sip_pref_util.c

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

 *
 * @retval 1 if string is a feature tag parameter
 * @retval 0 otherwise
 */
int sip_is_callerpref(char const *param)
{
#define MATCH(s) \
  (strncasecmp(param + 1, s + 1, strlen(s) - 1) == 0 && \
   (param[strlen(s)] == '=' || param[strlen(s)] == '\0'))

  int xor = 0, base = 0;

  if (!param || !param[0])
    return 0;

  if (param[0] == '+')
    param++, xor = 1;

  switch (param[0]) {
  case 'a': case 'A':
    base = MATCH("audio") || MATCH("automata") || MATCH("application") ||
      MATCH("actor");
    break;
  case 'c': case 'C':
    base = MATCH("class") || MATCH("control");
    break;
  case 'd': case 'D':
    base = MATCH("duplex") || MATCH("data") || MATCH("description");
    break;
  case 'e': case 'E':
    base = MATCH("events");
    break;
  case 'i': case 'I':
    base = MATCH("isfocus");
    break;
  case 'l': case 'L':
    base = MATCH("language");
    break;
  case 'm': case 'M':
    base = MATCH("mobility") || MATCH("methods");
    break;
  case 'p': case 'P':
    base = MATCH("priority");
    break;
  case 's': case 'S':
    base = MATCH("schemes");
    break;
  case 't': case 'T':
    base = MATCH("type");
    break;
  case 'v': case 'V':
    base = MATCH("video");
    break;
  default:
    base = 0;
    break;
  }
#undef MATCH

  return base ^ xor;
}

/** Check if @Contact is immune to callerprefs. */
int sip_contact_is_immune(sip_contact_t const *m)
{
  unsigned i;

  if (m->m_params)
    for (i = 0; m->m_params[i]; i++) {
      if (sip_is_callerpref(m->m_params[i]))
	return 0;
    }

  return 1;
}

/**Check if @Contact matches by @AcceptContact.
 * 
 * Matching @AcceptContact and @Contact headers is done as explained in
 * @RFC3841 section 7.2.4. The caller score can be calculated from the
 * returned S and N values.
 *
 * @par Matching
 * The @AcceptContact header contains number of feature tag parameters. The
 * count of feature tags is returned in @a return_N. For each feature tag in
 * @AcceptContact, the feature tag with same name is searched from the
 * @Contact header. If both headers contain the feature tag with same name,
 * their values are compared. If the value in @AcceptContact does not match
 * with the value in @Contact, there is mismatch and 0 is returned. If they
 * match, S is increased by 1.
 *
 * @param m   pointer to @Contact header structure
 * @param cp   pointer to @AcceptContact header structure
 * @param return_N   return-value parameter for number of 
 *                   feature tags in @AcceptContact
 * @param return_S   return-value parameter for number of 
 *                   matching feature tags
 * @param return_error   return-value parameter for parsing error
 *
 * For example,
 * @code
 * if (sip_contact_accept(contact, accept_contact, &S, &N, &error)) {
 *   if (N == 0)
 *     score == 1.0;
 *   else
 *     score = (double)S / (double)N;
 *   if (accept_contact->cp_explicit) {
 *     if (accept_contact->cp_require)
 *       goto drop;
 *     else
 *       score = 0.0;
 *   }
 * }
 * else if (!error) {
 *   score = 0.0;
 * }
 * @endcode
 *
 * @retval 1 if @Contact matches
 * @return @a return_S contains number of matching feature tags
 * @return @a return_N contains number of feature tags in @AcceptContact
 * @retval 0 if @Contact does not match
 * @return @a return_error contains -1 if feature tag value was malformed
 *
 * @sa @RFC3841 section 7.2.4, sip_contact_score(), sip_contact_reject(),
 * sip_contact_is_immune(), sip_contact_immunize(), sip_is_callerpref(),
 * sip_prefs_matching().
 */
int sip_contact_accept(sip_contact_t const *m, 
		       sip_accept_contact_t const *cp,
		       unsigned *return_S,
		       unsigned *return_N,
		       int *return_error)
{
  char const *cap, *acc;
  unsigned i, S, N;
  size_t eq;

  if (!return_N) return_N = &N;
  if (!return_S) return_S = &S;

