sres.c

sip协议栈

      }
      else if (MATCH("search")) {
	if (localdomain)	/* LOCALDOMAIN overrides */
	  continue;
	if (search) su_free(home, search), search = NULL;
	if (domain) su_free(home, domain), domain = NULL;
	search = su_strdup(home, value);
	if (!search)
	  return -1;
      }
      else if (MATCH("port")) {
	unsigned long port = strtoul(value, NULL, 10);
	if (port < 65536)
	  c->c_port = port;
      }
      else if (MATCH("options")) {
	sres_parse_options(c, value);
      }
    }
  }

  if (f)
    c->c_modified = sres_config_timestamp(c);

  if (localdomain)
    c->c_search[0] = localdomain;
  else if (domain)
    c->c_search[0] = domain;
  else if (search) {
    for (i = 0; search[0] && i < SRES_MAX_SEARCH; i++) {
      c->c_search[i] = search;
      search += strcspn(search, " \t");
      if (*search) {
	*search++ = '\0';
	search += strspn(search, " \t");
      }
    }
  }

  return i;
}

static int 
sres_parse_options(sres_config_t *c, char const *value)
{
  if (!value)
    return -1;

  while (value[0]) {
    char const *b;
    int len, extra = 0;
    unsigned long n = 0;

    b = value; len = strcspn(value, " \t:");
    value += len;

    if (value[0] == ':') {
      len++;
      n = strtoul(++value, NULL, 10);
      value += extra = strcspn(value, " \t");
    }

    if (*value)
      value += strspn(value, " \t");

    if (n > 65536) {
      SU_DEBUG_3(("sres: %s: invalid %*.s\n", c->c_filename, len + extra, b));
      continue;
    }

    /* Documented by BIND9 resolv.conf */
    if (MATCH("no-debug")) c->c_opt.debug = 0;
    else if (MATCH("debug")) c->c_opt.debug = 1;
    else if (MATCH("ndots:")) c->c_opt.ndots = n;
    else if (MATCH("timeout:")) c->c_opt.timeout = n;
    else if (MATCH("attempts:")) c->c_opt.attempts = n;
    else if (MATCH("no-rotate")) c->c_opt.rotate = 0;
    else if (MATCH("rotate")) c->c_opt.rotate = 1;
    else if (MATCH("no-check-names")) c->c_opt.check_names = 0;
    else if (MATCH("check-names")) c->c_opt.check_names = 1;
    else if (MATCH("no-inet6")) c->c_opt.ip6int = 0;
    else if (MATCH("inet6")) c->c_opt.inet6 = 1;
    else if (MATCH("no-ip6-dotint")) c->c_opt.ip6int = 0;
    else if (MATCH("ip6-dotint")) c->c_opt.ip6int = 1;
    else if (MATCH("no-ip6-bytestring")) c->c_opt.ip6bytestring = 0;
    else if (MATCH("ip6-bytestring")) c->c_opt.ip6bytestring = 1;
    /* Sofia-specific extensions: */
    else if (MATCH("no-edns0")) c->c_opt.edns = edns_not_supported;
    else if (MATCH("edns0")) c->c_opt.edns = edns0_configured;
    else {
      SU_DEBUG_3(("sres: %s: unknown option %*.s\n", c->c_filename, len + extra, b));
    }
  }

  return 0;
}

static
int sres_parse_nameserver(sres_config_t *c, char const *server)
{
  sres_nameserver_t *ns;
  struct sockaddr *sa;
  int err, i;

  for (i = 0; i < SRES_MAX_NAMESERVERS; i++)
    if (c->c_nameservers[i] == NULL)
      break;

  if (i >= SRES_MAX_NAMESERVERS)
    return 0 /* Silently discard extra nameservers */;

  ns = su_zalloc(c->c_home, (sizeof *ns) + strlen(server) + 1);
  if (!ns)
    return -1;

  sa = (void *)ns->ns_addr;

