From 72043327b933d8a4beb45b8dac11daf2359fc86e Mon Sep 17 00:00:00 2001
From: Andreas Eversberg <jolly@eversberg.eu>
Date: Sat, 4 Mar 2023 18:47:19 +0100
Subject: [PATCH] Send two B-channel frames when first frame is received

The size of both frames match the receive size.
---
 src/isdn/isdn.c | 36 +++++++++++++++++++-----------------
 1 file changed, 19 insertions(+), 17 deletions(-)

diff --git a/src/isdn/isdn.c b/src/isdn/isdn.c
index 5076c6b..aec2c0c 100644
--- a/src/isdn/isdn.c
+++ b/src/isdn/isdn.c
@@ -21,7 +21,7 @@
  *
  * Transmit data is taken from jitter buffer.
  *
- * When data is received from b-channel the first time, two chunks of data are transmitted to ISDN interface in one block.
+ * When data is received from b-channel the first time, two chunks of data are transmitted to ISDN interface.
  *
  * When more data is received from b-channel, this extra chunk is transmitted to ISDN interface.
  *
@@ -1615,34 +1615,36 @@ static void bchannel_rx_tx(isdn_t *isdn_ep, int index, struct mISDNhead *hh, uns
 	}
 
 	/* prepare ISDN TX buffer */
-	unsigned char buf[MISDN_HEADER_LEN + len + len];
+	unsigned char buf[MISDN_HEADER_LEN + len];
 	struct mISDNhead *frm = (struct mISDNhead *)buf;
-	int offset;
 	int rc = 0;
 	frm->prim = PH_DATA_REQ;
 	frm->id = 0;
-	if (!call->b_transmitting) {
-		PDEBUG(DISDN, DEBUG_DEBUG, "First received b-channel data, filling FIFO with double data of %d bytes.\n", len * 2);
-		memset(buf + MISDN_HEADER_LEN, 0xff, len);
-		offset = len;
-	} else {
-//		PDEBUG(DISDN, DEBUG_DEBUG, "More received b-channel data, filling FIFO with data of %d bytes.\n", len);
-		offset = 0;
-	}
 
 	/* load from TX jitter buffer and optionally overload with tones */
-	jitter_load(&call->tx_dejitter, buf + MISDN_HEADER_LEN + offset, len);
-	isdn_tone_copy(&call->isdn_tone, buf + MISDN_HEADER_LEN + offset, len);
+	jitter_load(&call->tx_dejitter, buf + MISDN_HEADER_LEN, len);
+	isdn_tone_copy(&call->isdn_tone, buf + MISDN_HEADER_LEN, len);
+
+	if (!call->b_transmitting) {
+		unsigned char init_buf[MISDN_HEADER_LEN + len];
+		PDEBUG(DISDN, DEBUG_DEBUG, "First received b-channel data, filling FIFO with two chunks of %d bytes.\n", len);
+		memcpy(init_buf, frm, MISDN_HEADER_LEN);
+		memset(init_buf + MISDN_HEADER_LEN, 0xff, len);
+		/* forward to interface */
+		if (call->isdn_ep->ph_socket)
+			ph_socket_tx_msg(call->isdn_ep->ph_socket, call->b_channel, PH_PRIM_DATA_REQ, init_buf + MISDN_HEADER_LEN, len);
+		else
+			rc = send(call->isdn_ep->b_sock[call->b_index].ofd.fd, init_buf, MISDN_HEADER_LEN + len, 0);
+		call->b_transmitting = 1;
+	}
 
 	/* forward to interface */
 	if (call->isdn_ep->ph_socket)
-		ph_socket_tx_msg(call->isdn_ep->ph_socket, call->b_channel, PH_PRIM_DATA_REQ, buf + MISDN_HEADER_LEN, offset + len);
+		ph_socket_tx_msg(call->isdn_ep->ph_socket, call->b_channel, PH_PRIM_DATA_REQ, buf + MISDN_HEADER_LEN, len);
 	else
-		rc = send(call->isdn_ep->b_sock[call->b_index].ofd.fd, buf, MISDN_HEADER_LEN + offset + len, 0);
+		rc = send(call->isdn_ep->b_sock[call->b_index].ofd.fd, buf, MISDN_HEADER_LEN + len, 0);
 	if (rc < 0)
 		PDEBUG(DISDN, DEBUG_ERROR, "Write error B-channel data (socket #%d errno=%d:%s)\n", call->isdn_ep->b_sock[call->b_index].ofd.fd, errno, strerror(errno));
-	else
-		call->b_transmitting = 1;
 }
 
 /* receive confirm from bchannel */