  *return_S = 0, *return_N = 0;

  if (!m || !cp || !m->m_params || !cp->cp_params)
    return 1;

  for (i = 0, S = 0, N = 0; cp->cp_params[i]; i++) {
    acc = cp->cp_params[i];
    if (!sip_is_callerpref(acc))
      continue;

    N++;

    cap = msg_params_find(m->m_params, acc);

    if (cap) {
      eq = strcspn(acc, "=");
      acc += eq + (acc[eq] == '=');

      if (!sip_prefs_matching(cap, acc, return_error)) 
	return 0;
      
      S++;
    }
  }

  *return_S = S; /* Matched feature tags */
  *return_N = N; /* Number of feature tags in @AcceptContact */

  return 1; 
}


/** Check if @Contact is rejected by @RejectContact.
 *
 * @param m pointer to @Contact header
 * @param reject pointer to @RejectContact header
 *
 * @retval 1 when rejecting
 * @retval 0 when @Contact does not match with @RejectContact
 *
 * @sa sip_contact_score(), sip_contact_accept(), sip_contact_immunize(),
 * sip_contact_is_immune(), @RFC3841, @RejectContact, @Contact
 */
int sip_contact_reject(sip_contact_t const *m, 
		       sip_reject_contact_t const *reject)
{
  unsigned S, N;
  int error;

  if (!m || !m->m_params || !reject || !reject->cp_params)
    return 0;

  return sip_contact_accept(m, reject, &S, &N, &error) && S == N && N > 0;
}

/**Immunize @Contact to callerprefs.
 *
 * Make a copy of @Contact header @a m and remove all parameters which
 * affect caller preferences.
 *
 * @param home   home object used when allocating copy
 * @param m   pointer to @Contact header structure to immunize
 *
 * @retval pointer to immunized copy if successful
 * @retval NULL upon an error
 * 
 * @sa @RFC3841, sip_is_callerpref(), sip_contact_score(),
 * sip_contact_accept(), sip_contact_reject(), @Contact
 */
sip_contact_t *sip_contact_immunize(su_home_t *home, sip_contact_t const *m)
{
  unsigned i, j;
  sip_contact_t m0[1], *m1;
  msg_param_t *params;

  if (!m)
    return NULL;

  *m0 = *m, m0->m_next = NULL;

  m1 = sip_contact_copy(home, m0);

  if (m1 == NULL || !m1->m_params)
    return m1;

  params = (msg_param_t *)m1->m_params;

  for (i = 0, j = 0; params[i]; i++) {
    if (!sip_is_callerpref(params[i]))
      params[j++] = params[i];
  }

  params[j] = NULL;

  return m1;
}

/** Calculate score for contact.
 *
 * The caller preference score is an integer in range of 0 to 1000.
 * 
 * @retval -1 if the contact is rejected
 * @retval 1000 if contact is immune to caller preferences
 * @retval 0..1000 reflecting @RFC3841 score in 0.000 - 1.000.
 *
 * @sa sip_q_value(),
 * sip_contact_accept(), sip_contact_reject(), sip_contact_is_immune(),
 * sip_contact_immunize(), sip_is_callerpref(), sip_prefs_matching(),
 * @RFC3841, @AcceptContact, @RejectContact, @Contact
 */
int sip_contact_score(sip_contact_t const *m,
		      sip_accept_contact_t const *ac,
		      sip_reject_contact_t const *rc)
{
  unsigned long S_total = 0;
  unsigned M = 0, scale = 1000;
  int error = 0;

  if (sip_contact_is_immune(m))
    return 1000;		/* Immune */

  for (; rc; rc = rc->cp_next)
    if (sip_contact_reject(m, rc)) 
      break;
  if (rc)
    return -1;			/* Rejected */

  for (; ac; ac = ac->cp_next) {
    unsigned S, N;
	
    if (!sip_contact_accept(m, ac, &S, &N, &error)) {
      if (ac->cp_require)
	return 0;		/* Discarded */
      continue;
    }

    M++;

    /* Apply score */
    if (S < N && ac->cp_explicit) {
      S = 0;
      if (ac->cp_require)
	return 0;		/* Dropped */
    }

    if (S > 0 && N > 0) 
      S_total += sip_q_value(ac->cp_q) * (scale * S / N + (2 * S >= N));
  }

  if (!M) 
    return 0;

  S_total /= M;

  if (S_total < scale * 1000)
    return S_total / scale;
  else
    return 1000;
}