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Beniamino Galvani bee01292f8 n-dhcp4: don't fail dispatch in case of receive errors
Currently any error encountered in n_dhcp4_c_connection_dispatch_io()
causes a dispatch failure and interrupts the library state
machine. The recvmsg() on the socket can fail for different reasons;
one of these is for example that the UDP request previously sent got a
ICMP port-unreachable response. This can be reproduced in the
following way:

 ip netns add ns1
 ip link add veth0 type veth peer name veth1
 ip link set veth1 netns ns1
 ip link set veth0 up

 cat > dhcpd.conf <<EOF
 server-identifier 172.25.0.1;
 max-lease-time 120;
 default-lease-time 120;
 subnet 172.25.0.0 netmask 255.255.255.0 {
        range 172.25.0.100 172.25.0.200;
 }
 EOF

 ip -n ns1 link set veth1 up
 ip -n ns1 address add dev veth1 172.25.0.1/24
 ip netns exec ns1 iptables -A INPUT -p udp --dport 67 -j REJECT
 ip netns exec ns1 dhcpd -4 -cf dhcpd.conf -pf /tmp/dhcp-server.pid

If a client is started on veth0, it is able to obtain a lease despite
the firewall rule blocking DHCP, because dhcpd uses a packet
socket. Then it fails during the renewal because the recvmsg() fails:

 dhcp4 (veth0): send REQUEST of 172.25.0.178 to 172.25.0.1
 dhcp4 (veth0): error -111 dispatching events
 dhcp4 (veth0): state changed bound -> fail

The client should consider such errors non fatal and keep running.

https://bugzilla.redhat.com/show_bug.cgi?id=1829178
https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/486
(cherry picked from commit c5d1d4c498)
2020-04-30 18:15:42 +02:00
clients libnm/doc: clarify use of "ipv[46].gateway in nm-settings manual 2020-04-26 13:30:13 +02:00
contrib contrib/rpm: fix spec file using bare words 2020-04-19 21:45:05 +02:00
data meson: merge branch 'inigomartinez/meson-license' 2020-03-28 12:45:19 +01:00
dispatcher meson: merge branch 'inigomartinez/meson-license' 2020-03-28 12:45:19 +01:00
docs license: Add license using SPDX identifiers to meson build files 2020-02-17 13:16:57 +01:00
examples license: Add license using SPDX identifiers to meson build files 2020-02-17 13:16:57 +01:00
introspection man: fix obsolete references to monitor-connection-files in manual pages 2020-04-10 15:02:20 +02:00
libnm libnm/doc: fix spelling in nm_client_add_and_activate_connection2() documentation 2020-04-28 18:36:47 +02:00
libnm-core libnm/doc: clarify use of "ipv[46].gateway in nm-settings manual 2020-04-26 13:30:13 +02:00
m4 build: remove subshells and fix invalid test syntax 2020-04-20 08:54:38 +02:00
man man: mention the meaning of may-fail in the nm-online man page 2020-04-23 17:43:58 +02:00
po po: mark broken translations as fuzzy 2020-04-14 09:23:44 +02:00
shared n-dhcp4: don't fail dispatch in case of receive errors 2020-04-30 18:15:42 +02:00
src wifi: clear scan_request_ssids_hash if not needed 2020-04-30 11:21:22 +02:00
tools tests: abort test runner if exec fails 2020-04-20 11:52:11 +02:00
vapi license: Add license using SPDX identifiers to meson build files 2020-02-17 13:16:57 +01:00
.dir-locals.el misc: add toplevel .dir-locals file that tells Emacs to show trailing whitespace 2013-03-08 15:15:28 +01:00
.gitignore git: ignore clangd and ctags generated files 2020-01-29 17:25:21 +01:00
.gitlab-ci.yml gitlab-ci: use old meson version on Ubuntu 16.04 to work with ninja-1.5.1 2020-04-02 09:54:26 +02:00
.mailmap license: Add Frédéric to RELICENSE.md 2020-04-08 07:39:18 +02:00
.travis.yml travis-ci: update build platform to Ubuntu 16.04 (xenial) 2019-12-02 17:25:14 +01:00
.triage-policies.yml gitlab-ci: use ruby:2.7 for triage pipeline 2020-03-18 17:40:59 +01:00
AUTHORS misc: update maintainers and authors 2016-04-21 13:39:03 -05:00
autogen.sh all: goodbye libnm-glib 2019-04-16 15:52:27 +02:00
ChangeLog all: point git references to the GitLab instance 2018-08-27 11:36:56 +02:00
config-extra.h.meson build: remove duplicate and unused RUNDIR define 2019-05-17 21:24:18 +02:00
config-extra.h.mk build: regenerate config-extra.h if configure was re-run with different arguments 2019-09-25 15:55:37 +02:00
config.h.meson clients: polkit-agent: implement polkit agent without using libpolkit 2019-12-24 10:13:51 +01:00
configure.ac build: remove subshells and fix invalid test syntax 2020-04-20 08:54:38 +02:00
CONTRIBUTING CONTRIBUTING: update comment about requiring LGPL-2.1+ license instead of LGPL-2.0+ 2019-10-01 07:50:52 +02:00
COPYING COPYING: make sure we ship the relevant license texts 2019-09-10 11:10:52 +02:00
COPYING.GFDL COPYING: make sure we ship the relevant license texts 2019-09-10 11:10:52 +02:00
COPYING.LGPL COPYING: make sure we ship the relevant license texts 2019-09-10 11:10:52 +02:00
linker-script-binary.ver iface-helper/build: add linker version script 2016-10-13 21:33:33 +02:00
linker-script-devices.ver devices/build: use one linker-script-devices.ver for all device plugins 2016-10-13 21:36:06 +02:00
linker-script-settings.ver settings/build: add linker version script for settings plugins 2016-10-13 21:33:33 +02:00
MAINTAINERS misc: update maintainers and authors 2016-04-21 13:39:03 -05:00
Makefile.am build: remove subshells and fix invalid test syntax 2020-04-20 08:54:38 +02:00
Makefile.examples examples: add examples/python/gi/nm-update2.py example script 2019-07-25 22:02:00 +02:00
Makefile.glib all: drop emacs file variables from source files 2019-06-11 10:04:00 +02:00
Makefile.vapigen build: fix make always re-making vapigen target 2016-10-21 18:46:03 +02:00
meson.build release: bump version to 1.23.90 (1.24-rc1) 2020-04-10 17:55:22 +02:00
meson_options.txt core: add main.auth-polkit option "root-only" 2019-12-11 11:52:05 +01:00
NetworkManager.pc.in build: update NetworkManager.pc 2013-01-29 16:17:30 -05:00
NEWS NEWS: update 2020-04-22 15:05:39 +02:00
README all: drop empty first line from sources 2019-06-11 10:15:06 +02:00
RELICENSE.md license: Add Frédéric to RELICENSE.md 2020-04-08 07:39:18 +02:00
TODO all: say Wi-Fi instead of "wifi" or "WiFi" 2018-11-29 17:53:35 +01:00
valgrind.suppressions all: goodbye libnm-glib 2019-04-16 15:52:27 +02:00

