On Fri, Mar 20, 2020 at 9:57 AM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote:
>
> From: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
>
> This adds a new function to set the XDP fd while specifying the old fd to
> replace, using the newly added IFLA_XDP_EXPECTED_FD netlink parameter.
>
> Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
> ---
> tools/lib/bpf/libbpf.h | 2 ++
> tools/lib/bpf/libbpf.map | 1 +
> tools/lib/bpf/netlink.c | 22 +++++++++++++++++++++-
> 3 files changed, 24 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index d38d7a629417..b5ca4f741e28 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -445,6 +445,8 @@ struct xdp_link_info {
> };
>
> LIBBPF_API int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags);
> +LIBBPF_API int bpf_set_link_xdp_fd_replace(int ifindex, int fd, int old_fd,
> + __u32 flags);
If we end up doing it in XDP-specific way, I'd argue for using OPTS to
specify optional expected FD. That will allow to extend this API
further without adding many small variations of the same API.
> LIBBPF_API int bpf_get_link_xdp_id(int ifindex, __u32 *prog_id, __u32 flags);
> LIBBPF_API int bpf_get_link_xdp_info(int ifindex, struct xdp_link_info *info,
> size_t info_size, __u32 flags);
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 5129283c0284..154f1d94fa63 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -244,4 +244,5 @@ LIBBPF_0.0.8 {
> bpf_link__pin_path;
> bpf_link__unpin;
> bpf_program__set_attach_target;
> + bpf_set_link_xdp_fd_replace;
> } LIBBPF_0.0.7;
> diff --git a/tools/lib/bpf/netlink.c b/tools/lib/bpf/netlink.c
> index 431bd25c6cdb..39bd0ead1546 100644
> --- a/tools/lib/bpf/netlink.c
> +++ b/tools/lib/bpf/netlink.c
> @@ -132,7 +132,8 @@ static int bpf_netlink_recv(int sock, __u32 nl_pid, int seq,
> return ret;
> }
>
> -int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
> +static int __bpf_set_link_xdp_fd_replace(int ifindex, int fd, int old_fd,
> + __u32 flags)
> {
> int sock, seq = 0, ret;
> struct nlattr *nla, *nla_xdp;
> @@ -178,6 +179,14 @@ int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
> nla->nla_len += nla_xdp->nla_len;
> }
>
> + if (flags & XDP_FLAGS_EXPECT_FD) {
> + nla_xdp = (struct nlattr *)((char *)nla + nla->nla_len);
> + nla_xdp->nla_type = IFLA_XDP_EXPECTED_FD;
> + nla_xdp->nla_len = NLA_HDRLEN + sizeof(int);
> + memcpy((char *)nla_xdp + NLA_HDRLEN, &old_fd, sizeof(old_fd));
> + nla->nla_len += nla_xdp->nla_len;
> + }
> +
> req.nh.nlmsg_len += NLA_ALIGN(nla->nla_len);
>
> if (send(sock, &req, req.nh.nlmsg_len, 0) < 0) {
> @@ -191,6 +200,17 @@ int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
> return ret;
> }
>
> +int bpf_set_link_xdp_fd_replace(int ifindex, int fd, int old_fd, __u32 flags)
> +{
> + return __bpf_set_link_xdp_fd_replace(ifindex, fd, old_fd,
> + flags | XDP_FLAGS_EXPECT_FD);
> +}
> +
> +int bpf_set_link_xdp_fd(int ifindex, int fd, __u32 flags)
> +{
> + return __bpf_set_link_xdp_fd_replace(ifindex, fd, -1, flags);
> +}
> +
> static int __dump_link_nlmsg(struct nlmsghdr *nlh,
> libbpf_dump_nlmsg_t dump_link_nlmsg, void *cookie)
> {
>
