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diff --git a/doc/overview.org b/doc/overview.org index d399a16..019638d 100644 --- a/doc/overview.org +++ b/doc/overview.org @@ -1,5 +1,161 @@ +* Goals + - auto configuration + - internet on wan port automatically detected and shared + - cloud without internet access announces the sad fact + - no persistent writes during normal use (e.g. avoid uci commit for + things like internet up/down) + - splash status of users is distributed + - tbc... + +* Networks + - 10.17.?.0/? - semi-public IPv4 + - each GW and each client gets an address in this range + - routes to IPv4 internet + - GW addresses a managed by P2P table + - site-wide global IPv6 + - every node & client + - public in IPv6 internet + - automatic address for mesh nodes, DHCPv6 for clients + - mesh-wide link-local IPv6 + - used for UDP broadcasts and default for all other node2node + communication + - Robinson net (see below) + +* State machines (FSMs) + State machines are implemented using the /sbin/fsm script (see + below). +** Network + Controls the different network states that result of the local + availability of internet connection and the state of the cloud. + +#+begin_dot FSM_Update.png -Tpng +digraph dsd { + Boot -> {Queen; Drone; Robinson}; + Queen -> {Ghost; Robinson}; + Ghost -> {Queen; Drone; Robinson}; + Drone -> {Queen; Robinson}; + Robinson -> {Queen; Drone}; +} +#+end_dot +*** Boot + The node has recently started and is still looking for its mommy. + - gw_mode=0 +*** Queen + The node as a working direct internet connection. + - gw_mode=1, bandwidth >> 0 + - DHCP range: derived from router-id +*** Ghost + The node was a queen recently (within the last 3600s), but now its + direct internet access does not work anymore. There still is a + working connection in the cloud. + - gw_mode=0 + - all traffic redirected to another GW (determine how?) + - no new DHCP leases (handled via BATMAN by GW nodes) +*** Drone + The node has no direct internet connection but is in a cloud with + working internet connection. + - gw_mode=0 + - no DHCP (handled via BATMAN by GW nodes) +*** Robinson + The node is in a cloud without working internet connection. + - gw_mode=1, bandwidth = 0+epsilon + - DHCP range: ??? + - fake DNS, resolving all A queries to a the Robinson net; host + part of the addr is derived from hash of name to resolve + - all internet traffic is redirected to a local httpd, yelling the + network status and explaining FFJ + +** Update + Implements all-or-nothing update of nodes (e.g. if the network + protocol changes incompatibly). Synchronized via p2ptable + firmware-versions with the fields + - machine_id + - current firmware (sha256) + - target firmware (sha256); empty if no update shall be performed + - time target: set by admin to time when update shall happen + - acknowledge time: set by device to time target once ready for an + upgrade + + The security model relies on the requirement to store the update in + a secure location on the node. This is intended to happen via ssh. + +#+begin_dot FSM_Update.png -Tpng +digraph { + Idle -> Ready; + Ready ->{ Scheduled; Idle }; + Scheduled ->{Applying; Idle }; +} +#+end_dot +*** Idle + Current firmware is installed and no update is required/possible. +*** Ready + Target firmware is stored in /tmp/firmware-update and verified. +*** Scheduled + Node has received target time and copied the value to + acknowledge time. And this time point has not passed, yet. +*** Applying + For all nodes of the firmware-versions table one of the following + conditions hold: + 1. target firmware, update time target and acknowledge update time + are empty + 2. current time > time target == acknowledge time; And target + firmware points to a new version that is locally stored an + verified + + Once this state is reached the update is performed. + * Components -** HBBP +** Firmware ID + /etc/firmware stores sha256 of the current firmware. If a node is + intensively modified after flashing the value is replaced (e.g. by + "custom"). +** Router IDs + - unique ID :: all routers use /proc/sys/kernel/random/boot_id as + unique ID + - gateway ID :: 0..254, given only to Queens and Ghosts, managed + via p2ptbl "gwid" +** Connectivity tests + - /sbin/test_connectivity <internet|vpn> + - ping some test hosts over a specified interface; if at least one + responds, we are online + - returns connectivity status + - TODO: ping multiple hosts in parallel +** Finite state machine + FSMs are implemented using + - /sbin/fsm :: a script to monitor and change the state: + - fsm watch <name> :: check whether a state change shall occur + - fsm change <name> <new-state> :: force a state transition + - /etc/fsm/<name>/initial_state :: the state set on startup + - /etc/fsm/<name>/watch/<state> :: watch scripts that print the + next state; If that file does not exist + /etc/fsm/<name>/watch/default is tried. The script may assume that: + - the state they denote is the current state reached via + non-failing transition functions + - the CWD is /etc/fsm/<name>/watch + - cmd line param $1 is set to the current state + - /etc/fsm/<name>/trans/<transition> :: scripts implementing the + transition between states, probed in the following order: + 1. If a transition name <oldstate>-<newstate>.trans exists it + is executed + 2. Otherwise first <oldstate>.leave and then <newstate>.enter + are executed if they exist. + 3. If one of them does not exist default.enter and + default.leave is tried. + 4. If none exists, the state transition happens, but has no + effect. + + The script may assume that: + - the CWD is /etc/fsm/<name>/trans + - cmd line param $1 is set to the old state and $2 is set to + the new state + - it is called exactly once for a state change + - /var/fsm/<name> :: a tmpfs-based storage of the current state + + TODO: + - proper handling of errors occurring in one of the many scripts + (e.g. changing to an error-state or rebooting the device). + - handle invalid states +** HBBP: Home-Based Broadcast Protocol - UDP `broadcast` and `listener` - transmit a zero-terminated key and an optional arbitrary-binary payload: key is comparable to an HTTP URI, the payload to HTTP @@ -49,3 +205,26 @@ *** Gossip protocol HBBP with key "p2ptbl/<table-name>" and gzip-compressed shuffled random subsets of a table as payload. +** Preferred gateway + - each node has a preferred gateway, which is used to access the + internets if no local connection is available + - how to determine? ... extract from batman? +** Robinson net + - captured .mil-network (/16) + - when no internet is available, fake DNS responses resolve to a + stable address in this range (via hash of name) + - once internet becomes available and the names known, a + redirection is set up via iptables + - after a certain time, the redirection is forgotten + +* Thoughts, Fragments, Questions + - VPN node takes part in batman mesh? + - no (memory intensive) NAT on mesh nodes + - roaming without sticking to the old gateway + - continuous bandwidth tests for internet uplinks to update + advertised batman gw capabilities? + - occasional flooding to/from VPN node (with idle QoS class) + - IPv6: use multiple routers for roaming w/o breaking existing + connections? + - how to support uplinks that do not use the WAN port (e.g. 3G + modems)? |