From 51eaba28a3d4c83ecee4ca98544635d47c771380 Mon Sep 17 00:00:00 2001
From: Harald Welte <laforge@gnumonks.org>
Date: Sat, 29 Nov 2008 13:48:12 +0530
Subject: [gsm-tvoid] new gsmtap header, raw burst pcap support

* split burst decoding context out of GS_ctx and have one for each TS
* add PCAP output for GSMTAP_TYPE_UM_BURST (142 bit burst per packet)
---
 gsm-tvoid/src/lib/gsmstack.c | 96 +++++++++++++++++++++++++++++++-------------
 1 file changed, 69 insertions(+), 27 deletions(-)

(limited to 'gsm-tvoid/src/lib/gsmstack.c')

diff --git a/gsm-tvoid/src/lib/gsmstack.c b/gsm-tvoid/src/lib/gsmstack.c
index c0f422e..a46bc87 100644
--- a/gsm-tvoid/src/lib/gsmstack.c
+++ b/gsm-tvoid/src/lib/gsmstack.c
@@ -17,6 +17,28 @@
 
 static void out_gsmdecode(char type, int arfcn, int ts, int fn, char *data, int len);
 
+/* encode a decoded burst (1 bit per byte) into 8-bit-per-byte */
+static void burst_octify(unsigned char *dest, 
+			 const unsigned char *data, int length)
+{
+	int bitpos = 0;
+
+	while (bitpos < USEFUL_BITS) {
+		unsigned char tbyte;
+		int i; 
+
+		tbyte = 0;
+		for (i = 0; (i < 8) && (bitpos < length); i++) {
+			tbyte <<= 1;
+			tbyte |= data[bitpos++];
+		}
+		if (i < 8)
+			tbyte <<= 8 - i;
+		*dest++ = tbyte;
+	}	
+}
+
+
 #if 0
 static void
 diff_decode(char *dst, char *src, int len)
@@ -58,9 +80,14 @@ GS_new(GS_CTX *ctx)
 	if (ctx->pcap_fd < 0)
 		fprintf(stderr, "cannot open PCAP file: %s\n", strerror(errno));
 
+	ctx->burst_pcap_fd = open_pcap_file("tvoid-burst.pcap");
+	if (ctx->burst_pcap_fd < 0)
+		fprintf(stderr, "cannot open burst PCAP file: %s\n", strerror(errno));
+
 	return 0;
 }
 
+#define BURST_BYTES	((USEFUL_BITS/8)+1)
 /*
  * 142 bit
  */
@@ -72,7 +99,17 @@ GS_process(GS_CTX *ctx, int ts, int type, const unsigned char *src)
 	int ret;
 	unsigned char *data;
 	int len;
+	struct gs_ts_ctx *ts_ctx = &ctx->ts_ctx[ts];
+	unsigned char octified[BURST_BYTES];
 
+	memset(ctx->msg, 0, sizeof(ctx->msg));
+
+	/* write burst to burst PCAP file */
+	burst_octify(octified, src, USEFUL_BITS);
+	write_pcap_packet(ctx->burst_pcap_fd, 0 /* arfcn */, ts, ctx->fn,
+			  1, type, octified, BURST_BYTES);
+	
+#if 0
 	if (ts != 0) {
 		/* non-0 timeslots should end up in PCAP */
 		data = decode_cch(ctx, ctx->burst, &len);
@@ -81,51 +118,56 @@ GS_process(GS_CTX *ctx, int ts, int type, const unsigned char *src)
 		write_pcap_packet(ctx->pcap_fd, 0 /* arfcn */, ts, ctx->fn, data, len);
 		return;
 	}
+#endif
 
-	if (type == SCH)
-	{
-		ret = decode_sch(src, &fn, &bsic);
-		if (ret != 0)
+	if (ts == 0) {
+		if (type == SCH) {
+			ret = decode_sch(src, &fn, &bsic);
+			if (ret != 0)
+				return 0;
+			if ((ctx->bsic > 0) && (bsic != ctx->bsic))
+				fprintf(stderr, "WARN: BSIC changed.\n");
+			//DEBUGF("FN %d, BSIC %d\n", fn, bsic);
+			ctx->fn = fn;
+			ctx->bsic = bsic;
+			/* Reset message concatenator */
+			ts_ctx->burst_count = 0;
 			return 0;
-		if ((ctx->bsic > 0) && (bsic != ctx->bsic))
-			fprintf(stderr, "WARN: BSIC changed.\n");
-		//DEBUGF("FN %d, BSIC %d\n", fn, bsic);
-		ctx->fn = fn;
-		ctx->bsic = bsic;
-		/* Reset message concatenator */
-		ctx->burst_count = 0;
-		return 0;
-	}
+		}
 
-	/* If we did not get Frame Number yet then return */
-	if (ctx->fn < 0)
-		return 0;
+		/* If we did not get Frame Number yet then return */
+		if (ctx->fn < 0)
+			return 0;
 
-	ctx->fn++;
-	if (type == NORMAL)
-	{
+		ctx->fn++;
+	}
+
+	if (type == NORMAL) {
 		/* Interested in these frame numbers (cch)
  		 * 2-5, 12-15, 22-25, 23-35, 42-45
  		 * 6-9, 16-19, 26-29, 36-39, 46-49
  		 */
 		/* Copy content data into new array */
 		//DEBUGF("burst count %d\n", ctx->burst_count);
-		memcpy(ctx->burst + (116 * ctx->burst_count), src, 58);
-		memcpy(ctx->burst + (116 * ctx->burst_count) + 58, src + 58 + 26, 58);
-		ctx->burst_count++;
+		memcpy(ts_ctx->burst + (116 * ts_ctx->burst_count), src, 58);
+		memcpy(ts_ctx->burst + (116 * ts_ctx->burst_count) + 58, src + 58 + 26, 58);
+		ts_ctx->burst_count++;
 		/* Return if not enough bursts for a full gsm message */
-		if (ctx->burst_count < 4)
+		if (ts_ctx->burst_count < 4)
 			return 0;
 
-		ctx->burst_count = 0;
-		data = decode_cch(ctx, ctx->burst, &len);
-		if (data == NULL)
+		ts_ctx->burst_count = 0;
+		data = decode_cch(ctx, ts_ctx->burst, &len);
+		if (data == NULL) {
+			DEBUGF("cannot decode fnr=0x%08x ts=%d\n", ctx->fn, ts);
 			return -1;
+		}
 		//DEBUGF("OK TS %d, len %d\n", ts, len);
 
 		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, ctx->fn, data, len);
+		write_pcap_packet(ctx->pcap_fd, 0 /* arfcn */, ts, ctx->fn,
+				  0, NORMAL, data, len);
 #if 0
 		if (ctx->fn % 51 != 0) && ( (((ctx->fn % 51 + 5) % 10 == 0) || (((ctx->fn % 51) + 1) % 10 ==0) ) )
 			ready = 1;
-- 
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