On Sun, 29 Nov 2020 12:41:49 -0700
David Ahern [off-list ref] wrote:

On 11/28/20 11:16 PM, Stephen Hemminger wrote:

quoted

Luca wants to put this in Debian 11 (good idea), but that means:

1. It has to work with 5.10 release and kernel.
2. Someone has to test it.
3. The 5.10 is a LTS kernel release which means BPF developers have
   to agree to supporting LTS releases.

If someone steps up to doing this then I would be happy to merge it now
for 5.10. Otherwise it won't show up until 5.11.  

It would be good for Bullseye to have the option to use libbpf with
iproute2. If Debian uses the 5.10 kernel then it should use the 5.10
version of iproute2 and 5.10 version libbpf. All the components align
with consistent versioning.

I have some use cases I can move from bpftool loading to iproute2 as
additional testing to what Hangbin has already done. If that goes well,
I can re-send the patch series against iproute2-main branch by next weekend.

It would be good for others (Jesper, Toke, Jiri) to run their own
testing as well.

I have tested this on a Ubuntu 20.04.1 LTS.

I had to compile tc my own "old" version (based it on iproute2 git
tree), because Ubuntu vendor tc util version didn't even support loading
BPF-ELF objects... weird!

Copy-pasted by compile instruction below signature (including one
failure, that people can find via Google search).

I tested difference combinations old vs. new loader with map pinning
and reuse of maps (as instructed by Toke over IRC), all the cases
worked.

I took it one step further and implemented tc libbpf detection:
 https://github.com/netoptimizer/bpf-examples/commit/048c960756eb65

So, my EDT-pacing code[1] now support BTF-maps, via configure detection
and code gets compiled with support, which allows me to inspect the
content really easily (data from production system):

$ bpftool map lookup id 1351 key 0x10 0x0 0x0 0x0
{
    "key": 16,
    "value": {
        "rate": 0,
        "t_last": 3299496947649930,
        "t_horizon_drop": 0,
        "t_horizon_ecn": 0,
        "codel": {
            "first_above_time": 3299496641781522,
            "drop_next": 3299497041788432,
            "count": 9,
            "dropping": 1
        }
    }
}

[1] https://github.com/netoptimizer/bpf-examples/tree/master/traffic-pacing-edt
- - 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer


Very recently iproute2 got support for using libbpf as BPF-ELF loader.

Testing this on Ubuntu 20.04.1 LTS.

Currently avail is iproute2-next tree:
- https://git.kernel.org/pub/scm/network/iproute2/iproute2-next.git/
- git clone git://git.kernel.org/pub/scm/network/iproute2/iproute2-next.git


First get libbpf:
  git clone https://github.com/libbpf/libbpf.git
  cd libbpf

Build libbpf and install it locally:

  cd ~/git/libbpf/
  mkdir build
  cd ~/git/libbpf/src
  DESTDIR=../build make install
  DESTDIR=../build make install_headers


Attempt#1: Try to get iproute2 compiling against:

  cd ~/git/iproute2-next
  $ LIBBPF_DIR=../libbpf/build/ ./configure 
  TC schedulers
   ATM	no
  
  libc has setns: yes
  SELinux support: no
  libbpf support: yes
  	libbpf version 0.3.0
  ELF support: yes
  libmnl support: yes
  Berkeley DB: no
  need for strlcpy: no
  libcap support: no

Make fails:
  $ make

  lib
      CC       bpf_libbpf.o
  bpf_libbpf.c:20:10: fatal error: bpf/libbpf.h: No such file or directory
     20 | #include <bpf/libbpf.h>
        |          ^~~~~~~~~~~~~~
  compilation terminated.


The problem is use of "relative path" in LIBBPF_DIR (../libbpf/build/), as
the Makefile enter subdir 'lib' and have these include path CFLAGS:

  CFLAGS += -DHAVE_LIBBPF  -I../libbpf/build//usr/include

Attempt#2 works: Try to get iproute2 compiling against:

  cd ~/git/iproute2-next
  $ LIBBPF_DIR=~/git/libbpf/build/ ./configure
  make


Install as stow version:

  export STOW=/usr/local/stow/iproute2-libbpf-next-git-c29f65db34
  make
  make PREFIX=$STOW SYSCONFDIR=$STOW CONFDIR=$STOW/etc/iproute2 SBINDIR=$STOW/sbin -n install
  make PREFIX=$STOW SYSCONFDIR=$STOW CONFDIR=$STOW/etc/iproute2 SBINDIR=$STOW/sbin install

Current state:
  $ tc -V
  tc utility, iproute2-5.9.0, libbpf 0.3.0