Linux 4.20 / incomplete ipv4 addr list / RTM_GETADDR

[Ondrej Zajicek]

On Thu, Dec 27, 2018 at 05:01:52PM +0000, Arthur Gautier wrote:
> Hello bird users,
> 
> Today I tried to upgrade one of platform to from linux 4.19 to linux 4.20.
> I started noticing the bgp protocol could not start after this message:
>   <TRACE> uplink: Waiting for 1.2.3.4 to become my neighbor
> 
> The neighbor (directly connected on an interface) would never appear to
> bird (as in show interfaces) because the AF_INET/RTM_GETADDR reply from the
> kernel looks incomplete. It works fine in v6.
> 
> The results from kernel are capped to 104 ip address (and we run servers
> with >700 ip address) on loopback.

Hello

Aren't there any error messages in log? I would guess it is truncated
message due to some more information pushed from kernel or putting
multiple information into one messsage.

Does it help if the constant NL_RX_SIZE (in sysdep/linux/netlink.c) is
increased?

> I confirm this behavour with nlmon / tcpdump / wireshark.
> Tested with bird v2.0.2 and v1.6.3 (debian stable).

Is capped the result from kernel, or its parsing in BIRD? But
perhaps limited buffer size would cause kernel to limit output
of data it sends.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
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"To err is human -- to blame it on a computer is even more so."