Improve address family handling in sockets

Many functions use low-level socket interface for connection or
various checks. However, most of the time we don't respect
automatic address family detection but rather try to force our
values. This may cause either redundat connection tries when an
address family is disabled on system tries or even crashes
when socket exceptions are not properly caught.

Instead of forcing address families to socket, rather use
getaddrinfo interface to automatically retrieve a list of all
relevant address families and other connection settings when
connecting to remote/local machine or binding to a local port.
Now, we will also fill correctly all connection parameters like
flowinfo and scopeid for IPv6 connections which will for example
prevent issues with scoped IPv6 addresses.

bind_port_responder function was changed to at first try to bind
to IPv6 wildcard address before IPv4 as IPv6 socket is able to
accept both IPv4 and IPv6 connections (unlike IPv4 socket).

nsslib connection was refactored to use nss.io.AddrInfo class to
get all the available connections. Socket is now not created by
default in NSSConnection class initializer, but rather when the
actual connection is being made, becase we do not an address family
where connection is successful.

https://fedorahosted.org/freeipa/ticket/2913
https://fedorahosted.org/freeipa/ticket/2695

6 files changed, 160 insertions, 162 deletions

diff --git a/install/tools/ipa-replica-conncheck b/install/tools/ipa-replica-conncheck
index 6ec3be2a9..8e4536cf6 100755
--- a/install/tools/ipa-replica-conncheck
+++ b/install/tools/ipa-replica-conncheck
@@ -236,15 +236,15 @@ class PortResponder(threading.Thread):
         self._stop_request = True
 
 def port_check(host, port_list):
-    ip = installutils.resolve_host(host)
-
-    if not ip:
-        raise RuntimeError("Port check failed! Unable to resolve host name '%s'" % host)
-
     ports_failed = []
     ports_udp_warning = []  # conncheck could not verify that port is open
     for port in port_list:
-        if ipautil.host_port_open(host, port.port, port.port_type, socket_timeout=CONNECT_TIMEOUT):
+        try:
+            port_open = ipautil.host_port_open(host, port.port,
+                    port.port_type, socket_timeout=CONNECT_TIMEOUT)
+        except socket.gaierror:
+            raise RuntimeError("Port check failed! Unable to resolve host name '%s'" % host)
+        if port_open:
             result = "OK"
         else:
             if port.port_type == socket.SOCK_DGRAM:
diff --git a/ipa-client/ipa-install/ipa-client-install b/ipa-client/ipa-install/ipa-client-install
index ef0dc293c..081ae7f28 100755
--- a/ipa-client/ipa-install/ipa-client-install
+++ b/ipa-client/ipa-install/ipa-client-install
@@ -979,19 +979,36 @@ def configure_ssh(fstore, ssh_dir, options):
 def resolve_ipaddress(server):
     """ Connect to the server's LDAP port in order to determine what ip
         address this machine uses as "public" ip (relative to the server).
+
+        Returns a tuple with the IP address and address family when
+        connection was successful. Socket error is raised otherwise.
     """
+    last_socket_error = None
 
-    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM, socket.IPPROTO_TCP)
-    try:
-        s.connect((server, 389))
-        addr, port = s.getsockname()
-    except socket.gaierror:
-        s = socket.socket(socket.AF_INET6, socket.SOCK_STREAM, socket.IPPROTO_TCP)
-        s.connect((server, 389))
-        addr, port, foo, bar = s.getsockname()
-    s.close()
+    for res in socket.getaddrinfo(server, 389, socket.AF_UNSPEC,
+            socket.SOCK_STREAM):
+        af, socktype, proto, canonname, sa = res
+        try:
+            s = socket.socket(af, socktype, proto)
+        except socket.error, e:
+            last_socket_error = e
+            s = None
+            continue
+
+        try:
+            s.connect(sa)
+            sockname = s.getsockname()
+
+            # For both IPv4 and IPv6 own IP address is always the first item
+            return (sockname[0], af)
+        except socket.error, e:
+            last_socket_error = e
+        finally:
+            if s:
+                s.close()
 
-    return addr
+    if last_socket_error is not None:
+        raise last_socket_error  # pylint: disable=E0702
 
 def do_nsupdate(update_txt):
     root_logger.debug("Writing nsupdate commands to %s:", UPDATE_FILE)
@@ -1037,7 +1054,13 @@ CCACHE_FILE = "/etc/ipa/.dns_ccache"
 
 def update_dns(server, hostname):
 
