93 lines
3.3 KiB
Plaintext
93 lines
3.3 KiB
Plaintext
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== mgw_nat ==
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== files ==
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=== mgw_nat_app.erl ===
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This file contains the OTP application wrapper for running mgw_nat as an
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OTP application. It exports the start/2 and stop/1 functions which are
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required for application:{start,stop}(mgw_nat) to work.
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There is also mgw_nat_app:reload_config/0, which will re-read the config
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file given to the erl machine as '-config' shell argument.
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=== mgw_nat_sup.erl ===
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This is the supervisor code, it starts:
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* one mgw_nat_adm process
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* one mgw_nat_usr for each signalling link in the config file
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=== mgw_nat_adm.erl ===
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This is a permanent server running under the supervisor, taking care of
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realoading configuration or dumping some information as well as casting
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messages to all of the mgw_nat_usr children.
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=== mgw_nat_usr.erl ===
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This is a gen_server OTP behavior which wraps the sctp_helper. Among
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the arguments passed to the sctp_helper are the 'rewrite_act_mod', whcih
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is the name of the Erlang module actually doing the rewriting.
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=== sctp_helper.erl ===
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Erlang module for wrapping both a listen-type and a connect-type SCTP
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connection, taking care of re-connects, etc. Each actual user payload
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message is handled via handle_rx_data/5, which will in turn call the
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rewrite_actor/5 function of the 'rewrite_act_mod'
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=== mgw_nat_act_vfuk_onw ===
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This is a rewrite actor module for patching the advertised CAMEL Phase
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during Location update of inbound roaming subsribers.
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the rewrite_actor/5 is first called with sctp as the first element, at
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which time mgw_nat:mangle_rx_data/4 is being called. mangle_rx_data
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will parse all higher level protocols (m2ua/mtp3/sccp/tcap/map),
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and each time one protocol layer has been decoded, it will again call
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the rewrite_actor/5 function with the first argument set to the protocol
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in question.
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m2ua/mtp3/sccp is handled without modification by the default clause of
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rewrite_actor/5.
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Once the map level is reached, the mangle_map_camel_phase/3 function is
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called. If the direction is STP->MSC, then the message is in the
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direction we are not interested in.
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In the MSC->STP direction, we decode the called_party_addr, do a global
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title match on it. If there is a match against the int_camel_ph_tbl,
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then the hierarchical record data structure is walked by
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osmo_util:tuple_walk/3 which will call caleph_twalk_cb/3. If there is a
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match on UpdateLocationArg, the supportedCamelPhases is rewritten
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accordingly.
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=== mgw_nat_act_bow_onw.erl ===
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This is a much more complex rewrite actor doing a lot of different
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rewrites whihc are not described here in detail.
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=== imsi_list.erl ===
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maintains a list of 1:1 IMSI mappings, internally represented by tw
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gb_tree's.
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* read_list/1 populates the gb_trees from an Erlang list
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* read_file/1 populates the gb_trees from a CSV file
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* match_imsi/3 matches an IMSI either in forward or reverse direction
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=== mangle_tt_sri_sm.erl ===
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Contains utility code for rewriting the translation type of the global
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title present in SRI-for-SM messages.
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=== sccp_masq.erl ===
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This code implements SCCP masquerading:
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The mgw_nat gateway has a pool of dynamically-allocated SCCP global
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titles. Whenever needed (decided by other code), the original GT is
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replaced with one dynamically allocated from the pool. If ther ever is
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a SCCP mesage directed at one of the dynamic addresses in response, the
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inverse translation back to the original address is performed.
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