diff options
Diffstat (limited to 'samples/bpf/xdp_fwd_kern.c')
| -rw-r--r-- | samples/bpf/xdp_fwd_kern.c | 39 |
1 files changed, 30 insertions, 9 deletions
diff --git a/samples/bpf/xdp_fwd_kern.c b/samples/bpf/xdp_fwd_kern.c index a7e94e7ff87d..701a30f258b1 100644 --- a/samples/bpf/xdp_fwd_kern.c +++ b/samples/bpf/xdp_fwd_kern.c @@ -23,7 +23,8 @@ #define IPV6_FLOWINFO_MASK cpu_to_be32(0x0FFFFFFF) -struct bpf_map_def SEC("maps") tx_port = { +/* For TX-traffic redirect requires net_device ifindex to be in this devmap */ +struct bpf_map_def SEC("maps") xdp_tx_ports = { .type = BPF_MAP_TYPE_DEVMAP, .key_size = sizeof(int), .value_size = sizeof(int), @@ -102,14 +103,34 @@ static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags) fib_params.ifindex = ctx->ingress_ifindex; 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. + /* + * Some rc (return codes) from bpf_fib_lookup() are important, + * to understand how this XDP-prog interacts with network stack. + * + * BPF_FIB_LKUP_RET_NO_NEIGH: + * Even if route lookup was a success, then the MAC-addresses are also + * needed. This is obtained from arp/neighbour table, but if table is + * (still) empty then BPF_FIB_LKUP_RET_NO_NEIGH is returned. To avoid + * doing ARP lookup directly from XDP, then send packet to normal + * network stack via XDP_PASS and expect it will do ARP resolution. + * + * BPF_FIB_LKUP_RET_FWD_DISABLED: + * The bpf_fib_lookup respect sysctl net.ipv{4,6}.conf.all.forwarding + * setting, and will return BPF_FIB_LKUP_RET_FWD_DISABLED if not + * enabled this on ingress device. */ - if (rc == 0) { + if (rc == BPF_FIB_LKUP_RET_SUCCESS) { + /* 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)) @@ -117,7 +138,7 @@ static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags) memcpy(eth->h_dest, fib_params.dmac, ETH_ALEN); memcpy(eth->h_source, fib_params.smac, ETH_ALEN); - return bpf_redirect_map(&tx_port, fib_params.ifindex, 0); + return bpf_redirect_map(&xdp_tx_ports, fib_params.ifindex, 0); } return XDP_PASS; |