun, LinkMetrics.LossRunUp, LinkMetrics.LossRunDown, LinkMetrics.Reorder, LinkMetrics.Dup, LinkMetrics.SamplesUdp,
-        TcpMetrics.Rtt, TcpMetrics.Slow, TcpMetrics.Stall, TcpMetrics.StallMax, TcpMetrics.Retrans, TcpMetrics.Srtt, TcpMetrics.BulkRate, TcpMetrics.BulkPeak, TcpMetrics.SamplesTcp,
+        TcpMetrics.Rtt, TcpMetrics.Slow, TcpMetrics.Stall, TcpMetrics.StallMax, TcpMetrics.Retrans, TcpMetrics.RetransUp, TcpMetrics.RetransDown, TcpMetrics.Srtt, TcpMetrics.BulkRate, TcpMetrics.BulkPeak, TcpMetrics.SamplesTcp,
         SessionMetrics.ConnectSuccess, SessionMetrics.ConnectTcp, SessionMetrics.ConnectTls,
         SessionMetrics.FailTimeout, SessionMetrics.FailReset, SessionMetrics.FailTls,
         SessionMetrics.HoldResets, SessionMetrics.HoldLifetime,
@@ -24,7 +24,7 @@ public static class MetricRegistry
     [
         new("quic", "QUIC Datagram", ["loss.up", "loss.down", "loss.total", "rtt.p50", "rtt.p95", "rtt.p99", "jitter.up.p95", "jitter.down.p95", "loss.run.up_max", "loss.run.down_max", "reorder", "dup"]),
         new("udp", "QUIC Datagram (legacy alias)", ["loss.up", "loss.down", "loss.total", "rtt.p50", "rtt.p95", "rtt.p99", "jitter.up.p95", "jitter.down.p95", "loss.run_max", "reorder", "dup"]),
-        new("tcp", "TCP", ["tcp.rtt.p50", "tcp.rtt.p95", "tcp.rtt.p99", "tcp.rtt.p999", "tcp.rtt.max", "tcp.rtt.tail", "tcp.slow", "tcp.stall.per_min", "tcp.stall_max", "tcp.retrans", "tcp.srtt.p95"]),
+        new("tcp", "TCP", ["tcp.rtt.p50", "tcp.rtt.p95", "tcp.rtt.p99", "tcp.rtt.p999", "tcp.rtt.max", "tcp.rtt.tail", "tcp.slow", "tcp.stall.per_min", "tcp.stall_max", "tcp.retrans", "tcp.retrans.up", "tcp.retrans.down", "tcp.srtt.p95"]),
         new("connect", "Connect", ["connect.success", "connect.tcp_ms.p95", "connect.tls_ms.p95", "connect.fail.timeout", "connect.fail.rst", "connect.fail.tls"]),
         new("session", "Session", ["hold.resets.per_h", "hold.lifetime_max"]),
         new("scores", "Scores", ["score.base", "score.mc", "score.hy2", "score.reality"]),

backend/src/MoShiro.Backend.Analysis/Metrics/TcpMetrics.cs

@@ -27,6 +27,14 @@ public static class TcpMetrics
     public static readonly MetricDef Retrans = Metric.Ratio(
         "tcp.retrans", s_tcpInfo, Ops.KernelDelta("retrans_total", "segs_out"), "TCP retransmissions", "Retransmitted segments as a share of segments sent (kernel counters).", good: 0.5, poor: 3);
 
+    public static readonly MetricDef RetransUp = Metric.Ratio(
+        "tcp.retrans.up", s_tcpInfo, Ops.KernelDelta("retrans_total", "segs_out", TcpSide.Forward), "TCP retransmissions (forward)",
+        "Retransmitted segments as a share of segments sent by the 拨号方 (kernel counters): loss on the 拨号方 to Agent path.", good: 0.5, poor: 3);
+
+    public static readonly MetricDef RetransDown = Metric.Ratio(
+        "tcp.retrans.down", s_tcpInfo, Ops.KernelDelta("retrans_total", "segs_out", TcpSide.Return), "TCP retransmissions (return)",
+        "Retransmitted segments as a share of segments sent by the Agent (kernel counters): loss on the Agent to 拨号方 path.", good: 0.5, poor: 3);
+
     public static readonly MetricDef Srtt = Metric.Histogram(
         "tcp.srtt", s_tcpInfo, Ops.Column("srtt_us", 0.001), "Kernel srtt", "Smoothed RTT sampled from the kernel.", Unit.Ms, [Stat.P95], good: 60, poor: 200);
 

