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authorJacob Erlbeck <jerlbeck@sysmocom.de>2014-09-03 11:59:48 +0200
committerJacob Erlbeck <jerlbeck@sysmocom.de>2014-09-09 10:10:00 +0200
commit31591142e97268b3add6b99ad5eb9b203a0a37f7 (patch)
tree44548b50bd6e1945b9106cc28d6219bd2b2b687c /openbsc/src/gprs/gb_proxy.c
parentea1698e32203de923ce40b7cf13027b5a9254760 (diff)
gbproxy: Reset IMSI acquisition and free stored messages in tlli_info
Currently the stored messages are only removed, when IMSI acquisition has succeeded. In addition, receiving two ATTACH_REQ messages in sequence (e.g. due to loss of a Identity Req/Resp message) will not restart the IMSI acquisition procedure. This patch adds gbproxy_tlli_info_discard_messages() to clean up the message list and calls it from gbproxy_delete_tlli() fixing a potential memory leak. It is also called when an Attach Request message has been received. In that case the imsi_acq_pending flag is cleared, too. This would (re-)trigger the IMSI acquisition procedure at each of these messages. If an Ident Response has been lost, resending the Ident Request with the same N(U) will not work. Therefore the N(U) gets incremented on each Ident Request generated by the gbproxy. The first N(U) used is 256 which shouldn't collide with the V(UT) used by the SGSN given that P-TMSI patching is enabled (since a new random TLLI is used initially on every new (no tlli_info) connection and V(U) starts with zero then). Ticket: OW#1261 Sponsored-by: On-Waves ehf
Diffstat (limited to 'openbsc/src/gprs/gb_proxy.c')
-rw-r--r--openbsc/src/gprs/gb_proxy.c40
1 files changed, 35 insertions, 5 deletions
diff --git a/openbsc/src/gprs/gb_proxy.c b/openbsc/src/gprs/gb_proxy.c
index 8b014ea..fbac298 100644
--- a/openbsc/src/gprs/gb_proxy.c
+++ b/openbsc/src/gprs/gb_proxy.c
@@ -253,6 +253,22 @@ uint32_t gbproxy_make_sgsn_tlli(struct gbproxy_peer *peer,
return sgsn_tlli;
}
+/* Returns != 0 iff IMSI acquisition was in progress */
+int gbproxy_reset_imsi_acquisition(struct gbproxy_tlli_info* tlli_info)
+{
+ int in_progress = 0;
+ if (!tlli_info)
+ return 0;
+
+ if (tlli_info->imsi_acq_pending)
+ in_progress = 1;
+
+ gbproxy_tlli_info_discard_messages(tlli_info);
+ tlli_info->imsi_acq_pending = 0;
+
+ return in_progress;
+}
+
/* patch BSSGP message */
static int gbprox_process_bssgp_ul(struct gbproxy_config *cfg,
struct msgb *msg,
@@ -315,10 +331,21 @@ static int gbprox_process_bssgp_ul(struct gbproxy_config *cfg,
gbprox_update_current_raid(parse_ctx.bssgp_raid_enc, peer,
parse_ctx.llc_msg_name);
+ gprs_gb_log_parse_context(&parse_ctx, "BSSGP");
+
+ tlli_info = gbproxy_update_tlli_state_ul(peer, now, &parse_ctx);
+
if (parse_ctx.g48_hdr) {
switch (parse_ctx.g48_hdr->msg_type) {
case GSM48_MT_GMM_ATTACH_REQ:
rate_ctr_inc(&peer->ctrg->ctr[GBPROX_PEER_CTR_ATTACH_REQS]);
+ if (gbproxy_reset_imsi_acquisition(tlli_info)) {
+ LOGP(DLLC, LOGL_INFO,
+ "NSEI=%d(BSS) IMSI acquisition was in progress "
+ "when receiving an ATTACH_REQ.\n",
+ msgb_nsei(msg));
+ tlli_info->imsi_acq_retries += 1;
+ }
break;
default:
@@ -326,10 +353,6 @@ static int gbprox_process_bssgp_ul(struct gbproxy_config *cfg,
}
}
- gprs_gb_log_parse_context(&parse_ctx, "BSSGP");
-
- tlli_info = gbproxy_update_tlli_state_ul(peer, now, &parse_ctx);
-
if (tlli_info && cfg->route_to_sgsn2 && gbproxy_check_tlli(peer, tlli_info)) {
sgsn_nsei = cfg->nsip_sgsn2_nsei;
send_msg_directly = 1;
@@ -415,8 +438,15 @@ static int gbprox_process_bssgp_ul(struct gbproxy_config *cfg,
/* Send IDENT REQ */
idreq_msg = gsm48_msgb_alloc();
gprs_put_identity_req(idreq_msg, GSM_MI_TYPE_IMSI);
+ /* Workaround to avoid N(U) collisions and to enable a restart
+ * of the IMSI acquisition procedure. This will work unless the
+ * SGSN has an initial V(UT) within [256-32, 256+n_retries]
+ * (see GSM 04.64, 8.4.2).
+ * TODO: Check whether it is sensible to rely on this, it might
+ * be an issue when P-TMSI patching is _not_ enabled and the SGSN
+ * doesn't reset V(UT) after a detach. */
gprs_push_llc_ui(idreq_msg, 0, GPRS_SAPI_GMM,
- /* TODO: use a real N(U) */0);
+ (tlli_info->imsi_acq_retries + 256) % 512);
gprs_push_bssgp_dl_unitdata(idreq_msg, tlli_info->tlli.current);
gbprox_relay2peer(idreq_msg, peer, msgb_bvci(msg));
msgb_free(idreq_msg);