* plugin/autopath: Fixes a nil pointer dereference panic in autopath during search path walk
When a plugin later in the chain returns a ClientWrite rcode without
writing a response (for example acl's drop action, which returns
(dns.RcodeSuccess, nil) without calling WriteMsg), autopath dereferences
a nil nw.Msg at nw.Msg.Rcode and panics. The final fallback
w.WriteMsg(firstReply) can also receive a nil firstReply for the same
reason.
Skip search path elements that produced no message, and only write the
first reply when it is non-nil. This mirrors the nil guards recently
added in plugin/minimal (#8506), plugin/dns64 (#8511) and plugin/cache
(#8512).
Signed-off-by: zjncs <18910855655@163.com>
* plugin/autopath: silence unused-parameter lint and assert no client write
Address review feedback on #8517: rename the unused 'w' parameter in
TestAutoPathNilMsgFromNext to '_w' so the revive unused-parameter check
passes, and assert that the recorder receives no message so the intended
drop/no-client-write behavior is explicit.
Signed-off-by: zjncs <18910855655@163.com>
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Signed-off-by: zjncs <18910855655@163.com>
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