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Message-ID: <9ad272ae-936c-1bb1-5a56-657b13ac69ba@intel.com>
Date:   Fri, 31 May 2019 13:55:52 +0200
From:   Björn Töpel <bjorn.topel@...el.com>
To:     Jonathan Lemon <jonathan.lemon@...il.com>, netdev@...r.kernel.org,
        magnus.karlsson@...el.com
Cc:     kernel-team@...com, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH v2 bpf-next 2/2] libbpf: remove qidconf and better support
 external bpf programs.

On 2019-05-30 20:57, Jonathan Lemon wrote:
> Use the recent change to XSKMAP bpf_map_lookup_elem() to test if
> there is a xsk present in the map instead of duplicating the work
> with qidconf.
> 
> Fix things so callers using XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD
> bypass any internal bpf maps, so xsk_socket__{create|delete} works
> properly.
> 
> Signed-off-by: Jonathan Lemon <jonathan.lemon@...il.com>
> ---
>   tools/lib/bpf/xsk.c | 79 +++++++++------------------------------------
>   1 file changed, 16 insertions(+), 63 deletions(-)
> 
> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
> index 38667b62f1fe..a150493d51ec 100644
> --- a/tools/lib/bpf/xsk.c
> +++ b/tools/lib/bpf/xsk.c
> @@ -60,10 +60,8 @@ struct xsk_socket {
>   	struct xsk_umem *umem;
>   	struct xsk_socket_config config;
>   	int fd;
> -	int xsks_map;
>   	int ifindex;
>   	int prog_fd;
> -	int qidconf_map_fd;
>   	int xsks_map_fd;
>   	__u32 queue_id;
>   	char ifname[IFNAMSIZ];
> @@ -265,15 +263,11 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
>   	/* This is the C-program:
>   	 * SEC("xdp_sock") int xdp_sock_prog(struct xdp_md *ctx)
>   	 * {
> -	 *     int *qidconf, index = ctx->rx_queue_index;
> +	 *     int index = ctx->rx_queue_index;
>   	 *
>   	 *     // A set entry here means that the correspnding queue_id
>   	 *     // has an active AF_XDP socket bound to it.
> -	 *     qidconf = bpf_map_lookup_elem(&qidconf_map, &index);
> -	 *     if (!qidconf)
> -	 *         return XDP_ABORTED;
> -	 *
> -	 *     if (*qidconf)
> +	 *     if (bpf_map_lookup_elem(&xsks_map, &index))
>   	 *         return bpf_redirect_map(&xsks_map, index, 0);
>   	 *
>   	 *     return XDP_PASS;
> @@ -286,15 +280,10 @@ static int xsk_load_xdp_prog(struct xsk_socket *xsk)
>   		BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_1, -4),
>   		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
>   		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4),
> -		BPF_LD_MAP_FD(BPF_REG_1, xsk->qidconf_map_fd),
> +		BPF_LD_MAP_FD(BPF_REG_1, xsk->xsks_map_fd),
>   		BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
>   		BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
> -		BPF_MOV32_IMM(BPF_REG_0, 0),
> -		/* if r1 == 0 goto +8 */
> -		BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 0, 8),
>   		BPF_MOV32_IMM(BPF_REG_0, 2),
> -		/* r1 = *(u32 *)(r1 + 0) */
> -		BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_1, 0),
>   		/* if r1 == 0 goto +5 */
>   		BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 0, 5),
>   		/* r2 = *(u32 *)(r10 - 4) */
> @@ -366,18 +355,11 @@ static int xsk_create_bpf_maps(struct xsk_socket *xsk)
>   	if (max_queues < 0)
>   		return max_queues;
>   
> -	fd = bpf_create_map_name(BPF_MAP_TYPE_ARRAY, "qidconf_map",
> +	fd = bpf_create_map_name(BPF_MAP_TYPE_ARRAY, "xsks_map",
>   				 sizeof(int), sizeof(int), max_queues, 0);
>   	if (fd < 0)
>   		return fd;
> -	xsk->qidconf_map_fd = fd;
>   
> -	fd = bpf_create_map_name(BPF_MAP_TYPE_XSKMAP, "xsks_map",
> -				 sizeof(int), sizeof(int), max_queues, 0);
> -	if (fd < 0) {
> -		close(xsk->qidconf_map_fd);
> -		return fd;
> -	}

Uhm, you're removing the XSKMAP here, replacing it with an ARRAY. Have
you run this?


