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Add ERCodeRule #6147

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merged 5 commits into from Jan 9, 2018

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@zeha
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zeha commented Jan 5, 2018

Short description

Add ERCodeRule to match on EDNS Extended RCodes.

Separate rule to avoid performance cost for non-EDNS packets. Unclear if this is a good idea for correctness.

Checklist

I have:

  • read the CONTRIBUTING.md document
  • compiled and tested this code
  • included documentation (including possible behaviour changes)
  • documented the code
  • added or modified regression test(s)
  • added or modified unit test(s)

@zeha zeha force-pushed the zeha:dnsdist-ercode branch from bab1fdb to d83feb6 Jan 5, 2018

@zeha zeha requested a review from rgacogne Jan 5, 2018

@rgacogne

Nice work, just a few minor nits!

bool matches(const DNSQuestion* dq) const override
{
// avoid parsing EDNS OPT RR when not needed.
if (d_rcode != dq->dh->rcode) {

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@rgacogne

rgacogne Jan 8, 2018

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Given that dq->dh->rcode is unsigned, perhaps d_rcode should be too? Same for d_extrcode since edns0.extRCode is an uint8_t.

char * optStart = NULL;
size_t optLen = 0;
bool last = false;
int res = locateEDNSOptRR((char*)dq->dh, dq->len, &optStart, &optLen, &last);

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@rgacogne

rgacogne Jan 8, 2018

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const_cast<char*>(reinterpret_cast<const char*>(dq->dh)) ? I don't think we'll manage to get rid of the existing C-style casts, but it would be nice to add new ones as few as possible :)

}
EDNS0Record edns0;
static_assert(sizeof(EDNS0Record) == sizeof(uint32_t), "sizeof(EDNS0Record) must match sizeof(uint32_t) AKA RR TTL size");
memcpy(&edns0, optStart + 5, sizeof edns0);

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@rgacogne

rgacogne Jan 8, 2018

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Adding a comment explaining where does the 5 comes from might be nice for later review.

@zeha

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zeha commented Jan 8, 2018

Nits addressed

@rgacogne rgacogne merged commit 1a26cc5 into PowerDNS:master Jan 9, 2018

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@zeha zeha deleted the zeha:dnsdist-ercode branch Jan 29, 2018

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