backend/src/MoShiro.Backend.Analysis/Ops/Ops.cs

@@ -23,7 +23,7 @@ public static class Ops
 
     public static MetricOp RowCount { get; } = new RowCountOp();
 
-    public static MetricOp KernelDelta(string field, string over) => new KernelDeltaOp(field, over);
+    public static MetricOp KernelDelta(string field, string over, TcpSide only = TcpSide.Both) => new KernelDeltaOp(field, over, only);
 
     public static MetricOp Column(string column, double scale) => new ColumnValueOp(column, scale);
 

backend/src/MoShiro.Backend.Analysis/Ops/SessionOps.cs

@@ -9,19 +9,32 @@ internal static class TcpInfoTime
         side is not null && side.Values[row] == 0 ? view.DialerToUtcMs(ts.Values[row]) : view.AgentToUtcMs(ts.Values[row]);
 }
 
-/// <summary>两次采样之间累计计数的差值（分子）与另一个累计计数的差值（分母），按 (side, conn) 分别计算；旧数据没有 conn 时按 side 计算。</summary>
+/// <summary>哪一侧的内核采样：拨号方 一侧发出的段走去程（拨号方到 Agent），Agent 一侧发出的段走回程。</summary>
+public enum TcpSide
+{
+    Both,
+    Forward,
+    Return,
+}
+
+/// <summary>
+/// 两次采样之间累计计数的差值（分子）与另一个累计计数的差值（分母），按 (side, conn) 分别计算；旧数据没有 conn 时按 side 计算。
+/// 只取一侧时，另一侧的行整个跳过（基线也不记），所以去程和回程的重传各自只由自己这一侧发出的段算出。
+/// </summary>
 internal sealed class KernelDeltaOp : MetricOp
 {
     private readonly string _field;
     private readonly string _over;
+    private readonly TcpSide _only;
 
-    public KernelDeltaOp(string field, string over)
+    public KernelDeltaOp(string field, string over, TcpSide only = TcpSide.Both)
     {
         _field = field;
         _over = over;
+        _only = only;
     }
 
-    public override string Signature => $"kernel_delta/{_field}/{_over}/2";
+    public override string Signature => _only == TcpSide.Both ? $"kernel_delta/{_field}/{_over}/2" : $"kernel_delta/{_field}/{_over}/{_only}/2";
 
     public override void Evaluate(ChunkView view, RawStream stream, IObservationSink sink)
     {
@@ -43,7 +56,13 @@ internal sealed class KernelDeltaOp : MetricOp
                 continue;
             }
 
-            var key = (side?.Values[i] ?? 0, connection?.IsValid(i) == true ? connection.Values[i] : 0);
+            long rowSide = side?.Values[i] ?? 0;
+            if ((_only == TcpSide.Forward && rowSide != 0) || (_only == TcpSide.Return && rowSide == 0))
+            {
+                continue;
+            }
+
+            var key = (rowSide, connection?.IsValid(i) == true ? connection.Values[i] : 0);
             if (last.TryGetValue(key, out (long Ts, long Field, long Over) previous))
             {
                 // Ignore delayed/duplicate samples without replacing the newer baseline.

backend/tests/MoShiro.Backend.Analysis.Tests/OpTests.cs

@@ -260,6 +260,23 @@ public sealed class OpTests
         Assert.Equal(300UL, retrans.Denominator);
     }
 