Björn

>   	xsk->xsks_map_fd = fd;
>   
>   	return 0;
> @@ -385,10 +367,8 @@ static int xsk_create_bpf_maps(struct xsk_socket *xsk)
>   
>   static void xsk_delete_bpf_maps(struct xsk_socket *xsk)
>   {
> -	close(xsk->qidconf_map_fd);
> +	bpf_map_delete_elem(xsk->xsks_map_fd, &xsk->queue_id);
>   	close(xsk->xsks_map_fd);
> -	xsk->qidconf_map_fd = -1;
> -	xsk->xsks_map_fd = -1;
>   }
>   
>   static int xsk_lookup_bpf_maps(struct xsk_socket *xsk)
> @@ -417,10 +397,9 @@ static int xsk_lookup_bpf_maps(struct xsk_socket *xsk)
>   	if (err)
>   		goto out_map_ids;
>   
> -	for (i = 0; i < prog_info.nr_map_ids; i++) {
> -		if (xsk->qidconf_map_fd != -1 && xsk->xsks_map_fd != -1)
> -			break;
> +	xsk->xsks_map_fd = -1;
>   
> +	for (i = 0; i < prog_info.nr_map_ids; i++) {
>   		fd = bpf_map_get_fd_by_id(map_ids[i]);
>   		if (fd < 0)
>   			continue;
> @@ -431,11 +410,6 @@ static int xsk_lookup_bpf_maps(struct xsk_socket *xsk)
>   			continue;
>   		}
>   
> -		if (!strcmp(map_info.name, "qidconf_map")) {
> -			xsk->qidconf_map_fd = fd;
> -			continue;
> -		}
> -
>   		if (!strcmp(map_info.name, "xsks_map")) {
>   			xsk->xsks_map_fd = fd;
>   			continue;
> @@ -445,40 +419,18 @@ static int xsk_lookup_bpf_maps(struct xsk_socket *xsk)
>   	}
>   
>   	err = 0;
> -	if (xsk->qidconf_map_fd < 0 || xsk->xsks_map_fd < 0) {
> +	if (xsk->xsks_map_fd == -1)
>   		err = -ENOENT;
> -		xsk_delete_bpf_maps(xsk);
> -	}
>   
>   out_map_ids:
>   	free(map_ids);
>   	return err;
>   }
>   
> -static void xsk_clear_bpf_maps(struct xsk_socket *xsk)
> -{
> -	int qid = false;
> -
> -	bpf_map_update_elem(xsk->qidconf_map_fd, &xsk->queue_id, &qid, 0);
> -	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;
> +	return bpf_map_update_elem(xsk->xsks_map_fd, &xsk->queue_id,
> +				   &xsk->fd, 0);
>   }
>   
>   static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
> @@ -514,6 +466,7 @@ static int xsk_setup_xdp_prog(struct xsk_socket *xsk)
>   
>   out_load:
>   	close(xsk->prog_fd);
> +	xsk->prog_fd = -1;
>   out_maps:
>   	xsk_delete_bpf_maps(xsk);
>   	return err;
> @@ -643,9 +596,7 @@ 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;
> -
> +	xsk->prog_fd = -1;
>   	if (!(xsk->config.libbpf_flags & XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD)) {
>   		err = xsk_setup_xdp_prog(xsk);
>   		if (err)
> @@ -708,8 +659,10 @@ void xsk_socket__delete(struct xsk_socket *xsk)
>   	if (!xsk)
>   		return;
>   
> -	xsk_clear_bpf_maps(xsk);
> -	xsk_delete_bpf_maps(xsk);
> +	if (xsk->prog_fd != -1) {
> +		xsk_delete_bpf_maps(xsk);
> +		close(xsk->prog_fd);
> +	}
>   
>   	optlen = sizeof(off);
>   	err = getsockopt(xsk->fd, SOL_XDP, XDP_MMAP_OFFSETS, &off, &optlen);
> 

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