sgsn: Re-add searching for MM ctx based on TLLI / P-TMSI matches
If an MM context cannot be found based on BBSGP info and a RA UPDATE
REQUEST is received, try to find an MM context with an P-TMSI from
which the TLLI could have been derived. This also checks, whether the
routing area matches.
This is similar to the old behaviour removed by the commits
"sgsn: Only look at TLLIs in sgsn_mm_ctx_by_tlli" and
"sgsn: Remove tlli_foreign2local", except that this will only
be done for RA UPDATE REQUESTs now.
Sponsored-by: On-Waves ehf
diff --git a/openbsc/src/gprs/gprs_gmm.c b/openbsc/src/gprs/gprs_gmm.c
index 5aea76f..d93ba3f 100644
--- a/openbsc/src/gprs/gprs_gmm.c
+++ b/openbsc/src/gprs/gprs_gmm.c
@@ -1172,13 +1172,33 @@
* if the TLLI matches foreign_tlli (P-TMSI). Note that this
* is an optimization to avoid the RA reject (impl detached)
* below, which will cause a new attach cycle. */
- }
+ /* Look-up the MM context based on old RA-ID and TLLI */
+ mmctx = sgsn_mm_ctx_by_tlli_and_ptmsi(msgb_tlli(msg), &old_ra_id);
+ if (mmctx) {
+ LOGMMCTXP(LOGL_INFO, mmctx,
+ "Looked up by matching TLLI and P_TMSI. "
+ "BSSGP TLLI: %08x, P-TMSI: %08x (%08x), "
+ "TLLI: %08x (%08x), RA: %d-%d-%d-%d\n",
+ msgb_tlli(msg),
+ mmctx->p_tmsi, mmctx->p_tmsi_old,
+ mmctx->tlli, mmctx->tlli_new,
+ mmctx->ra.mcc, mmctx->ra.mnc,
+ mmctx->ra.lac, mmctx->ra.rac);
- if (!mmctx || !gprs_ra_id_equals(&mmctx->ra, &old_ra_id) ||
+ mmctx->mm_state = GMM_COMMON_PROC_INIT;
+ }
+ } else if (!gprs_ra_id_equals(&mmctx->ra, &old_ra_id) ||
mmctx->mm_state == GMM_DEREGISTERED)
{
/* We cannot use the mmctx */
+ LOGMMCTXP(LOGL_INFO, mmctx,
+ "The MM context cannot be used, RA: %d-%d-%d-%d\n",
+ mmctx->ra.mcc, mmctx->ra.mnc,
+ mmctx->ra.lac, mmctx->ra.rac);
+ mmctx = NULL;
+ }
+ if (!mmctx) {
/* send a XID reset to re-set all LLC sequence numbers
* in the MS */
LOGMMCTXP(LOGL_NOTICE, mmctx, "LLC XID RESET\n");
diff --git a/openbsc/src/gprs/gprs_sgsn.c b/openbsc/src/gprs/gprs_sgsn.c
index f71066d..b7bda49 100644
--- a/openbsc/src/gprs/gprs_sgsn.c
+++ b/openbsc/src/gprs/gprs_sgsn.c
@@ -105,6 +105,31 @@
return NULL;
}
+struct sgsn_mm_ctx *sgsn_mm_ctx_by_tlli_and_ptmsi(uint32_t tlli,
+ const struct gprs_ra_id *raid)
+{
+ struct sgsn_mm_ctx *ctx;
+ int tlli_type;
+
+ /* TODO: Also check the P_TMSI signature to be safe. That signature
+ * should be different (at least with a sufficiently high probability)
+ * after SGSN restarts and for multiple SGSN instances.
+ */
+
+ tlli_type = gprs_tlli_type(tlli);
+ if (tlli_type != TLLI_FOREIGN && tlli_type != TLLI_LOCAL)
+ return NULL;
+
+ llist_for_each_entry(ctx, &sgsn_mm_ctxts, list) {
+ if ((gprs_tmsi2tlli(ctx->p_tmsi, tlli_type) == tlli ||
+ gprs_tmsi2tlli(ctx->p_tmsi_old, tlli_type) == tlli) &&
+ gprs_ra_id_equals(raid, &ctx->ra))
+ return ctx;
+ }
+
+ return NULL;
+}
+
struct sgsn_mm_ctx *sgsn_mm_ctx_by_ptmsi(uint32_t p_tmsi)
{
struct sgsn_mm_ctx *ctx;