1 files changed, 446 insertions, 0 deletions
diff --git a/openbsc/src/rtp_proxy.c b/openbsc/src/rtp_proxy.c
new file mode 100644
index 000000000..a581b9fdf
--- /dev/null
+++ b/openbsc/src/rtp_proxy.c
@@ -0,0 +1,446 @@
+/* RTP proxy handling for ip.access nanoBTS */
+
+/* (C) 2009 by Harald Welte <laforge@gnumonks.org>
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <errno.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+
+#include <openbsc/talloc.h>
+#include <openbsc/gsm_data.h>
+#include <openbsc/msgb.h>
+#include <openbsc/select.h>
+#include <openbsc/debug.h>
+#include <openbsc/rtp_proxy.h>
+
+static LLIST_HEAD(rtp_sockets);
+
+/* should we mangle the CNAME inside SDES of RTCP packets? We disable
+ * this by default, as it seems to be not needed */
+static int mangle_rtcp_cname = 0;
+
+enum rtp_bfd_priv {
+	RTP_PRIV_NONE,
+	RTP_PRIV_RTP,
+	RTP_PRIV_RTCP
+};
+
+#define RTP_ALLOC_SIZE	1500
+
+/* according to RFC 1889 */
+struct rtcp_hdr {
+	u_int8_t byte0;
+	u_int8_t type;
+	u_int16_t length;
+} __attribute__((packed));
+
+#define RTCP_TYPE_SDES	202
+	
+#define RTCP_IE_CNAME	1
+
+/* iterate over all chunks in one RTCP message, look for CNAME IEs and
+ * replace all of those with 'new_cname' */
+static int rtcp_sdes_cname_mangle(struct msgb *msg, struct rtcp_hdr *rh,
+				  u_int16_t *rtcp_len, const char *new_cname)
+{
+	u_int8_t *rtcp_end;
+	u_int8_t *cur = (u_int8_t *) rh;
+	u_int8_t tag, len = 0;
+
+	rtcp_end = cur + *rtcp_len;
+	/* move cur to end of RTP header */
+	cur += sizeof(*rh);
+
+	/* iterate over Chunks */
+	while (cur+4 < rtcp_end) {
+		/* skip four bytes SSRC/CSRC */
+		cur += 4;
+	
+		/* iterate over IE's inside the chunk */
+		while (cur+1 < rtcp_end) {
+			tag = *cur++;
+			if (tag == 0) {
+				/* end of chunk, skip additional zero */
+				while (*cur++ == 0) { }
+				break;
+			}
+			len = *cur++;
+	
+			if (tag == RTCP_IE_CNAME) {
+				/* we've found the CNAME, lets mangle it */
+				if (len < strlen(new_cname)) {
+					/* we need to make more space */
+					int increase = strlen(new_cname) - len;
+
+					msgb_push(msg, increase);
+					memmove(cur+len+increase, cur+len,
+						rtcp_end - (cur+len));
+					/* FIXME: we have to respect RTCP
+					 * padding/alignment rules! */
+					len += increase;
+					*(cur-1) += increase;
+					rtcp_end += increase;
+					*rtcp_len += increase;
+				}
+				/* copy new CNAME into message */
+				memcpy(cur, new_cname, strlen(new_cname));
+				/* FIXME: zero the padding in case new CNAME
+				 * is smaller than old one !!! */
+			}
+			cur += len;
+		}
+	}
+
+	return 0;
+}
+
+static int rtcp_mangle(struct msgb *msg, struct rtp_socket *rs)
+{
+	struct rtp_sub_socket *rss = &rs->rtcp;
+	struct rtcp_hdr *rtph;
+	u_int16_t old_len;
+	int rc;
+
+	if (!mangle_rtcp_cname)
+		return 0;
+
+	/* iterate over list of RTCP messages */
+	rtph = (struct rtcp_hdr *)msg->data;
+	while ((void *)rtph + sizeof(*rtph) < (void *)msg->data + msg->len) {
+		old_len = (ntohs(rtph->length) + 1) * 4;
+		if (rtph->type == RTCP_TYPE_SDES) {
+			char new_cname[255];
+			strncpy(new_cname, inet_ntoa(rss->sin_local.sin_addr),
+				sizeof(new_cname));
+			new_cname[sizeof(new_cname)-1] = '\0';
+			rc = rtcp_sdes_cname_mangle(msg, rtph, &old_len,
+						    new_cname);
+			if (rc < 0)
+				return rc;
+		}
+		rtph = (void *)rtph + old_len;
+	}
+
+	return 0;
+}
+
+/* read from incoming RTP/RTCP socket */
