OsmoSGSN [PATCH], Network Service

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Michal Grznár mihal.grznar at gmail.com
Wed May 28 12:38:52 UTC 2014


Hi, it wasn´t handly written diffs but here I send diff made by using git
diff. And the problem you can see in packets with number 27-40 (especially
see in number 30 you see there the old tlli and newly generated P-TMSI in
message attach accept and in number 31 there is new TLLI which is the same
as generated P-TMSI in previous message) and that is the problem I needed
to solve, that the new TLLI was not LOCAL.

regards Michal


2014-05-23 13:16 GMT+02:00 Holger Hans Peter Freyther <holger at freyther.de>:

> On Fri, May 23, 2014 at 11:44:40AM +0200, Michal Grznár wrote:
>
> Hi,
>
> > And the problem was as I said in Imsi attach procedure new TLLI == new
> > allocated P-tmsi, and there was a problem that the function
>  gprs_tmsi2tlli()
> > function there was not called and so I had to mask the upper bits in
> > function where the p-tmsi is allocated, there is also a pcap trace where
> > you can see it.
>
> Could you please elaborate of what/were (e.g. packet numbers) we
> can see "it" and what it should be instead? And please use "git diff"
> or preferable "git commit" and git format-patch. The "diff" you include
> is hand-written and sadly not usable because of this.
>
> And as written by Harald before. The place you patch is not correct.
> The method you patch should generate a unique P-TMSI. It might should
> mask some of the higher bits. But you need to look at the callers of
> this function if the tlli is not updated.
>
> e.g. in src/gprs/gprs_gmm.c you will see something like this:
>
>         ctx->p_tmsi = sgsn_alloc_ptmsi();
> #endif
>
>         /* Even if there is no P-TMSI allocated, the MS will switch from
>          * foreign TLLI to local TLLI */
>         ctx->tlli_new = gprs_tmsi2tlli(ctx->p_tmsi, TLLI_LOCAL);
>
>         /* Inform LLC layer about new TLLI but keep old active */
>         gprs_llgmm_assign(ctx->llme, ctx->tlli, ctx->tlli_new,
>                           GPRS_ALGO_GEA0, NULL);
>
> So this call to gprs_tmsi2tlli will make sure that 0xc0000000 will
> be set. In fact I see two calls to sgsn_alloc_ptmsi and both of them
> do the above and assign the new tlli to the context. So please could
> you try to explain what you are trying to solve?
>
> holger
>
>
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diff --git a/home/michal/Plocha/gprs_sgsn_before_patch.c b/home/michal/Plocha/gp
index 753d85f..f637a82 100644
--- a/home/michal/Plocha/gprs_sgsn_before_patch.c
+++ b/home/michal/Plocha/gprs_sgsn_patch.c
@@ -361,7 +361,7 @@ uint32_t sgsn_alloc_ptmsi(void)
        uint32_t ptmsi;
 
 restart:
-       ptmsi = rand();
+       ptmsi = rand() | 0xc0000000; //because of GPRS IMSI ATTACH
        llist_for_each_entry(mm, &sgsn_mm_ctxts, list) {
                if (mm->p_tmsi == ptmsi)
                        goto restart;
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diff --git a/home/michal/Plocha/gprs_ns_before_patch.c b/home/michal/Plocha/gprs_ns_patch.c
index c939003..1bc965e 100644
--- a/home/michal/Plocha/gprs_ns_before_patch.c
+++ b/home/michal/Plocha/gprs_ns_patch.c
@@ -1217,16 +1217,14 @@ int gprs_ns_process_msg(struct gprs_ns_inst *nsi, struct msgb *msg,
 
        switch (nsh->pdu_type) {
        case NS_PDUT_ALIVE:
-               /* If we're dead and blocked and suddenly receive a
-                * NS-ALIVE out of the blue, we might have been re-started
-                * and should send a NS-RESET to make sure everything recovers
-                * fine. */
-
-LOGP(DNS, LOGL_INFO, "Rx NS ALIVE\n");         
-if ((*nsvc)->state == NSE_S_BLOCKED)
-                       rc = gprs_ns_tx_reset((*nsvc), NS_CAUSE_PDU_INCOMP_PSTATE);
-               else
-                       rc = gprs_ns_tx_alive_ack(*nsvc);
+               LOGP(DNS, LOGL_INFO, "Rx NS ALIVE\n");
+               rc = gprs_ns_tx_alive_ack(*nsvc);
+               /*mark NS-VC as unblocked and active*/
+               (*nsvc)->state = NSE_S_ALIVE;
+               (*nsvc)->remote_state = NSE_S_ALIVE;
+               /*Initiate TEST proc.: Send ALIVE_ACK and start timer*/
+               rc = gprs_ns_tx_simple((*nsvc), NS_PDUT_ALIVE_ACK);
+               nsvc_start_timer((*nsvc), NSVC_TIMER_TNS_TEST);
                break;
        case NS_PDUT_ALIVE_ACK:
                /* stop Tns-alive and start Tns-test */

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