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Diffstat (limited to 'cloudinit/sources/helpers/netlink.py')
| -rw-r--r-- | cloudinit/sources/helpers/netlink.py | 250 |
1 files changed, 250 insertions, 0 deletions
diff --git a/cloudinit/sources/helpers/netlink.py b/cloudinit/sources/helpers/netlink.py new file mode 100644 index 00000000..d377ae3d --- /dev/null +++ b/cloudinit/sources/helpers/netlink.py @@ -0,0 +1,250 @@ +# Author: Tamilmani Manoharan <tamanoha@microsoft.com> +# +# 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.''' + pass + + +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 = <MAX_SIZE>) 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 |