dnsc: Fallback to getaddrinfo without any DNS servers #1195
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sreimers
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Oct 11, 2024
sreimers
reviewed
Oct 11, 2024
sreimers
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On current Android and iOS platforms, access to the system DNS server lists is restricted (e.g. https://developer.android.com/about/versions/oreo/android-8.0-changes.html#o-pri). Even when it is available, it is often broken in certain situations (e.g. https://forums.developer.apple.com/forums/thread/75449). It is therefore practically impossible to perform manual DNS queries as
retypically does for SIP.Currently,
repartially supports these platforms by offering the option to usegetaddrinfo, but even this fails when no DNS servers are known due to/etc/resolv.confnot being accessible. Note that manually specifying 'well-known' DNS servers like8.8.8.8is not an acceptable workaround for private networks. Nor is it acceptable to manually specify a fixed private DNS, IT admins will require DNS to be centrally distributed via DHCP.This change fixes the above use case by making two changes:
getaddrinfois configured.getaddrinfodoesn't need to know the servers so we don't need to reject it withEINVAL.getaddrinfois configured and there are no DNS servers, if SIP transport is set but not the port (e.g.sip:my-proxy.com;transport=tls, use the default transport port and do a A / AAAA query instead of attempting a SRV / NAPTR that cannot possibly work.I have tested this on Android where
dns_srv_getalways fails to return any servers. Previously Baresip would fail to even register, with this change it is able to register and make calls using a URI such assip:my-proxy.com;transport=tls.