samples/bpf: xdp_rxq_info action XDP_TX must adjust MAC-addrs

XDP_TX requires also changing the MAC-addrs, else some hardware
may drop the TX packet before reaching the wire.  This was
observed with driver mlx5.

If xdp_rxq_info select --action XDP_TX the swapmac functionality
is activated.  It is also possible to manually enable via cmdline
option --swapmac.  This is practical if wanting to measure the
overhead of writing/updating payload for other action types.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/samples/bpf/xdp_rxq_info_kern.c b/samples/bpf/xdp_rxq_info_kern.c
index 61af6210df2fde72b3c9b8fe3488a17eb86ca895..222a83eed1cbf0b213998a47153334b3fd4127b9 100644 (file)
--- a/samples/bpf/xdp_rxq_info_kern.c
+++ b/samples/bpf/xdp_rxq_info_kern.c
@@ -21,6 +21,7 @@ struct config {
 enum cfg_options_flags {
        NO_TOUCH = 0x0U,
        READ_MEM = 0x1U,
+       SWAP_MAC = 0x2U,
 };
 struct bpf_map_def SEC("maps") config_map = {
        .type           = BPF_MAP_TYPE_ARRAY,
@@ -52,6 +53,23 @@ struct bpf_map_def SEC("maps") rx_queue_index_map = {
        .max_entries    = MAX_RXQs + 1,
 };
 
+static __always_inline
+void swap_src_dst_mac(void *data)
+{
+       unsigned short *p = data;
+       unsigned short dst[3];
+
+       dst[0] = p[0];
+       dst[1] = p[1];
+       dst[2] = p[2];
+       p[0] = p[3];
+       p[1] = p[4];
+       p[2] = p[5];
+       p[3] = dst[0];
+       p[4] = dst[1];
+       p[5] = dst[2];
+}
+
 SEC("xdp_prog0")
 int  xdp_prognum0(struct xdp_md *ctx)
 {
@@ -98,7 +116,7 @@ int  xdp_prognum0(struct xdp_md *ctx)
                rxq_rec->issue++;
 
        /* Default: Don't touch packet data, only count packets */
-       if (unlikely(config->options & READ_MEM)) {
+       if (unlikely(config->options & (READ_MEM|SWAP_MAC))) {
                struct ethhdr *eth = data;
 
                if (eth + 1 > data_end)
@@ -107,6 +125,12 @@ int  xdp_prognum0(struct xdp_md *ctx)
                /* Avoid compiler removing this: Drop non 802.3 Ethertypes */
                if (ntohs(eth->h_proto) < ETH_P_802_3_MIN)
                        return XDP_ABORTED;
+
+               /* XDP_TX requires changing MAC-addrs, else HW may drop.
+                * Can also be enabled with --swapmac (for test purposes)
+                */
+               if (unlikely(config->options & SWAP_MAC))
+                       swap_src_dst_mac(data);
        }
 
        return config->action;

diff --git a/samples/bpf/xdp_rxq_info_user.c b/samples/bpf/xdp_rxq_info_user.c
index 435485d4f49efa3857f011fcc83d61952aeb43d7..248a7eab9531eba322f6fb5b404c9a26a516adba 100644 (file)
--- a/samples/bpf/xdp_rxq_info_user.c
+++ b/samples/bpf/xdp_rxq_info_user.c
@@ -51,6 +51,7 @@ static const struct option long_options[] = {
        {"no-separators", no_argument,          NULL, 'z' },
        {"action",      required_argument,      NULL, 'a' },
        {"readmem",     no_argument,            NULL, 'r' },
+       {"swapmac",     no_argument,            NULL, 'm' },
        {0, 0, NULL,  0 }
 };
 
@@ -72,6 +73,7 @@ struct config {
 enum cfg_options_flags {
        NO_TOUCH = 0x0U,
        READ_MEM = 0x1U,
+       SWAP_MAC = 0x2U,
 };
 #define XDP_ACTION_MAX (XDP_TX + 1)
 #define XDP_ACTION_MAX_STRLEN 11
@@ -119,6 +121,8 @@ static char* options2str(enum cfg_options_flags flag)
 {
        if (flag == NO_TOUCH)
                return "no_touch";
+       if (flag & SWAP_MAC)
+               return "swapmac";
        if (flag & READ_MEM)
                return "read";
        fprintf(stderr, "ERR: Unknown config option flags");
@@ -517,6 +521,9 @@ int main(int argc, char **argv)
                case 'r':
                        cfg_options |= READ_MEM;
                        break;
+               case 'm':
+                       cfg_options |= SWAP_MAC;
+                       break;
                case 'h':
                error:
                default:
@@ -543,6 +550,10 @@ int main(int argc, char **argv)
                }
        }
        cfg.action = action;
+
+       /* XDP_TX requires changing MAC-addrs, else HW may drop */
+       if (action == XDP_TX)
+               cfg_options |= SWAP_MAC;
        cfg.options = cfg_options;
 
        /* Trick to pretty printf with thousands separators use %' */