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request.Scrub: test for rl==size case (#1631)

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* request.Scrub: test for rl==size case

Make a test case for the new break statement in Scrub and also
account for the OPT record that may get re-added in SizeAndDo() -
otherwise we may break clients that expect this.

* Fix comment
This commit is contained in:
Miek Gieben
2018-03-24 11:50:55 +00:00
committed by GitHub
parent 1c6efbd962
commit a8d02d970c
2 changed files with 63 additions and 8 deletions
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21
request/request.go
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@@ -167,7 +167,6 @@ func (r *Request) SizeAndDo(m *dns.Msg) bool {
if odo {
o.SetDo()
}
m.Extra = append(m.Extra, o)
return true
}
@@ -202,8 +201,13 @@ func (r *Request) Scrub(reply *dns.Msg) (*dns.Msg, Result) {
return reply, ScrubIgnored
}
// Account for the OPT record that gets added in SizeAndDo(), subtract that length.
sub := 0
if r.Do() {
sub = optLen
}
origExtra := reply.Extra
re := len(reply.Extra)
re := len(reply.Extra) - sub
l, m := 0, 0
for l < re {
m = (l + re) / 2
@@ -221,8 +225,8 @@ func (r *Request) Scrub(reply *dns.Msg) (*dns.Msg, Result) {
break
}
}
// We may come out of this loop with one rotation too many as we don't break on rl == size.
// I.e. m makes it too large, but m-1 works.
// We may come out of this loop with one rotation too many, m makes it too large, but m-1 works.
if rl > size && m > 0 {
reply.Extra = origExtra[:m-1]
rl = reply.Len()
@@ -252,16 +256,16 @@ func (r *Request) Scrub(reply *dns.Msg) (*dns.Msg, Result) {
break
}
}
// We may come out of this loop with one rotation too many as we don't break on rl == size.
// I.e. m makes it too large, but m-1 works.
// We may come out of this loop with one rotation too many, m makes it too large, but m-1 works.
if rl > size && m > 0 {
reply.Answer = origAnswer[:m-1]
// No need to recalc length, as we don't use it. We set truncated anyway. Doing
// this extra m-1 step does make it fit in the client's buffer however.
}
// It now fits, but Truncated.
r.SizeAndDo(reply)
// It now fits, but Truncated. We can't call sizeAndDo() because that adds a new record (OPT)
// in the additional section.
reply.Truncated = true
return reply, ScrubAnswer
}
@@ -389,4 +393,5 @@ const (
// TODO(miek): make this less awkward.
doTrue = 1
doFalse = 2
optLen = 12 // OPT record length.
)