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Date: Tue, 30 Apr 2019 20:34:12 -0700
From: William Tu <u9012063@...il.com>
To: bpf@...r.kernel.org,
Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf 2/2] libbpf: proper XSKMAP cleanup
On Tue, Apr 30, 2019 at 5:46 AM Björn Töpel <bjorn.topel@...il.com> wrote:
>
> From: Björn Töpel <bjorn.topel@...el.com>
>
> The bpf_map_update_elem() function, when used on an XSKMAP, will fail
> if not a valid AF_XDP socket is passed as value. Therefore, this is
> function cannot be used to clear the XSKMAP. Instead, the
> bpf_map_delete_elem() function should be used for that.
>
> This patch also simplifies the code by breaking up
> xsk_update_bpf_maps() into three smaller functions.
>
> Reported-by: William Tu <u9012063@...il.com>
> Fixes: 1cad07884239 ("libbpf: add support for using AF_XDP sockets")
> Signed-off-by: Björn Töpel <bjorn.topel@...el.com>
> ---
Thank you.
Tested-by: William Tu <u9012063@...il.com>
> tools/lib/bpf/xsk.c | 115 +++++++++++++++++++++++---------------------
> 1 file changed, 60 insertions(+), 55 deletions(-)
>
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index af5f310ecca1..c2e6da464504 100644
> --- a/tools/lib/bpf/xsk.c
> +++ b/tools/lib/bpf/xsk.c
> @@ -386,21 +386,17 @@ static void xsk_delete_bpf_maps(struct xsk_socket *xsk)
> {
> close(xsk->qidconf_map_fd);
> close(xsk->xsks_map_fd);
> + xsk->qidconf_map_fd = -1;
> + xsk->xsks_map_fd = -1;
> }
>
> -static int xsk_update_bpf_maps(struct xsk_socket *xsk, int qidconf_value,
> - int xsks_value)
> +static int xsk_lookup_bpf_maps(struct xsk_socket *xsk)
> {
> - bool qidconf_map_updated = false, xsks_map_updated = false;
> + __u32 i, *map_ids, num_maps, prog_len = sizeof(struct bpf_prog_info);
> + __u32 map_len = sizeof(struct bpf_map_info);
> struct bpf_prog_info prog_info = {};
> - __u32 prog_len = sizeof(prog_info);
> struct bpf_map_info map_info;
> - __u32 map_len = sizeof(map_info);
> - __u32 *map_ids;
> - int reset_value = 0;
> - __u32 num_maps;
> - unsigned int i;
> - int err;
> + int fd, err;
>
> err = bpf_obj_get_info_by_fd(xsk->prog_fd, &prog_info, &prog_len);
> if (err)
> @@ -421,66 +417,71 @@ static int xsk_update_bpf_maps(struct xsk_socket *xsk, int qidconf_value,
> goto out_map_ids;
>
> for (i = 0; i < prog_info.nr_map_ids; i++) {
> - int fd;
> + if (xsk->qidconf_map_fd != -1 && xsk->xsks_map_fd != -1)
> + break;
>
> fd = bpf_map_get_fd_by_id(map_ids[i]);
> - if (fd < 0) {
> - err = -errno;
> - goto out_maps;
> - }
> + if (fd < 0)
> + continue;
>
> err = bpf_obj_get_info_by_fd(fd, &map_info, &map_len);
> - if (err)
> - goto out_maps;
> + if (err) {
> + close(fd);
> + continue;
> + }
>
> if (!strcmp(map_info.name, "qidconf_map")) {
> - err = bpf_map_update_elem(fd, &xsk->queue_id,
> - &qidconf_value, 0);
> - if (err)
> - goto out_maps;
> - qidconf_map_updated = true;
> xsk->qidconf_map_fd = fd;
> - } else if (!strcmp(map_info.name, "xsks_map")) {
> - err = bpf_map_update_elem(fd, &xsk->queue_id,
> - &xsks_value, 0);
> - if (err)
> - goto out_maps;
> - xsks_map_updated = true;
