Add PCAP (LINKTYPE GSM incl. gsmtap hdr) support

6 files changed, 162 insertions, 4 deletions

diff --git a/gsm-tvoid/src/lib/Makefile.am b/gsm-tvoid/src/lib/Makefile.am
index d8d504f..4f2ba65 100644
--- a/gsm-tvoid/src/lib/Makefile.am
+++ b/gsm-tvoid/src/lib/Makefile.am
@@ -51,7 +51,8 @@ _gsm_la_SOURCES = 		\
 	mm_f.cc				\
 	gsm_burst_cf.cc		\
 	gsm_burst_sink_c.cc	\
-	tun.c
+	tun.c			\
+	out_pcap.c
 	
 
 # magic flags
@@ -82,7 +83,9 @@ grinclude_HEADERS =		\
 	gsm_burst_cf.h		\
 	gsm_burst_sink_c.h	\
 	gsm_constants.h		\
-	tun.h
+	tun.h			\
+	out_pcap.h		\
+	gsmtap.h
 
 
 # These swig headers get installed in ${prefix}/include/gnuradio/swig
diff --git a/gsm-tvoid/src/lib/gsmstack.c b/gsm-tvoid/src/lib/gsmstack.c
index ecea4f9..e09420c 100644
--- a/gsm-tvoid/src/lib/gsmstack.c
+++ b/gsm-tvoid/src/lib/gsmstack.c
@@ -5,6 +5,7 @@
 #include "system.h"
 #include <stdlib.h>
 #include <stdio.h>
+#include <errno.h>
 #include <string.h>
 #include "gsmstack.h"
 #include "gsm_constants.h"
@@ -12,6 +13,8 @@
 #include "sch.h"
 #include "cch.h"
 
+#include "out_pcap.h"
+
 static void out_gsmdecode(char type, int arfcn, int ts, int fn, char *data, int len);
 
 #if 0
@@ -46,9 +49,14 @@ GS_new(GS_CTX *ctx)
 	interleave_init(&ctx->interleave_ctx, 456, 114);
 	ctx->fn = -1;
 	ctx->bsic = -1;
+
 	ctx->tun_fd = mktun("gsm", ctx->ether_addr);
 	if (ctx->tun_fd < 0)
-		return -1;
+		fprintf(stderr, "cannot open 'gsm' tun device, did you create it?\n");
+
+	ctx->pcap_fd = open_pcap_file("tvoid.pcap");
+	if (ctx->pcap_fd < 0)
+		fprintf(stderr, "cannot open PCAP file: %s\n", strerror(errno));
 
 	return 0;
 }
@@ -65,8 +73,14 @@ GS_process(GS_CTX *ctx, int ts, int type, const unsigned char *src)
 	unsigned char *data;
 	int len;
 
-	if (ts != 0)
+	if (ts != 0) {
+		/* non-0 timeslots should end up in PCAP */
+		data = decode_cch(ctx, ctx->burst, &len);
+		if (data == NULL)
+			return -1;
+		write_pcap_packet(ctx->pcap_fd, 0 /* arfcn */, ts, 0, data, len);
 		return;
+	}
 
 	if (type == SCH)
 	{
@@ -111,6 +125,7 @@ GS_process(GS_CTX *ctx, int ts, int type, const unsigned char *src)
 
 		out_gsmdecode(0, 0, ts, ctx->fn - 4, data, len);
 		write_interface(ctx->tun_fd, data+1, len-1, ctx->ether_addr);
+		write_pcap_packet(ctx->pcap_fd, 0 /* arfcn */, ts, fn, data, len);
 #if 0
 		if (ctx->fn % 51 != 0) && ( (((ctx->fn % 51 + 5) % 10 == 0) || (((ctx->fn % 51) + 1) % 10 ==0) ) )
 			ready = 1;
diff --git a/gsm-tvoid/src/lib/gsmstack.h b/gsm-tvoid/src/lib/gsmstack.h
index 8230442..b4a5c96 100644
--- a/gsm-tvoid/src/lib/gsmstack.h
+++ b/gsm-tvoid/src/lib/gsmstack.h
@@ -23,6 +23,8 @@ typedef struct
 
 	int tun_fd;
 	unsigned char ether_addr[ETH_ALEN];
+
+	int pcap_fd;
 } GS_CTX;
 
