name mode size
test 040000
Makefile 100644 188B
README 100644 12.4kB
config.h 100644 3.27kB
defs.h 100644 1.18kB
fix_lumps.h 100644 2.34kB
h_table.c 100644 8.95kB
h_table.h 100644 7.3kB
lock.c 100644 11.55kB
lock.h 100644 3.18kB
sip_msg.c 100644 16.58kB
sip_msg.h 100644 1.35kB
t_cancel.c 100644 3.14kB
t_cancel.h 100644 2.36kB
t_dlg.c 100644 1.2kB
t_dlg.h 100644 1.26kB
t_funcs.c 100644 7.03kB
t_funcs.h 100644 3.53kB
t_fwd.c 100644 12.08kB
t_fwd.h 100644 1.83kB
t_hooks.c 100644 2.25kB
t_hooks.h 100644 5.42kB
t_lookup.c 100644 28.18kB
t_lookup.h 100644 2.72kB
t_msgbuilder.c 100644 14.01kB
t_msgbuilder.h 100644 3.23kB
t_reply.c 100644 32.5kB
t_reply.h 100644 4.04kB
t_stats.c 100644 4.07kB
t_stats.h 100644 2.47kB
test.c 100644 1.93kB
timer.c 100644 24.26kB
timer.h 100644 3.26kB
tm.c 100644 16.31kB
tm_load.c 100644 3.03kB
tm_load.h 100644 2.21kB
uac.c 100644 33.09kB
uac.h 100644 4.16kB
ut.h 100644 1.99kB
# # $Id$ # # TM Module README # # Module depends on: none # TM Module enables stateful processing of SIP transactions. The main use of stateful logic, which is costly in terms of memory and CPU, is some services inherently need state. For example, transaction-based accounting (module acc) needs to process transaction state as opposed to individual messages, and any kinds of forking must be implemented statefuly. Other use of stateful processing is it trading CPU caused by retransmission processing for memory. That makes however only sense if CPU consumption per request is huge. For example, if you want to avoid costly DNS resolution for every retransmission of a request to an unresolveable destination, use stateful mode. Then, only the initial message burdens server by DNS queries, subsequent retranmissions will be dropped and will not result in more processes blocked by DNS resolution. The price is more memory consumption and higher processing latency. From user's perspective, there are two major functions : t_relay and t_relay_to. Both setup transaction state, absorb retransmissions from upstream, generate downstream retransmissions and correlate replies to requests. t_relay forwards to current uri (be it original request's uri or a uri changed by some of uri-modifying functions, such as sethost). t_relay_to forwards to a specific address. In general, if TM is used, it copies clones of received SIP messages in shared memory. That costs the memory and also CPU time (memcpys, lookups, shmem locks, etc.) Note that non-TM functions operate over the received message in private memory, that means that any core operations will have no effect on statefuly processed messages after creating the transactional state. For example, calling addRecordRoute *after* t_relay is pretty useless, as the RR is added to privately held message whereas its TM clone is being forwarded. TM is quite big and uneasy to programm -- lot of mutexes, shared memory access, malloc & free, timers -- you really need to be careful when you do anything. To simplify TM programming, there is the instrument of callbacks. The callback mechanisms allow programmers to register their functions to specific event. See t_hooks.h for a list of possible events. Other things programmers may want to know is UAC -- it is a very simplictic code which allows you to generate your own transactions. Particularly useful for things like NOTIFYs or IM gateways. The UAC takes care of all the transaction machinery: retransmissions , FR timeouts, forking, etc. See t_uac prototype in uac.h for more details. Who wants to see the transaction result may register for a callback. Exported parameters: -------------------- Name: fr_timer Type: int (seconds) Default: FR_TIME_OUT=30 Desc: timer which hits if no final reply for a request or ACK for a negative INVITE reply arrives Name: fr_inv_timer Type: int(seconds) Default: INV_FR_TIME_OUT=120 Desc: timer which hits if no final reply for an INVITE arrives after a provisional message was received Name: wt_timer Type: int (seconds) Default: WT_TIME_OUT=5 Desc: time for which a transaction stays in memory to absorb delayed messages after it completed; also, when this timer hits, retransmission of local cancels is stopped (a puristic but complex behviour would be not to enter wait state until local branches are finished by a final reply or FR timer -- we