-    ip = resolve_ipaddress(server)
+    try:
+        (ip, af) = resolve_ipaddress(server)
+    except socket.gaierror, e:
+        root_logger.debug("update_dns: could not connect to server: %s", e)
+        root_logger.error("Cannot update DNS records! "
+                          "Failed to connect to server '%s'.", server)
+        return
 
     sub_dict = dict(HOSTNAME=hostname,
                     IPADDRESS=ip,
@@ -1045,9 +1068,9 @@ def update_dns(server, hostname):
                     ZONE='.'.join(hostname.split('.')[1:])
                 )
 
-    if len(ip.split('.')) == 4:
+    if af == socket.AF_INET:
         template = UPDATE_TEMPLATE_A
-    elif ':' in ip:
+    elif af == socket.AF_INET6:
         template = UPDATE_TEMPLATE_AAAA
     else:
         root_logger.info("Failed to determine this machine's ip address.")
diff --git a/ipapython/ipautil.py b/ipapython/ipautil.py
index e80434cfd..22c8e2937 100644
--- a/ipapython/ipautil.py
+++ b/ipapython/ipautil.py
@@ -48,6 +48,7 @@ from dns.exception import DNSException
 from ipapython.ipa_log_manager import *
 from ipapython import ipavalidate
 from ipapython import config
+
 try:
     from subprocess import CalledProcessError
 except ImportError:
@@ -672,72 +673,103 @@ def get_gsserror(e):
 
 
 def host_port_open(host, port, socket_type=socket.SOCK_STREAM, socket_timeout=None):
-    families = (socket.AF_INET, socket.AF_INET6)
-    success = False
-
-    for family in families:
+    for res in socket.getaddrinfo(host, port, socket.AF_UNSPEC, socket_type):
+        af, socktype, proto, canonname, sa = res
         try:
             try:
-                s = socket.socket(family, socket_type)
+                s = socket.socket(af, socktype, proto)
             except socket.error:
+                s = None
                 continue
 
             if socket_timeout is not None:
                 s.settimeout(socket_timeout)
 
-            s.connect((host, port))
+            s.connect(sa)
 
             if socket_type == socket.SOCK_DGRAM:
                 s.send('')
                 s.recv(512)
 
-            success = True
+            return True
         except socket.error, e:
             pass
         finally:
-            s.close()
-
-        if success:
-            return True
+            if s:
+                s.close()
 
     return False
 
 def bind_port_responder(port, socket_type=socket.SOCK_STREAM, socket_timeout=None, responder_data=None):
-    families = (socket.AF_INET, socket.AF_INET6)
+    host = None   # all available interfaces
+    last_socket_error = None
 
-    host = ''   # all available interfaces
+    # At first try to create IPv6 socket as it is able to accept both IPv6 and
+    # IPv4 connections (when not turned off)
+    families = (socket.AF_INET6, socket.AF_INET)
+    s = None
 
     for family in families:
         try:
-            s = socket.socket(family, socket_type)
+            addr_infos = socket.getaddrinfo(host, port, family, socket_type, 0,
+                            socket.AI_PASSIVE)
         except socket.error, e:
-            if family == families[-1]:  # last available family
-                raise e
+            last_socket_error = e
+            continue
+        for res in addr_infos:
+            af, socktype, proto, canonname, sa = res
+            try:
+                s = socket.socket(af, socktype, proto)
+            except socket.error, e:
+                last_socket_error = e
+                s = None
+                continue
 
-    if socket_timeout is not None:
-        s.settimeout(socket_timeout)
+            if socket_timeout is not None:
+                s.settimeout(1)
 
-    if socket_type == socket.SOCK_STREAM:
-        s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+            if af == socket.AF_INET6:
+                try:
+                    # Make sure IPv4 clients can connect to IPv6 socket
+                    s.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 0)
+                except socket.error:
+                    pass
 
-    try:
-        s.bind((host, port))
+            if socket_type == socket.SOCK_STREAM:
+                s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 
-        if socket_type == socket.SOCK_STREAM:
-            s.listen(1)
-            connection, client_address = s.accept()
             try:
-                if responder_data:
-                    connection.sendall(responder_data) #pylint: disable=E1101
+                s.bind(sa)
+
+                while True:
+                    if socket_type == socket.SOCK_STREAM:
+                        s.listen(1)
+                        connection, client_address = s.accept()
+                        try:
+                            if responder_data:
+                                connection.sendall(responder_data) #pylint: disable=E1101
+                        finally:
+                            connection.close()
+                    elif socket_type == socket.SOCK_DGRAM:
+                        data, addr = s.recvfrom(1)
+
+                        if responder_data:
+                            s.sendto(responder_data, addr)
+            except socket.timeout:
+                # Timeout is expectable as it was requested by caller, raise
+                # the exception back to him
+                raise
+            except socket.error, e:
+                last_socket_error = e
+                s.close()
+                s = None
+                continue
             finally:
-                connection.close()
-        elif socket_type == socket.SOCK_DGRAM:
-            data, addr = s.recvfrom(1)
+                if s:
+                    s.close()
 