+static int rtp_socket_read(struct rtp_socket *rs, struct rtp_sub_socket *rss)
+{
+	int rc;
+	struct msgb *msg = msgb_alloc(RTP_ALLOC_SIZE, "RTP/RTCP");
+	struct rtp_sub_socket *other_rss;
+
+	if (!msg)
+		return -ENOMEM;
+
+	rc = read(rss->bfd.fd, msg->data, RTP_ALLOC_SIZE);
+	if (rc <= 0) {
+		rss->bfd.when &= ~BSC_FD_READ;
+		return rc;
+	}
+
+	msgb_put(msg, rc);
+
+	switch (rs->rx_action) {
+	case RTP_PROXY:
+		if (!rs->proxy.other_sock) {
+			rc = -EIO;
+			goto out_free;
+		}
+		if (rss->bfd.priv_nr == RTP_PRIV_RTP)
+			other_rss = &rs->proxy.other_sock->rtp;
+		else if (rss->bfd.priv_nr == RTP_PRIV_RTCP) {
+			other_rss = &rs->proxy.other_sock->rtcp;
+			/* modify RTCP SDES CNAME */
+			rc = rtcp_mangle(msg, rs);
+			if (rc < 0)
+				goto out_free;
+		} else {
+			rc = -EINVAL;
+			goto out_free;
+		}
+		msgb_enqueue(&other_rss->tx_queue, msg);
+		other_rss->bfd.when |= BSC_FD_WRITE;
+		break;
+	/* FIXME: other cases */
+	}
+
+	return rc;
+
+out_free:
+	msgb_free(msg);
+	return rc;
+}
+
+/* write from tx_queue to RTP/RTCP socket */
+static int rtp_socket_write(struct rtp_socket *rs, struct rtp_sub_socket *rss)
+{
+	struct msgb *msg;
+	int written;
+
+	msg = msgb_dequeue(&rss->tx_queue);
+	if (!msg) {
+		rss->bfd.when &= ~BSC_FD_WRITE;
+		return 0;
+	}
+
+	written = write(rss->bfd.fd, msg->data, msg->len);
+	if (written < msg->len) {
+		perror("short write");
+		msgb_free(msg);
+		return -EIO;
+	}
+
+	msgb_free(msg);
+
+	return 0;
+}
+
+
+/* callback for the select.c:bfd_* layer */
+static int rtp_bfd_cb(struct bsc_fd *bfd, unsigned int flags)
+{
+	struct rtp_socket *rs = bfd->data;
+	struct rtp_sub_socket *rss;
+
+	switch (bfd->priv_nr) {
+	case RTP_PRIV_RTP:
+		rss = &rs->rtp;
+		break;
+	case RTP_PRIV_RTCP:
+		rss = &rs->rtcp;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (flags & BSC_FD_READ)
+		rtp_socket_read(rs, rss);
+
+	if (flags & BSC_FD_WRITE)
+		rtp_socket_write(rs, rss);
+
+	return 0;
+}
+
+static void init_rss(struct rtp_sub_socket *rss, 
+		     struct rtp_socket *rs, int fd, int priv_nr)
+{
+	/* initialize bfd */
+	rss->bfd.fd = fd;
+	rss->bfd.data = rs;
+	rss->bfd.priv_nr = priv_nr;
+	rss->bfd.cb = rtp_bfd_cb;
+}
+
+struct rtp_socket *rtp_socket_create(void)
+{
+	int rc;
+	struct rtp_socket *rs;
+
+	DEBUGP(DMUX, "rtp_socket_create(): ");
+
+	rs = talloc_zero(tall_bsc_ctx, struct rtp_socket);
+	if (!rs)
+		return NULL;
+
+	INIT_LLIST_HEAD(&rs->rtp.tx_queue);
+	INIT_LLIST_HEAD(&rs->rtcp.tx_queue);
+
+	rc = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+	if (rc < 0)
+		goto out_free;
+
+	init_rss(&rs->rtp, rs, rc, RTP_PRIV_RTP);
+	rc = bsc_register_fd(&rs->rtp.bfd);
+	if (rc < 0)
+		goto out_rtp_socket;
+
+	rc = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+	if (rc < 0)
+		goto out_rtp_bfd;
+
+	init_rss(&rs->rtcp, rs, rc, RTP_PRIV_RTCP);
+	rc = bsc_register_fd(&rs->rtcp.bfd);
+	if (rc < 0)
+		goto out_rtcp_socket;
+
+	DEBUGPC(DMUX, "success\n");
+
+	rc = rtp_socket_bind(rs, INADDR_ANY);
+	if (rc < 0)
+		goto out_rtcp_bfd;
+
+	return rs;
+
+out_rtcp_bfd:
+	bsc_unregister_fd(&rs->rtcp.bfd);
+out_rtcp_socket:
+	close(rs->rtcp.bfd.fd);
+out_rtp_bfd:
+	bsc_unregister_fd(&rs->rtp.bfd);
+out_rtp_socket:
+	close(rs->rtp.bfd.fd);
+out_free:
+	talloc_free(rs);
+	DEBUGPC(DMUX, "failed\n");
+	return NULL;
+}
+
+static int rtp_sub_socket_bind(struct rtp_sub_socket *rss, u_int32_t ip,
