Mdns minimal mode #89
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Attempt to make nss code more readable by moving some conditional stuff to separate functions. Reduces ifdefs inside the resolution functions. Use file path to signal when minimal or full variant is being compiled. Move file opening only after it has correct mode.
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For .local domain mdns plugin behaved the same way as mdns_minimal, when configuration file were not present. Extend such behaviour to reverse queries as well. Because currently they are not changed by configuration, just add a check whether the config file is present in gethostbyaddr queries. That should allow to reduce used plugins to just non-minimal variants, which have minimal mode activated by not present config file. It adds single extra fopen compared to pure minimal plugins resolution call.
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zdohnal
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Aug 2, 2023
| @@ -78,14 +78,17 @@ addresses via mDNS, most people will want to use | |||
| `libnss_mdns.so.2` or `libnss_mdns6.so.2` in such a | |||
| situation causes long timeouts when resolving hosts since most modern | |||
| Unix/Linux applications check for IPv6 addresses first, followed by a | |||
| lookup for IPv4. | |||
| lookup for IPv4. When these plugins cannot open mdns.allow config file, | |||
| they will behave like minimal version below. | |||
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Mention the downside of having mdns.allow as well.
| /* Reverse addresses are not supported in config file. | ||
| * They just check if config is missing to enable minimal mode | ||
| * from non-minimal plugins. */ | ||
| static int avahi_is_file_present(const char *path) { |
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What about rather call it _nss_mdns_file_exists() and _nss_mdns_is_link_local() (and switch logic in the function to match the name) . They are static functions for this module with no relevance to avahi.
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After discussion on Fedora mailing list we have come to conclusion that non-minimal mdns plugin version might be sufficient, if it were able to mimick mdns_minimal version in case of missing or unreadable
/etc/mdns.allowfile. Handling of .local domain were already the same. This change improves readability a bit and does similar thing for reverse addresses lookups. Somdns4behaves exactly likemdns4_minimal, with an exception it tries to open /etc/mdns.allow first.