-            if responder_data:
-                s.sendto(responder_data, addr)
-    finally:
-        s.close()
+    if s is None and last_socket_error is not None:
+        raise last_socket_error # pylint: disable=E0702
 
 def is_host_resolvable(fqdn):
     for rdtype in (rdatatype.A, rdatatype.AAAA):
@@ -1015,34 +1047,24 @@ def utf8_encode_values(values):
 def wait_for_open_ports(host, ports, timeout=0):
     """
     Wait until the specified port(s) on the remote host are open. Timeout
-    in seconds may be specified to limit the wait.
+    in seconds may be specified to limit the wait. If the timeout is
+    exceeded, socket.timeout exception is raised.
     """
     if not isinstance(ports, (tuple, list)):
         ports = [ports]
 
-    root_logger.debug('wait_for_open_ports: %s %s timeout %d' % (host, ports, timeout))
+    root_logger.debug('wait_for_open_ports: %s %s timeout %d', host, ports, timeout)
     op_timeout = time.time() + timeout
-    ipv6_failover = False
 
     for port in ports:
         while True:
-            try:
-                if ipv6_failover:
-                    s = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
-                else:
-                    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-                s.connect((host, port))
-                s.close()
+            port_open = host_port_open(host, port)
+
+            if port_open:
                 break
-            except socket.error, e:
-                if e.errno == 111:  # 111: Connection refused
-                    if timeout and time.time() > op_timeout: # timeout exceeded
-                        raise e
-                    time.sleep(1)
-                elif not ipv6_failover: # fallback to IPv6 connection
-                    ipv6_failover = True
-                else:
-                    raise e
+            if timeout and time.time() > op_timeout: # timeout exceeded
+                raise socket.timeout()
+            time.sleep(1)
 
 def wait_for_open_socket(socket_name, timeout=0):
     """
diff --git a/ipapython/nsslib.py b/ipapython/nsslib.py
index aae24467f..06bcba648 100644
--- a/ipapython/nsslib.py
+++ b/ipapython/nsslib.py
@@ -115,6 +115,12 @@ def client_auth_data_callback(ca_names, chosen_nickname, password, certdb):
                 return False
         return False
 
+_af_dict = {
+    socket.AF_INET: io.PR_AF_INET,
+    socket.AF_INET6: io.PR_AF_INET6,
+    socket.AF_UNSPEC: io.PR_AF_UNSPEC
+}
+
 class NSSAddressFamilyFallback(object):
     def __init__(self, family):
         self.sock_family = family
@@ -124,67 +130,39 @@ class NSSAddressFamilyFallback(object):
         """
         Translate a family from python socket module to nss family.
         """
-        if sock_family in [ socket.AF_INET, socket.AF_UNSPEC ]:
-            return io.PR_AF_INET
-        elif sock_family == socket.AF_INET6:
-            return io.PR_AF_INET6
-        else:
+        try:
+            return _af_dict[sock_family]
+        except KeyError:
             raise ValueError('Uknown socket family %d\n', sock_family)
 
-    def _get_next_family(self):
-        if self.sock_family == socket.AF_UNSPEC and \
-           self.family == io.PR_AF_INET:
-            return io.PR_AF_INET6
-
-        return None
-
     def _create_socket(self):
         self.sock = io.Socket(family=self.family)
 
