diff options
author | Pablo Neira Ayuso <pablo@gnumonks.org> | 2012-01-24 14:32:37 +0100 |
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committer | Pablo Neira Ayuso <pablo@netfilter.org> | 2012-02-23 13:44:26 +0100 |
commit | 72cd95b3527ee45639f0445817781afc3e732f45 (patch) | |
tree | ae72c9aa167320b8c12cfbc9ab3700d2037f6d1d /src/rtp.c | |
parent | 2b5d3ce7c69e1149bb2af815ab8b8534026063ca (diff) |
add RTP support
This patch adds the initial RTP support for libosmo-netif, it's based
on Harald's RTP support available in openBSC.
I have also added a couple of example to show how our new channel
infrastructure interacts with the RTP layer.
Signed-off-by: Pablo Neira Ayuso <pablo@gnumonks.org>
Diffstat (limited to 'src/rtp.c')
-rw-r--r-- | src/rtp.c | 231 |
1 files changed, 231 insertions, 0 deletions
diff --git a/src/rtp.c b/src/rtp.c new file mode 100644 index 0000000..a3afbc4 --- /dev/null +++ b/src/rtp.c @@ -0,0 +1,231 @@ +#include <stdint.h> +#include <sys/time.h> +#include <endian.h> +#include <errno.h> +#include <string.h> /* for memcpy. */ +#include <arpa/inet.h> /* for ntohs. */ + +#include <osmocom/core/talloc.h> +#include <osmocom/core/msgb.h> +#include <osmocom/core/logging.h> + +#include <osmocom/netif/rtp.h> + +/* + * Definitions in RFC 3550. + */ + +/* RTP header. */ +struct rtp_hdr { +#if __BYTE_ORDER == __LITTLE_ENDIAN + uint8_t csrc_count:4, + extension:1, + padding:1, + version:2; + uint8_t payload_type:7, + marker:1; +#elif __BYTE_ORDER == __BIG_ENDIAN + uint8_t version:2, + padding:1, + extension:1, + csrc_count:4; + uint8_t marker:1, + payload_type:7; +#endif + uint16_t sequence; + uint32_t timestamp; + uint32_t ssrc; +} __attribute__((packed)); + +#define RTP_VERSION 2 + +/* 5.3.1 RTP Header Extension + * + * If the X bit in the RTP header is one, a variable-length header + * extension MUST be appended to the RTP header, following the CSRC list + * if present. The header extension contains a 16-bit length field that + * counts the number of 32-bit words in the extension, excluding the + * four-octet extension header (therefore zero is a valid length). Only + * a single extension can be appended to the RTP data header. + */ +struct rtp_x_hdr { + uint16_t by_profile; + uint16_t length; +} __attribute__((packed)); + +/* RTPC header. */ +struct rtcp_hdr { + uint8_t byte0; + uint8_t type; + uint16_t length; +} __attribute__((packed)); + +/* + * Internal definitions for this implementation. + */ + +struct osmo_rtp_handle { + struct { + uint16_t sequence; + uint32_t timestamp; + uint32_t ssrc; + struct timeval last_tv; + } tx; +}; + +struct osmo_rtp_handle *osmo_rtp_handle_create(void *ctx) +{ + struct osmo_rtp_handle *h; + + h = talloc_zero(ctx, struct osmo_rtp_handle); + if (h == NULL) { + LOGP(DLMUX, LOGL_ERROR, "OOM\n"); + return NULL; + } + return h; +} + +void osmo_rtp_handle_free(struct osmo_rtp_handle *h) +{ + DEBUGP(DLMUX, "%s (h=%p)\n", __FUNCTION__, h); + + talloc_free(h); +} + +int osmo_rtp_handle_tx_set_sequence(struct osmo_rtp_handle *h, uint16_t seq) +{ + DEBUGP(DLMUX, "%s (handle=%p, seq=%hu)\n", __FUNCTION__, h, seq); + + h->tx.sequence = seq; + + return 0; +} + +int osmo_rtp_handle_tx_set_ssrc(struct osmo_rtp_handle *h, uint32_t ssrc) +{ + DEBUGP(DLMUX, "%s (handle=%p, seq=%hu)\n", __FUNCTION__, h, ssrc); + + h->tx.ssrc = ssrc; + return 0; +} + +int osmo_rtp_handle_tx_set_timestamp(struct