******************
NetworkManager core daemon has moved to gitlab.freedesktop.org!

git clone https://gitlab.freedesktop.org/NetworkManager/NetworkManager.git
******************


Networking that Just Works
--------------------------

NetworkManager attempts to keep an active network connection available at all
times.  The point of NetworkManager is to make networking configuration and
setup as painless and automatic as possible.  NetworkManager is intended to
replace default route, replace other routes, set IP addresses, and in general
configure networking as NM sees fit (with the possibility of manual override as
necessary).  In effect, the goal of NetworkManager is to make networking Just
Work with a minimum of user hassle, but still allow customization and a high
level of manual network control.  If you have special needs, we'd like to hear
about them, but understand that NetworkManager is not intended for every
use-case.

NetworkManager will attempt to keep every network device in the system up and
active, as long as the device is available for use (has a cable plugged in,
the killswitch isn't turned on, etc).  Network connections can be set to
'autoconnect', meaning that NetworkManager will make that connection active
whenever it and the hardware is available.

"Settings services" store lists of user- or administrator-defined "connections",
which contain all the settings and parameters required to connect to a specific
network.  NetworkManager will _never_ activate a connection that is not in this
list, or that the user has not directed NetworkManager to connect to.


How it works:

The NetworkManager daemon runs as a privileged service (since it must access
and control hardware), but provides a D-Bus interface on the system bus to
allow for fine-grained control of networking.  NetworkManager does not store
connections or settings, it is only the mechanism by which those connections
are selected and activated.

To store pre-defined network connections, two separate services, the "system
settings service" and the "user settings service" store connection information
and provide these to NetworkManager, also via D-Bus.  Each settings service
can determine how and where it persistently stores the connection information;
for example, the GNOME applet stores its configuration in GConf, and the system
settings service stores its config in distro-specific formats, or in a distro-
agnostic format, depending on user/administrator preference.

A variety of other system services are used by NetworkManager to provide
network functionality: wpa_supplicant for wireless connections and 802.1x
wired connections, pppd for PPP and mobile broadband connections, DHCP clients
for dynamic IP addressing, dnsmasq for proxy nameserver and DHCP server
functionality for internet connection sharing, and avahi-autoipd for IPv4
link-local addresses.  Most communication with these daemons occurs, again,
via D-Bus.


Why doesn't my network Just Work?

Driver problems are the #1 cause of why NetworkManager sometimes fails to
connect to wireless networks.  Often, the driver simply doesn't behave in a
consistent manner, or is just plain buggy.  NetworkManager supports _only_
those drivers that are shipped with the upstream Linux kernel, because only
those drivers can be easily fixed and debugged.  ndiswrapper, vendor binary
drivers, or other out-of-tree drivers may or may not work well with
NetworkManager, precisely because they have not been vetted and improved by the
open-source community, and because problems in these drivers usually cannot
be fixed.

Sometimes, command-line tools like 'iwconfig' will work, but NetworkManager will
fail.  This is again often due to buggy drivers, because these drivers simply
aren't expecting the dynamic requests that NetworkManager and wpa_supplicant
make.  Driver bugs should be filed in the bug tracker of the distribution being
run, since often distributions customize their kernel and drivers.

Sometimes, it really is NetworkManager's fault.  If you think that's
the case, please file a bug at:

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/issues

Attaching NetworkManager debug logs from the journal (or wherever your
distribution directs syslog's 'daemon' facility output, as
/var/log/messages or /var/log/daemon.log) is often very helpful, and
(if you can get) a working wpa_supplicant config file helps
enormously.  See the logging section of file
contrib/fedora/rpm/NetworkManager.conf for how to enable debug logging
in NetworkManager.