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// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package wgengine
import (
"os"
"strconv"
"time"
"tailscale.com/net/flowtrack"
"tailscale.com/net/packet"
"tailscale.com/wgengine/filter"
"tailscale.com/wgengine/tstun"
)
const tcpTimeoutBeforeDebug = 5 * time.Second
// debugConnectFailures reports whether the local node should track
// outgoing TCP connections and log which ones fail and why.
func debugConnectFailures() bool {
s := os.Getenv("TS_DEBUG_CONNECT_FAILURES")
if s == "" {
return true
}
v, _ := strconv.ParseBool(s)
return v
}
type pendingOpenFlow struct {
timer *time.Timer // until giving up on the flow
}
func (e *userspaceEngine) removeFlow(f flowtrack.Tuple) (removed bool) {
e.mu.Lock()
defer e.mu.Unlock()
of, ok := e.pendOpen[f]
if !ok {
// Not a tracked flow (likely already removed)
return false
}
of.timer.Stop()
delete(e.pendOpen, f)
return true
}
func (e *userspaceEngine) trackOpenPreFilterIn(pp *packet.Parsed, t *tstun.TUN) (res filter.Response) {
res = filter.Accept // always
if pp.IPProto == packet.TSMP {
res = filter.DropSilently
rh, ok := pp.AsTailscaleRejectedHeader()
if !ok {
return
}
if f := rh.Flow(); e.removeFlow(f) {
e.logf("open-conn-track: flow %v %v > %v rejected due to %v", rh.Proto, rh.Src, rh.Dst, rh.Reason)
}
return
}
if pp.IPVersion == 0 ||
pp.IPProto != packet.TCP ||
pp.TCPFlags&(packet.TCPSyn|packet.TCPRst) == 0 {
return
}
// Either a SYN or a RST came back. Remove it in either case.
f := flowtrack.Tuple{Dst: pp.Src, Src: pp.Dst} // src/dst reversed
removed := e.removeFlow(f)
if removed && pp.TCPFlags&packet.TCPRst != 0 {
e.logf("open-conn-track: flow TCP %v got RST by peer", f)
}
return
}
func (e *userspaceEngine) trackOpenPostFilterOut(pp *packet.Parsed, t *tstun.TUN) (res filter.Response) {
res = filter.Accept // always
if pp.IPVersion == 0 ||
pp.IPProto != packet.TCP ||
pp.TCPFlags&packet.TCPSyn == 0 {
return
}
flow := flowtrack.Tuple{Src: pp.Src, Dst: pp.Dst}
timer := time.AfterFunc(tcpTimeoutBeforeDebug, func() {
e.onOpenTimeout(flow)
})
e.mu.Lock()
defer e.mu.Unlock()
if e.pendOpen == nil {
e.pendOpen = make(map[flowtrack.Tuple]*pendingOpenFlow)
}
if _, dup := e.pendOpen[flow]; dup {
// Duplicates are expected when the OS retransmits. Ignore.
return
}
e.pendOpen[flow] = &pendingOpenFlow{timer: timer}
return filter.Accept
}
func (e *userspaceEngine) onOpenTimeout(flow flowtrack.Tuple) {
e.mu.Lock()
if _, ok := e.pendOpen[flow]; !ok {
// Not a tracked flow, or already handled & deleted.
e.mu.Unlock()
return
}
delete(e.pendOpen, flow)
e.mu.Unlock()
// Diagnose why it might've timed out.
n, ok := e.magicConn.PeerForIP(flow.Dst.IP)
if !ok {
e.logf("open-conn-track: timeout opening %v; no associated peer node", flow)
return
}
if n.DiscoKey.IsZero() {
e.logf("open-conn-track: timeout opening %v; peer node %v running pre-0.100", flow, n.Key.ShortString())
return
}
if n.DERP == "" {
e.logf("open-conn-track: timeout opening %v; peer node %v not connected to any DERP relay", flow, n.Key.ShortString())
return
}
var lastSeen time.Time
if n.LastSeen != nil {
lastSeen = *n.LastSeen
}
var ps *PeerStatus
if st, err := e.getStatus(); err == nil {
for _, v := range st.Peers {
if v.NodeKey == n.Key {
v := v // copy
ps = &v
}
}
} else {
e.logf("open-conn-track: timeout opening %v to node %v; failed to get engine status: %v", flow, n.Key.ShortString(), err)
return
}
if ps == nil {
e.logf("open-conn-track: timeout opening %v; target node %v in netmap but unknown to wireguard", flow, n.Key.ShortString())
return
}
// TODO(bradfitz): figure out what PeerStatus.LastHandshake
// is. It appears to be the last time we sent a handshake,
// which isn't what I expected. I thought it was when a
// handshake completed, which is what I want.
_ = ps.LastHandshake
e.logf("open-conn-track: timeout opening %v to node %v; lastSeen=%v, lastRecv=%v",
flow, n.Key.ShortString(),
agoOrNever(lastSeen), agoOrNever(e.magicConn.LastRecvActivityOfDisco(n.DiscoKey)))
}
func agoOrNever(t time.Time) string {
if t.IsZero() {
return "never"
}
return time.Since(t).Round(time.Second).String()
}
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