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tailscale/wgengine/netlog/logger.go

276 lines
8.9 KiB
Go

// Copyright (c) 2022 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 netlog provides a logger that monitors a TUN device and
// periodically records any traffic into a log stream.
package netlog
import (
"context"
"encoding/json"
"fmt"
"io"
"log"
"net/http"
"net/netip"
"sync"
"time"
"tailscale.com/logpolicy"
"tailscale.com/logtail"
"tailscale.com/net/connstats"
"tailscale.com/net/tsaddr"
"tailscale.com/smallzstd"
"tailscale.com/tailcfg"
"tailscale.com/types/netlogtype"
"tailscale.com/util/multierr"
"tailscale.com/wgengine/router"
)
// pollPeriod specifies how often to poll for network traffic.
const pollPeriod = 5 * time.Second
// Device is an abstraction over a tunnel device or a magic socket.
// Both *tstun.Wrapper and *magicsock.Conn implement this interface.
type Device interface {
SetStatistics(*connstats.Statistics)
}
type noopDevice struct{}
func (noopDevice) SetStatistics(*connstats.Statistics) {}
// Logger logs statistics about every connection.
// At present, it only logs connections within a tailscale network.
// Exit node traffic is not logged for privacy reasons.
// The zero value is ready for use.
type Logger struct {
mu sync.Mutex // protects all fields below
logger *logtail.Logger
stats *connstats.Statistics
tun Device
sock Device
addrs map[netip.Addr]bool
prefixes map[netip.Prefix]bool
}
// Running reports whether the logger is running.
func (nl *Logger) Running() bool {
nl.mu.Lock()
defer nl.mu.Unlock()
return nl.logger != nil
}
var testClient *http.Client
// Startup starts an asynchronous network logger that monitors
// statistics for the provided tun and/or sock device.
//
// The tun Device captures packets within the tailscale network,
// where at least one address is a tailscale IP address.
// The source is always from the perspective of the current node.
// If one of the other endpoint is not a tailscale IP address,
// then it suggests the use of a subnet router or exit node.
// For example, when using a subnet router, the source address is
// the tailscale IP address of the current node, and
// the destination address is an IP address within the subnet range.
// In contrast, when acting as a subnet router, the source address is
// an IP address within the subnet range, and the destination is a
// tailscale IP address that initiated the subnet proxy connection.
// In this case, the node acting as a subnet router is acting on behalf
// of some remote endpoint within the subnet range.
// The tun is used to populate the VirtualTraffic, SubnetTraffic,
// and ExitTraffic fields in Message.
//
// The sock Device captures packets at the magicsock layer.
// The source is always a tailscale IP address and the destination
// is a non-tailscale IP address to contact for that particular tailscale node.
// The IP protocol and source port are always zero.
// The sock is used to populated the PhysicalTraffic field in Message.
func (nl *Logger) Startup(nodeID tailcfg.StableNodeID, nodeLogID, domainLogID logtail.PrivateID, tun, sock Device) error {
nl.mu.Lock()
defer nl.mu.Unlock()
if nl.logger != nil {
return fmt.Errorf("network logger already running for %v", nl.logger.PrivateID().Public())
}
// Startup a log stream to Tailscale's logging service.
httpc := &http.Client{Transport: logpolicy.NewLogtailTransport(logtail.DefaultHost)}
if testClient != nil {
httpc = testClient
}
nl.logger = logtail.NewLogger(logtail.Config{
Collection: "tailtraffic.log.tailscale.io",
PrivateID: nodeLogID,
CopyPrivateID: domainLogID,
Stderr: io.Discard,
// TODO(joetsai): Set Buffer? Use an in-memory buffer for now.
NewZstdEncoder: func() logtail.Encoder {
w, err := smallzstd.NewEncoder(nil)
if err != nil {
panic(err)
}
return w
},
HTTPC: httpc,
// Include process sequence numbers to identify missing samples.
IncludeProcID: true,
IncludeProcSequence: true,
}, log.Printf)
// Startup a data structure to track per-connection statistics.
// There is a maximum size for individual log messages that logtail
// can upload to the Tailscale log service, so stay below this limit.
const maxLogSize = 256 << 10
const maxConns = (maxLogSize - netlogtype.MaxMessageJSONSize) / netlogtype.MaxConnectionCountsJSONSize
nl.stats = connstats.NewStatistics(pollPeriod, maxConns, func(start, end time.Time, virtual, physical map[netlogtype.Connection]netlogtype.Counts) {
nl.mu.Lock()
addrs := nl.addrs
prefixes := nl.prefixes
nl.mu.Unlock()
recordStatistics(nl.logger, nodeID, start, end, virtual, physical, addrs, prefixes)
})
// Register the connection tracker into the TUN device.
if tun == nil {
tun = noopDevice{}
}
nl.tun = tun
nl.tun.SetStatistics(nl.stats)
// Register the connection tracker into magicsock.
if sock == nil {
sock = noopDevice{}
}
nl.sock = sock
nl.sock.SetStatistics(nl.stats)
return nil
}
func recordStatistics(logger *logtail.Logger, nodeID tailcfg.StableNodeID, start, end time.Time, connstats, sockStats map[netlogtype.Connection]netlogtype.Counts, addrs map[netip.Addr]bool, prefixes map[netip.Prefix]bool) {
m := netlogtype.Message{NodeID: nodeID, Start: start.UTC(), End: end.UTC()}
classifyAddr := func(a netip.Addr) (isTailscale, withinRoute bool) {
// NOTE: There could be mis-classifications where an address is treated
// as a Tailscale IP address because the subnet range overlaps with
// the subnet range that Tailscale IP addresses are allocated from.