+    [Fact]
+    public void Retrans_ForwardAndReturnAreSplitBySide()
+    {
+        long ts = ChunkFactory.DialerUs(0);
+        var builder = new StreamBuilder(Kinds.TcpEcho.FindStream("tcp_info")!);
+        builder.Add(ts, 0, 40_000, 0, 10, 10, 1000, 0, 1);
+        builder.Add(ts, 1, 40_000, 0, 10, 100, 2000, 0, 1);
+        builder.Add(ts + 1_000_000, 0, 40_000, 0, 10, 11, 1100, 0, 1);
+        builder.Add(ts + 1_000_000, 1, 40_000, 0, 10, 102, 2200, 0, 1);
+        RawChunk chunk = ChunkFactory.Echo(s_agent, "tcp_echo", T0, 10, 100,
+            _ => new EchoPacket(false, false, 20_000, 20_000), extraStreams: [builder.Build()]);
+        var forward = (RatioAcc)EvaluateOneBucket(chunk, "tcp.retrans.up").Items["tcp.retrans.up"];
+        var back = (RatioAcc)EvaluateOneBucket(chunk, "tcp.retrans.down").Items["tcp.retrans.down"];
+        Assert.Equal((1UL, 100UL), (forward.Numerator, forward.Denominator));
+        Assert.Equal((2UL, 200UL), (back.Numerator, back.Denominator));
+    }
+
     [Fact]
     public void Connect_Outcomes_AreCountedByClass()
     {

web/display/src/LineStrips.tsx

@@ -29,11 +29,11 @@ interface Props {
   m: Record<string, number | null | undefined>
 }
 
