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>
diff --git a/samples/bpf/xdp_rxq_info_kern.c b/samples/bpf/xdp_rxq_info_kern.c
index 61af621..222a83e 100644
--- a/samples/bpf/xdp_rxq_info_kern.c
+++ b/samples/bpf/xdp_rxq_info_kern.c
@@ -21,6 +21,7 @@
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 @@
.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 @@
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 @@
/* 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 435485d..248a7ea 100644
--- a/samples/bpf/xdp_rxq_info_user.c
+++ b/samples/bpf/xdp_rxq_info_user.c
@@ -51,6 +51,7 @@
{"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 @@
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 @@
{
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 @@
case 'r':
cfg_options |= READ_MEM;
break;
+ case 'm':
+ cfg_options |= SWAP_MAC;
+ break;
case 'h':
error:
default:
@@ -543,6 +550,10 @@
}
}
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 %' */