// This should never happen for IPv6, but could happen for IPv4.
withinRoute = addrs[a]
for p := range prefixes {
if p.Contains(a) && p.Bits() > 0 {
withinRoute = true
break
}
}
return withinRoute && tsaddr.IsTailscaleIP(a), withinRoute && !tsaddr.IsTailscaleIP(a)
}
exitTraffic := make(map[netlogtype.Connection]netlogtype.Counts)
for conn, cnts := range connstats {
srcIsTailscaleIP, srcWithinSubnet := classifyAddr(conn.Src.Addr())
dstIsTailscaleIP, dstWithinSubnet := classifyAddr(conn.Dst.Addr())
switch {
case srcIsTailscaleIP && dstIsTailscaleIP:
m.VirtualTraffic = append(m.VirtualTraffic, netlogtype.ConnectionCounts{Connection: conn, Counts: cnts})
case srcWithinSubnet || dstWithinSubnet:
m.SubnetTraffic = append(m.SubnetTraffic, netlogtype.ConnectionCounts{Connection: conn, Counts: cnts})
default:
const anonymize = true
if anonymize {
// Only preserve the address if it is a Tailscale IP address.
srcOrig, dstOrig := conn.Src, conn.Dst
conn = netlogtype.Connection{} // scrub everything by default
if srcIsTailscaleIP {
conn.Src = netip.AddrPortFrom(srcOrig.Addr(), 0)
}
if dstIsTailscaleIP {
conn.Dst = netip.AddrPortFrom(dstOrig.Addr(), 0)
}
}
exitTraffic[conn] = exitTraffic[conn].Add(cnts)
}
}
for conn, cnts := range exitTraffic {
m.ExitTraffic = append(m.ExitTraffic, netlogtype.ConnectionCounts{Connection: conn, Counts: cnts})
}
for conn, cnts := range sockStats {
m.PhysicalTraffic = append(m.PhysicalTraffic, netlogtype.ConnectionCounts{Connection: conn, Counts: cnts})
}
if len(m.VirtualTraffic)+len(m.SubnetTraffic)+len(m.ExitTraffic)+len(m.PhysicalTraffic) > 0 {
if b, err := json.Marshal(m); err != nil {
logger.Logf("json.Marshal error: %v", err)
} else {
logger.Logf("%s", b)
}
}
}
func makeRouteMaps(cfg *router.Config) (addrs map[netip.Addr]bool, prefixes map[netip.Prefix]bool) {
addrs = make(map[netip.Addr]bool)
for _, p := range cfg.LocalAddrs {
if p.IsSingleIP() {
addrs[p.Addr()] = true
}
}
prefixes = make(map[netip.Prefix]bool)
insertPrefixes := func(rs []netip.Prefix) {
for _, p := range rs {
if p.IsSingleIP() {
addrs[p.Addr()] = true
} else {
prefixes[p] = true
}
}
}
insertPrefixes(cfg.Routes)
insertPrefixes(cfg.SubnetRoutes)
return addrs, prefixes
}
// ReconfigRoutes configures the network logger with updated routes.
// The cfg is used to classify the types of connections captured by
// the tun Device passed to Startup.
func (nl *Logger) ReconfigRoutes(cfg *router.Config) {
nl.mu.Lock()
defer nl.mu.Unlock()
// TODO(joetsai): There is a race where deleted routes are not known at
// the time of extraction. We need to keep old routes around for a bit.
nl.addrs, nl.prefixes = makeRouteMaps(cfg)
}
// Shutdown shuts down the network logger.
// This attempts to flush out all pending log messages.
// Even if an error is returned, the logger is still shut down.
func (nl *Logger) Shutdown(ctx context.Context) error {
nl.mu.Lock()
defer nl.mu.Unlock()
if nl.logger == nil {
return nil
}
// Shutdown in reverse order of Startup.
// Do not hold lock while shutting down since this may flush one last time.
nl.mu.Unlock()
nl.sock.SetStatistics(nil)
nl.tun.SetStatistics(nil)
err1 := nl.stats.Shutdown(ctx)
err2 := nl.logger.Shutdown(ctx)
nl.mu.Lock()
// Purge state.
nl.logger = nil
nl.stats = nil
nl.tun = nil
nl.sock = nil
nl.addrs = nil
nl.prefixes = nil
return multierr.New(err1, err2)
}