 int GS_new(GS_CTX *ctx);
diff --git a/gsm-tvoid/src/lib/gsmtap.h b/gsm-tvoid/src/lib/gsmtap.h
new file mode 100644
index 0000000..6676d9a
--- /dev/null
+++ b/gsm-tvoid/src/lib/gsmtap.h
@@ -0,0 +1,26 @@
+#ifndef _GSMTAP_H
+#define _GSMTAP_H
+
+/* gsmtap header, pseudo-header in front of the actua GSM payload*/
+
+#include <sys/types.h>
+
+#define GSMTAP_VERSION		0x02
+
+#define GSMTAP_TYPE_UM		0x01
+#define GSMTAP_TYPE_ABIS	0x02
+
+struct gsmtap_hdr {
+	u_int8_t version;		/* version, set to 0x01 currently */
+	u_int8_t hdr_len;		/* length in number of 32bit words */
+	u_int8_t type;			/* see GSMTAP_TYPE_* */
+	u_int8_t timeslot;		/* timeslot (0..7 on Um) */
+
+	u_int16_t arfcn;		/* ARFCN (frequency) */
+	u_int8_t noise_db;
+	u_int8_t signal_db;
+
+	u_int32_t frame_number;
+
+} __attribute__((packed));
+#endif /* _GSMTAP_H */
diff --git a/gsm-tvoid/src/lib/out_pcap.c b/gsm-tvoid/src/lib/out_pcap.c
new file mode 100644
index 0000000..95f24f5
--- /dev/null
+++ b/gsm-tvoid/src/lib/out_pcap.c
@@ -0,0 +1,105 @@
+/* PCAP support for gsm-tvoid
+ * (C) 2008 by Harald Welte <laforge@gnumonks.org>
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <pcap.h>
+#include <errno.h>
+#include <time.h>
+
+#include "out_pcap.h"
+#include "gsmtap.h"
+
+#ifndef LINKTYPE_GSMTAP
+#define LINKTYPE_GSMTAP		2342
+#endif
+
+#define TCPDUMP_MAGIC   0xa1b2c3d4
+
+struct pcap_timeval {
+	int32_t tv_sec;
+	int32_t tv_usec;
+};
+	
+struct pcap_sf_pkthdr {
+	struct pcap_timeval ts;		/* time stamp */
+	u_int32_t caplen;		/* lenght of portion present */
+	u_int32_t len;			/* length of this packet */
+};
+
+static int write_pcap_file_header(int fd)
+{
+	struct pcap_file_header pfh;
+
+	pfh.magic = TCPDUMP_MAGIC;
+	pfh.version_major = PCAP_VERSION_MAJOR;
+	pfh.version_minor = PCAP_VERSION_MINOR;
+	pfh.thiszone = timezone;
+	pfh.sigfigs = 0;
+	pfh.snaplen = 1024; /* FIXME */ 
+	pfh.linktype = LINKTYPE_GSMTAP;
+
+	if (write(fd, &pfh, sizeof(pfh)) < sizeof(pfh))
+		return -1;
+
+	return 0;
+}
+
+/* open pcap file and write header */
+int open_pcap_file(char *fname)
+{
+	int fd;
+	int rc;
+
+ 	fd = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0660);
+	if (fd < 0)
+		return fd;
+
+	rc = write_pcap_file_header(fd);
+	if (rc < 0) {
+		close(fd);
+		fd = -EIO;
+	}
+
+	return fd;
+}
+
+int write_pcap_packet(int fd, int arfcn, int ts, int fn,
+		      char *data, unsigned int len)
+{
+	unsigned char buf[8192];
+	struct pcap_sf_pkthdr *ph;
+	struct gsmtap_hdr *gh;
+	struct timeval tv;
+	int rc;
+
+	printf("writing pcap packet fd=%d len=%d\n", fd, len);
+
+	ph = (struct pcap_sf_pkthdr *) &buf[0];
+	gh = (struct gsmtap_hdr *) &buf[sizeof(struct pcap_sf_pkthdr)];
+
+	gettimeofday(&tv, NULL);
+
+	ph->ts.tv_sec = tv.tv_sec;
+	ph->ts.tv_usec = tv.tv_usec;
+	ph->caplen = ph->len = len + sizeof(struct gsmtap_hdr);
+
+	gh->version = GSMTAP_VERSION;
+	gh->hdr_len = sizeof(struct gsmtap_hdr)>>2;
+	gh->type = GSMTAP_TYPE_UM;
+	gh->timeslot = ts;
+	gh->arfcn = htons(arfcn);
+	/* we don't support signal/noise yet */
+	gh->noise_db = gh->signal_db = 0;
+	gh->frame_number = htonl(fn);
+
+	memcpy(buf + sizeof(*ph) + sizeof(*gh), data, len);
+	
+	rc = write(fd, buf, sizeof(*ph) + sizeof(*gh) + len);
+
+	fsync(fd);
+
+	return rc;
+}
diff --git a/gsm-tvoid/src/lib/out_pcap.h b/gsm-tvoid/src/lib/out_pcap.h
new file mode 100644
index 0000000..e8d4b3c
--- /dev/null
+++ b/gsm-tvoid/src/lib/out_pcap.h
@@ -0,0 +1,7 @@
+#ifndef _PCAP_IF_H
+#define _PCAP_IF_H
+
+extern int open_pcap_file(char *fname);
+int write_pcap_packet(int fd, int arfcn, int ts, int fn, char *data, unsigned int len);
+
+#endif