Package: isc-dhcp-client
Version: 4.3.1-6+deb8u2
Severity: normal
Tags: upstream
Dear Maintainer,
dhclient does not cleanly support interface names with lengths > 13.
debian's packaging of systemd can routinely generate interface names with
length 15.
If the length is 15, dhclient fails with messages like this:
debian@beaglebone:~/isc-dhcp-client/isc-dhcp-4.3.1$ sudo dhclient -d
enxe46f13f3df43
Internet Systems Consortium DHCP Client 4.3.1
Copyright 2004-2014 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
Bind socket to interface: No such device
If you think you have received this message due to a bug rather
than a configuration issue please read the section on submitting
bugs on either our web page at www.isc.org or in the README file
before submitting a bug. These pages explain the proper
process and the information we find helpful for debugging..
exiting.
If the length is 14, dhclient fails with messages like this:
debian@beaglebone:~/isc-dhcp-client/isc-dhcp-4.3.1$ sudo dhclient -d
enxe46f13f3df4
Internet Systems Consortium DHCP Client 4.3.1
Copyright 2004-2014 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
Listening on LPF/enxe46f13f3df4/e4:6f:13:f3:df:43
Sending on LPF/enxe46f13f3df4/e4:6f:13:f3:df:43
Sending on Socket/fallback
DHCPDISCOVER on enxe46f13f3df4 to 255.255.255.255 port 67 interval 3
send_packet: No such device
dhclient.c:1966: Failed to send 300 byte long packet over
enxe46f13f3df4 interface.
DHCPDISCOVER on enxe46f13f3df4 to 255.255.255.255 port 67 interval 6
send_packet: No such device
dhclient.c:1966: Failed to send 300 byte long packet over
enxe46f13f3df4 interface.
Interface names lengths of no more than 13 worked as expected:
debian@beaglebone:~/isc-dhcp-client/isc-dhcp-4.3.1$ sudo dhclient -d
enxe46f13f3df
Internet Systems Consortium DHCP Client 4.3.1
Copyright 2004-2014 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
Listening on LPF/enxe46f13f3df/e4:6f:13:f3:df:43
Sending on LPF/enxe46f13f3df/e4:6f:13:f3:df:43
Sending on Socket/fallback
DHCPDISCOVER on enxe46f13f3df to 255.255.255.255 port 67 interval 7
DHCPDISCOVER on enxe46f13f3df to 255.255.255.255 port 67 interval 14
DHCPREQUEST on enxe46f13f3df to 255.255.255.255 port 67
DHCPOFFER from 192.168.1.1
DHCPACK from 192.168.1.1
bound to 192.168.1.159 -- renewal in 35492 seconds.
The difference in behaviour is apparently caused by the name being
truncated before the trailing
nul in the first case, but being truncated immediately prior to the
trailing nul in the second case.
The root cause is a strncpy in common/lpf.c:
/* Bind to the interface name */
memset (&sa, 0, sizeof sa);
sa.sa_family = AF_PACKET;
strncpy (sa.sa_data, (const char *)info -> ifp, sizeof sa.sa_data);
if (bind (sock, &sa, sizeof sa)) {
....
which silently performs a truncated copy of 16 byte structure (info->lfp) into
a 14 byte structure.
Since the results of silently truncating the name are undefined, it would be
better
if dhclient instead aborted with an error message indicating that the long
interface name
cannot be successfully copied.
Note that systemd can generate 15 character interface names derived from a mac
address of the
underlying device though, by default, it does not.
However, debian's packaging of udevd includes
/lib/udev/rules.d/73-usb-net-by-mac.rules which
causes USB ethernet devices on at least some platforms, BeagleBone, to generate
long
MAC-address based device names using the net_id udev plugin.
To experiment with different interface name lengths, I added
/etc/udev/rules.d/99-local.rules
#
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="ax88179_178a", ATTR{dev_id}=="0x0",
ATTR{type}=="1", NAME="enxe46f13f3df43"
To test different lengths, I truncated NAME to different lengths, then
re-hotplugged the relevant device.
-- System Information:
Debian Release: 8.7
APT prefers stable-updates
APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: armhf (armv7l)
Kernel: Linux 4.4.26-ti-r59 (SMP w/1 CPU core)
Locale: LANG=en_AU.UTF-8, LC_CTYPE=en_AU.UTF-8 (charmap=locale: Cannot set
LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_ALL to default locale: No such file or directory
ANSI_X3.4-1968)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
Versions of packages isc-dhcp-client depends on:
ii debianutils 4.4+b1
ii iproute2 3.16.0-2
ii isc-dhcp-common 4.3.1-6+deb8u2
ii libc6 2.19-18+deb8u7
ii libdns-export100 1:9.9.5.dfsg-9+deb8u10
ii libirs-export91 1:9.9.5.dfsg-9+deb8u10
ii libisc-export95 1:9.9.5.dfsg-9+deb8u10
isc-dhcp-client recommends no packages.
Versions of packages isc-dhcp-client suggests:
pn avahi-autoipd <none>
pn resolvconf <none>
-- debconf information:
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
LANGUAGE = (unset),
LC_ALL = (unset),
LANG = "en_AU.UTF-8"
are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_ALL to default locale: No such file or directory
