16 Oct
2015
16 Oct
'15
12:13 a.m.
Avoid sequence number collisions and allow routing a GGSN's response back to
the SGSN that sent a request:
- Towards each GGSN, send other sequence numbers than received from an SGSN,
- and remember the mapping (with timeouts).
- When receiving from a GGSN, find the SGSN from the sequence number returned.
This covers only requests by the SGSN followed by GGSN responses, it does not
cover requests initiated by a GGSN.
Sponsored-by: On-Waves ehi
diff --git a/openbsc/include/openbsc/gtphub.h b/openbsc/include/openbsc/gtphub.h
index 7354786..ccea5aa 100644
--- a/openbsc/include/openbsc/gtphub.h
+++ b/openbsc/include/openbsc/gtphub.h
@@ -23,6 +23,7 @@
#include <stdint.h>
#include <sys/socket.h>
+#include <sys/time.h>
#include <osmocom/core/select.h>
@@ -107,6 +108,18 @@ struct gtphub_peer {
struct gtphub_addr addr;
struct tei_map teim;
+ uint16_t next_peer_seq; /* the latest used sequence nr + 1 */
+ struct llist_head seq_map; /* of struct gtphub_seq_mapping */
+ int ref_count; /* references from other peers' seq_maps */
+};
+
+struct gtphub_seq_mapping {
+ struct llist_head entry;
+
+ uint16_t peer_seq;
+ struct gtphub_peer *from;
+ uint16_t from_seq;
+ struct timeval timeout;
};
struct gtphub_bind {
diff --git a/openbsc/src/gprs/gtphub.c b/openbsc/src/gprs/gtphub.c
index 9f3e021..f6733e3 100644
--- a/openbsc/src/gprs/gtphub.c
+++ b/openbsc/src/gprs/gtphub.c
@@ -22,6 +22,7 @@
#include <string.h>
#include <errno.h>
#include <inttypes.h>
+#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
@@ -35,6 +36,7 @@
#include <osmocom/core/socket.h>
#define GTPHUB_DEBUG 1
+#define MAP_SEQ 1
void *osmo_gtphub_ctx;
@@ -57,6 +59,8 @@ typedef int (*osmo_fd_cb_t)(struct osmo_fd *fd, unsigned int what);
#define ntoh16(x) ntohs(x)
#define ntoh32(x) ntohl(x)
+#define hton16(x) htons(x)
+
/* cheat to use gtpie.h API.
* TODO publish gtpie.h upon openggsn installation */
union gtpie_member;
@@ -87,7 +91,7 @@ enum gtp_rc {
};
struct gtp_packet_desc {
- const union gtp_packet *data;
+ union gtp_packet *data;
int data_len;
int header_len;
int version;
@@ -481,6 +485,63 @@ static int gtphub_read(struct osmo_fd *from,
return received;
}
+#if MAP_SEQ
+
+inline uint16_t get_seq(struct gtp_packet_desc *p)
+{
+ OSMO_ASSERT(p->version == 1);
+ return ntoh16(p->data->gtp1l.h.seq);
+}
+
+inline void set_seq(struct gtp_packet_desc *p, uint16_t seq)
+{
+ OSMO_ASSERT(p->version == 1);
+ p->data->gtp1l.h.seq = hton16(seq);
+}
+
+static int gtphub_map_seq(struct gtp_packet_desc *p,
+ struct gtphub_peer *from_peer, struct gtphub_peer *to_peer)
+{
+
+ struct gtphub_seq_mapping *m = talloc_zero(osmo_gtphub_ctx, struct gtphub_seq_mapping);
+ OSMO_ASSERT(m);
+
+ m->peer_seq = to_peer->next_peer_seq++;
+ m->from = from_peer;
+ m->from_seq = get_seq(p);
+ LOG(" MAP %d --> %d\n", (int)m->from_seq, (int)m->peer_seq);
+
+ llist_add(&m->entry, &to_peer->seq_map);
+ set_seq(p, m->peer_seq);
+
+ return 0;
+}
+
+static struct gtphub_peer *gtphub_unmap_seq(struct gtp_packet_desc *p,
+ struct gtphub_peer *from_peer)
+{
+ OSMO_ASSERT(p->version == 1);
+
+ uint16_t from_seq = get_seq(p);
+
+ struct gtphub_seq_mapping *mapping;
+ llist_for_each_entry(mapping, &from_peer->seq_map, entry) {
+ if (mapping->peer_seq == from_seq)
+ break;
+ }
+
+ if (&mapping->entry == &from_peer->seq_map) {
+ /* not found. */
+ return NULL;
+ }
+
+ LOG("UNMAP %d <-- %d\n", (int)(mapping->from_seq), (int)from_seq);
+ set_seq(p, mapping->from_seq);
+ return mapping->from;
+}
+
+#endif
+
static int gtphub_write(struct osmo_fd *to,
struct sockaddr_storage *to_addr,
socklen_t to_addr_len,
@@ -517,11 +578,14 @@ int from_ggsns_read_cb(struct osmo_fd *from_ggsns_ofd, unsigned int
what)
struct gtphub *hub = from_ggsns_ofd->data;
+ struct gtphub_peer *ggsn = NULL;
+ struct gtphub_peer *sgsn = NULL;
+
/* TODO this will not be hardcoded. */
- struct gtphub_peer *sgsn = llist_first(&hub->to_sgsns[port_idx].peers,
- struct gtphub_peer, entry);
- if (!sgsn) {
- LOGERR("no sgsn");
+ ggsn = llist_first(&hub->to_ggsns[port_idx].peers,
+ struct gtphub_peer, entry);
+ if (!ggsn) {
+ LOGERR("no ggsn\n");
return 0;
}
@@ -539,6 +603,20 @@ int from_ggsns_read_cb(struct osmo_fd *from_ggsns_ofd, unsigned int
what)
return 0;
#endif
+#if MAP_SEQ
+ sgsn = gtphub_unmap_seq(&p, ggsn);
+#else
+ /* TODO this will not be hardcoded. */
+ sgsn = llist_first(&hub->to_sgsns[port_idx].peers,
+ struct gtphub_peer, entry);
+#endif
+
+ if (!sgsn) {
+ LOGERR("no sgsn");
+ return 0;
+ }
+
+
return gtphub_write(&hub->to_sgsns[port_idx].ofd,
&sgsn->addr.a, sgsn->addr.l,
(uint8_t*)p.data, p.data_len);
@@ -583,6 +661,10 @@ int from_sgsns_read_cb(struct osmo_fd *from_sgsns_ofd, unsigned int
what)
return 0;
#endif
+#if MAP_SEQ
+ gtphub_map_seq(&p, sgsn, ggsn);
+#endif
+
return gtphub_write(&hub->to_ggsns[port_idx].ofd,
&ggsn->addr.a, ggsn->addr.l,
(uint8_t*)p.data, p.data_len);
@@ -616,7 +698,9 @@ struct gtphub_peer *gtphub_peer_new(struct gtphub_bind *bind)
{
struct gtphub_peer *n = talloc_zero(osmo_gtphub_ctx, struct gtphub_peer);
+ INIT_LLIST_HEAD(&n->seq_map);
tei_map_init(&n->teim, &bind->teip);
+ n->next_peer_seq = rand(); /* TODO seed or use something else */
llist_add(&n->entry, &bind->peers);
return n;
--
2.1.4