#if HAVE_SIN6
  if (strchr(server, ':')) {
    struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sa;
    memset(sa, 0, ns->ns_addrlen = sizeof *sin6);
    err = inet_pton(sa->sa_family = AF_INET6, server, &sin6->sin6_addr);
  } 
  else 
#endif
    {
      struct sockaddr_in *sin = (struct sockaddr_in *)sa;
      memset(sa, 0, ns->ns_addrlen = sizeof *sin);
      err = inet_pton(sa->sa_family = AF_INET, server, &sin->sin_addr);
    }

  if (err <= 0) {
    SU_DEBUG_3(("sres: nameserver %s: invalid address\n", server));
    su_free(c->c_home, ns);
    return 0;
  }

#if HAVE_SA_LEN
  sa->sa_len = ns->ns_addrlen;
#endif

  c->c_nameservers[i] = ns;

  return 1;
}

/** Get current timestamp of resolv.conf file */
static
time_t sres_config_timestamp(sres_config_t const *c)
{
#ifndef _WIN32
  struct stat st;

  if (stat(c->c_filename, &st) == 0)
    return st.st_mtime;

  /** @return If the resolv.conf file does not exists, return old timestamp. */
  return c->c_modified;
#else
  /** On WIN32, return always different timestamp */
  return c->c_modified + SRES_UPDATE_INTERVAL_SECS;
#endif
}


/* ---------------------------------------------------------------------- */

/** Check if the new configuration has different servers than the old */
static 
int sres_config_changed_servers(sres_config_t const *new_c, 
				sres_config_t const *old_c)
{
  int i;
  sres_nameserver_t const *new_ns, *old_ns;

  if (old_c == NULL)
    return 1;

  for (i = 0; i < SRES_MAX_NAMESERVERS; i++) {
    new_ns = new_c->c_nameservers[i];
    old_ns = old_c->c_nameservers[i];

    if (!new_ns != !old_ns)
      return 1;
    if (!new_ns)
      return 0;
    if (new_ns->ns_addrlen != old_ns->ns_addrlen)
      return 1;
    if (memcmp(new_ns->ns_addr, old_ns->ns_addr, new_ns->ns_addrlen))
      return 1;
  }

  return 0;
}

/** Allocate new servers structure */
static
sres_server_t **sres_servers_new(sres_resolver_t *res,
				 sres_config_t const *c)
{
  sres_server_t **servers, *dns;
  sres_nameserver_t *ns;
  int N, i;
  size_t size;

  for (N = 0; c->c_nameservers[N] && N < SRES_MAX_NAMESERVERS; N++)
    ;

  size = (N + 1) * (sizeof *servers) + N * (sizeof **servers);

  servers = su_zalloc(res->res_home, size); if (!servers) return servers;
  dns = (void *)(servers + N + 1);
  for (i = 0; i < N; i++) {
    dns->dns_socket = -1;
    ns = c->c_nameservers[i];
    memcpy(dns->dns_addr, ns->ns_addr, dns->dns_addrlen = ns->ns_addrlen);
    inet_ntop(dns->dns_addr->ss_family, SS_ADDR(dns->dns_addr), 
	      dns->dns_name, sizeof dns->dns_name);
    dns->dns_edns = c->c_opt.edns;
    servers[i] = dns++;
  }

  return servers;
}

static
void sres_servers_unref(sres_resolver_t *res,
			sres_server_t **servers)
{
  int i;

  if (res == NULL || servers == NULL)
    return;

  for (i = 0; i < SRES_MAX_NAMESERVERS; i++) {
    if (!servers[i])
      break;

    if (servers[i]->dns_socket != -1) {
      if (res->res_updcb)
	res->res_updcb(res->res_async, -1, servers[i]->dns_socket);
      closesocket(servers[i]->dns_socket);
    }
  }

