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https://github.com/tailscale/tailscale.git
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net/dnsfallback: run recursive resolver and compare results
When performing a fallback DNS query, run the recursive resolver in a separate goroutine and compare the results returned by the recursive resolver with the results we get from "regular" bootstrap DNS. This will allow us to gather data about whether the recursive DNS resolver works better, worse, or about the same as "regular" bootstrap DNS. Updates #5853 Signed-off-by: Andrew Dunham <andrew@du.nham.ca> Change-Id: Ifa0b0cc9eeb0dccd6f7a3d91675fe44b3b34bd48
This commit is contained in:
Andrew Dunham
parent
ffaa6be8a4
commit
a7648a6723
@ -32,6 +32,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
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L 💣 github.com/mdlayher/netlink/nlenc from github.com/jsimonetti/rtnetlink+
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L github.com/mdlayher/netlink/nltest from github.com/google/nftables
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L 💣 github.com/mdlayher/socket from github.com/mdlayher/netlink
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github.com/miekg/dns from tailscale.com/net/dns/recursive
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💣 github.com/mitchellh/go-ps from tailscale.com/cmd/tailscale/cli+
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github.com/peterbourgon/ff/v3 from github.com/peterbourgon/ff/v3/ffcli
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github.com/peterbourgon/ff/v3/ffcli from tailscale.com/cmd/tailscale/cli
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@ -93,6 +94,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
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tailscale.com/ipn from tailscale.com/cmd/tailscale/cli+
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tailscale.com/ipn/ipnstate from tailscale.com/cmd/tailscale/cli+
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tailscale.com/metrics from tailscale.com/derp
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tailscale.com/net/dns/recursive from tailscale.com/net/dnsfallback
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tailscale.com/net/dnscache from tailscale.com/derp/derphttp+
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tailscale.com/net/dnsfallback from tailscale.com/control/controlhttp
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tailscale.com/net/flowtrack from tailscale.com/wgengine/filter+
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@ -172,7 +174,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
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golang.org/x/crypto/nacl/secretbox from golang.org/x/crypto/nacl/box
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golang.org/x/crypto/pbkdf2 from software.sslmate.com/src/go-pkcs12
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golang.org/x/crypto/salsa20/salsa from golang.org/x/crypto/nacl/box+
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golang.org/x/exp/constraints from golang.org/x/exp/slices
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golang.org/x/exp/constraints from golang.org/x/exp/slices+
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golang.org/x/exp/maps from tailscale.com/types/views
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golang.org/x/exp/slices from tailscale.com/net/tsaddr+
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golang.org/x/net/bpf from github.com/mdlayher/netlink+
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@ -235,7 +237,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
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embed from tailscale.com/cmd/tailscale/cli+
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encoding from encoding/json+
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encoding/asn1 from crypto/x509+
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encoding/base32 from tailscale.com/tka
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encoding/base32 from tailscale.com/tka+
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encoding/base64 from encoding/json+
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encoding/binary from compress/gzip+
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encoding/hex from crypto/x509+
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@ -118,6 +118,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
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L github.com/mdlayher/netlink/nltest from github.com/google/nftables
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L github.com/mdlayher/sdnotify from tailscale.com/util/systemd
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L 💣 github.com/mdlayher/socket from github.com/mdlayher/netlink
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github.com/miekg/dns from tailscale.com/net/dns/recursive
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💣 github.com/mitchellh/go-ps from tailscale.com/safesocket
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L github.com/pierrec/lz4/v4 from github.com/u-root/uio/uio
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L github.com/pierrec/lz4/v4/internal/lz4block from github.com/pierrec/lz4/v4+
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@ -254,6 +255,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
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tailscale.com/net/connstats from tailscale.com/net/tstun+
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tailscale.com/net/dns from tailscale.com/ipn/ipnlocal+
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tailscale.com/net/dns/publicdns from tailscale.com/net/dns/resolver+
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tailscale.com/net/dns/recursive from tailscale.com/net/dnsfallback
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tailscale.com/net/dns/resolvconffile from tailscale.com/net/dns+
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tailscale.com/net/dns/resolver from tailscale.com/ipn/ipnlocal+
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tailscale.com/net/dnscache from tailscale.com/control/controlclient+
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@ -442,7 +444,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
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embed from tailscale.com+
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encoding from encoding/json+
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encoding/asn1 from crypto/x509+
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encoding/base32 from tailscale.com/tka
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encoding/base32 from tailscale.com/tka+
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encoding/base64 from encoding/json+
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encoding/binary from compress/gzip+
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encoding/hex from crypto/x509+