simplified) Name: delete_timer Type: int (seconds) Default: DEL_TIME_OUT=2 Desc: time after which a to-be-deleted transaction currently ref-ed by a process will be tried to be deleted again Name: retr_timer1p1, 2, 3 Type: int (seconds) Default: RETR_T1=1, 2*RETR_T1, 4*RETR_T1 Desc: retransmission period Name: retr_timer2 Type: int (seconds) Default: RETR_T2=4 Desc: maximum retransmission period Name: noisy_ctimer Type: int (boolean) Default: 0 (FALSE) Desc: if set, on FR timer INVITE transactions will be explicitly cancelled if possible, silently dropped otherwise; preferably, it is turned off to allow very long ringing; this behaviour is overridden if a request is forked, or some functionality explicitly turned it off for a transaction (like acc does to avoid unaccounted transactions due to expired timer) Exported Functions: ------------------- For use in scripts, t_relay_to and t_relay are design. All other functions are advanced and should be used with care. Name: t_relay_to Params: ip address, port number Desc: relay a message statefuly to a fixed destination; this along with t_relay is the function most users want to use -- all other are mostly for programming; programmers interested in writing TM logic should review how t_relay is implemented in tm.c and how TM callbacks work Name: t_relay Params: 0 Desc: relay a message statefuly to destination indicated in current URI; (if the original URI was rewritten by UsrLoc, RR, strip/prefix, etc., the new URI will be taken); returns a negative value on failure -- you may still want to send a negative reply upstream statelessly not to leave upstream UAC in lurch Example: if (!t_relay()) { sl_reply_error(); break; }; Name: t_on_negative Params: reply_route Desc: sets reply routing block, to which control is passed after a transaction completed with a negative result but before sending a final reply; In the refered block, you can either start a new branch (good for services such as forward_on_no_reply) or send a final reply on your own (good for example for message silo, which received a negative reply from upstream and wants to tell upstream "202 I will take care of it"); Note that the set of command which are useable within reply_routes is strictly limited to rewriting URI, initiating new branches, logging, and sending stateful replies (t_reply). Any other commands may result in unpredictable behaviour and possible server failure. Note that whenever reply_route is entered, uri is reset to value which it had on relaying. If it temporarily changed during a reply_route processing, subsequent reply_route will ignore the changed value and use again the original one. Example: route { t_on_negative("1"); t_relay(); } reply_route[1] { revert_uri(); setuser("voicemail"); append_branch(); } see test/onr.cfg for a more complex example of combination of serial with parallel forking Name: append_branch (actually part of core now) Params: uri Desc: adds a new destination to destination set; if used, a subsequent call to t_relay (or t_forward_nonack, on which t_relay is based) than introduces a new branch and forks a transaction; append_branch may also be called from reply processing -- this may be particularly useful for services such as "fork_on_no_reply" Name: append_branch Params: 0 Desc: similarly to t_fork_to, it extends destination set by a new entry; the difference is that current uri is taken as new entry; Example: set_user("john"); t_fork(); set_user("alice"); t_fork(); t_relay(); ----- ---- ---- medium-advanced commands here --- on ----- Name: t_newtran Params: 0 Desc: creates a new transaction, returns a negative value on error; this is the only way a script can add a new transaction in an atomic way; typically, it is used to deploy a UAS Example: see test/uas.cfg: if (t_newtran()) { log("UAS logic"); t_reply("999","hello"); } else sl_reply_error(); Name: t_reply Params: code, reason phrase Desc: sends a stateful reply after a transaction has been established; see t_newtran for usage; ----- only --- advanced --- commands --- from --- here --- on ----- Name: t_lookup_request Params: 0 Desc: checks if a transaction exists; returns a positive value if so, negative otherwise; most likely you will not want to use it, as a typicall application of a looku-up is to introduce a new transaction if