2020-10-29 21:22:36 +01:00
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* The scanner, 2020-10-29, Hacking Villa Diesbach
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** Motivation
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- The purpose of cdist is to ensure systems are in a configured state
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- If systems reboot into a clean (think: netboot) state they are
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stuck in an unconfigured mode
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- We can either trigger *from* those machines
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- this is what cdist trigger is for
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- Or we can regulary *scan* for machines
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- This method does not need any modification to standard OS
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** How it works
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- cdist scan uses the all nodes multicast group ff02::1
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- It sends a ping packet there in regular intervals
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- This even works in non-IPv6 networks, as all operating systems
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are IPv6 capable and usually IPv6 enabled by default
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- Link local is always accessible!
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- cdist scan receives an answer from all alive hosts
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- These results are stored in ~/.cdist/scan/${hostip}
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- We record the last_seen date ~/.cdist/scan/${hostip}/last_seen
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- After a host is detected, cdist *can* try to configure it
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- It saves the result (+/- logging needs to be defined) in
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~/.cdist/scan/${hostip}/{config, install}_result
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- If logging is saved: maybe in ~/.cdist/scan/${hostip}/{config, install}_log
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- Final naming TBD
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** Benefits from the scanning approach
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- We know when a host is alive/dead
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- We can use standard OS w/o trigger customisation
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- Only requirement: we can ssh into it
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- Can make use f.i. of Alpine Linux w/ ssh keys feeding in
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- We can trigger regular reconfiguration
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- If alive && last_config_time > 1d -> reconfigure
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- Data can be exported to f.i. prometheus
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- Record when configured (successfully)
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- Record when seen
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- Enables configurations in stateless environments
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2020-10-29 23:16:08 +01:00
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** Sample output v2020-10-29
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23:14] bridge:~% sudo cdist scan -b -I wlan0 -vv
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VERBOSE: cdist: version 6.8.0-36-g91d99bf0
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VERBOSE: scan: Host fe80::21d:72ff:fe86:46b is alive
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VERBOSE: scan: Host fe80::ce2d:e0ff:fed4:2611 is alive
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VERBOSE: scan: Host fe80::21b:fcff:feee:f4c1 is alive
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VERBOSE: scan: Host fe80::e2ff:f7ff:fe00:20e6 is alive
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VERBOSE: scan: Host fe80::20d:b9ff:fe49:ac11 is alive
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VERBOSE: scan: Host fe80::9e93:4eff:fe6c:c1f4 is alive
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VERBOSE: scan: Host fe80::ce32:e5ff:fe79:7ea7 is alive
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VERBOSE: scan: Host fe80::219:d2ff:feb2:2e12 is alive
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VERBOSE: scan: Host fe80::d66d:6dff:fe33:e00 is alive
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VERBOSE: scan: Host fe80::21b:fcff:feee:f446 is alive
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VERBOSE: scan: Host fe80::21b:fcff:feee:f4b1 is alive
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VERBOSE: scan: Host fe80::20d:b9ff:fe4c:547d is alive
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VERBOSE: scan: Host fe80::bad8:12ff:fe65:313d is alive
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VERBOSE: scan: Host fe80::42b0:34ff:fe6f:f6f0 is alive
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VERBOSE: scan: Host fe80::ba69:f4ff:fec5:6041 is alive
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VERBOSE: scan: Host fe80::f29f:c2ff:fe7c:275e is alive
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VERBOSE: scan: Host fe80::ba69:f4ff:fec5:8db7 is alive
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VERBOSE: scan: Host fe80::42b0:34ff:fe6f:f863 is alive
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VERBOSE: scan: Host fe80::21b:fcff:feee:f4bc is alive
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...
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