Subject: Re: [iproute2 net-next 1/8] lib bpf: Add support for BPF_PROG_ATTACH and BPF_PROG_DETACH

From: Daniel Borkmann <[email-masked]>
Date: Sat, 10 Dec 2016 22:16:48 +0100

On 12/10/2016 09:32 PM, David Ahern wrote:
> For consistency with other bpf commands, the functions are named
> bpf_prog_attach and bpf_prog_detach. The existing bpf_prog_attach is
> renamed to bpf_prog_load_and_report since it calls bpf_prog_load and
> bpf_prog_report.
>
> Signed-off-by: David Ahern <[email-masked]>
> ---
>   include/bpf_util.h |  3 +++
>   lib/bpf.c          | 31 ++++++++++++++++++++++++++-----
>   2 files changed, 29 insertions(+), 5 deletions(-)
>
> diff --git a/include/bpf_util.h b/include/bpf_util.h
> index 05baeecda57f..49b96bbc208f 100644
> --- a/include/bpf_util.h
> +++ b/include/bpf_util.h
> @@ -75,6 +75,9 @@ int bpf_trace_pipe(void);
>
>   void bpf_print_ops(FILE *f, struct rtattr *bpf_ops, __u16 len);
>
> +int bpf_prog_attach(int prog_fd, int target_fd, enum bpf_attach_type type);
> +int bpf_prog_detach(int target_fd, enum bpf_attach_type type);
> +
>   #ifdef HAVE_ELF
>   int bpf_send_map_fds(const char *path, const char *obj);
>   int bpf_recv_map_fds(const char *path, int *fds, struct bpf_map_aux *aux,
> diff --git a/lib/bpf.c b/lib/bpf.c
> index 2a8cd51d4dae..103fc1ef0593 100644
> --- a/lib/bpf.c
> +++ b/lib/bpf.c
> @@ -850,6 +850,27 @@ int bpf_graft_map(const char *map_path, uint32_t *key, int argc, char **argv)
>   	return ret;
>   }
>
> +int bpf_prog_attach(int prog_fd, int target_fd, enum bpf_attach_type type)
> +{
> +	union bpf_attr attr = {
> +		.target_fd = target_fd,
> +		.attach_bpf_fd = prog_fd,
> +		.attach_type = type,
> +	};

Please make this consistent with the other bpf(2) cmds we
have in the current lib code. There were some gcc issues in
the past, see:

https://git.kernel.org/cgit/linux/kernel/git/shemminger/iproute2.git/commit/?id=67584e3ab289a22eb9a2e51f90d23e2ced2e76b0

F.e. bpf_map_create() currently looks like:

	union bpf_attr attr = {};

	attr.map_type = type;
	attr.key_size = size_key;
	attr.value_size = size_value;
	attr.max_entries = max_elem;
	attr.map_flags = flags;

> +	return bpf(BPF_PROG_ATTACH, &attr, sizeof(attr));
> +}
> +
> +int bpf_prog_detach(int target_fd, enum bpf_attach_type type)
> +{
> +	union bpf_attr attr = {
> +		.target_fd = target_fd,
> +		.attach_type = type,
> +	};

Ditto.

> +	return bpf(BPF_PROG_DETACH, &attr, sizeof(attr));
> +}
> +
>   #ifdef HAVE_ELF
>   struct bpf_elf_prog {
>   	enum bpf_prog_type	type;
> @@ -1262,9 +1283,9 @@ static void bpf_prog_report(int fd, const char *section,
>   	bpf_dump_error(ctx, "Verifier analysis:\n\n");
>   }
>
> -static int bpf_prog_attach(const char *section,
> -			   const struct bpf_elf_prog *prog,
> -			   struct bpf_elf_ctx *ctx)
> +static int bpf_prog_load_and_report(const char *section,
> +				    const struct bpf_elf_prog *prog,
> +				    struct bpf_elf_ctx *ctx)
>   {

Please name it bpf_prog_create() then, it would be consistent to
bpf_map_create() and shorter as well.

>   	int tries = 0, fd;
>   retry:
> @@ -1656,7 +1677,7 @@ static int bpf_fetch_prog(struct bpf_elf_ctx *ctx, const char *section,
>   		prog.size    = data.sec_data->d_size;
>   		prog.license = ctx->license;
>
> -		fd = bpf_prog_attach(section, &prog, ctx);
> +		fd = bpf_prog_load_and_report(section, &prog, ctx);
>   		if (fd < 0)
>   			return fd;
>
> @@ -1755,7 +1776,7 @@ static int bpf_fetch_prog_relo(struct bpf_elf_ctx *ctx, const char *section,
>   		prog.size    = data_insn.sec_data->d_size;
>   		prog.license = ctx->license;
>
> -		fd = bpf_prog_attach(section, &prog, ctx);
> +		fd = bpf_prog_load_and_report(section, &prog, ctx);
>   		if (fd < 0) {
>   			*lderr = true;
>   			return fd;
>