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-rw-r--r--src/osmo_client_core.c119
1 files changed, 119 insertions, 0 deletions
diff --git a/src/osmo_client_core.c b/src/osmo_client_core.c
index c8bd8bd..d116b1b 100644
--- a/src/osmo_client_core.c
+++ b/src/osmo_client_core.c
@@ -20,17 +20,133 @@
*
*/
+#define _BSD_SOURCE
#include <osmo-pcap/osmo_pcap_client.h>
#include <osmo-pcap/common.h>
+#include <osmocom/gprs/gprs_bssgp.h>
+#include <osmocom/gprs/protocol/gsm_08_16.h>
+#include <osmocom/gprs/protocol/gsm_08_18.h>
+
#include <osmocom/core/talloc.h>
+#include <netinet/ip.h>
+#include <netinet/udp.h>
+
#include <limits.h>
#ifndef PCAP_NETMASK_UNKNOWN
#define PCAP_NETMASK_UNKNOWN 0xffffffff
#endif
+#define IP_LEN sizeof(struct ip)
+#define UDP_LEN sizeof(struct udphdr)
+#define NS_LEN 1
+
+static int saw_llc = 0;
+static int failed_to_parse = 0;
+
+static int check_gprs(const u_char *data, bpf_u_int32 len)
+{
+ struct tlv_parsed tp;
+ struct gprs_ns_hdr *hdr = (struct gprs_ns_hdr *) data;
+ struct bssgp_ud_hdr *bssgp_hdr;
+ uint8_t llc_sapi;
+
+ switch (hdr->pdu_type) {
+ case NS_PDUT_UNITDATA:
+ break;
+ default:
+ return 1;
+ }
+
+ len -= sizeof(*hdr);
+
+ /* NS_PDUT_UNITDATA from here.. */
+ /* skip NS SDU control bits and BVCI */
+ if (len < 3)
+ return 1;
+ len -= 3;
+
+ /* Check if the BSSGP UD hdr fits */
+ if (len < sizeof(*bssgp_hdr))
+ return 1;
+ bssgp_hdr = (struct bssgp_ud_hdr *) &hdr->data[3];
+
+ /* We only need to check UL/DL messages for the sapi */
+ if (bssgp_hdr->pdu_type != BSSGP_PDUT_DL_UNITDATA
+ && bssgp_hdr->pdu_type != BSSGP_PDUT_UL_UNITDATA)
+ return 1;
+ len -= sizeof(*bssgp_hdr);
+
+ /* now parse the rest of the IEs */
+ memset(&tp, 0, sizeof(tp));
+ if (bssgp_tlv_parse(&tp, &bssgp_hdr->data[0], len) < 0)
+ return 1;
+
+ if (!TLVP_PRESENT(&tp, BSSGP_IE_LLC_PDU))
+ return 1;
+ if (TLVP_LEN(&tp, BSSGP_IE_LLC_PDU) < 1)
+ return 1;
+
+ llc_sapi = TLVP_VAL(&tp, BSSGP_IE_LLC_PDU)[0] & 0x0f;
+ /* Skip user data 3, 5, 9, 11 */
+ if (llc_sapi == 3 || llc_sapi == 5 || llc_sapi == 9 || llc_sapi == 11)
+ return 0;
+ return 1;
+}
+
+static int forward_packet(
+ struct osmo_pcap_client *client,
+ struct pcap_pkthdr *hdr,
+ const u_char *data)
+{
+ int ll_type;
+ int offset;
+ struct ip *ip_hdr;
+ const u_char *ip_data;
+ const u_char *udp_data;
+ const u_char *payload_data;
+ bpf_u_int32 payload_len;
+
+ if (!client->gprs_filtering)
+ return 1;
+
+ ll_type = pcap_datalink(client->handle);
+ switch (ll_type) {
+ case DLT_EN10MB:
+ offset = 14;
+ break;
+ case DLT_LINUX_SLL:
+ offset = 16;
+ break;
+ default:
+ LOGP(DCLIENT, LOGL_ERROR, "LL type %d/%s not handled.\n",
+ ll_type, pcap_datalink_val_to_name(ll_type));
+ return 1;
+ }
+
+ /* Check if this can be a full UDP frame with NS */
+ if (offset + IP_LEN + UDP_LEN + NS_LEN > hdr->caplen)
+ return 1;
+
+ ip_data = data + offset;
+ ip_hdr = (struct ip *) ip_data;
+
+ /* Only handle IPv4 */
+ if (ip_hdr->ip_v != 4)
+ return 1;
+ /* Only handle UDP */
+ if (ip_hdr->ip_p != 17)
+ return 1;
+
+ udp_data = ip_data + IP_LEN;
+ payload_data = udp_data + UDP_LEN;
+ payload_len = hdr->caplen - offset - IP_LEN - UDP_LEN;
+
+ return check_gprs(payload_data, payload_len);
+}
+
static int pcap_read_cb(struct osmo_fd *fd, unsigned int what)
{
@@ -42,6 +158,9 @@ static int pcap_read_cb(struct osmo_fd *fd, unsigned int what)
if (!data)
return -1;
+ if (!forward_packet(client, &hdr, data))
+ return 0;
+
osmo_client_send_data(client, &hdr, data);
return 0;
}