-/** 一条线路的 QUIC/TCP 双行摘要，各自显示时延、质量点阵和丢包/重传率。 */
+/** 一条线路的 QUIC/TCP 摘要：RTT 是往返（⇄）；去程是拨号方到监听方（→），回程反过来（←）；QUIC 看各方向丢包，TCP 看各方向重传，都配质量点阵。 */
 export function LineStrips({ lineId, range, m }: Props) {
   const info = OVERVIEW_RANGES.find((r) => r.value === range) ?? OVERVIEW_RANGES[0]
   const series = useQuery(
-    () => api.get<SeriesDto>(`/api/public/lines/${encodeURIComponent(lineId)}/series`, { range: info.value, anchor: 'now', step: info.step, preset: 'quic,tcp', metrics: 'loss.up,loss.down,loss.total,rtt.p50,rtt.p95,rtt.p99,tcp.retrans,tcp.rtt.p50' }),
+    () => api.get<SeriesDto>(`/api/public/lines/${encodeURIComponent(lineId)}/series`, { range: info.value, anchor: 'now', step: info.step, preset: 'quic,tcp', metrics: 'loss.up,loss.down,loss.total,rtt.p50,rtt.p95,rtt.p99,tcp.retrans.up,tcp.retrans.down,tcp.rtt.p50' }),
     [lineId, info.value],
     30_000,
   )
@@ -57,24 +57,25 @@ export function LineStrips({ lineId, range, m }: Props) {
   const at = shown !== null && t[shown] !== undefined ? shown : null
   const lossUp = col('loss.up')
   const lossDown = col('loss.down')
-  const retrans = col('tcp.retrans')
+  const retransUp = col('tcp.retrans.up')
+  const retransDown = col('tcp.retrans.down')
   const up = m['loss.up']
   const down = m['loss.down']
   const upText = up === null || up === undefined ? '丢包 —' : `${fmtPct(up)} 丢包`
   const downText = down === null || down === undefined ? '丢包 —' : `${fmtPct(down)} 丢包`
-  const retransValue = m['tcp.retrans']
-  const retransTone = levelOf(retransValue)
-  const retransText = retransValue === null || retransValue === undefined ? '重传 —' : `${fmtPct(retransValue)} 重传`
+  const retransUpValue = m['tcp.retrans.up']
+  const retransDownValue = m['tcp.retrans.down']
+  const retransText = (v: number | null | undefined) => (v === null || v === undefined ? '重传 —' : `${fmtPct(v)} 重传`)
   return (
     <div className="strips" ref={box} onMouseMove={onMove} onMouseLeave={() => setHover(null)}>
       <div className="line-mini-stack">
         <div className="line-mini-quic-head" title={`QUIC RTT p50 ${fmtMs(m['rtt.p50'])} · p95 ${fmtMs(m['rtt.p95'])} · p99 ${fmtMs(m['rtt.p99'])}`}>
-          <span>QUIC</span><strong className="num">{fmtMs(m['rtt.p50'])}</strong><small>悬停看 p95 / p99</small>
+          <span>QUIC RTT ⇄</span><strong className="num">{fmtMs(m['rtt.p50'])}</strong><small>悬停看 p95 / p99</small>
           {series.error ? <span className="line-mini-badge bad" title={`上一次取数失败：${series.error.message}`}>数据未更新</span> : null}
         </div>
         <div className="line-mini-direction">
           <div className="line-mini-direction-head" title={`去程 拨号方 → 监听方 丢包 ${fmtPct(up)}`}>
-            <span>去程</span>
+            <span>去程 →</span>
             <span className={`line-mini-badge ${levelOf(up)}`}>{upText}</span>
           </div>
           <div className="bars" role="img" aria-label={`近 ${common.hoursText}每 ${common.stepText}的去程丢包`}>
@@ -85,7 +86,7 @@ export function LineStrips({ lineId, range, m }: Props) {
         </div>
         <div className="line-mini-direction">
           <div className="line-mini-direction-head" title={`回程 监听方 → 拨号方 丢包 ${fmtPct(down)}`}>
-            <span>回程</span>
+            <span>回程 ←</span>
             <span className={`line-mini-badge ${levelOf(down)}`}>{downText}</span>
           </div>
           <div className="bars" role="img" aria-label={`近 ${common.hoursText}每 ${common.stepText}的回程丢包`}>
@@ -96,12 +97,28 @@ export function LineStrips({ lineId, range, m }: Props) {
         </div>
         <div className="line-mini-tcp">
           <div className="line-mini-tcp-head" title={`TCP RTT p50 ${fmtMs(m['tcp.rtt.p50'])}`}>
-            <span>TCP</span><strong className="num">{fmtMs(m['tcp.rtt.p50'])}</strong>
-            <span className={`line-mini-badge ${retransTone}`}>{retransText}</span>
+            <span>TCP RTT ⇄</span><strong className="num">{fmtMs(m['tcp.rtt.p50'])}</strong>
           </div>
-          <div className="bars" role="img" aria-label={`近 ${common.hoursText}每 ${common.stepText}的 TCP 重传`}>
-            {(s ? retrans : Array.from({ length: common.cells }, () => null)).map((value, i) => (
-              <span key={`retrans-${t[i] ?? i}`} className={`bar ${s ? levelOf(value) : 'none'}${hover === i ? ' on' : ''}`} />
+        </div>
+        <div className="line-mini-direction">
+          <div className="line-mini-direction-head" title={`TCP 去程 拨号方 → 监听方 重传 ${fmtPct(retransUpValue)}`}>
+            <span>去程 →</span>
+            <span className={`line-mini-badge ${levelOf(retransUpValue)}`}>{retransText(retransUpValue)}</span>
+          </div>
+          <div className="bars" role="img" aria-label={`近 ${common.hoursText}每 ${common.stepText}的 TCP 去程重传`}>
+            {(s ? retransUp : Array.from({ length: common.cells }, () => null)).map((value, i) => (
+              <span key={`retrans-up-${t[i] ?? i}`} className={`bar ${s ? levelOf(value) : 'none'}${hover === i ? ' on' : ''}`} />
+            ))}
+          </div>
+        </div>
+        <div className="line-mini-direction">
+          <div className="line-mini-direction-head" title={`TCP 回程 监听方 → 拨号方 重传 ${fmtPct(retransDownValue)}`}>
+            <span>回程 ←</span>
+            <span className={`line-mini-badge ${levelOf(retransDownValue)}`}>{retransText(retransDownValue)}</span>
+          </div>
+          <div className="bars" role="img" aria-label={`近 ${common.hoursText}每 ${common.stepText}的 TCP 回程重传`}>
+            {(s ? retransDown : Array.from({ length: common.cells }, () => null)).map((value, i) => (
+              <span key={`retrans-down-${t[i] ?? i}`} className={`bar ${s ? levelOf(value) : 'none'}${hover === i ? ' on' : ''}`} />
             ))}
           </div>
         </div>
@@ -127,7 +144,10 @@ export function LineStrips({ lineId, range, m }: Props) {
             <div className="pop-group">
               <span className="pop-name">TCP</span>
               <span>
-                重传 <em className={levelOf(col('tcp.retrans')[at])}>{fmtPct(col('tcp.retrans')[at])}</em>
+                去程重传 <em className={levelOf(col('tcp.retrans.up')[at])}>{fmtPct(col('tcp.retrans.up')[at])}</em>
+              </span>
+              <span>
+                回程重传 <em className={levelOf(col('tcp.retrans.down')[at])}>{fmtPct(col('tcp.retrans.down')[at])}</em>
               </span>
               <span>
                 RTT p50 <em>{fmtMs(col('tcp.rtt.p50')[at])}</em>

