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GPRS/GMM: Correctly look up MM Context in RA Update 

If a MS changes RA, the RA will arrive in the new cell using the old
TLLI (masked as foreign TLLI).  So we need to look-up the TLLI
in a special way, using the old RA as indicated in the 04.08 GMM
message.

There is still another bug remaining: As we somehow create a new LLC,
the sequence numbers of our responses start from 0 again, which is not
what the MS expects.  This needs to be fixed in a follow-up patch.
This commit is contained in:
Harald Welte 2010-12-23 23:34:43 +01:00
parent 985263e55f
commit f6bd340df6
2 changed files with 19 additions and 1 deletions
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1
openbsc/src/gprs/gprs_gmm.c
View File

@ -899,6 +899,7 @@ static int gsm48_rx_gmm_ra_upd_req(struct sgsn_mm_ctx *mmctx, struct msgb *msg,
}
/* Look-up the MM context based on old RA-ID and TLLI */
mmctx = sgsn_mm_ctx_by_tlli(msgb_tlli(msg), &old_ra_id);
if (!mmctx || mmctx->mm_state == GMM_DEREGISTERED) {
/* The MS has to perform GPRS attach */
DEBUGPC(DMM, " REJECT\n");

19
openbsc/src/gprs/gprs_sgsn.c
View File

@ -82,6 +82,12 @@ static int ra_id_equals(const struct gprs_ra_id *id1,
id1->lac == id2->lac && id1->rac == id2->rac);
}
/* See 03.02 Chapter 2.6 */
static inline uint32_t tlli_foreign(uint32_t tlli)
{
return ((tlli | 0x80000000) & ~0x40000000);
}
/* look-up a SGSN MM context based on TLLI + RAI */
struct sgsn_mm_ctx *sgsn_mm_ctx_by_tlli(uint32_t tlli,
const struct gprs_ra_id *raid)
@ -96,7 +102,8 @@ struct sgsn_mm_ctx *sgsn_mm_ctx_by_tlli(uint32_t tlli,
}
tlli_type = gprs_tlli_type(tlli);
if (tlli_type == TLLI_LOCAL) {
switch (tlli_type) {
case TLLI_LOCAL:
llist_for_each_entry(ctx, &sgsn_mm_ctxts, list) {
if ((ctx->p_tmsi | 0xC0000000) == tlli ||
(ctx->p_tmsi_old && (ctx->p_tmsi_old | 0xC0000000) == tlli)) {
@ -104,6 +111,16 @@ struct sgsn_mm_ctx *sgsn_mm_ctx_by_tlli(uint32_t tlli,
return ctx;
}
}
break;
case TLLI_FOREIGN:
llist_for_each_entry(ctx, &sgsn_mm_ctxts, list) {
if (tlli == tlli_foreign(ctx->tlli) &&
ra_id_equals(raid, &ctx->ra))
return ctx;
}
break;
default:
break;
}
return NULL;