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bcda834980
This doesn't actually change functionality, because this is how std::unordered_map worked anyway... ...but it's better for us to be explicit, I think.
54 lines
2.7 KiB
Markdown
54 lines
2.7 KiB
Markdown
# DNS.mitm
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As of 0.18.0, atmosphère provides a mechanism for redirecting DNS resolution requests.
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By default, atmosphère redirects resolution requests for official telemetry servers, redirecting them to a loopback address.
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## Hosts files
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DNS.mitm can be configured through the usage of a slightly-extended `hosts` file format, which is parsed only once on system startup.
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In particular, hosts files parsed by DNS.mitm have the following extensions to the usual format:
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+ `*` is treated as a wildcard character, matching any collection of 0 or more characters wherever it occurs in a hostname.
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+ `%` is treated as a stand-in for the value of `nsd!environment_identifier`. This is always `lp1`, on production devices.
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If multiple entries in a host file match a domain, the last-defined match is used.
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Please note that homebrew may trigger a hosts file re-parse by sending the extension IPC command 65000 ("AtmosphereReloadHostsFile") to a connected `sfdnsres` session.
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### Hosts file selection
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Atmosphère will try to read hosts from the following file paths, in order, stopping once it successfully performs a file read:
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+ (emummc only) `/atmosphere/hosts/emummc_%04lx.txt`, formatted with the emummc's id number (see `emummc.ini`).
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+ (emummc only) `/atmosphere/hosts/emummc.txt`.
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+ (sysmmc only) `/atmosphere/hosts/sysmmc.txt`.
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+ `/atmosphere/hosts/default.txt`
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If `/atmosphere/hosts/default.txt` does not exist, atmosphère will create it to contain the defaults.
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### Atmosphère defaults
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By default, atmosphère's default redirections are parsed **in addition to** the contents of the loaded hosts file.
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This is equivalent to thinking of the loaded hosts file as having the atmosphère defaults prepended to it.
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This setting is considered desirable, because it minimizes the telemetry risks if a user forgets to update a custom hosts file on a system update which changes the telemetry servers.
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This behavior can be opted-out from by setting `atmosphere!add_defaults_to_dns_hosts = u8!0x0` in `system_settings.ini`.
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The current default redirections are:
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```
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# Nintendo telemetry servers
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127.0.0.1 receive-%.dg.srv.nintendo.net receive-%.er.srv.nintendo.net
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```
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## Debugging
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On startup (or on hosts file re-parse), DNS.mitm will log both what hosts file it selected and the contents of all redirections it parses to `/atmosphere/logs/dns_mitm_startup.log`.
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In addition, if the user sets `atmosphere!enable_dns_mitm_debug_log = u8!0x1` in `system_settings.ini`, DNS.mitm will log all requests to GetHostByName/GetAddrInfo to `/atmosphere/logs/dns_mitm_debug.log`. All redirections will be noted when they occur.
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## Opting-out of DNS.mitm entirely
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If you wish to disable DNS.mitm entirely, `system_settings.ini` can be edited to set `atmosphere!enable_dns_mitm = u8!0x0`.
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