Add support for EDNS0 (RFC6891) udp payload size negotiation #1980
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Hey @jsipprell, sorry for the delay here. I'll review in depth here soon, but at first glance this sounds great! |
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@jsipprell - Would it be possible to fix the merge conflicts here ? |
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Hey there, This looks like a reasonable chance, but we do not feel confident without some test coverage. Could you please add some tests and rebase? Thanks! 😄 |
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This is a refactor of GH-1980. Originally I tried to do a straight rebase, but the code has changed too much.
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This is a refactor of GH-1980. Originally I tried to do a straight rebase, but the code has changed too much.
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This is a refactor of GH-1980. Originally I tried to do a straight rebase, but the code has changed too much.
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Jun 14, 2017
This is a refactor of GH-1980. Originally I tried to do a straight rebase, but the code has changed too much.
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This ended up going in via #3131, closing this one out. |
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Modern stub resolvers can be configured to always send EDNS(0)/RFC6891 extended requests to resolvers which, among other things, permits relaxation of the traditional 512 byte maximum UDP payload limit by sending a desired maximum size (usually 4k) and allowing the server to reduce as appropriate in the response frame.
Additionally, caching/recursive resolvers such as Unbound and BIND will prefer to use EDNS(0) when prefetching as well as honoring EDNS(0) when forwarding requests or performing recursion on behalf of a stub-resolver or other client.
This PR adds support for EDNS(0), if and only if set in the request frame; it relaxes certain Answer section limits and synchronizes Answer UDP trimming to match the requested EDNS(0) UDP maximum size.