Re: [gentoo-portage-dev] [PATCH] Use RTNETLINK to configure the loopback interface

[Alec Warner]

unit tests?

-A

On Mon, Aug 26, 2019 at 8:03 PM Mike Gilbert <floppym@g.o> wrote:

> This eliminates the dependency on iproute2 on Linux.
>
> Signed-off-by: Mike Gilbert <floppym@g.o>
> ---
>  lib/portage/process.py      | 25 ++++------
>  lib/portage/util/netlink.py | 91 +++++++++++++++++++++++++++++++++++++
>  2 files changed, 100 insertions(+), 16 deletions(-)
>  create mode 100644 lib/portage/util/netlink.py
>
> diff --git a/lib/portage/process.py b/lib/portage/process.py
> index 2a2cbd972..bb4462c7f 100644
> --- a/lib/portage/process.py
> +++ b/lib/portage/process.py
> @@ -10,7 +10,6 @@ import multiprocessing
>  import platform
>  import signal
>  import socket
> -import struct
>  import subprocess
>  import sys
>  import traceback
> @@ -489,17 +488,6 @@ def _configure_loopback_interface():
>         Configure the loopback interface.
>         """
>
> -       IFF_UP = 0x1
> -       ifreq = struct.pack('16sh', b'lo', IFF_UP)
> -       SIOCSIFFLAGS = 0x8914
> -
> -       sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, 0)
> -       try:
> -               fcntl.ioctl(sock, SIOCSIFFLAGS, ifreq)
> -       except IOError as e:
> -               writemsg("Unable to enable loopback interface: %s\n" %
> e.strerror, noiselevel=-1)
> -       sock.close()
> -
>         # We add some additional addresses to work around odd behavior in
> glibc's
>         # getaddrinfo() implementation when the AI_ADDRCONFIG flag is set.
>         #
> @@ -514,12 +502,17 @@ def _configure_loopback_interface():
>         # Bug: https://bugs.gentoo.org/690758
>         # Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=12377#c13
>
> +       from portage.util.netlink import RtNetlink
> +
>         try:
> -               subprocess.call(['ip', 'address', 'add', '10.0.0.1/8',
> 'dev', 'lo'])
> -               if _has_ipv6():
> -                       subprocess.call(['ip', 'address', 'add',
> 'fd00::1/8', 'dev', 'lo'])
> +               with RtNetlink() as rtnl:
> +                       ifindex = rtnl.get_link_ifindex(b'lo')
> +                       rtnl.set_link_up(ifindex)
> +                       rtnl.add_address(ifindex, socket.AF_INET,
> '10.0.0.1', 8)
> +                       if _has_ipv6():
> +                               rtnl.add_address(ifindex, socket.AF_INET6,
> 'fd::1', 8)
>         except EnvironmentError as e:
> -               writemsg("Error calling 'ip': %s\n" % e.strerror,
> noiselevel=-1)
> +               writemsg("Unable to configure loopback interface: %s\n" %
> e.strerror, noiselevel=-1)
>
>  def _exec(binary, mycommand, opt_name, fd_pipes,
>         env, gid, groups, uid, umask, cwd,
> diff --git a/lib/portage/util/netlink.py b/lib/portage/util/netlink.py
> new file mode 100644
> index 000000000..5b18b8f95
> --- /dev/null
> +++ b/lib/portage/util/netlink.py
> @@ -0,0 +1,91 @@
> +# Copyright 2019 Gentoo Authors
> +# Distributed under the terms of the GNU General Public License v2
> +
> +from io import BytesIO
> +from os import strerror
> +from struct import Struct
> +
> +from socket import (
> +       AF_NETLINK, AF_UNSPEC,
> +       MSG_PEEK, MSG_TRUNC,
> +       NETLINK_ROUTE,
> +       SOCK_DGRAM,
> +       inet_pton, socket,
> +)
> +
> +IFA_LOCAL = 2
> +IFF_UP = 0x1
> +IFLA_IFNAME = 3
> +NLMSG_ERROR = 2
> +RTM_NEWLINK = 16
> +RTM_GETLINK = 18
> +RTM_NEWADDR = 20
> +NLM_F_REQUEST = 0x1
> +NLM_F_ACK = 0x4
> +NLM_F_EXCL = 0x200
> +NLM_F_CREATE = 0x400
> +
> +nlmsghdr = Struct('=IHHII')
> +nlmsgerr = Struct('i')
> +rtattr = Struct('HH')
> +ifinfomsg = Struct('BHiII')
> +ifaddrmsg = Struct('BBBBi')
> +
> +def create_nlmsg(nlmsg_type, nlmsg_flags, nlmsg_seq, nlmsg_pid, data):
> +       nlmsg_len = nlmsghdr.size + len(data)
> +       return nlmsghdr.pack(nlmsg_len, nlmsg_type, nlmsg_flags,
> nlmsg_seq, nlmsg_pid) + data
> +
> +def create_rtattr(rta_type, data):
> +       rta_len = rtattr.size + len(data)
> +       return rtattr.pack(rta_len, rta_type) + data
> +
> +def parse_message(msg):
> +       buf = BytesIO(msg)
> +       hdr = nlmsghdr.unpack(buf.read(nlmsghdr.size))
> +       if hdr[1] == NLMSG_ERROR:
> +               err = nlmsgerr.unpack(buf.read(nlmsgerr.size))
> +               error = -err[0]
> +               if error != 0:
> +                       raise OSError(error, strerror(error))
> +       elif hdr[1] == RTM_NEWLINK:
> +               return ifinfomsg.unpack(buf.read(ifinfomsg.size))
> +
> +class RtNetlink:
> +       def __init__(self):
> +               self.sock = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE)
> +               self.addr = (0, 0)
> +               self.sock.bind(self.addr)
> +
> +       def __enter__(self):
> +               return self
> +
> +       def __exit__(self, exc_type, exc_value, traceback):
> +               self.sock.close()
> +
> +       def send_message(self, msg):
> +               self.sock.sendto(msg, self.addr)
> +               # Messages are variable length, but 128 is enough for the
> the ones we care about.
> +               resp = self.sock.recv(128)
> +               return parse_message(resp)
> +
> +       def get_link_ifindex(self, ifname):
> +               body = ifinfomsg.pack(AF_UNSPEC, 0, 0, 0, 0)
> +               body += create_rtattr(IFLA_IFNAME, ifname)
> +               flags = NLM_F_REQUEST
> +               msg = create_nlmsg(RTM_GETLINK, flags, 1, 0, body)
> +               resp = self.send_message(msg)
> +               return resp[2]
> +
> +       def set_link_up(self, ifindex):
> +               body = ifinfomsg.pack(AF_UNSPEC, 0, ifindex, IFF_UP,
> IFF_UP)
> +               flags = NLM_F_REQUEST|NLM_F_ACK
> +               msg = create_nlmsg(RTM_NEWLINK, flags, 1, 0, body)
> +               self.send_message(msg)
> +
> +       def add_address(self, ifindex, family, address, prefixlen):
> +               body = ifaddrmsg.pack(family, prefixlen, 0, 0, ifindex)
> +               addr = inet_pton(family, address)
> +               body += create_rtattr(IFA_LOCAL, addr)
> +               flags = NLM_F_REQUEST|NLM_F_ACK|NLM_F_EXCL|NLM_F_CREATE
> +               msg = create_nlmsg(RTM_NEWADDR, flags, 1, 0, body)
> +               self.send_message(msg)
> --
> 2.23.0
>
>
>