web/display/src/pages/Compare.tsx

@@ -22,14 +22,16 @@ const METRICS: MetricInfo[] = [
   { id: 'rtt.p50', label: '延迟 p50', unit: 'ms', better: 'lower' },
   { id: 'rtt.p95', label: '延迟 p95', unit: 'ms', better: 'lower' },
   { id: 'loss.total', label: 'QUIC 丢包', unit: '%', better: 'lower' },
-  { id: 'loss.up', label: 'QUIC 上行丢包', unit: '%', better: 'lower' },
-  { id: 'loss.down', label: 'QUIC 下行丢包', unit: '%', better: 'lower' },
-  { id: 'loss.run.up_max', label: 'QUIC 上行最长连续丢包', unit: '', better: 'lower' },
-  { id: 'loss.run.down_max', label: 'QUIC 下行最长连续丢包', unit: '', better: 'lower' },
-  { id: 'jitter.up.p95', label: '上行抖动', unit: 'ms', better: 'lower' },
-  { id: 'jitter.down.p95', label: '下行抖动', unit: 'ms', better: 'lower' },
+  { id: 'loss.up', label: 'QUIC 去程丢包', unit: '%', better: 'lower' },
+  { id: 'loss.down', label: 'QUIC 回程丢包', unit: '%', better: 'lower' },
+  { id: 'loss.run.up_max', label: 'QUIC 去程最长连续丢包', unit: '', better: 'lower' },
+  { id: 'loss.run.down_max', label: 'QUIC 回程最长连续丢包', unit: '', better: 'lower' },
+  { id: 'jitter.up.p95', label: 'QUIC 去程抖动', unit: 'ms', better: 'lower' },
+  { id: 'jitter.down.p95', label: 'QUIC 回程抖动', unit: 'ms', better: 'lower' },
   { id: 'tcp.rtt.p50', label: 'TCP RTT p50', unit: 'ms', better: 'lower' },
   { id: 'tcp.retrans', label: 'TCP 重传', unit: '%', better: 'lower' },
+  { id: 'tcp.retrans.up', label: 'TCP 去程重传', unit: '%', better: 'lower' },
+  { id: 'tcp.retrans.down', label: 'TCP 回程重传', unit: '%', better: 'lower' },
   { id: 'score.reality', label: 'REALITY 评分', unit: '', better: 'higher' },
   { id: 'score.hy2', label: 'Hy2 评分', unit: '', better: 'higher' },
   { id: 'score.mc', label: 'MC 评分', unit: '', better: 'higher' },

