samples/bpf: make xdp_fwd more practically usable via devmap lookup

[sfrench/cifs-2.6.git] / samples / bpf / xdp_fwd_kern.c

diff --git a/samples/bpf/xdp_fwd_kern.c b/samples/bpf/xdp_fwd_kern.c
index e6ffc4ea06f4fbbb40cc96c793a41e5849156ce1..a43d6953c0548ce9d8cf900420976f70934d9f16 100644 (file)
--- a/samples/bpf/xdp_fwd_kern.c
+++ b/samples/bpf/xdp_fwd_kern.c
@@ -104,13 +104,18 @@ static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags)
 
        rc = bpf_fib_lookup(ctx, &fib_params, sizeof(fib_params), flags);
 
-       /* verify egress index has xdp support
-        * TO-DO bpf_map_lookup_elem(&tx_port, &key) fails with
-        *       cannot pass map_type 14 into func bpf_map_lookup_elem#1:
-        * NOTE: without verification that egress index supports XDP
-        *       forwarding packets are dropped.
-        */
        if (rc == 0) {
+               /* Verify egress index has been configured as TX-port.
+                * (Note: User can still have inserted an egress ifindex that
+                * doesn't support XDP xmit, which will result in packet drops).
+                *
+                * Note: lookup in devmap supported since 0cdbb4b09a0.
+                * If not supported will fail with:
+                *  cannot pass map_type 14 into func bpf_map_lookup_elem#1:
+                */
+               if (!bpf_map_lookup_elem(&xdp_tx_ports, &fib_params.ifindex))
+                       return XDP_PASS;
+
                if (h_proto == htons(ETH_P_IP))
                        ip_decrease_ttl(iph);
                else if (h_proto == htons(ETH_P_IPV6))