sdp_parse.c

Sofia SIP is an open-source SIP User-Agent library, compliant with the IETF RFC3261 specification.

  sdp_rtpmap_celb = RTPMAP(25, "CelB", 90000, 0),
  sdp_rtpmap_jpeg = RTPMAP(26, "JPEG", 90000, 0),
  sdp_rtpmap_nv = RTPMAP(28, "nv",   90000, 0),
  sdp_rtpmap_h261 = RTPMAP(31, "H261", 90000, 0),
  sdp_rtpmap_mpv = RTPMAP(32, "MPV",  90000, 0),
  sdp_rtpmap_mp2t = RTPMAP(33, "MP2T", 90000, 0),
  sdp_rtpmap_h263 = RTPMAP(34, "H263", 90000, 0);

/** Table of rtpmap structures by payload type numbers.
 *
 * The table of reserved payload numbers is constructed from @RFC3551
 * and @RFC1890. Note the clock rate of G722.
 *
 * Use sdp_rtpmap_dup() to copy these structures.
 */
sdp_rtpmap_t const * const sdp_rtpmap_well_known[128] =
{
  &sdp_rtpmap_pcmu,		/* 0 */
  &sdp_rtpmap_1016,		/* 1 */
  &sdp_rtpmap_g721,		/* 2 */
  &sdp_rtpmap_gsm,		/* 3 */
  &sdp_rtpmap_g723,		/* 4 */
  &sdp_rtpmap_dvi4_8000,	/* 5 */
  &sdp_rtpmap_dvi4_16000,	/* 6 */
  &sdp_rtpmap_lpc,		/* 7 */
  &sdp_rtpmap_pcma,		/* 8 */
  &sdp_rtpmap_g722,		/* 9 */
  &sdp_rtpmap_l16_2,		/* 10 */
  &sdp_rtpmap_l16,		/* 11 */
  &sdp_rtpmap_qcelp,		/* 12 */
  &sdp_rtpmap_cn,		/* 13 */
  &sdp_rtpmap_mpa,		/* 14 */
  &sdp_rtpmap_g728,		/* 15 */
  &sdp_rtpmap_dvi4_11025,	/* 16 */
  &sdp_rtpmap_dvi4_22050,	/* 17 */
  &sdp_rtpmap_g729,		/* 18 */
  &sdp_rtpmap_reserved_cn,	/* 19 */
  NULL,				/* 20 */
  NULL,				/* 21 */
  NULL,				/* 22 */
  NULL,				/* 23 */
  NULL,				/* 24 */
  &sdp_rtpmap_celb,		/* 25 */
  &sdp_rtpmap_jpeg,		/* 26 */
  NULL,				/* 27 */
  &sdp_rtpmap_nv,		/* 28 */
  NULL,				/* 29 */
  NULL,				/* 30 */
  &sdp_rtpmap_h261,		/* 31 */
  &sdp_rtpmap_mpv,		/* 32 */
  &sdp_rtpmap_mp2t,		/* 33 */
  &sdp_rtpmap_h263,		/* 34 */
  NULL,
};

/**
 * The function parse_payload() parses an RTP payload type list, and
 * creates an rtpmap structure for each payload type.
 *
 * @param p       pointer to SDP parser object
 * @param r       pointer to record data
 * @param result  pointer to which parsed record is assigned
 */
static void parse_payload(sdp_parser_t *p, char *r, sdp_rtpmap_t **result)
{
  while (*r) {
    unsigned long value;

    if (parse_ul(p, &r, &value, 128) == 0) {
      PARSE_ALLOC(p, sdp_rtpmap_t, rm);

      assert(0 <= value && value < 128);

      *result = rm; result = &rm->rm_next;

      if (sdp_rtpmap_well_known[value]) {
	*rm = *sdp_rtpmap_well_known[value];
      }
      else {
	rm->rm_predef = 1;
	rm->rm_pt = value;
	rm->rm_encoding = "";
	rm->rm_rate = 0;
      }
    }
    else if (p->pr_config && r[0] == '*' && (r[1] == ' ' || r[1] == '\0')) {
      PARSE_ALLOC(p, sdp_rtpmap_t, rm);