osmo_rtp_handle *h, uint32_t timestamp) +{ + DEBUGP(DLMUX, "%s (handle=%p, ts=%hu)\n", __FUNCTION__, h, timestamp); + + h->tx.timestamp = timestamp; + return 0; +} + +/* decode and pull RTP header out and return payload_type. The msg->data + points to data payload after this is called. This function returns the + RTP payload type on success. */ +int osmo_rtp_parse(struct osmo_rtp_handle *h, struct msgb *msg) +{ + struct rtp_hdr *rtph = (struct rtp_hdr *)msg->data; + struct rtp_x_hdr *rtpxh; + uint8_t *payload; + int payload_len; + int x_len; + int csrc_len; + + if (msg->len < sizeof(struct rtp_hdr)) { + DEBUGPC(DLMUX, "received RTP frame too short (len = %d)\n", + msg->len); + return -EINVAL; + } + if (rtph->version != RTP_VERSION) { + DEBUGPC(DLMUX, "received RTP version %d not supported.\n", + rtph->version); + return -EINVAL; + } + csrc_len = rtph->csrc_count << 2; + payload = msg->data + sizeof(struct rtp_hdr) + csrc_len; + payload_len = msg->len - sizeof(struct rtp_hdr) - csrc_len; + if (payload_len < 0) { + DEBUGPC(DLMUX, "received RTP frame too short (len = %d, " + "csrc count = %d)\n", msg->len, rtph->csrc_count); + return -EINVAL; + } + if (rtph->extension) { + if (payload_len < sizeof(struct rtp_x_hdr)) { + DEBUGPC(DLMUX, "received RTP frame too short for " + "extension header\n"); + return -EINVAL; + } + rtpxh = (struct rtp_x_hdr *)payload; + x_len = ntohs(rtpxh->length) * 4 + sizeof(struct rtp_x_hdr); + payload += x_len; + payload_len -= x_len; + if (payload_len < 0) { + DEBUGPC(DLMUX, "received RTP frame too short, " + "extension header exceeds frame length\n"); + return -EINVAL; + } + } + if (rtph->padding) { + if (payload_len < 0) { + DEBUGPC(DLMUX, "received RTP frame too short for " + "padding length\n"); + return -EINVAL; + } + payload_len -= payload[payload_len - 1]; + if (payload_len < 0) { + DEBUGPC(DLMUX, "received RTP frame with padding " + "greater than payload\n"); + return -EINVAL; + } + } + + msgb_pull(msg, msg->len - payload_len); + + return rtph->payload_type; +} + +struct msgb * +osmo_rtp_build(struct osmo_rtp_handle *h, uint8_t payload_type, + uint32_t payload_len, const void *data, uint32_t duration) +{ + struct msgb *msg; + struct rtp_hdr *rtph; + struct timeval tv, tv_diff = {}; + long int usec_diff, frame_diff; + + gettimeofday(&tv, NULL); + timersub(&tv_diff, &h->tx.last_tv, &tv); + h->tx.last_tv = tv; + + usec_diff = tv_diff.tv_sec * 1000000 + tv_diff.tv_usec; + frame_diff = (usec_diff / 20000); + + if (abs(frame_diff) > 1) { + long int frame_diff_excess = frame_diff - 1; + + LOGP(DLMUX, LOGL_NOTICE, + "Correcting frame difference of %ld frames\n", + frame_diff_excess); + h->tx.sequence += frame_diff_excess; + h->tx.timestamp += frame_diff_excess * duration; + } + + msg = msgb_alloc(sizeof(struct rtp_hdr) + payload_len, "RTP"); + if (!msg) { + LOGP(DLMUX, LOGL_ERROR, "OOM\n"); + return NULL; + } + rtph = (struct rtp_hdr *)msg->data; + rtph->version = RTP_VERSION; + rtph->padding = 0; + rtph->extension = 0; + rtph->csrc_count = 0; + rtph->marker = 0; + rtph->payload_type = payload_type; + rtph->sequence = htons(h->tx.sequence++); + rtph->timestamp = htonl(h->tx.timestamp); + h->tx.timestamp += duration; + rtph->ssrc = htonl(h->tx.ssrc); + memcpy(msg->data + sizeof(struct rtp_hdr), data, payload_len); + msgb_put(msg, sizeof(struct rtp_hdr) + payload_len); + + return msg; +} |