diff options
Diffstat (limited to 'request/request.go')
| -rw-r--r-- | request/request.go | 30 |
1 files changed, 19 insertions, 11 deletions
diff --git a/request/request.go b/request/request.go index f560612c8..260d73f5e 100644 --- a/request/request.go +++ b/request/request.go @@ -250,18 +250,16 @@ func (r *Request) Scrub(reply *dns.Msg) *dns.Msg { } // Account for the OPT record that gets added in SizeAndDo(), subtract that length. - sub := 0 + re := len(reply.Extra) if r.Req.IsEdns0() != nil { - sub = optLen + size -= optLen + // re can never be 0 because we have an OPT RR. + re-- } - // subtract to make spaces for re-added EDNS0 OPT RR. - re := len(reply.Extra) - sub - size -= sub - l, m := 0, 0 origExtra := reply.Extra - for l < re { + for l <= re { m = (l + re) / 2 reply.Extra = origExtra[:m] rl = reply.Len() @@ -278,13 +276,18 @@ func (r *Request) Scrub(reply *dns.Msg) *dns.Msg { } } - // We may come out of this loop with one rotation too many, m makes it too large, but m-1 works. + // The binary search only breaks on an exact match, which will be + // pretty rare. Normally, the loop will exit when l > re, meaning that + // in the previous iteration either: + // rl < size: no need to do anything. + // rl > size: the final size is too large, and if m > 0, the preceeding + // iteration the size was too small. Select that preceeding size. if rl > size && m > 0 { reply.Extra = origExtra[:m-1] rl = reply.Len() } - if rl < size { + if rl <= size { r.SizeAndDo(reply) return reply } @@ -292,7 +295,7 @@ func (r *Request) Scrub(reply *dns.Msg) *dns.Msg { ra := len(reply.Answer) l, m = 0, 0 origAnswer := reply.Answer - for l < ra { + for l <= ra { m = (l + ra) / 2 reply.Answer = origAnswer[:m] rl = reply.Len() @@ -309,7 +312,12 @@ func (r *Request) Scrub(reply *dns.Msg) *dns.Msg { } } - // We may come out of this loop with one rotation too many, m makes it too large, but m-1 works. + // The binary search only breaks on an exact match, which will be + // pretty rare. Normally, the loop will exit when l > ra, meaning that + // in the previous iteration either: + // rl < size: no need to do anything. + // rl > size: the final size is too large, and if m > 0, the preceeding + // iteration the size was too small. Select that preceeding size. 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 |