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net/dns/resolver: wrap errors with more context

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To aid in debugging why we're seeing DNS resolution errors.

Updates #TODO

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I9b3f438d5d675f757e9043dbbdc413fd722fb81a
This commit is contained in:
Andrew Dunham 2024-04-11 16:29:22 -04:00
parent 91692495d8
commit 089d15d8c2
2 changed files with 12 additions and 7 deletions
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14
net/dns/resolver/forwarder.go
View File

@ -840,7 +840,7 @@ func (f *forwarder) forwardWithDestChan(ctx context.Context, query packet, respo
domain, err := nameFromQuery(query.bs) domain, err := nameFromQuery(query.bs)
if err != nil { if err != nil {
metricDNSFwdErrorName.Add(1) metricDNSFwdErrorName.Add(1)
return err return fmt.Errorf("getting name from DNS query: %w", err)
} }
// Guarantee that the ctx we use below is done when this function returns. // Guarantee that the ctx we use below is done when this function returns.
@ -888,7 +888,7 @@ func (f *forwarder) forwardWithDestChan(ctx context.Context, query packet, respo
} }
select { select {
case <-ctx.Done(): case <-ctx.Done():
return ctx.Err() return fmt.Errorf("sending SERVFAIL due to no resolvers: %w", ctx.Err())
case responseChan <- res: case responseChan <- res:
return nil return nil
} }
@ -918,6 +918,7 @@ func (f *forwarder) forwardWithDestChan(ctx context.Context, query packet, respo
} }
resb, err := f.send(ctx, fq, *rr) resb, err := f.send(ctx, fq, *rr)
if err != nil { if err != nil {
err = fmt.Errorf("querying resolver %q: %w", rr.name.Addr, err)
select { select {
case errc <- err: case errc <- err:
case <-ctx.Done(): case <-ctx.Done():
@ -939,7 +940,7 @@ func (f *forwarder) forwardWithDestChan(ctx context.Context, query packet, respo
select { select {
case <-ctx.Done(): case <-ctx.Done():
metricDNSFwdErrorContext.Add(1) metricDNSFwdErrorContext.Add(1)
return ctx.Err() return fmt.Errorf("sending response: %w", ctx.Err())
case responseChan <- packet{v, query.family, query.addr}: case responseChan <- packet{v, query.family, query.addr}:
metricDNSFwdSuccess.Add(1) metricDNSFwdSuccess.Add(1)
return nil return nil
@ -954,7 +955,7 @@ func (f *forwarder) forwardWithDestChan(ctx context.Context, query packet, respo
res, err := servfailResponse(query) res, err := servfailResponse(query)
if err != nil { if err != nil {
f.logf("building servfail response: %v", err) f.logf("building servfail response: %v", err)
return firstErr return fmt.Errorf("building SERVFAIL: %w", firstErr)
} }
select { select {
@ -970,9 +971,10 @@ func (f *forwarder) forwardWithDestChan(ctx context.Context, query packet, respo
metricDNSFwdErrorContext.Add(1) metricDNSFwdErrorContext.Add(1)
if firstErr != nil { if firstErr != nil {
metricDNSFwdErrorContextGotError.Add(1) metricDNSFwdErrorContextGotError.Add(1)
return firstErr } else {
firstErr = ctx.Err()
} }
return ctx.Err() return fmt.Errorf("waiting for response: %w", firstErr)
} }
} }
} }

5
net/dns/resolver/tsdns.go
View File

@ -288,9 +288,12 @@ func (r *Resolver) Query(ctx context.Context, bs []byte, family string, from net
// This is present in some errors paths, such as when all upstream // This is present in some errors paths, such as when all upstream
// DNS servers replied with an error. // DNS servers replied with an error.
case resp := <-responses: case resp := <-responses:
if err != nil {
err = fmt.Errorf("forwarder response error: %w", err)
}
return resp.bs, err return resp.bs, err
default: default:
return nil, err return nil, fmt.Errorf("forwarder error: %w", err)
} }
} }
return (<-responses).bs, nil return (<-responses).bs, nil