tailscale/wgengine/pendopen.go

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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 (
"fmt"
"runtime"
"time"
"tailscale.com/ipn/ipnstate"
"tailscale.com/net/flowtrack"
"tailscale.com/net/packet"
"tailscale.com/net/tsaddr"
"tailscale.com/net/tstun"
"tailscale.com/types/ipproto"
"tailscale.com/util/mak"
"tailscale.com/wgengine/filter"
)
const tcpTimeoutBeforeDebug = 5 * time.Second
type pendingOpenFlow struct {
timer *time.Timer // until giving up on the flow
// guarded by userspaceEngine.mu:
// problem is non-zero if we got a MaybeBroken (non-terminal)
// TSMP "reject" header.
problem packet.TailscaleRejectReason
}
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) noteFlowProblemFromPeer(f flowtrack.Tuple, problem packet.TailscaleRejectReason) {
e.mu.Lock()
defer e.mu.Unlock()
of, ok := e.pendOpen[f]
if !ok {
// Not a tracked flow (likely already removed)
return
}
of.problem = problem
}
func (e *userspaceEngine) trackOpenPreFilterIn(pp *packet.Parsed, t *tstun.Wrapper) (res filter.Response) {
res = filter.Accept // always
if pp.IPProto == ipproto.TSMP {
res = filter.DropSilently
rh, ok := pp.AsTailscaleRejectedHeader()
if !ok {
return
}
if rh.MaybeBroken {
e.noteFlowProblemFromPeer(rh.Flow(), rh.Reason)
} else 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 != ipproto.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{Proto: pp.IPProto, 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.Wrapper) (res filter.Response) {
res = filter.Accept // always
if pp.IPVersion == 0 ||
pp.IPProto != ipproto.TCP ||
pp.TCPFlags&packet.TCPAck != 0 ||
pp.TCPFlags&packet.TCPSyn == 0 {
return
}
flow := flowtrack.Tuple{Proto: pp.IPProto, Src: pp.Src, Dst: pp.Dst}
// iOS likes to probe Apple IPs on all interfaces to check for connectivity.
// Don't start timers tracking those. They won't succeed anyway. Avoids log spam
// like:
// open-conn-track: timeout opening (100.115.73.60:52501 => 17.125.252.5:443); no associated peer node
if runtime.GOOS == "ios" && flow.Dst.Port() == 443 && !tsaddr.IsTailscaleIP(flow.Dst.Addr()) {
if _, ok := e.PeerForIP(flow.Dst.Addr()); !ok {
return
}
}
timer := time.AfterFunc(tcpTimeoutBeforeDebug, func() {
e.onOpenTimeout(flow)
})
e.mu.Lock()
defer e.mu.Unlock()
if _, dup := e.pendOpen[flow]; dup {
// Duplicates are expected when the OS retransmits. Ignore.
return
}
mak.Set(&e.pendOpen, flow, &pendingOpenFlow{timer: timer})
return filter.Accept
}
func (e *userspaceEngine) onOpenTimeout(flow flowtrack.Tuple) {
e.mu.Lock()
of, ok := e.pendOpen[flow]
if !ok {
// Not a tracked flow, or already handled & deleted.
e.mu.Unlock()
return
}
delete(e.pendOpen, flow)
problem := of.problem
e.mu.Unlock()
if !problem.IsZero() {
e.logf("open-conn-track: timeout opening %v; peer reported problem: %v", flow, problem)
}
// Diagnose why it might've timed out.
pip, ok := e.PeerForIP(flow.Dst.Addr())
if !ok {
e.logf("open-conn-track: timeout opening %v; no associated peer node", flow)
return
}
n := pip.Node
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 ps *ipnstate.PeerStatusLite
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 {
onlyZeroRoute := true // whether peerForIP returned n only because its /0 route matched
for _, r := range n.AllowedIPs {
if r.Bits() != 0 && r.Contains(flow.Dst.Addr()) {
onlyZeroRoute = false
break
}
}
if onlyZeroRoute {
// This node was returned by peerForIP because
// its exit node /0 route(s) matched, but this
// might not be the exit node that's currently
// selected. Rather than log misleading
// errors, just don't log at all for now.
// TODO(bradfitz): update this code to be
// exit-node-aware and make peerForIP return
// the node of the currently selected exit
// node.
return
}
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
online := "?"
if n.Online != nil {
if *n.Online {
online = "yes"
} else {
online = "no"
}
}
if n.LastSeen != nil && online != "yes" {
online += fmt.Sprintf(", lastseen=%v", durFmt(*n.LastSeen))
}
e.logf("open-conn-track: timeout opening %v to node %v; online=%v, lastRecv=%v",
flow, n.Key.ShortString(),
online,
e.magicConn.LastRecvActivityOfNodeKey(n.Key))
}
func durFmt(t time.Time) string {
if t.IsZero() {
return "never"
}
d := time.Since(t).Round(time.Second)
if d < 10*time.Minute {
// node.LastSeen times are rounded very coarsely, and
// we compare times from different clocks (server vs
// local), so negative is common when close. Format as
// "recent" if negative or actually recent.
return "recent"
}
return d.String()
}