netdev - Re: VRF and/or cgroups problem on Fedora-30, 5.2.21+ kernel

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Message-ID: <fb74534d-f5e8-7b9b-b8c0-b6d6e718a275@gmail.com>
Date:   Sat, 23 Nov 2019 11:10:06 -0700
From:   David Ahern <dsahern@...il.com>
To:     Ben Greear <greearb@...delatech.com>,
        netdev <netdev@...r.kernel.org>
Subject: Re: VRF and/or cgroups problem on Fedora-30, 5.2.21+ kernel

On 11/22/19 5:23 PM, Ben Greear wrote:
>>
> 
> Setting:  ulimit -l 1024
> 
> 'fixed' the problem.
> 
> I'd rather waste a bit of memory and not have any of my users hit such
> an esoteric
> bug, so I'll set it to at least 1024 going forward.

agreed.

> 
> Would large numbers of vrf and/or network devices mean you need more
> locked memory?

I have seen this problem way too much, but not taken the time to track
down all of the locked memory use. A rough estimate is that each 'ip vrf
exec' uses 1 page (4kB) of locked memory until the command exits. If you
use that as a rule you would be on the high end. Commands in the same
cgroup hierarchy should all be using the same program.

> 
> And surely 'ip' could output a better error than just 'permission
> denied' for
> this error case?  Or even something that would show up in dmesg to give
> a clue?

That error comes from the bpf syscall:

bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_CGROUP_SOCK, insn_cnt=6,
insns=0x7ffc8e5d1e00, license="GPL", log_level=1, log_size=262144,
log_buf="", kern_version=KERNEL_VERSION(0, 0, 0), prog_flags=0,
prog_name="", prog_ifindex=0,
expected_attach_type=BPF_CGROUP_INET_INGRESS, prog_btf_fd=0,
func_info_rec_size=0, func_info=NULL, func_info_cnt=0,
line_info_rec_size=0, line_info=NULL, line_info_cnt=0}, 112) = -1 EPERM
(Operation not permitted)

Yes it is odd and unhelpful for a memory limit to cause the failure and
then return EPERM.