26 lines
1.3 KiB
Markdown
26 lines
1.3 KiB
Markdown
# Proposal to do SRV lookups after .well-known to discover homeservers
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Currently there is a logistical error proposed by [MSC1708](https://github.com/matrix-org/matrix-doc/pull/1708)
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which results in some homeservers unable to migrate to the new functionality
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proposed by [MSC1711](https://github.com/matrix-org/matrix-doc/pull/1711). This
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can happen if the delegated homeserver cannot obtain a valid TLS certificate for
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the domain, and an SRV record is used for backwards compatibility reasons.
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Specifically, in order to be compatible with requests from both Synapse 0.34 and 1.0,
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servers can have both a SRV and a .well-known file, with Synapse presenting a certificate
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corresponding to the target of the .well-known. Synapse 0.34 is then happy because it
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will follow the SRV (and won't care about the incorrect certificate); Synapse 1.0 is
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happy because it will follow the .well-known (and will see the correct cert).
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## Proposal
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We change the order of operations to perform a .well-known lookup before falling
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back to resolving the SRV record. This allows for domains to delegate to other
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hostnames and maintains backwards compatibility with older homeservers.
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## Tradeoffs
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More HTTP hits will be made due to the .well-known lookup being first. This is
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somewhat mitigated by servers caching the responses appropriately, and using
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connection pools where possible.
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