netdev - Re: [PATCHv3 iproute2-next 3/5] lib: add libbpf support

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Message-ID: <20201104082203.GP2408@dhcp-12-153.nay.redhat.com>
Date:   Wed, 4 Nov 2020 16:22:03 +0800
From:   Hangbin Liu <haliu@...hat.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        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: [PATCHv3 iproute2-next 3/5] lib: add libbpf support

On Mon, Nov 02, 2020 at 08:41:09AM -0700, David Ahern wrote:
> On 10/29/20 9:11 AM, Hangbin Liu wrote:
> > diff --git a/ip/ipvrf.c b/ip/ipvrf.c
> > index 33150ac2..afaf1de7 100644
> > --- a/ip/ipvrf.c
> > +++ b/ip/ipvrf.c
> > @@ -28,8 +28,14 @@
> >  #include "rt_names.h"
> >  #include "utils.h"
> >  #include "ip_common.h"
> > +
> >  #include "bpf_util.h"
> >  
> > +#ifdef HAVE_LIBBPF
> > +#include <bpf/bpf.h>
> > +#include <bpf/libbpf.h>
> > +#endif
> > +
> >  #define CGRP_PROC_FILE  "/cgroup.procs"
> >  
> >  static struct link_filter vrf_filter;
> > @@ -256,8 +262,13 @@ static int prog_load(int idx)
> >  		BPF_EXIT_INSN(),
> >  	};
> >  
> > +#ifdef HAVE_LIBBPF
> > +	return bpf_load_program(BPF_PROG_TYPE_CGROUP_SOCK, prog, sizeof(prog),
> > +				"GPL", 0, bpf_log_buf, sizeof(bpf_log_buf));
> > +#else
> >  	return bpf_prog_load_buf(BPF_PROG_TYPE_CGROUP_SOCK, prog, sizeof(prog),
> >  			         "GPL", bpf_log_buf, sizeof(bpf_log_buf));
> > +#endif
> >  }
> >  
> >  static int vrf_configure_cgroup(const char *path, int ifindex)
> > @@ -288,7 +299,11 @@ static int vrf_configure_cgroup(const char *path, int ifindex)
> >  		goto out;
> >  	}
> >  
> > +#ifdef HAVE_LIBBPF
> > +	if (bpf_prog_attach(prog_fd, cg_fd, BPF_CGROUP_INET_SOCK_CREATE, 0)) {
> > +#else
> >  	if (bpf_prog_attach_fd(prog_fd, cg_fd, BPF_CGROUP_INET_SOCK_CREATE)) {
> > +#endif
> >  		fprintf(stderr, "Failed to attach prog to cgroup: '%s'\n",
> >  			strerror(errno));
> >  		goto out;
> 
> I would prefer to have these #ifdef .. #endif checks consolidated in the
> lib code. Create a bpf_compat file for these. e.g.,
> 
> int bpf_program_load(enum bpf_prog_type type, const struct bpf_insn *insns,
>                      size_t size_insns, const char *license, char *log,
>                      size_t size_log)
> {
> +#ifdef HAVE_LIBBPF
> +	return bpf_load_program(BPF_PROG_TYPE_CGROUP_SOCK, prog, sizeof(prog),
> +				"GPL", 0, bpf_log_buf, sizeof(bpf_log_buf));
> +#else
>  	return bpf_prog_load_buf(BPF_PROG_TYPE_CGROUP_SOCK, prog, sizeof(prog),
>  			         "GPL", bpf_log_buf, sizeof(bpf_log_buf));
> +#endif
> }
> 
> Similarly for bpf_program_attach.
> 
> 
> I think even the includes can be done once in bpf_util.h with a single
> +#ifdef HAVE_LIBBPF
> +#include <bpf/bpf.h>
> +#include <bpf/libbpf.h>
> +#endif
> +

Oh, I just found why I didn't include libbpf.h in bpf_legacy.c.
The reason is there are more function conflicts. e.g.
bpf_obj_get, bpf_obj_pin, bpf_prog_attach.

If we move this #ifdef HAVE_LIBBPF to bpf_legacy.c, we need to rename
them all. With current patch, we limit all the legacy functions in bpf_legacy
and doesn't mix them with libbpf.h. What do you think?

Thanks
Hangbin