      *result = rm; result = &rm->rm_next;

      rm->rm_predef = 1;
      rm->rm_any = 1;
      rm->rm_encoding = "*";
      rm->rm_rate = 0;

      return;
    }
    else {
      parsing_error(p, "m= invalid format for RTP/AVT");

      return;
    }
  }
}

/* -------------------------------------------------------------------------
 * Function parse_media_attr() - parse a media-specific "a=" field
 *
 * Description:
 *   This function parses a media-specific attribute field.
 *
 * Parameters:
 *   p      - pointer to SDP parser object
 *   r      - pointer to record data
 *   result - pointer to which parsed record is assigned
 */
static void parse_media_attr(sdp_parser_t *p, char *r, sdp_media_t *m,
			     sdp_attribute_t **result)
{
  /*
   attribute-fields =    *("a=" attribute CRLF)

   attribute =           (att-field ":" att-value) | att-field

   att-field =           1*(alpha-numeric) 

   att-value =           byte-string

   a=rtpmap:<payload type> <encoding name>/<clock rate>[/<encoding parameters>]
   a=fmtp:<payload type> <parameters>
   */
  int rtp = sdp_media_has_rtp(m);
  char *name = NULL, *value = NULL;
  int n;

  if (!(name = token(&r, ":", ALPHA DIGIT "-", SPACE TAB))) {
    parsing_error(p,"invalid attribute name");
    return;
  }

  if (*r)
    value = r;
  else 
    PARSE_CHECK_REST(p, r, "a");

  if (p->pr_mode_manual) 
    ;
  else if (strcasecmp(name, "inactive") == 0) {
    m->m_mode = sdp_inactive;
    return;
  }
  else if (strcasecmp(name, "sendonly") == 0) {
    m->m_mode = sdp_sendonly;
    return;
  }
  else if (strcasecmp(name, "recvonly") == 0) {
    m->m_mode = sdp_recvonly;
    return;
  }
  else if (strcasecmp(name, "sendrecv") == 0) {
    m->m_mode = sdp_sendrecv;
    return;
  }

  if (rtp && strcasecmp(name, "rtpmap") == 0) {
    if ((n = parse_rtpmap(p, r, m)) == 0 || n < -1)
      return;
  }
  else if (rtp && strcasecmp(name, "fmtp") == 0) {
    if ((n = parse_fmtp(p, r, m)) == 0 || n < -1)
      return;
  }
  else {
    PARSE_ALLOC(p, sdp_attribute_t, a);
    *result = a;

    a->a_name  = name;
    a->a_value = value;
  }
}

/** Parse rtpmap attribute.
 *
 * a=rtpmap:<payload type> <encoding name>/<clock rate>[/<encoding parameters>]
 */
static int parse_rtpmap(sdp_parser_t *p, char *r, sdp_media_t *m)
{
  unsigned long pt, rate;
  char *encoding, *params;
  sdp_rtpmap_t *rm;

  int strict = STRICT(p);

  if (parse_ul(p, &r, &pt, 128)) {
    if (strict)
      parsing_error(p, "a=rtpmap: invalid payload type");
    return -1;
  }

  for (rm = m->m_rtpmaps; rm; rm = rm->rm_next)
    if (rm->rm_pt == pt)
      break;

  if (!rm) {
    if (strict)
      parsing_error(p, "a=rtpmap:%lu: unknown payload type", pt);
    return -1;
  }

  encoding = token(&r, "/", ALPHA DIGIT "-", NULL);
  if (!r) {
    parsing_error(p, "a=rtpmap:%lu: missing <clock rate>", pt);
    return -2;
  }
  if (parse_ul(p, &r, &rate, 0)) {
    parsing_error(p, "a=rtpmap:%lu %s: invalid <clock rate>", pt, encoding);
    return -2;
  }

  if (*r == '/') 
    params = ++r;
  else
    params = 0;
    
  rm->rm_predef = 0;
  rm->rm_encoding = encoding;
  rm->rm_rate = rate;
  rm->rm_params = params;

  return 0;
}

/** Parse fmtp attribute.
 *
 * a=fmtp:<payload type> <parameters>
 */
static int parse_fmtp(sdp_parser_t *p, char *r, sdp_media_t *m)
{
  unsigned long pt;
  sdp_rtpmap_t *rm;

  int strict = STRICT(p);

  if (parse_ul(p, &r, &pt, 128)) {
    if (strict)
      parsing_error(p, "a=rtpmap: invalid payload type");
    return -1;
  }

  for (rm = m->m_rtpmaps; rm; rm = rm->rm_next)
    if (rm->rm_pt == pt)
      break;

  if (!rm) {
    if (strict)
      parsing_error(p, "a=fmtp:%lu: unknown payload type", pt);
    return -1;
  }

