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net/dns/resolver: log source IP of forwarded queries

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When the TS_DEBUG_DNS_FORWARD_SEND envknob is turned on, also log the
source IP:port of the query that tailscaled is forwarding.

Updates #TODO

Signed-off-by: Andrew Dunham <andrew@tailscale.com>
This commit is contained in:
Andrew Dunham
2025-12-16 17:19:16 -05:00
parent f174ecb6fd
commit 1fc99ff95e
2 changed files with 35 additions and 2 deletions
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6
net/dns/resolver/forwarder.go
View File

@@ -526,9 +526,9 @@ func (f *forwarder) send(ctx context.Context, fq *forwardQuery, rr resolverAndDe
if f.verboseFwd {
id := forwarderCount.Add(1)
domain, typ, _ := nameFromQuery(fq.packet)
f.logf("forwarder.send(%q, %d, %v, %d) [%d] ...", rr.name.Addr, fq.txid, typ, len(domain), id)
f.logf("forwarder.send(%q, %d, %v, %d) from %v [%d] ...", rr.name.Addr, fq.txid, typ, len(domain), fq.src, id)
defer func() {
f.logf("forwarder.send(%q, %d, %v, %d) [%d] = %v, %v", rr.name.Addr, fq.txid, typ, len(domain), id, len(ret), err)
f.logf("forwarder.send(%q, %d, %v, %d) from %v [%d] = %v, %v", rr.name.Addr, fq.txid, typ, len(domain), fq.src, id, len(ret), err)
}()
}
if strings.HasPrefix(rr.name.Addr, "http://") {
@@ -904,6 +904,7 @@ type forwardQuery struct {
txid txid
packet []byte
family string // "tcp" or "udp"
src netip.AddrPort
// closeOnCtxDone lets send register values to Close if the
// caller's ctx expires. This avoids send from allocating its
@@ -988,6 +989,7 @@ func (f *forwarder) forwardWithDestChan(ctx context.Context, query packet, respo
txid: getTxID(query.bs),
packet: query.bs,
family: query.family,
src: query.addr,
closeOnCtxDone: new(closePool),
}
defer fq.closeOnCtxDone.Close()

31
net/dns/resolver/forwarder_test.go
View File

@@ -864,3 +864,34 @@ func TestNXDOMAINIncludesQuestion(t *testing.T) {
t.Errorf("invalid response\ngot: %+v\nwant: %+v", res, response)
}
}
func TestForwarderVerboseLogs(t *testing.T) {
const domain = "test.tailscale.com."
response := makeTestResponse(t, domain, dns.RCodeServerFailure)
request := makeTestRequest(t, domain)
port := runDNSServer(t, nil, response, func(isTCP bool, gotRequest []byte) {
if !bytes.Equal(request, gotRequest) {
t.Errorf("invalid request\ngot: %+v\nwant: %+v", gotRequest, request)
}
})
var logBuf bytes.Buffer
fwdLogf := func(format string, args ...any) {
t.Logf("[forwarder] "+format, args...)
fmt.Fprintf(&logBuf, format+"\n", args...)
}
_, err := runTestQuery(t, request, func(f *forwarder) {
f.logf = fwdLogf
f.verboseFwd = true
}, port)
if err != nil {
t.Fatal(err)
}
logStr := logBuf.String()
if !strings.Contains(logStr, "forwarder.send(") {
t.Errorf("expected forwarding log, got:\n%s", logStr)
}
}