rlcmac: keep looking up GRE based on old TLLI

This is needed after RAU Update since the PCU may still be using the old
TLLI to reference the MS for a while until it finds out about the TLLI update.

Change-Id: I2653db3dac58342df02a1b4d0c76e69e0e8d583f
---
M include/osmocom/gprs/rlcmac/gre.h
M src/rlcmac/gre.c
M src/rlcmac/rlcmac.c
M src/rlcmac/rlcmac_prim.c
4 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/include/osmocom/gprs/rlcmac/gre.h b/include/osmocom/gprs/rlcmac/gre.h
index a7317cd..be36e23 100644
--- a/include/osmocom/gprs/rlcmac/gre.h
+++ b/include/osmocom/gprs/rlcmac/gre.h
@@ -21,6 +21,7 @@
 struct gprs_rlcmac_entity {
 	struct llist_head entry; /* item in (struct gprs_rlcmac_ctx)->gre_list */
 	uint32_t tlli;
+	uint32_t old_tlli;
 
 	/* Used to match paging requests coming from CS domain: */
 	uint32_t ptmsi;
diff --git a/src/rlcmac/gre.c b/src/rlcmac/gre.c
index 0eb6a8c..9102124 100644
--- a/src/rlcmac/gre.c
+++ b/src/rlcmac/gre.c
@@ -66,6 +66,7 @@
 		goto err_free_gre;
 
 	gre->tlli = tlli;
+	gre->old_tlli = GPRS_RLCMAC_TLLI_UNASSIGNED;
 	gre->ptmsi = GSM_RESERVED_TMSI;
 	llist_add_tail(&gre->entry, &g_rlcmac_ctx->gre_list);
 
diff --git a/src/rlcmac/rlcmac.c b/src/rlcmac/rlcmac.c
index f35c04d..a6d0e71 100644
--- a/src/rlcmac/rlcmac.c
+++ b/src/rlcmac/rlcmac.c
@@ -137,7 +137,7 @@
 {
 	struct gprs_rlcmac_entity *gre;
 	llist_for_each_entry(gre, &g_rlcmac_ctx->gre_list, entry) {
-		if (gre->tlli == tlli)
+		if (gre->tlli == tlli || gre->old_tlli == tlli)
 			return gre;
 	}
 	return NULL;
diff --git a/src/rlcmac/rlcmac_prim.c b/src/rlcmac/rlcmac_prim.c
index f13ac3d..1ce7c9e 100644
--- a/src/rlcmac/rlcmac_prim.c
+++ b/src/rlcmac/rlcmac_prim.c
@@ -469,6 +469,8 @@
 			rc = -ENOENT;
 			goto free_ret;
 		}
+		gre->old_tlli = old_tlli;
+		gre->tlli = GPRS_RLCMAC_TLLI_UNASSIGNED;
 		gprs_rlcmac_entity_free(gre);
 		gre = NULL;
 		goto free_ret;
@@ -481,7 +483,9 @@
 			goto free_ret;
 		}
 		LOGGRE(gre, LOGL_INFO, "Update TLLI 0x%08x -> 0x%08x\n", old_tlli, new_tlli);
+		gre->old_tlli = old_tlli;
 		gre->tlli = new_tlli;
+
 	}
 
 	/* cache/update knowledge about this GMME's PTMSI and IMSI. It will be

