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feat: Introduce jittered tunnel recycling for tunnel connections and … #14

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Merged
ParsaKSH merged 1 commit into from
Mar 23, 2026
Merged

feat: Introduce jittered tunnel recycling for tunnel connections and … #14

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17 changes: 15 additions & 2 deletions cmd/centralserver/main.go
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Original file line number Diff line number Diff line change
Expand Up @@ -206,7 +206,7 @@ func (cs *centralServer) dispatchFrame(frame *tunnel.Frame, source net.Conn) {
cs.handleRST(frame)
return
}
cs.handleData(frame)
cs.handleData(frame, source)
}

func (cs *centralServer) handleSYN(frame *tunnel.Frame, source net.Conn) {
Expand Down Expand Up @@ -424,7 +424,7 @@ func (cs *centralServer) sendFrame(connID uint32, frame *tunnel.Frame) {
log.Printf("[central] conn=%d: all sources failed", connID)
}

func (cs *centralServer) handleData(frame *tunnel.Frame) {
func (cs *centralServer) handleData(frame *tunnel.Frame, source net.Conn) {
cs.mu.RLock()
state, ok := cs.conns[frame.ConnID]
cs.mu.RUnlock()
Expand All @@ -435,6 +435,19 @@ func (cs *centralServer) handleData(frame *tunnel.Frame) {
state.mu.Lock()
defer state.mu.Unlock()

// If this source isn't known yet (e.g., after tunnel recycling), add it.
// This ensures responses can flow back through the new connection.
found := false
for _, s := range state.sources {
if s == source {
found = true
break
}
}
if !found {
state.sources = append(state.sources, source)
}

state.reorderer.Insert(frame.SeqNum, frame.Payload)
if state.target == nil {
return // buffered, flushed when upstream connects
Expand Down
13 changes: 9 additions & 4 deletions internal/tunnel/pool.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ import (
"fmt"
"io"
"log"
"math/rand"
"net"
"sync"
"sync/atomic"
Expand All @@ -30,8 +31,9 @@ type TunnelConn struct {
closed bool
incoming chan *Frame
createdAt time.Time
lastRead atomic.Int64 // unix timestamp of last successful read
writeErrs atomic.Int32 // consecutive write errors
maxAge time.Duration // per-connection jittered max age
lastRead atomic.Int64 // unix timestamp of last successful read
writeErrs atomic.Int32 // consecutive write errors
}

// TunnelPool manages persistent connections to all healthy instances.
Expand Down Expand Up @@ -151,8 +153,7 @@ func (p *TunnelPool) refreshConnections() {

if !activeIDs[id] || tc.closed {
shouldRemove = true
} else if now.Sub(tc.createdAt) > tunnelMaxAge {
// Connection too old → recycle to get a fresh QUIC stream
} else if now.Sub(tc.createdAt) > tc.maxAge {
log.Printf("[tunnel-pool] recycling instance %d connection (age=%s)",
id, now.Sub(tc.createdAt).Round(time.Second))
shouldRemove = true
Expand Down Expand Up @@ -202,11 +203,15 @@ func (p *TunnelPool) connectInstance(inst *engine.Instance) (*TunnelConn, error)
tc.SetNoDelay(true)
}

// Jittered max age: tunnelMaxAge ± 50%
jitter := time.Duration(rand.Int63n(int64(tunnelMaxAge))) - tunnelMaxAge/2

tunnel := &TunnelConn{
inst: inst,
conn: conn,
incoming: make(chan *Frame, 256),
createdAt: time.Now(),
maxAge: tunnelMaxAge + jitter,
}
tunnel.lastRead.Store(time.Now().Unix())

Expand Down
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