53 lines
2.1 KiB
ReStructuredText
53 lines
2.1 KiB
ReStructuredText
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DNS caching
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===========
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User experience may be greatly improved when dns is accelerated. Also, it
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seems like a good idea to keep the number of packages being exchanged
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between node and gateway as small as possible. In order to do this, a
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DNS cache may be used on a node. The dnsmasq instance listening on port
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53 on the node will be reconfigured to answer requests, use a list of
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upstream servers and a specific cache size if the options listed below are
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added to site.conf. Upstream servers are the DNS servers which are normally
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used by the nodes to resolve hostnames (e.g. gateways/supernodes).
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There are the following settings:
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servers
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cacheentries
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To use the node's DNS server, both options should be set. The node will cache at
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most 'cacheentries' many DNS records in RAM. The 'servers' list will be used to
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resolve the received DNS queries if the request cannot be answered from
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cache. Gateways should announce the "next node" address via DHCP and RDNSS (if
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any). Note that not setting 'servers' here will lead to DNS not working: Once
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the gateways all announce the "next node" address for DNS, there is no way for
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nodes to automatically determine DNS servers. They have to be baked into the
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firmware.
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If these settings do not exist, the cache is not initialized and RAM usage will
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not increase.
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When next_node.name is set, an A record and an AAAA record for the
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next-node IP address are placed in the dnsmasq configuration. This means that
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the content of next_node.name may be resolved even without upstream connectivity.
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It is suggested to use the same name as the DNS server provides:
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e.g. nextnode.location.community.example.org (This way the name also works if a
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client uses static DNS Servers). Hint: If next_node.name does not contain a dot
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some browsers would open the searchpage instead.
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::
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dns = {
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cacheentries = 5000,
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servers = { '2001:db8::1', },
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},
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next_node = {
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name = { 'nextnode.location.community.example.org', 'nextnode', 'nn' },
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ip6 = '2001:db8:8::1',
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ip4 = '198.51.100.1',
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}
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The cache will be initialized during startup.
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Each cache entry will occupy about 90 bytes of RAM.
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