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@ -22,22 +22,85 @@ import (
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"sync/atomic"
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"time"
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"golang.org/x/exp/slices"
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"tailscale.com/atomicfile"
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"tailscale.com/envknob"
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"tailscale.com/net/dns/recursive"
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"tailscale.com/net/netmon"
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"tailscale.com/net/netns"
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"tailscale.com/net/tlsdial"
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"tailscale.com/net/tshttpproxy"
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"tailscale.com/tailcfg"
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"tailscale.com/types/logger"
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"tailscale.com/util/clientmetric"
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"tailscale.com/util/slicesx"
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)
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var disableRecursiveResolver = envknob.RegisterBool("TS_DNSFALLBACK_DISABLE_RECURSIVE_RESOLVER")
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// MakeLookupFunc creates a function that can be used to resolve hostnames
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// (e.g. as a LookupIPFallback from dnscache.Resolver).
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// The netMon parameter is optional; if non-nil it's used to do faster interface lookups.
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func MakeLookupFunc(logf logger.Logf, netMon *netmon.Monitor) func(ctx context.Context, host string) ([]netip.Addr, error) {
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return func(ctx context.Context, host string) ([]netip.Addr, error) {
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return lookup(ctx, host, logf, netMon)
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if disableRecursiveResolver() {
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return lookup(ctx, host, logf, netMon)
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}
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addrsCh := make(chan []netip.Addr, 1)
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// Run the recursive resolver in the background so we can
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// compare the results.
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go func() {
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logf := logger.WithPrefix(logf, "recursive: ")
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// Ensure that we catch panics while we're testing this
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// code path; this should never panic, but we don't
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// want to take down the process by having the panic
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// propagate to the top of the goroutine's stack and
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// then terminate.
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defer func() {
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if r := recover(); r != nil {
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logf("bootstrap DNS: recovered panic: %v", r)
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metricRecursiveErrors.Add(1)
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}
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}()
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resolver := recursive.Resolver{
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Dialer: netns.NewDialer(logf, netMon),
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Logf: logf,
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}
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addrs, minTTL, err := resolver.Resolve(ctx, host)
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if err != nil {
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logf("error using recursive resolver: %v", err)
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metricRecursiveErrors.Add(1)
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return
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}
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slices.SortFunc(addrs, func(a, b netip.Addr) bool { return a.Less(b) })
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// Wait for a response from the main function
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oldAddrs := <-addrsCh
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slices.SortFunc(oldAddrs, func(a, b netip.Addr) bool { return a.Less(b) })
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matches := slices.Equal(addrs, oldAddrs)
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logf("bootstrap DNS comparison: matches=%v oldAddrs=%v addrs=%v minTTL=%v", matches, oldAddrs, addrs, minTTL)
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if matches {
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metricRecursiveMatches.Add(1)
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} else {
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metricRecursiveMismatches.Add(1)
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}
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}()
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addrs, err := lookup(ctx, host, logf, netMon)
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if err != nil {
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addrsCh <- nil
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return nil, err
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}
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addrsCh <- slices.Clone(addrs)
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return addrs, nil
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}
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}
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@ -254,3 +317,9 @@ func SetCachePath(path string, logf logger.Logf) {
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cachedDERPMap.Store(dm)
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logf("[v2] dnsfallback: SetCachePath loaded cached DERP map")
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}
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var (
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metricRecursiveMatches = clientmetric.NewCounter("dnsfallback_recursive_matches")
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metricRecursiveMismatches = clientmetric.NewCounter("dnsfallback_recursive_mismatches")
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metricRecursiveErrors = clientmetric.NewCounter("dnsfallback_recursive_errors")
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)
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