Re: [PATCH v2 bpf-next 2/2] libbpf: remove qidconf and better support external bpf programs.

[Jonathan Lemon]

On 31 May 2019, at 4:55, Björn Töpel wrote:

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.le...@gmail.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?

Err... I've been running the code, but this version is wrong.   Let me 
respin this.
--
Jonathan