Bug#814667: systemd-networkd overrides default kernel net.ipv6.conf.interface.accept_ra

[pdormeau at free.fr]

Package: systemd
Version: 229-1
Severity: normal

Dear Maintainer,

man systemd.network says:

"IPv6AcceptRouterAdvertisements=
Force the setting of the accept_ra (router advertisements) setting for 
the interface. When unset, the kernel default is used, and router 
advertisements are accepted only when local forwarding is disabled for 
that interface.
When router advertisements are accepted, they will trigger the start of 
the DHCPv6 client if the relevant flags are passed, or if no routers are 
found on the link. Takes a boolean. If true, router advertisements are 
accepted, when false, router advertisements are ignored, independently 
of the local forwarding state."

But although IPv6AcceptRouterAdvertisements is not set, DHCP is not set 
to ipv6, and forwarding is disabled, systemd-networkd overrides default 
kernel (net.ipv6.conf.wlp3s0.accept_ra switched from 1 to 0 after 
systemd-networkd.service starts). Consequently, SLAAC fails.

Setting IPv6AcceptRouterAdvertisements to true or false does not help 
either.

# cat /etc/systemd/network/wlp3s0.network 
[Match]
Name=wlp3s0

[Network]
DHCP=ipv4

[DHCP]
UseDNS=true


# sysctl net.ipv6.conf.wlp3s0.accept_ra=1
net.ipv6.conf.wlp3s0.accept_ra = 1
# sysctl net.ipv6.conf.wlp3s0.forwarding
net.ipv6.conf.wlp3s0.forwarding = 0
# systemctl restart systemd-networkd.service
# sysctl net.ipv6.conf.wlp3s0.accept_ra
net.ipv6.conf.wlp3s0.accept_ra = 0

This does not happen with version 228-6

Best regards

Pascal Dormeau


-- Package-specific info:

-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (990, 'unstable'), (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 4.3.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=fr_FR.utf8, LC_CTYPE=fr_FR.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages systemd depends on:
ii  adduser         3.113+nmu3
ii  libacl1         2.2.52-3
ii  libapparmor1    2.10-3
ii  libaudit1       1:2.4.5-1
ii  libblkid1       2.27.1-3
ii  libc6           2.21-7
ii  libcap2         1:2.24-12
ii  libcap2-bin     1:2.24-12
ii  libcryptsetup4  2:1.7.0-2
ii  libgcrypt20     1.6.5-2
ii  libgpg-error0   1.21-1
ii  libkmod2        22-1
ii  liblzma5        5.1.1alpha+20120614-2.1
ii  libmount1       2.27.1-3
ii  libpam0g        1.1.8-3.2
ii  libseccomp2     2.2.3-3
ii  libselinux1     2.4-3
ii  libsystemd0     229-1
ii  mount           2.27.1-3
ii  util-linux      2.27.1-3

Versions of packages systemd recommends:
ii  dbus            1.10.6-1
ii  libpam-systemd  229-1

Versions of packages systemd suggests:
pn  systemd-container  <none>
pn  systemd-ui         <none>

Versions of packages systemd is related to:
ii  udev  229-1

-- Configuration Files:
/etc/systemd/journald.conf changed:
[Journal]
Storage=volatile
RuntimeMaxUse=50M
ForwardToSyslog=no
ForwardToConsole=yes
TTYPath=/dev/tty12

/etc/systemd/resolved.conf changed:
[Resolve]
DNS=212.27.40.240 2a01:e00::1 212.27.40.241 2a01:e00::2


-- no debconf information