web/display/src/pages/Line.tsx

@@ -38,7 +38,8 @@ const TILES: { group: Exclude<MetricGroup, 'score'>; label: string; key: string;
   { group: 'tcp-connect', label: 'TCP RTT p50', key: 'tcp.rtt.p50', fmt: fmtMs },
   { group: 'tcp-connect', label: 'TCP RTT p99', key: 'tcp.rtt.p99', fmt: fmtMs },
   { group: 'tcp-connect', label: 'TCP RTT 最大', key: 'tcp.rtt.max', fmt: fmtMs },
-  { group: 'tcp-connect', label: 'TCP 重传率', key: 'tcp.retrans', fmt: fmtPct, good: 0.5, poor: 3 },
+  { group: 'tcp-connect', label: 'TCP 去程重传率', key: 'tcp.retrans.up', fmt: fmtPct, good: 0.5, poor: 3 },
+  { group: 'tcp-connect', label: 'TCP 回程重传率', key: 'tcp.retrans.down', fmt: fmtPct, good: 0.5, poor: 3 },
   { group: 'tcp-connect', label: 'TCP 建连 p95', key: 'connect.tcp_ms.p95', fmt: fmtMs, optional: true },
   { group: 'tcp-connect', label: 'TLS 握手 p95', key: 'connect.tls_ms.p95', fmt: fmtMs, optional: true },
   { group: 'tcp-connect', label: '建连成功率', key: 'connect.success', fmt: fmtPct, optional: true },
@@ -64,11 +65,11 @@ const GROUPS = [
 
 const CHARTS: ChartDef[] = [
   { id: 'rtt', title: '延迟', group: 'quic', unit: 'ms', series: [{ key: 'rtt.p50', label: 'p50', color: '--chart-1' }, { key: 'rtt.p95', label: 'p95', color: '--chart-2' }, { key: 'rtt.p99', label: 'p99', color: '--chart-3' }] },
-  { id: 'jitter', title: '抖动（p95）', group: 'quic', unit: 'ms', series: [{ key: 'jitter.up.p95', label: '上行', color: '--chart-2' }, { key: 'jitter.down.p95', label: '下行', color: '--chart-1' }] },
-  { id: 'loss', title: '丢包', group: 'quic', unit: '%', series: [{ key: 'loss.up', label: '上行', color: '--chart-2' }, { key: 'loss.down', label: '下行', color: '--chart-3' }, { key: 'loss.total', label: '合计', color: '--chart-1', dash: [4, 3] }] },
-  { id: 'loss-runs', title: '最长连续丢包', group: 'quic', unit: '包', series: [{ key: 'loss.run.up_max', label: '上行', color: '--chart-2' }, { key: 'loss.run.down_max', label: '下行', color: '--chart-3' }] },
+  { id: 'jitter', title: '抖动（p95）', group: 'quic', unit: 'ms', series: [{ key: 'jitter.up.p95', label: '去程', color: '--chart-2' }, { key: 'jitter.down.p95', label: '回程', color: '--chart-1' }] },
+  { id: 'loss', title: '丢包', group: 'quic', unit: '%', series: [{ key: 'loss.up', label: '去程', color: '--chart-2' }, { key: 'loss.down', label: '回程', color: '--chart-3' }, { key: 'loss.total', label: '合计', color: '--chart-1', dash: [4, 3] }] },
+  { id: 'loss-runs', title: '最长连续丢包', group: 'quic', unit: '包', series: [{ key: 'loss.run.up_max', label: '去程', color: '--chart-2' }, { key: 'loss.run.down_max', label: '回程', color: '--chart-3' }] },
   { id: 'tcp', title: '往返时延（RTT）', group: 'tcp-connect', unit: 'ms', series: [{ key: 'tcp.rtt.p50', label: 'p50', color: '--chart-1' }, { key: 'tcp.rtt.p95', label: 'p95', color: '--chart-2' }, { key: 'tcp.rtt.max', label: '最大', color: '--chart-3' }] },
-  { id: 'retrans', title: '重传率', group: 'tcp-connect', unit: '%', fill: true, series: [{ key: 'tcp.retrans', label: '重传率', color: '--chart-3' }] },
+  { id: 'retrans', title: '重传率', group: 'tcp-connect', unit: '%', series: [{ key: 'tcp.retrans.up', label: '去程', color: '--chart-2' }, { key: 'tcp.retrans.down', label: '回程', color: '--chart-3' }, { key: 'tcp.retrans', label: '合计', color: '--chart-1', dash: [4, 3] }] },
   { id: 'connect-time', title: '建连耗时（p95）', group: 'tcp-connect', unit: 'ms', series: [{ key: 'connect.tcp_ms.p95', label: 'TCP 建连', color: '--chart-1' }, { key: 'connect.tls_ms.p95', label: 'TLS 握手', color: '--chart-2' }] },
   { id: 'connect-ok', title: '建连成功率', group: 'tcp-connect', unit: '%', zero: false, series: [{ key: 'connect.success', label: '成功率', color: '--chart-3' }] },
   { id: 'score', title: '综合评分', group: 'score', wide: true, unit: '', series: [{ key: 'score.reality', label: 'REALITY', color: '--chart-1' }, { key: 'score.hy2', label: 'Hy2', color: '--chart-2' }, { key: 'score.mc', label: 'MC', color: '--chart-4' }, { key: 'score.base', label: '综合', color: '--chart-5', dash: [4, 3] }] },
@@ -316,7 +317,7 @@ export function Line() {
               <div className="line-combo-card">
                 <h3>QUIC Datagram 丢包</h3>
                 <div className="line-combo-primary"><span>总丢包</span><strong className={`combo-tone-${tone(m['loss.total'], 0.5, 3)}`}>{fmtPct(m['loss.total'])}</strong></div>
-                <div className="line-combo-secondary"><span>↑ {fmtPct(m['loss.up'])}</span><span>/</span><span>↓ {fmtPct(m['loss.down'])}</span></div>
+                <div className="line-combo-secondary"><span>去 {fmtPct(m['loss.up'])}</span><span>/</span><span>回 {fmtPct(m['loss.down'])}</span></div>
                 <span className="line-combo-badge">最长连续 ↑ {fmtNum(m['loss.run.up_max'])} / ↓ {fmtNum(m['loss.run.down_max'])} 包</span>
               </div>
               <div className="line-combo-card">

