gbproxy: Implement IMSI acquisition
To modify or route messages based on the IMSI the latter must be known
when the action shall take place.
This patch modifies the gbproxy to optionally retain and enqueue
messages from the MS while initiating an identification procedure.
Further message processing of the LLC PTP link towards the SGSN will
be done, when the identity of the MS has been acquired.
Note that the N(U) of the LLC GMM SAPI are not adjusted, so it is
possible that adjacent messages of a single LLC link arriving either
at the BSS or the SGSN have the same N(U) and might get discarded,
leading to retransmissions and additional delay.
Note also that retransmissions and packet loss are not yet handled
explicitely. If for instance the generated IDENT REQ gets lost, the
gbproxy will not act on its own. In this case, the MS will time out
and eventually resend the Attach Request on which the gbproxy will
act exactly like before (thus having two Attach Req messages in its
queue, which will both be sent after the Ident Resp arrives).
This has been tested successfully with an E71, needing one
retransmission by the SGSN due to an N(U) collision.
Ticket: OW#1261
Sponsored-by: On-Waves ehf
diff --git a/openbsc/include/openbsc/gb_proxy.h b/openbsc/include/openbsc/gb_proxy.h
index 5c31321..0bda003 100644
--- a/openbsc/include/openbsc/gb_proxy.h
+++ b/openbsc/include/openbsc/gb_proxy.h
@@ -82,7 +82,10 @@
enum gbproxy_patch_mode patch_mode;
int tlli_max_age;
int tlli_max_len;
+
+ /* Experimental config */
int patch_ptmsi;
+ int acquire_imsi;
/* IMSI checking/matching */
int check_imsi;
@@ -143,6 +146,8 @@
uint8_t *mi_data;
size_t mi_data_len;
+ int imsi_acq_pending;
+ struct llist_head stored_msgs;
int enable_patching;
};