-    def _connect_socket_family(self, host, port, family):
-        root_logger.debug("connect_socket_family: host=%s port=%s family=%s",
-                                  host, port, io.addr_family_name(family))
-        try:
-            addr_info = [ ai for ai in io.AddrInfo(host) if ai.family == family ]
-            # No suitable families
-            if len(addr_info) == 0:
-                raise NSPRError(error.PR_ADDRESS_NOT_SUPPORTED_ERROR,
-                                "Cannot resolve %s using family %s" % (host, io.addr_family_name(family)))
-
-            # Try connecting to the NetworkAddresses
-            for net_addr in addr_info:
-                net_addr.port = port
-                root_logger.debug("connecting: %s", net_addr)
-                try:
-                    self.sock.connect(net_addr)
-                except Exception, e:
-                    root_logger.debug("Could not connect socket to %s, error: %s, retrying..",
-                                              net_addr, str(e))
-                    continue
-                else:
-                    return
-
-            # Could not connect with any of NetworkAddresses
-            raise NSPRError(error.PR_ADDRESS_NOT_SUPPORTED_ERROR,
-                            "Could not connect to %s using any address" % host)
-        except ValueError, e:
-            raise NSPRError(error.PR_ADDRESS_NOT_SUPPORTED_ERROR, e.message)
-
     def connect_socket(self, host, port):
         try:
-            self._connect_socket_family(host, port, self.family)
-        except NSPRError, e:
-            if e.errno == error.PR_ADDRESS_NOT_SUPPORTED_ERROR:
-                next_family = self._get_next_family()
-                if next_family:
-                    self.family = next_family
-                    self._create_socket()
-                    self._connect_socket_family(host, port, self.family)
-                else:
-                    root_logger.debug('No next family to try..')
-                    raise e
-            else:
-                raise e
+            addr_info = io.AddrInfo(host, family=self.family)
+        except Exception:
+             raise NSPRError(error.PR_ADDRESS_NOT_SUPPORTED_ERROR,
+                             "Cannot resolve %s using family %s" % (host,
+                                 io.addr_family_name(self.family)))
+
+        for net_addr in addr_info:
+            root_logger.debug("Connecting: %s", net_addr)
+            net_addr.port = port
+            self.family = net_addr.family
+            try:
+                self._create_socket()
+                self.sock.connect(net_addr)
+                return
+            except Exception, e:
+                root_logger.debug("Could not connect socket to %s, error: %s",
+                        net_addr, str(e))
+                root_logger.debug("Try to continue with next family...")
+                continue
+
+        raise NSPRError(error.PR_ADDRESS_NOT_SUPPORTED_ERROR,
+                "Could not connect to %s using any address" % host)
+
 
 class NSSConnection(httplib.HTTPConnection, NSSAddressFamilyFallback):
     default_port = httplib.HTTPSConnection.default_port
@@ -218,12 +196,10 @@ class NSSConnection(httplib.HTTPConnection, NSSAddressFamilyFallback):
         nss.nss_init(dbdir)
         ssl.set_domestic_policy()
         nss.set_password_callback(self.password_callback)
-        self._create_socket()
 
     def _create_socket(self):
-
-        #TODO remove the try block once python-nss is guaranteed to
-	#contain these values
+        # TODO: remove the try block once python-nss is guaranteed to contain
+        # these values
         try :
                 ssl_enable_renegotiation  = SSL_ENABLE_RENEGOTIATION   #pylint: disable=E0602
                 ssl_require_safe_negotiation = SSL_REQUIRE_SAFE_NEGOTIATION  #pylint: disable=E0602
diff --git a/ipaserver/install/dsinstance.py b/ipaserver/install/dsinstance.py
index 9c137af03..25c449a6e 100644
--- a/ipaserver/install/dsinstance.py
+++ b/ipaserver/install/dsinstance.py
@@ -119,8 +119,15 @@ def get_ds_instances():
     return instances
 
 def check_ports():
-    ds_unsecure = installutils.port_available(389)
-    ds_secure = installutils.port_available(636)
+    """
+    Check of Directory server ports are open.
+
+    Returns a tuple with two booleans, one for unsecure port 389 and one for
+    secure port 636. True means that the port is free, False means that the
+    port is taken.
+    """
+    ds_unsecure = not ipautil.host_port_open(None, 389)
+    ds_secure = not ipautil.host_port_open(None, 636)
     return (ds_unsecure, ds_secure)
 
 def is_ds_running(server_id=''):
diff --git a/ipaserver/install/installutils.py b/ipaserver/install/installutils.py
index b65958eda..903e8f185 100644
--- a/ipaserver/install/installutils.py
+++ b/ipaserver/install/installutils.py
@@ -256,36 +256,6 @@ def read_dns_forwarders():
 
     return addrs
 
-def port_available(port):
-    """Try to bind to a port on the wildcard host
-       Return 1 if the port is available
-       Return 0 if the port is in use
-    """
-    rv = 1
-
-    try:
-        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-        s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
-        fcntl.fcntl(s, fcntl.F_SETFD, fcntl.FD_CLOEXEC)
-        s.bind(('', port))
-        s.close()
-    except socket.error, e:
-        if e[0] == errno.EADDRINUSE:
-            rv = 0
-
-    if rv:
-        try:
-            s = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
-            s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
-            fcntl.fcntl(s, fcntl.F_SETFD, fcntl.FD_CLOEXEC)
-            s.bind(('', port))
-            s.close()
-        except socket.error, e:
-            if e[0] == errno.EADDRINUSE:
-                rv = 0
-
-    return rv
-
 def get_password(prompt):
     if os.isatty(sys.stdin.fileno()):
         return getpass.getpass(prompt)