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rtp.c
/*
 * rtp.c
 *
 * library functions for the real-time transport protocol
 *
 * David A. McGrew
 * Cisco Systems, Inc.
 */


#include "rtp_priv.h"

#include <stdio.h>
#include <string.h>

#include <sys/types.h>
#ifdef HAVE_SYS_SOCKET_H
# include <sys/socket.h>
#endif

#define PRINT_DEBUG    0    /* set to 1 to print out debugging data */
#define VERBOSE_DEBUG  0    /* set to 1 to print out more data      */

int
rtp_sendto(rtp_sender_t sender, const void* msg, int len) {
  int octets_sent;
  err_status_t stat;
  int pkt_len = len + RTP_HEADER_LEN;

  /* marshal data */
  strncpy(sender->message.body, msg, len);
  
  /* update header */
  sender->message.header.seq = ntohs(sender->message.header.seq) + 1;
  sender->message.header.seq = htons(sender->message.header.seq);
  sender->message.header.ts = ntohl(sender->message.header.ts) + 1;
  sender->message.header.ts = htonl(sender->message.header.ts);
  
  /* apply srtp */
  stat = srtp_protect(sender->srtp_ctx, &sender->message.header, &pkt_len);
  if (stat) {
#if PRINT_DEBUG
    fprintf(stderr, "error: srtp protection failed with code %d\n", stat);
#endif
    return -1;
  }
#if VERBOSE_DEBUG
  srtp_print_packet(&sender->message.header, pkt_len);
#endif
  octets_sent = sendto(sender->socket, (void*)&sender->message,
                   pkt_len, 0, (struct sockaddr *)&sender->addr,
                   sizeof (struct sockaddr_in));

  if (octets_sent != pkt_len) {
#if PRINT_DEBUG
    fprintf(stderr, "error: couldn't send message %s", (char *)msg);
    perror("");
#endif
  }

  return octets_sent;
}

int
rtp_recvfrom(rtp_receiver_t receiver, void *msg, int *len) {
  int octets_recvd;
  err_status_t stat;
  
  octets_recvd = recvfrom(receiver->socket, (void *)&receiver->message,
                   *len, 0, (struct sockaddr *) NULL, 0);

  if (octets_recvd == -1) {
    *len = 0;
    return -1;
  }

  /* verify rtp header */
  if (receiver->message.header.version != 2) {
    *len = 0;
    return -1;
  }

#if PRINT_DEBUG
  fprintf(stderr, "%d octets received from SSRC %u\n",
        octets_recvd, receiver->message.header.ssrc);
#endif
#if VERBOSE_DEBUG
  srtp_print_packet(&receiver->message.header, octets_recvd);
#endif

  /* apply srtp */
  stat = srtp_unprotect(receiver->srtp_ctx,
                  &receiver->message.header, &octets_recvd);
  if (stat) {
    fprintf(stderr,
          "error: srtp unprotection failed with code %d%s\n", stat,
          stat == err_status_replay_fail ? " (replay check failed)" :
          stat == err_status_auth_fail ? " (auth check failed)" : "");
    return -1;
  }
  strncpy(msg, receiver->message.body, octets_recvd);
  
  return octets_recvd;
}

int
rtp_sender_init(rtp_sender_t sender, 
            int sock, 
            struct sockaddr_in addr,
            unsigned int ssrc) {

  /* set header values */
  sender->message.header.ssrc    = htonl(ssrc);
  sender->message.header.ts      = 0;
  sender->message.header.seq     = (uint16_t) rand();
  sender->message.header.m       = 0;
  sender->message.header.pt      = 0x1;
  sender->message.header.version = 2;
  sender->message.header.p       = 0;
  sender->message.header.x       = 0;
  sender->message.header.cc      = 0;

  /* set other stuff */
  sender->socket = sock;
  sender->addr = addr;

  return 0;
}

int
rtp_receiver_init(rtp_receiver_t rcvr, 
              int sock, 
              struct sockaddr_in addr,
              unsigned int ssrc) {
  
  /* set header values */
  rcvr->message.header.ssrc    = htonl(ssrc);
  rcvr->message.header.ts      = 0;
  rcvr->message.header.seq     = 0;
  rcvr->message.header.m       = 0;
  rcvr->message.header.pt      = 0x1;
  rcvr->message.header.version = 2;
  rcvr->message.header.p       = 0;
  rcvr->message.header.x       = 0;
  rcvr->message.header.cc      = 0;

  /* set other stuff */
  rcvr->socket = sock;
  rcvr->addr = addr;

  return 0;
}

int
rtp_sender_init_srtp(rtp_sender_t sender, const srtp_policy_t *policy) {
  return srtp_create(&sender->srtp_ctx, policy);
}

int
rtp_sender_deinit_srtp(rtp_sender_t sender) {
  return srtp_dealloc(sender->srtp_ctx);
}

int
rtp_receiver_init_srtp(rtp_receiver_t sender, const srtp_policy_t *policy) {
  return srtp_create(&sender->srtp_ctx, policy);
}

int
rtp_receiver_deinit_srtp(rtp_receiver_t sender) {
  return srtp_dealloc(sender->srtp_ctx);
}

rtp_sender_t 
rtp_sender_alloc(void) {
  return (rtp_sender_t)malloc(sizeof(rtp_sender_ctx_t));
}

void
rtp_sender_dealloc(rtp_sender_t rtp_ctx) {
  free(rtp_ctx);
}

rtp_receiver_t 
rtp_receiver_alloc(void) {
  return (rtp_receiver_t)malloc(sizeof(rtp_receiver_ctx_t));
}

void
rtp_receiver_dealloc(rtp_receiver_t rtp_ctx) {
  return free(rtp_ctx);
}

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