web/display/src/pages/Overview.tsx

@@ -12,7 +12,7 @@ import { PageError } from '../lib'
 import { IPV6_STATES, IpVersionPicker, ipVersionOf } from '@shared/ipVersions'
 import { LineStrips, OVERVIEW_RANGES, type OverviewRange } from '../LineStrips'
 
-const METRICS = ['rtt.p50', 'rtt.p95', 'rtt.p99', 'loss.total', 'loss.up', 'loss.down', 'tcp.rtt.p50', 'tcp.retrans'].join(',')
+const METRICS = ['rtt.p50', 'rtt.p95', 'rtt.p99', 'loss.total', 'loss.up', 'loss.down', 'tcp.rtt.p50', 'tcp.retrans', 'tcp.retrans.up', 'tcp.retrans.down'].join(',')
 
 type SortKey = 'name' | 'rtt' | 'loss'
 
@@ -136,7 +136,7 @@ function NodeCard({ node, labels, infos }: { node: HostItem; labels: string[]; i
   )
 }
 
-/** 一条线路（拨号方 → 监听方）：近一段时间的 QUIC Datagram 上下行丢包、RTT 和 TCP 重传。 */
+/** 一条线路（拨号方 ⇄ 监听方）：RTT 是往返；去程是拨号方到监听方（左到右），回程是监听方到拨号方（右到左）。QUIC 看两个方向的丢包，TCP 看两个方向的重传。 */
 function LineCard({ l, range, infos }: { l: OverviewLineDto; range: OverviewRange; infos: Map<string, NodeInfoDto> }) {
   const dialerInfo = infos.get(l.dialer_id)
   const agentInfo = infos.get(l.agent_id)
@@ -159,7 +159,7 @@ function LineCard({ l, range, infos }: { l: OverviewLineDto; range: OverviewRang
           {dialerInfo?.country ? <Flag code={dialerInfo.country} /> : null}
           <span className="name">{l.dialer_name}</span>
           {dialerInfo?.isp_key ? <IspIcon ispKey={dialerInfo.isp_key} name={dialerInfo.isp_name} /> : null}
-          <span className="arrow">→</span>
+          <span className="arrow" title="RTT 是往返；去程：左 → 右，回程：右 → 左">⇄</span>
           {agentInfo?.country ? <Flag code={agentInfo.country} /> : null}
           <span className="name">{l.name}</span>
         </span>