none was found; however this is safely (atomically) done using t_newtran Name: t_retransmit_reply Params: 0 Desc: retransmits a reply sent previously by UAS transaction Name: t_release Params: 0 Desc: remove transaction from memory (it will be first put on a wait timer to absorb delayed messages) Name: t_forward_nonack Params: ip, port Desc: mainly for internal -- forward a non-ACK request statefuly Name: register_tmcb Params: callback type, callback function Desc: for programmatic use only -- register a function to be called back on an event; see t_hooks.h for more details Name: load_tm Params: *import_structure Desc: for programmatic use only -- import exported TM functions; see the acc module for an example of use External Usage of TM --------------------- There are applications which would like to generate SIP transactions without too big involvement in SIP stack, transaction management, etc. An example of such an application is sending instant messages from a website. To address needs of such apps, SER accepts requests for new transactions via fifo pipes too. If you want to enable this feature, start FIFO server with configuration option fifo="/tmp/ser_fifo" Then, an application can easily launch a new transaction by writing a transaction request to this named pipe. The request must follow very simple format, which is :t_uac_from:[<file_name>]\n <method>\n <sender's uri>\n <dst uri>\n <CR_separated_headers>\n <body>\n .\n \n (Filename is to where a report will be dumped. ser assumes /tmp as file's directory.) Note the the request write must be atomic, otherwise it might get intermixed with writes from other writers. You can easily use it via Unix command-line tools, see the following example: --- [jiri@bat jiri]$ cat > /tmp/ser_fifo :t_uac_from:xxx MESSAGE header:value foo:bar bznk:hjhjk p_header: p_value body body body yet body end of body . or cat test/transaction.fifo > /tmp/ser_fifo Defines ------- - ACK_TAG enables stricter matching of acknowledgemnts including to-tags; without it, to-tags are ignored; it is disabled by default for two reasons: a) it eliminates an unlikely race condition in which transaction's to-tag is being rewritten by a 200 OK whereas an ACK is being looked up by to-tag b) it makes UACs happy who set wrong to-tags It should not make a difference, as there may be only one negative reply sent upstream and 200/ACKs are not matched as they consititute another transaction. It will make no difference at all when the new magic cookie matching is enabled anyway. - CANCEL_TAG similarly enables strict matching of CANCELs including to-tags -- act of mercy to UACs, who screw up the to-tags (however, it still depends on how forgiving the downstream UAS is); like with ACK_TAG, all this complex transactions matching goes with RFC3261's magic cookie away anyway Known Issues ----------- - we don't have authentication merging on forking - local ACK/CANCELs copy'n'pastes Route and ignores deleted Routes - 6xx should be delayed - possibly, performance could be improved by not parsing non-INVITEs, as they do not be replied with 100, and do not result in ACK/CANCELs, and other things which take parsing. However, we need to rethink whether we don't need parsed headers later for something else. Remember, when we now conserver a request in sh_mem, we can't apply any pkg_mem operations to it any more. (that might be redesigned too) - another performance improvement may be achieved by not parsing CSeq in replies until reply branch matches branch of an INVITE/CANCEL in transaction table - t_replicate should be done more cleanly -- Vias, Routes, etc. should be removed from a message prior to replicating it - SNMP support - lookup fails to recognize subsequent requests which have additional leading spaces in header field values - make UAC session-aware (as opposed to just transaction aware) -- needed for keeing SUB-NOT dialog state, etc. Currently, there are only place-holders for in in TM. - places labeled with "HACK" strongly deserve beautification * *************************************************** * IMPORTANT NOTE * * All UACs but t_uac_dlg are being deprecated now * and will be removed from future versions of TM * module. Eliminate all dependancies on them asap. * * ****************************************************