  su_free(res->res_home, servers);
}

static
int sres_servers_count(sres_server_t *const *servers)
{
  int i;

  if (!servers)
    return 0;

  for (i = 0; i < SRES_MAX_NAMESERVERS; i++) {
    if (!servers[i])
      break;
  }  

  return i;
}

static
int sres_server_socket(sres_resolver_t *res, sres_server_t *dns)
{
  int family = dns->dns_addr->ss_family;
  int s;

  if (dns->dns_socket != -1)
    return dns->dns_socket;

  s = socket(family, SOCK_DGRAM, IPPROTO_UDP);
  if (s == -1) {
    SU_DEBUG_1(("%s: %s: %s\n", "sres_server_socket", "socket",
		su_strerror(su_errno())));
    dns->dns_error = time(NULL);
    return s;
  }

#if HAVE_IP_RECVERR
  if (family == AF_INET || family == AF_INET6) {
    int const one = 1;
    if (setsockopt(s, SOL_IP, IP_RECVERR, &one, sizeof(one)) < 0) {
      if (family == AF_INET)
	SU_DEBUG_3(("setsockopt(IPVRECVERR): %s\n", su_strerror(su_errno())));
    }
  }
#endif
#if HAVE_IPV6_RECVERR
  if (family == AF_INET6) {
    int const one = 1;
    if (setsockopt(s, SOL_IPV6, IPV6_RECVERR, &one, sizeof(one)) < 0)
      SU_DEBUG_3(("setsockopt(IPV6_RECVERR): %s\n", su_strerror(su_errno())));
  }
#endif

  if (connect(s, (void *)dns->dns_addr, dns->dns_addrlen) < 0) {
    char ipaddr[64];
    char const *lb = "", *rb = "";

    if (family == AF_INET) {
      void *addr = &((struct sockaddr_in *)dns->dns_addr)->sin_addr;
      inet_ntop(family, addr, ipaddr, sizeof ipaddr);
    }
#if HAVE_SIN6
    else if (family == AF_INET6) {
      void *addr = &((struct sockaddr_in6 *)dns->dns_addr)->sin6_addr;
      inet_ntop(family, addr, ipaddr, sizeof ipaddr);
      lb = "[", rb = "]";
    }
#endif
    else
      snprintf(ipaddr, sizeof ipaddr, "<af=%u>", family);

    SU_DEBUG_1(("%s: %s: %s: %s%s%s:%u\n", "sres_server_socket", "connect",
		su_strerror(su_errno()), lb, ipaddr, rb,
		ntohs(((struct sockaddr_in *)dns->dns_addr)->sin_port)));
    closesocket(s);
    dns->dns_error = time(NULL);
    return -1;
  }
  
  if (res->res_updcb) {
    if (res->res_updcb(res->res_async, s, -1) < 0) {
      SU_DEBUG_1(("%s: %s: %s\n", "sres_server_socket", "update callback",
		  su_strerror(su_errno())));
      closesocket(s);
      dns->dns_error = time(NULL);
      return -1;
    }
  }

  dns->dns_socket = s;
  
  return s;
}

/* ---------------------------------------------------------------------- */

/** Send a query packet */
static 
int 
sres_send_dns_query(sres_resolver_t *res, 
		    sres_query_t *q)
{                        
  sres_message_t m[1];
  uint8_t i, i0, N = res->res_n_servers;
  int s, transient, error = 0;
  unsigned size, no_edns_size, edns_size;
  uint16_t id = q->q_id;
  uint16_t type = q->q_type;
  char const *domain = q->q_name;
  time_t now = res->res_now;
  sres_server_t **servers = res->res_servers, *dns;
  char b[8];

  if (now == 0) time(&now);

  SU_DEBUG_9(("sres_send_dns_query(%p, %p) called\n", res, q));

  if (domain == NULL)
    return -1;
  if (servers == NULL)
    return -1;

  memset(m, 0, offsetof(sres_message_t, m_data[sizeof m->m_packet.mp_header]));

