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

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Date:   Mon, 2 Nov 2020 08:41:09 -0700
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: [PATCHv3 iproute2-next 3/5] lib: add libbpf support

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
+

The iproute2_* functions added later in this patch can be in the compat
file as well.