On Fri, Aug 9, 2019 at 6:35 AM Daniel T. Lee <danieltim...@gmail.com> wrote:
>
> By this commit, using `bpftool net attach`, user can attach XDP prog on
> interface. New type of enum 'net_attach_type' has been made, as stated at
> cover-letter, the meaning of 'attach' is, prog will be attached on interface.
>
> With 'overwrite' option at argument, attached XDP program could be replaced.
> Added new helper 'net_parse_dev' to parse the network device at argument.
>
> BPF prog will be attached through libbpf 'bpf_set_link_xdp_fd'.
>
> Signed-off-by: Daniel T. Lee <danieltim...@gmail.com>
> ---
> tools/bpf/bpftool/net.c | 136 +++++++++++++++++++++++++++++++++++++---
> 1 file changed, 129 insertions(+), 7 deletions(-)
>
> diff --git a/tools/bpf/bpftool/net.c b/tools/bpf/bpftool/net.c
> index 67e99c56bc88..74cc346c36cd 100644
> --- a/tools/bpf/bpftool/net.c
> +++ b/tools/bpf/bpftool/net.c
> @@ -55,6 +55,35 @@ struct bpf_attach_info {
> __u32 flow_dissector_id;
> };
>
> +enum net_attach_type {
> + NET_ATTACH_TYPE_XDP,
> + NET_ATTACH_TYPE_XDP_GENERIC,
> + NET_ATTACH_TYPE_XDP_DRIVER,
> + NET_ATTACH_TYPE_XDP_OFFLOAD,
> +};
> +
> +static const char * const attach_type_strings[] = {
> + [NET_ATTACH_TYPE_XDP] = "xdp",
> + [NET_ATTACH_TYPE_XDP_GENERIC] = "xdpgeneric",
> + [NET_ATTACH_TYPE_XDP_DRIVER] = "xdpdrv",
> + [NET_ATTACH_TYPE_XDP_OFFLOAD] = "xdpoffload",
> +};
> +
> +const size_t net_attach_type_size = ARRAY_SIZE(attach_type_strings);
> +
> +static enum net_attach_type parse_attach_type(const char *str)
> +{
> + enum net_attach_type type;
> +
> + for (type = 0; type < net_attach_type_size; type++) {
> + if (attach_type_strings[type] &&
> + is_prefix(str, attach_type_strings[type]))
> + return type;
> + }
> +
> + return net_attach_type_size;
> +}
> +
> static int dump_link_nlmsg(void *cookie, void *msg, struct nlattr **tb)
> {
> struct bpf_netdev_t *netinfo = cookie;
> @@ -223,6 +252,97 @@ static int query_flow_dissector(struct bpf_attach_info
> *attach_info)
> return 0;
> }
>
> +static int net_parse_dev(int *argc, char ***argv)
> +{
> + int ifindex;
> +
> + if (is_prefix(**argv, "dev")) {
> + NEXT_ARGP();
> +
> + ifindex = if_nametoindex(**argv);
> + if (!ifindex)
> + p_err("invalid devname %s", **argv);
> +
> + NEXT_ARGP();
> + } else {
> + p_err("expected 'dev', got: '%s'?", **argv);
> + return -1;
> + }
> +
> + return ifindex;
> +}
> +
> +static int do_attach_detach_xdp(int progfd, enum net_attach_type attach_type,
> + int ifindex, bool overwrite)
> +{
> + __u32 flags = 0;
> +
> + if (!overwrite)
> + flags = XDP_FLAGS_UPDATE_IF_NOEXIST;
> + if (attach_type == NET_ATTACH_TYPE_XDP_GENERIC)
> + flags |= XDP_FLAGS_SKB_MODE;
> + if (attach_type == NET_ATTACH_TYPE_XDP_DRIVER)
> + flags |= XDP_FLAGS_DRV_MODE;
> + if (attach_type == NET_ATTACH_TYPE_XDP_OFFLOAD)
> + flags |= XDP_FLAGS_HW_MODE;
> +
> + return bpf_set_link_xdp_fd(ifindex, progfd, flags);
> +}
> +
> +static int do_attach(int argc, char **argv)
> +{
> + enum net_attach_type attach_type;
> + int progfd, ifindex, err = 0;
> + bool overwrite = false;
> +
> + /* parse attach args */
> + if (!REQ_ARGS(5))
> + return -EINVAL;
> +
> + attach_type = parse_attach_type(*argv);
> + if (attach_type == net_attach_type_size) {
> + p_err("invalid net attach/detach type: %s", *argv);
> + return -EINVAL;
> + }
> + NEXT_ARG();
> +
> + progfd = prog_parse_fd(&argc, &argv);
> + if (progfd < 0)
> + return -EINVAL;
> +
> + ifindex = net_parse_dev(&argc, &argv);
> + if (ifindex < 1) {
> + close(progfd);
> + return -EINVAL;
> + }
> +
> + if (argc) {
> + if (is_prefix(*argv, "overwrite")) {
> + overwrite = true;
> + } else {
> + p_err("expected 'overwrite', got: '%s'?", *argv);
> + close(progfd);
> + return -EINVAL;
> + }
> + }
> +
> + /* attach xdp prog */
> + if (is_prefix("xdp", attach_type_strings[attach_type]))
> + err = do_attach_detach_xdp(progfd, attach_type, ifindex,
> + overwrite);
> +
> + if (err < 0) {
> + p_err("interface %s attach failed: %s",
> + attach_type_strings[attach_type], strerror(errno));
> + return err;
> + }
I tried the below example,
-bash-4.4$ sudo ./bpftool net attach x pinned /sys/fs/bpf/xdp_example
dev v1
-bash-4.4$ sudo ./bpftool net attach x pinned /sys/fs/bpf/xdp_example dev v1
Kernel error message: XDP program already attached
Error: interface xdp attach failed: Success
-bash-4.4$
It printed out "Success" as errno here is 0.
The errno is encoded in variable err. Function bpf_set_link_xdp_fd()
uses netlink interface to do setting. The syscall may be find (errno = 0)
but the netlink msg may contain error code, which is returned with err.
So the above strerror(errno) should be strerror(-err).
libbpf API libbpf_strerror_r() accepts positive or negative err code which
you could use as well here.
With this issue fixed. You can add:
Acked-by: Yonghong Song <y...@fb.com>
> +
> + if (json_output)
> + jsonw_null(json_wtr);
> +
> + return 0;
> +}
> +
[...]
