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

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

[Mike Gilbert]

This eliminates the dependency on iproute2 on Linux.

Signed-off-by: Mike Gilbert <floppym@gentoo.org>
---
 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

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

[Alec Warner]

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unit tests?

-A

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

> This eliminates the dependency on iproute2 on Linux.
>
> Signed-off-by: Mike Gilbert <floppym@gentoo.org>
> ---
>  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
>
>
>

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

[Zac Medico]

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On 8/27/19 9:24 AM, Alec Warner wrote:
> unit tests?
> 
> -A

Maybe something like this:

diff --git a/lib/portage/tests/process/test_unshare_net.py b/lib/portage/tests/process/test_unshare_net.py
new file mode 100644
index 000000000..2d3eebad0
--- /dev/null
+++ b/lib/portage/tests/process/test_unshare_net.py
@@ -0,0 +1,30 @@
+# Copyright 2019 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+import os
+import platform
+
+import portage.process
+from portage.const import BASH_BINARY
+from portage.tests import TestCase
+
+UNSHARE_NET_TEST_SCRIPT = """
+ping -c 1 -W 1 127.0.0.1 || exit 1
+[[ -n ${IPV6} ]] || exit 0
+ping -c 1 -W 1 ::1 || exit 1
+"""
+
+class UnshareNetTestCase(TestCase):
+
+       def testUnshareNet(self):
+
+               if os.geteuid() != 0:
+                       self.skipTest('not root')
+               if platform.system() != 'Linux':
+                       self.skipTest('not Linux')
+               if portage.process.find_binary('ping') is None:
+                       self.skipTest('ping not found')
+
+               env = os.environ.copy()
+               env['IPV6'] = '1' if portage.process._has_ipv6() else ''
+               self.assertEqual(portage.process.spawn([BASH_BINARY, '-c', UNSHARE_NET_TEST_SCRIPT], unshare_net=True, env=env), 0)

-- 
Thanks,
Zac


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

[Mike Gilbert]

On Tue, Aug 27, 2019 at 7:11 PM Zac Medico <zmedico@gentoo.org> wrote:
>
> On 8/27/19 9:24 AM, Alec Warner wrote:
> > unit tests?
> >
> > -A
>
> Maybe something like this:
>
> diff --git a/lib/portage/tests/process/test_unshare_net.py b/lib/portage/tests/process/test_unshare_net.py
> new file mode 100644
> index 000000000..2d3eebad0
> --- /dev/null
> +++ b/lib/portage/tests/process/test_unshare_net.py
> @@ -0,0 +1,30 @@
> +# Copyright 2019 Gentoo Authors
> +# Distributed under the terms of the GNU General Public License v2
> +
> +import os
> +import platform
> +
> +import portage.process
> +from portage.const import BASH_BINARY
> +from portage.tests import TestCase
> +
> +UNSHARE_NET_TEST_SCRIPT = """
> +ping -c 1 -W 1 127.0.0.1 || exit 1
> +[[ -n ${IPV6} ]] || exit 0
> +ping -c 1 -W 1 ::1 || exit 1
> +"""
> +
> +class UnshareNetTestCase(TestCase):
> +
> +       def testUnshareNet(self):
> +
> +               if os.geteuid() != 0:
> +                       self.skipTest('not root')
> +               if platform.system() != 'Linux':
> +                       self.skipTest('not Linux')
> +               if portage.process.find_binary('ping') is None:
> +                       self.skipTest('ping not found')
> +
> +               env = os.environ.copy()
> +               env['IPV6'] = '1' if portage.process._has_ipv6() else ''
> +               self.assertEqual(portage.process.spawn([BASH_BINARY, '-c', UNSHARE_NET_TEST_SCRIPT], unshare_net=True, env=env), 0)

Thanks, that's helpful.

I have made a couple tweaks to the original patch that I will send
along shortly.