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: Ifa0b0cc9eeb0dccd6f7a3d91675fe44b3b34bd48andrew/dnsfallback-recursive
Andrew Dunham
parent
909e9eabe4
commit
2b3bb87154
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@ -24,6 +24,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
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L 💣 github.com/mdlayher/netlink from github.com/jsimonetti/rtnetlink+
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L 💣 github.com/mdlayher/netlink/nlenc from github.com/jsimonetti/rtnetlink+
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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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@ -68,6 +69,7 @@ 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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@ -145,7 +147,7 @@ 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/slices from tailscale.com/net/tsaddr+
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golang.org/x/net/bpf from github.com/mdlayher/netlink+
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golang.org/x/net/dns/dnsmessage from net+
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@ -207,7 +209,7 @@ 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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@ -111,6 +111,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
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L 💣 github.com/mdlayher/netlink/nlenc from github.com/jsimonetti/rtnetlink+
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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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@ -242,6 +243,7 @@ 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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@ -428,7 +430,7 @@ 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 +22,72 @@ 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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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 +304,9 @@ 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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Loading…
Reference in New Issue