> + continue;
> + }
> +
> + if (!strcmp(map_info.name, "xsks_map")) {
> xsk->xsks_map_fd = fd;
> + continue;
> }
>
> - if (qidconf_map_updated && xsks_map_updated)
> - break;
> + close(fd);
> }
>
> - if (!(qidconf_map_updated && xsks_map_updated)) {
> + err = 0;
> + if (xsk->qidconf_map_fd < 0 || xsk->xsks_map_fd < 0) {
> err = -ENOENT;
> - goto out_maps;
> + xsk_delete_bpf_maps(xsk);
> }
>
> - err = 0;
> - goto out_success;
> -
> -out_maps:
> - if (qidconf_map_updated)
> - (void)bpf_map_update_elem(xsk->qidconf_map_fd, &xsk->queue_id,
> - &reset_value, 0);
> - if (xsks_map_updated)
> - (void)bpf_map_update_elem(xsk->xsks_map_fd, &xsk->queue_id,
> - &reset_value, 0);
> -out_success:
> - if (qidconf_map_updated)
> - close(xsk->qidconf_map_fd);
> - if (xsks_map_updated)
> - close(xsk->xsks_map_fd);
> out_map_ids:
> free(map_ids);
> return err;
> }
>
> +static void xsk_clear_bpf_maps(struct xsk_socket *xsk)
> +{
> + int qid = false;
> +
> + (void)bpf_map_update_elem(xsk->qidconf_map_fd, &xsk->queue_id, &qid, 0);
> + (void)bpf_map_delete_elem(xsk->xsks_map_fd, &xsk->queue_id);
> +}
> +
> +static int xsk_set_bpf_maps(struct xsk_socket *xsk)
> +{
> + int qid = true, fd = xsk->fd, err;
> +
> + err = bpf_map_update_elem(xsk->qidconf_map_fd, &xsk->queue_id, &qid, 0);
> + if (err)
> + goto out;
> +
> + err = bpf_map_update_elem(xsk->xsks_map_fd, &xsk->queue_id, &fd, 0);
> + if (err)
> + goto out;
> +
> + return 0;
> +out:
> + xsk_clear_bpf_maps(xsk);
> + return err;
> +}
> +
> static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
> {
> - bool prog_attached = false;
> __u32 prog_id = 0;
> int err;
>
> @@ -490,7 +491,6 @@ static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
> return err;
>
> if (!prog_id) {
> - prog_attached = true;
> err = xsk_create_bpf_maps(xsk);
> if (err)
> return err;
> @@ -500,20 +500,21 @@ static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
> goto out_maps;
> } else {
> xsk->prog_fd = bpf_prog_get_fd_by_id(prog_id);
> + err = xsk_lookup_bpf_maps(xsk);
> + if (err)
> + goto out_load;
> }
>
> - err = xsk_update_bpf_maps(xsk, true, xsk->fd);
> + err = xsk_set_bpf_maps(xsk);
> if (err)
> goto out_load;
>
> return 0;
>
> out_load:
> - if (prog_attached)
> - close(xsk->prog_fd);
> + close(xsk->prog_fd);
> out_maps:
> - if (prog_attached)
> - xsk_delete_bpf_maps(xsk);
> + xsk_delete_bpf_maps(xsk);
> return err;
> }
>
> @@ -641,6 +642,9 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
> goto out_mmap_tx;
> }
>
> + xsk->qidconf_map_fd = -1;
> + xsk->xsks_map_fd = -1;
> +
> if (!(xsk->config.libbpf_flags & XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD)) {
> err = xsk_setup_xdp_prog(xsk);
> if (err)
> @@ -705,7 +709,8 @@ void xsk_socket__delete(struct xsk_socket *xsk)
> if (!xsk)
> return;
>
> - (void)xsk_update_bpf_maps(xsk, 0, 0);
> + xsk_clear_bpf_maps(xsk);
> + xsk_delete_bpf_maps(xsk);
>
> optlen = sizeof(off);
> err = getsockopt(xsk->fd, SOL_XDP, XDP_MMAP_OFFSETS, &off, &optlen);
> --
> 2.20.1
>
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