# Author: Tamilmani Manoharan # # This file is part of cloud-init. See LICENSE file for license information. from cloudinit import log as logging from cloudinit import util from collections import namedtuple import os import select import socket import struct LOG = logging.getLogger(__name__) # http://man7.org/linux/man-pages/man7/netlink.7.html RTMGRP_LINK = 1 NLMSG_NOOP = 1 NLMSG_ERROR = 2 NLMSG_DONE = 3 RTM_NEWLINK = 16 RTM_DELLINK = 17 RTM_GETLINK = 18 RTM_SETLINK = 19 MAX_SIZE = 65535 RTA_DATA_OFFSET = 32 MSG_TYPE_OFFSET = 16 SELECT_TIMEOUT = 60 NLMSGHDR_FMT = "IHHII" IFINFOMSG_FMT = "BHiII" NLMSGHDR_SIZE = struct.calcsize(NLMSGHDR_FMT) IFINFOMSG_SIZE = struct.calcsize(IFINFOMSG_FMT) RTATTR_START_OFFSET = NLMSGHDR_SIZE + IFINFOMSG_SIZE RTA_DATA_START_OFFSET = 4 PAD_ALIGNMENT = 4 IFLA_IFNAME = 3 IFLA_OPERSTATE = 16 # https://www.kernel.org/doc/Documentation/networking/operstates.txt OPER_UNKNOWN = 0 OPER_NOTPRESENT = 1 OPER_DOWN = 2 OPER_LOWERLAYERDOWN = 3 OPER_TESTING = 4 OPER_DORMANT = 5 OPER_UP = 6 RTAAttr = namedtuple('RTAAttr', ['length', 'rta_type', 'data']) InterfaceOperstate = namedtuple('InterfaceOperstate', ['ifname', 'operstate']) NetlinkHeader = namedtuple('NetlinkHeader', ['length', 'type', 'flags', 'seq', 'pid']) class NetlinkCreateSocketError(RuntimeError): '''Raised if netlink socket fails during create or bind.''' def create_bound_netlink_socket(): '''Creates netlink socket and bind on netlink group to catch interface down/up events. The socket will bound only on RTMGRP_LINK (which only includes RTM_NEWLINK/RTM_DELLINK/RTM_GETLINK events). The socket is set to non-blocking mode since we're only receiving messages. :returns: netlink socket in non-blocking mode :raises: NetlinkCreateSocketError ''' try: netlink_socket = socket.socket(socket.AF_NETLINK, socket.SOCK_RAW, socket.NETLINK_ROUTE) netlink_socket.bind((os.getpid(), RTMGRP_LINK)) netlink_socket.setblocking(0) except socket.error as e: msg = "Exception during netlink socket create: %s" % e raise NetlinkCreateSocketError(msg) LOG.debug("Created netlink socket") return netlink_socket def get_netlink_msg_header(data): '''Gets netlink message type and length :param: data read from netlink socket :returns: netlink message type :raises: AssertionError if data is None or data is not >= NLMSGHDR_SIZE struct nlmsghdr { __u32 nlmsg_len; /* Length of message including header */ __u16 nlmsg_type; /* Type of message content */ __u16 nlmsg_flags; /* Additional flags */ __u32 nlmsg_seq; /* Sequence number */ __u32 nlmsg_pid; /* Sender port ID */ }; ''' assert (data is not None), ("data is none") assert (len(data) >= NLMSGHDR_SIZE), ( "data is smaller than netlink message header") msg_len, msg_type, flags, seq, pid = struct.unpack(NLMSGHDR_FMT, data[:MSG_TYPE_OFFSET]) LOG.debug("Got netlink msg of type %d", msg_type) return NetlinkHeader(msg_len, msg_type, flags, seq, pid) def read_netlink_socket(netlink_socket, timeout=None): '''Select and read from the netlink socket if ready. :param: netlink_socket: specify which socket object to read from :param: timeout: specify a timeout value (integer) to wait while reading, if none, it will block indefinitely until socket ready for read :returns: string of data read (max length = ) from socket, if no data read, returns None :raises: AssertionError if netlink_socket is None ''' assert (netlink_socket is not None), ("netlink socket is none") read_set, _, _ = select.select([netlink_socket], [], [], timeout) # Incase of timeout,read_set doesn't contain netlink socket. # just return from this function if netlink_socket not in read_set: return None LOG.debug("netlink socket ready for read") data = netlink_socket.recv(MAX_SIZE) if data is None: LOG.error("Reading from Netlink socket returned no data") return data def unpack_rta_attr(data, offset): '''Unpack a single rta attribute. :param: data: string of data read from netlink socket :param: offset: starting offset of RTA Attribute :return: RTAAttr object with length, type and data. On error, return None. :raises: AssertionError if data is