  rm->rm_fmtp = r;
  return 0;
}

/* -------------------------------------------------------------------------
 * Function parse_descs() - parse media descriptors
 *
 * Description:
 *   This function parses media descriptors at the end of SDP message.
 *
 * Parameters:
 *   p      - pointer to SDP parser object
 *   record - pointer to first media field
 *   message - pointer to rest 
 *   medias - pointer to which parsed media structures are assigned
 */
static void parse_descs(sdp_parser_t *p, 
			char *record, 
			char *message, 
			sdp_media_t **medias)
{
  char *rest;
  const char *strip;
  sdp_media_t *m = NULL;
  sdp_connection_t **connections = NULL;
  sdp_bandwidth_t **bandwidths = NULL;
  sdp_attribute_t **attributes = NULL;

  if (!STRICT(p))
    strip = SPACE TAB;		/* skip initial whitespace */
  else
    strip = "";
  
  for (;
       record && p->pr_ok;
       record = next(&message, CRLF, strip)) {
    char field = record[0];

    rest = record + 2; rest += strspn(rest, strip);

    if (record[1] == '=') switch (field) {
    case 'c':
      assert(connections);
      parse_connection(p, rest, connections);
      connections = &(*connections)->c_next;
      break;

    case 'b':
      assert(bandwidths);
      parse_bandwidth(p, rest, bandwidths);
      bandwidths = &(*bandwidths)->b_next;
      break;

    case 'k':
      parse_key(p, rest, &m->m_key);
      break;

    case 'a':
      assert(attributes);
      parse_media_attr(p, rest, m, attributes);
      if (*attributes)
	attributes = &(*attributes)->a_next;
      break;

    case 'm':
      parse_media(p, rest, medias);
      m = *medias;
      if (m) {
	m->m_mode = p->pr_session_mode;
	medias = &m->m_next;
	connections = &m->m_connections;
	bandwidths = &m->m_bandwidths;
	attributes = &m->m_attributes;
      }
    }
  }
}

static void parse_text_list(sdp_parser_t *p, char *r, sdp_list_t **result)
{
  PARSE_ALLOC(p, sdp_list_t, l);

  *result = l;

  l->l_text = r;
}

/*
 * parse_ul: parse an unsigned long
 */
static int parse_ul(sdp_parser_t *p, char **r, 
		    unsigned long *result, unsigned long max)
{
  char *ul = *r; 

  ul += strspn(ul, SPACE TAB);

  *result = strtoul(ul, r, 10);
  if (ul != *r && !(max && max <= *result)) {
    *r += strspn(*r, SPACE TAB);
    return 0;
  }

  return -1;
}

#if !HAVE_STRTOULL
unsigned longlong strtoull(char const *string, char **return_end, int base);
#endif

/*
 * parse_ull: parse an unsigned long long
 */
static int parse_ull(sdp_parser_t *p, char **r, 
		     uint64_t *result, uint64_t max)
{
  unsigned longlong ull;

  char *s = *r; 

  s += strspn(s, SPACE TAB);

  ull = strtoull(s, r, 10);

  if (s != *r && !(max && max <= ull)) {
    *result = (uint64_t)ull;
    *r += strspn(*r, SPACE TAB);
    return 0;
  }

  return -1;
}

static char *token(char **message, 
		   const char *sep, 
		   const char *legal, 
		   const char *strip)
{
  size_t n;
  char *retval = *message;

  if (strip)
    retval += strspn(retval, strip);

  if (legal)
    n = strspn(retval, legal);
  else 
    n = strcspn(retval, sep);

  if (n == 0)
    return NULL;

  if (retval[n]) {
    retval[n++] = '\0';
    n += strspn(retval + n, sep);
  }

  *message = retval + n;

  if (*retval == '\0')
    return NULL;

  return retval;
}

static char *next(char **message, const char *sep, const char *strip)
{
  size_t n;
  char *retval = *message;

  if (strip[0])
    retval += strspn(retval, strip);

  n = strcspn(retval, sep);

  if (n == 0)
    return NULL;

  if (retval[n]) {
    retval[n++] = '\0';
    n += strspn(retval + n, sep);
  }

  *message = retval + n;

  if (*retval == '\0')
    return NULL;

  return retval;
}

static int parsing_error(sdp_parser_t *p, char const *fmt, ...)
{
  int n;
  va_list ap;
  va_start(ap, fmt); 
  
  memset(p->pr_error, 0, sizeof(p->pr_error));
  n = vsnprintf(p->pr_error, sizeof(p->pr_error), fmt, ap);
  va_end(ap);

  p->pr_ok = 0;

  return -1;
}

static void parse_alloc_error(sdp_parser_t *p, const char *typename)
{
  parsing_error(p, "memory exhausted (while allocating memory for %s)", 
		typename);
}