gprs_gmm: introduce a GMM Attach Request FSM

The old GMM Attach Request handling used a recursive function
which can not handle certain states and is quite complex and hard to
extend.

The new FSM handles such request in a FSM and can be called multiple
times.

Change-Id: I58b9c17be9776a03bb2a5b21e99135cfefc8c912

4 files changed, 50 insertions, 0 deletions

diff --git a/include/osmocom/sgsn/Makefile.am b/include/osmocom/sgsn/Makefile.am
index 269cebcd6..3b563c401 100644
--- a/include/osmocom/sgsn/Makefile.am
+++ b/include/osmocom/sgsn/Makefile.am
@@ -5,6 +5,7 @@ noinst_HEADERS = \
 	gb_proxy.h \
 	gprs_gb_parse.h \
 	gprs_gmm.h \
+	gprs_gmm_attach.h \
 	gprs_llc.h \
 	gprs_llc_xid.h \
 	gprs_sgsn.h \
diff --git a/include/osmocom/sgsn/gprs_gmm.h b/include/osmocom/sgsn/gprs_gmm.h
index d12eaf9bb..ffcebd353 100644
--- a/include/osmocom/sgsn/gprs_gmm.h
+++ b/include/osmocom/sgsn/gprs_gmm.h
@@ -40,6 +40,8 @@ int gsm48_tx_gmm_att_rej(struct sgsn_mm_ctx *mm,
 				uint8_t gmm_cause);
 int gsm48_tx_gmm_att_ack(struct sgsn_mm_ctx *mm);
 
+int gprs_gmm_attach_req_ies(struct msgb *a, struct msgb *b);
+
 /* TODO: move extract_subscr_* when gsm48_gmm_authorize() got removed */
 void extract_subscr_msisdn(struct sgsn_mm_ctx *ctx);
 void extract_subscr_hlr(struct sgsn_mm_ctx *ctx);
diff --git a/include/osmocom/sgsn/gprs_gmm_attach.h b/include/osmocom/sgsn/gprs_gmm_attach.h
new file mode 100644
index 000000000..22fbd6f9d
--- /dev/null
+++ b/include/osmocom/sgsn/gprs_gmm_attach.h
@@ -0,0 +1,37 @@
+#ifndef GPRS_GMM_ATTACH_H
+#define GPRS_GMM_ATTACH_H
+
+#include <osmocom/core/fsm.h>
+
+struct sgsn_mm_ctx;
+
+enum gmm_attach_req_fsm_states {
+	ST_INIT,
+	ST_IDENTIY,
+	ST_RETRIEVE_AUTH,
+	ST_AUTH,
+	ST_ASK_VLR,
+	ST_ACCEPT,
+	ST_REJECT
+};
+
+enum gmm_attach_req_fsm_events {
+	E_ATTACH_REQ_RECV,
+	E_IDEN_RESP_RECV,
+	E_AUTH_RESP_RECV_SUCCESS,
+	E_AUTH_RESP_RECV_RESYNC,
+	E_ATTACH_ACCEPTED,
+	E_ATTACH_ACCEPT_SENT,
+	E_ATTACH_COMPLETE_RECV,
+	E_REJECT,
+	E_VLR_ANSWERED,
+};
+
+#define GMM_DISCARD_MS_WITHOUT_REJECT -1
+
+extern const struct value_string gmm_attach_req_fsm_event_names[];
+extern struct osmo_fsm gmm_attach_req_fsm;
+
+void gmm_att_req_free(struct sgsn_mm_ctx *mm);
+
+#endif // GPRS_GMM_ATTACH_H
diff --git a/include/osmocom/sgsn/gprs_sgsn.h b/include/osmocom/sgsn/gprs_sgsn.h
index 6f16dc75f..a5ca959a4 100644
--- a/include/osmocom/sgsn/gprs_sgsn.h
+++ b/include/osmocom/sgsn/gprs_sgsn.h
@@ -4,6 +4,7 @@
 #include <stdint.h>
 #include <netinet/in.h>
 
+#include <osmocom/core/fsm.h>
 #include <osmocom/core/timer.h>
 
 #include <osmocom/gsm/gsm48.h>
@@ -168,6 +169,15 @@ struct sgsn_mm_ctx {
 		struct ranap_ue_conn_ctx	*ue_ctx;
 		struct service_info	service;
 	} iu;
+	struct {
+		struct osmo_fsm_inst *fsm;
+
+		/* when a second attach req arrives while in this procedure,
+		 * the fsm needs to compare it against old to decide what to do */
+		struct msgb *attach_req;
+		uint32_t id_type;
+		bool auth_reattempt;
+	} gmm_att_req;
 	/* VLR number */
 	uint32_t		new_sgsn_addr;
 	/* Authentication Triplet */