None or offset is not integer. ''' assert (data is not None), ("data is none") assert (type(offset) == int), ("offset is not integer") assert (offset >= RTATTR_START_OFFSET), ( "rta offset is less than expected length") length = rta_type = 0 attr_data = None try: length = struct.unpack_from("H", data, offset=offset)[0] rta_type = struct.unpack_from("H", data, offset=offset+2)[0] except struct.error: return None # Should mean our offset is >= remaining data # Unpack just the attribute's data. Offset by 4 to skip length/type header attr_data = data[offset+RTA_DATA_START_OFFSET:offset+length] return RTAAttr(length, rta_type, attr_data) def read_rta_oper_state(data): '''Reads Interface name and operational state from RTA Data. :param: data: string of data read from netlink socket :returns: InterfaceOperstate object containing if_name and oper_state. None if data does not contain valid IFLA_OPERSTATE and IFLA_IFNAME messages. :raises: AssertionError if data is None or length of data is smaller than RTATTR_START_OFFSET. ''' assert (data is not None), ("data is none") assert (len(data) > RTATTR_START_OFFSET), ( "length of data is smaller than RTATTR_START_OFFSET") ifname = operstate = None offset = RTATTR_START_OFFSET while offset <= len(data): attr = unpack_rta_attr(data, offset) if not attr or attr.length == 0: break # Each attribute is 4-byte aligned. Determine pad length. padlen = (PAD_ALIGNMENT - (attr.length % PAD_ALIGNMENT)) % PAD_ALIGNMENT offset += attr.length + padlen if attr.rta_type == IFLA_OPERSTATE: operstate = ord(attr.data) elif attr.rta_type == IFLA_IFNAME: interface_name = util.decode_binary(attr.data, 'utf-8') ifname = interface_name.strip('\0') if not ifname or operstate is None: return None LOG.debug("rta attrs: ifname %s operstate %d", ifname, operstate) return InterfaceOperstate(ifname, operstate) def wait_for_media_disconnect_connect(netlink_socket, ifname): '''Block until media disconnect and connect has happened on an interface. Listens on netlink socket to receive netlink events and when the carrier changes from 0 to 1, it considers event has happened and return from this function :param: netlink_socket: netlink_socket to receive events :param: ifname: Interface name to lookout for netlink events :raises: AssertionError if netlink_socket is None or ifname is None. ''' assert (netlink_socket is not None), ("netlink socket is none") assert (ifname is not None), ("interface name is none") assert (len(ifname) > 0), ("interface name cannot be empty") carrier = OPER_UP prevCarrier = OPER_UP data = bytes() LOG.debug("Wait for media disconnect and reconnect to happen") while True: recv_data = read_netlink_socket(netlink_socket, SELECT_TIMEOUT) if recv_data is None: continue LOG.debug('read %d bytes from socket', len(recv_data)) data += recv_data LOG.debug('Length of data after concat %d', len(data)) offset = 0 datalen = len(data) while offset < datalen: nl_msg = data[offset:] if len(nl_msg) < NLMSGHDR_SIZE: LOG.debug("Data is smaller than netlink header") break nlheader = get_netlink_msg_header(nl_msg) if len(nl_msg) < nlheader.length: LOG.debug("Partial data. Smaller than netlink message") break padlen = (nlheader.length+PAD_ALIGNMENT-1) & ~(PAD_ALIGNMENT-1) offset = offset + padlen LOG.debug('offset to next netlink message: %d', offset) # Ignore any messages not new link or del link if nlheader.type not in [RTM_NEWLINK, RTM_DELLINK]: continue interface_state = read_rta_oper_state(nl_msg) if interface_state is None: LOG.debug('Failed to read rta attributes: %s', interface_state) continue if interface_state.ifname != ifname: LOG.debug( "Ignored netlink event on interface %s. Waiting for %s.", interface_state.ifname, ifname) continue if interface_state.operstate not in [OPER_UP, OPER_DOWN]: continue prevCarrier = carrier carrier = interface_state.operstate # check for carrier down, up sequence isVnetSwitch = (prevCarrier == OPER_DOWN) and (carrier == OPER_UP) if isVnetSwitch: LOG.debug("Media switch happened on %s.", ifname) return data = data[offset:] # vi: ts=4 expandtab