// 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" "os" "runtime" "strconv" "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/wgengine/filter" ) 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 // 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.IP()) { if _, err := e.peerForIP(flow.Dst.IP()); err != nil { return } } 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() 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. n, err := e.peerForIP(flow.Dst.IP()) if err != nil { e.logf("open-conn-track: timeout opening %v; peerForIP: %v", flow, err) return } if n == nil { 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 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.IP()) { 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.LastRecvActivityOfDisco(n.DiscoKey)) } 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() }