  /* Create a DNS message */
  m->m_size = sizeof(m->m_data);
  m->m_offset = size = sizeof(m->m_packet.mp_header);
  
  m->m_id = id;
  m->m_flags = htons(SRES_HDR_QUERY | SRES_HDR_RD);
  
  /* Query record */
  m->m_qdcount = htons(1);
  m_put_domain(m, domain, 0, NULL);
  m_put_uint16(m, type);
  m_put_uint16(m, sres_class_in);
  
  no_edns_size = m->m_offset;

  /* EDNS0 record (optional) */
  m_put_domain(m, ".", 0, NULL);
  m_put_uint16(m, sres_type_opt);
  m_put_uint16(m, sizeof(m->m_packet)); /* Class: our UDP payload size */
  m_put_uint32(m, 0);		/* TTL: extended RCODE & flags */
  m_put_uint16(m, 0);
  
  edns_size = m->m_offset;

  if (m->m_error) {
    SU_DEBUG_3(("%s(): encoding: %s\n", "sres_send_dns_query", m->m_error));
    su_seterrno(EIO);
    return -1;
  }

  transient = 0;

  i0 = q->q_i_server; assert(i0 < N);

  if (res->res_config->c_opt.rotate || 
      servers[i0]->dns_error || servers[i0]->dns_icmp)
    dns = sres_next_server(res, &q->q_i_server, 0), i = q->q_i_server;
  else 
    dns = servers[i0], i = i0;

  for (; dns; dns = sres_next_server(res, &i, 0)) {
    /* If server supports EDNS, include EDNS0 record */
    q->q_edns = dns->dns_edns;
    /* 0 (no EDNS) or 1 (EDNS supported) additional data records */
    m->m_arcount = htons(q->q_edns != 0); 
    /* Size with or without EDNS record */
    size = q->q_edns ? edns_size : no_edns_size; 

    s = sres_server_socket(res, dns);

    /* Send the DNS message via the UDP socket */
    if (s != -1 && send(s, m->m_data, size, 0) == size)
      break;

    error = su_errno();
    dns->dns_icmp = now;
    /* EINVAL is returned if destination address is bad */
    if (transient++ < 3 && error != EINVAL && s != -1)
      continue;
    transient = 0;

    dns->dns_error = now;	/* Mark as a bad destination */
  }

  if (!dns) {
    /* All servers have reported errors */
    SU_DEBUG_5(("%s(): sendto: %s\n", "sres_send_dns_query",
		su_strerror(error)));
    return su_seterrno(error);
  }

  q->q_i_server = i;

  SU_DEBUG_5(("%s(%p, %p) id=%u %s %s (to [%s]:%u)\n", 
	      "sres_send_dns_query",
	      res, q, id, sres_record_type(type, b), domain, 
	      dns->dns_name, 
	      htons(((struct sockaddr_in *)dns->dns_addr)->sin_port)));

  return 0;
}


/** Select next server */
static
sres_server_t *sres_next_server(sres_resolver_t *res, 
				uint8_t *in_out_i,
				int timeout)
{
  int i, j, N;
  sres_server_t **servers;

  assert(res && in_out_i);

  N = res->res_n_servers;
  servers = res->res_servers;
  i = *in_out_i;

  assert(res->res_servers && res->res_servers[i]);
  
  /* Retry using another server? */
  for (j = (i + 1) % N; (j != i); j = (j + 1) % N) {
    if (servers[j]->dns_icmp == 0) {
      return *in_out_i = j, servers[j];
    }
  }

  for (j = (i + 1) % N; (j != i); j = (j + 1) % N) {
    if (servers[j]->dns_error == 0) {
      return *in_out_i = j, servers[j];
    }
  }

  if (timeout)
    return servers[i];
  
  return NULL;
}

/**
 * Callback function for subqueries
 */
static
void sres_answer_subquery(