netdev - Re: [PATCHv2 iproute2-next 0/5] iproute2: add libbpf support

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Date:   Wed, 28 Oct 2020 17:02:34 -0600
From:   David Ahern <dsahern@...il.com>
To:     Hangbin Liu <haliu@...hat.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>
Cc:     Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>,
        Yonghong Song <yhs@...com>, David Miller <davem@...emloft.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        Jiri Benc <jbenc@...hat.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Toke Høiland-Jørgensen 
        <toke@...hat.com>
Subject: Re: [PATCHv2 iproute2-next 0/5] iproute2: add libbpf support

On 10/28/20 7:25 AM, Hangbin Liu wrote:
> This series converts iproute2 to use libbpf for loading and attaching
> BPF programs when it is available. This means that iproute2 will
> correctly process BTF information and support the new-style BTF-defined
> maps, while keeping compatibility with the old internal map definition
> syntax.
> 
> This is achieved by checking for libbpf at './configure' time, and using
> it if available. By default the system libbpf will be used, but static
> linking against a custom libbpf version can be achieved by passing
> LIBBPF_DIR to configure. FORCE_LIBBPF can be set to force configure to
> abort if no suitable libbpf is found (useful for automatic packaging
> that wants to enforce the dependency).
> 
> The old iproute2 bpf code is kept and will be used if no suitable libbpf
> is available. When using libbpf, wrapper code ensures that iproute2 will
> still understand the old map definition format, including populating
> map-in-map and tail call maps before load.
> 
> The examples in bpf/examples are kept, and a separate set of examples
> are added with BTF-based map definitions for those examples where this
> is possible (libbpf doesn't currently support declaratively populating
> tail call maps).
> 
> At last, Thanks a lot for Toke's help on this patch set.
> 
> 
> v2:
> a) Remove self defined IS_ERR_OR_NULL and use libbpf_get_error() instead.
> b) Add ipvrf with libbpf support.
> 
> 

fails to compile on Ubuntu 20.10:

root@...10-sfo3:~/iproute2.git# ./configure
TC schedulers
 ATM	yes
 IPT	using xtables
 IPSET  yes

iptables modules directory: /usr/lib/x86_64-linux-gnu/xtables
libc has setns: yes
SELinux support: yes
libbpf support: yes
ELF support: yes
libmnl support: yes
Berkeley DB: no
need for strlcpy: yes
libcap support: yes

root@...10-sfo3:~/iproute2.git# make clean

root@...10-sfo3:~/iproute2.git# make -j 4
...
/usr/bin/ld: ../lib/libutil.a(bpf_libbpf.o): in function `load_bpf_object':
bpf_libbpf.c:(.text+0x3cb): undefined reference to
`bpf_program__section_name'
/usr/bin/ld: bpf_libbpf.c:(.text+0x438): undefined reference to
`bpf_program__section_name'
/usr/bin/ld: bpf_libbpf.c:(.text+0x716): undefined reference to
`bpf_program__section_name'
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:27: ip] Error 1
make[1]: *** Waiting for unfinished jobs....
make: *** [Makefile:64: all] Error 2