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net/dns/resolver: add a bunch of extra logging

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Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I38f8556d61105551939b0e62eb5213aa3c124f25
This commit is contained in:
Andrew Dunham 2024-07-05 14:18:56 -04:00
parent c4b20c5411
commit cfb1c4b811
1 changed files with 19 additions and 1 deletions
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20
net/dns/resolver/forwarder.go
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@ -511,10 +511,16 @@ func (f *forwarder) send(ctx context.Context, fq *forwardQuery, rr resolverAndDe
isUDPQuery := fq.family == "udp" isUDPQuery := fq.family == "udp"
skipTCP := skipTCPRetry() || (f.controlKnobs != nil && f.controlKnobs.DisableDNSForwarderTCPRetries.Load()) skipTCP := skipTCPRetry() || (f.controlKnobs != nil && f.controlKnobs.DisableDNSForwarderTCPRetries.Load())
var vlogf logger.Logf = logger.Discard
if verboseDNSForward() {
vlogf = f.logf
}
// Print logs about retries if this was because of a truncated response. // Print logs about retries if this was because of a truncated response.
var explicitRetry atomic.Bool // true if truncated UDP response retried var explicitRetry atomic.Bool // true if truncated UDP response retried
defer func() { defer func() {
if !explicitRetry.Load() { if !explicitRetry.Load() {
vlogf("forwarder.send(%q): no retry needed", rr.name.Addr)
return return
} }
if err == nil { if err == nil {
@ -525,12 +531,16 @@ func (f *forwarder) send(ctx context.Context, fq *forwardQuery, rr resolverAndDe
}() }()
firstUDP := func(ctx context.Context) ([]byte, error) { firstUDP := func(ctx context.Context) ([]byte, error) {
t0 := time.Now()
vlogf("starting UDP query for %q", rr.name.Addr)
resp, err := f.sendUDP(ctx, fq, rr) resp, err := f.sendUDP(ctx, fq, rr)
vlogf("UDP query for %q took %v; err=%v", rr.name.Addr, time.Since(t0), err)
if err != nil { if err != nil {
return nil, err return nil, err
} }
if !truncatedFlagSet(resp) { if !truncatedFlagSet(resp) {
// Successful, non-truncated response; no retry. // Successful, non-truncated response; no retry.
vlogf("reply from %q was not truncated; returning", rr.name.Addr)
return resp, nil return resp, nil
} }
@ -540,12 +550,14 @@ func (f *forwarder) send(ctx context.Context, fq *forwardQuery, rr resolverAndDe
// falling back to TCP for a truncated query if we can't return // falling back to TCP for a truncated query if we can't return
// the results to the client. // the results to the client.
if isUDPQuery { if isUDPQuery {
vlogf("reply from %q was truncated, but client was UDP; returning", rr.name.Addr)
return resp, nil return resp, nil
} }
if skipTCP { if skipTCP {
// Envknob or control knob disabled the TCP retry behaviour; // Envknob or control knob disabled the TCP retry behaviour;
// just return what we have. // just return what we have.
vlogf("reply from %q was truncated, but TCP retries are disabled; returning", rr.name.Addr)
return resp, nil return resp, nil
} }
@ -554,6 +566,7 @@ func (f *forwarder) send(ctx context.Context, fq *forwardQuery, rr resolverAndDe
// error to cause our retry helper to immediately kick off the // error to cause our retry helper to immediately kick off the
// TCP retry. // TCP retry.
explicitRetry.Store(true) explicitRetry.Store(true)
vlogf("reply from %q was truncated; signaling to retry via TCP", rr.name.Addr)
return nil, truncatedResponseError{resp} return nil, truncatedResponseError{resp}
} }
thenTCP := func(ctx context.Context) ([]byte, error) { thenTCP := func(ctx context.Context) ([]byte, error) {
@ -561,11 +574,16 @@ func (f *forwarder) send(ctx context.Context, fq *forwardQuery, rr resolverAndDe
// context is canceled and return that error (i.e. not // context is canceled and return that error (i.e. not
// returning anything). // returning anything).
if skipTCP { if skipTCP {
vlogf("skipping TCP query for %q", rr.name.Addr)
<-ctx.Done() <-ctx.Done()
return nil, ctx.Err() return nil, ctx.Err()
} }
return f.sendTCP(ctx, fq, rr) t0 := time.Now()
vlogf("starting TCP query for %q", rr.name.Addr)
ret, err := f.sendTCP(ctx, fq, rr)
vlogf("TCP query for %q took %v; err=%v", rr.name.Addr, time.Since(t0), err)
return ret, err
} }
// If the input query is TCP, then don't have a timeout between // If the input query is TCP, then don't have a timeout between