+				u_int16_t port)
+{
+	int rc;
+	socklen_t alen = sizeof(rss->sin_local);
+
+	rss->sin_local.sin_family = AF_INET;
+	rss->sin_local.sin_addr.s_addr = htonl(ip);
+	rss->sin_local.sin_port = htons(port);
+	rss->bfd.when |= BSC_FD_READ;
+
+	rc = bind(rss->bfd.fd, (struct sockaddr *)&rss->sin_local,
+		  sizeof(rss->sin_local));
+	if (rc < 0)
+		return rc;
+
+	/* retrieve the address we actually bound to, in case we
+	 * passed INADDR_ANY as IP address */
+	return getsockname(rss->bfd.fd, (struct sockaddr *)&rss->sin_local,
+			   &alen);
+}
+
+#define RTP_PORT_BASE	30000
+static unsigned int next_udp_port = RTP_PORT_BASE;
+
+/* bind a RTP socket to a local address */
+int rtp_socket_bind(struct rtp_socket *rs, u_int32_t ip)
+{
+	int rc = -EIO;
+	struct in_addr ia;
+
+	ia.s_addr = htonl(ip);
+	DEBUGP(DMUX, "rtp_socket_bind(rs=%p, IP=%s): ", rs,
+		inet_ntoa(ia));
+
+	/* try to bind to a consecutive pair of ports */
+	for (next_udp_port = next_udp_port % 0xffff;
+	     next_udp_port < 0xffff; next_udp_port += 2) {
+		rc = rtp_sub_socket_bind(&rs->rtp, ip, next_udp_port);
+		if (rc != 0)
+			continue;
+
+		rc = rtp_sub_socket_bind(&rs->rtcp, ip, next_udp_port+1);
+		if (rc == 0)
+			break;
+	}
+	if (rc < 0) {
+		DEBUGPC(DMUX, "failed\n");
+		return rc;
+	}
+
+	ia.s_addr = rs->rtp.sin_local.sin_addr.s_addr;
+	DEBUGPC(DMUX, "BOUND_IP=%s, BOUND_PORT=%u\n",
+		inet_ntoa(ia), ntohs(rs->rtp.sin_local.sin_port));
+	return ntohs(rs->rtp.sin_local.sin_port);
+}
+
+static int rtp_sub_socket_connect(struct rtp_sub_socket *rss,
+				  u_int32_t ip, u_int16_t port)
+{
+	int rc;
+	socklen_t alen = sizeof(rss->sin_local);
+
+	rss->sin_remote.sin_family = AF_INET;
+	rss->sin_remote.sin_addr.s_addr = htonl(ip);
+	rss->sin_remote.sin_port = htons(port);
+
+	rc = connect(rss->bfd.fd, (struct sockaddr *) &rss->sin_remote,
+		     sizeof(rss->sin_remote));
+	if (rc < 0)
+		return rc;
+
+	return getsockname(rss->bfd.fd, (struct sockaddr *)&rss->sin_local,
+			   &alen);
+}
+
+/* 'connect' a RTP socket to a remote peer */
+int rtp_socket_connect(struct rtp_socket *rs, u_int32_t ip, u_int16_t port)
+{
+	int rc;
+	struct in_addr ia;
+
+	ia.s_addr = htonl(ip);
+	DEBUGP(DMUX, "rtp_socket_connect(rs=%p, ip=%s, port=%u)\n",
+		rs, inet_ntoa(ia), port);
+
+	rc = rtp_sub_socket_connect(&rs->rtp, ip, port);
+	if (rc < 0)
+		return rc;
+
+	return rtp_sub_socket_connect(&rs->rtcp, ip, port+1);
+}
+
+/* bind two RTP/RTCP sockets together */
+int rtp_socket_proxy(struct rtp_socket *this, struct rtp_socket *other)
+{
+	DEBUGP(DMUX, "rtp_socket_proxy(this=%p, other=%p)\n",
+		this, other);
+
+	this->rx_action = RTP_PROXY;
+	this->proxy.other_sock = other;
+
+	other->rx_action = RTP_PROXY;
+	other->proxy.other_sock = this;
+
+	return 0;
+}
+
+static void free_tx_queue(struct rtp_sub_socket *rss)
+{
+	struct msgb *msg;
+	
+	while ((msg = msgb_dequeue(&rss->tx_queue)))
+		msgb_free(msg);
+}
+
+int rtp_socket_free(struct rtp_socket *rs)
+{
+	DEBUGP(DMUX, "rtp_socket_free(rs=%p)\n", rs);
+
+	/* make sure we don't leave references dangling to us */
+	if (rs->rx_action == RTP_PROXY &&
+	    rs->proxy.other_sock)
+		rs->proxy.other_sock->proxy.other_sock = NULL;
+
+	bsc_unregister_fd(&rs->rtp.bfd);
+	close(rs->rtp.bfd.fd);
+	free_tx_queue(&rs->rtp);
+
+	bsc_unregister_fd(&rs->rtcp.bfd);
+	close(rs->rtcp.bfd.fd);
+	free_tx_queue(&rs->rtcp);
+
+	talloc_free(rs);
+
+	return 0;
+}