diff options
Diffstat (limited to 'samples/bpf/xdp_fwd_kern.c')
| -rw-r--r-- | samples/bpf/xdp_fwd_kern.c | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/samples/bpf/xdp_fwd_kern.c b/samples/bpf/xdp_fwd_kern.c new file mode 100644 index 000000000..a7e94e7ff --- /dev/null +++ b/samples/bpf/xdp_fwd_kern.c @@ -0,0 +1,138 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2017-18 David Ahern <dsahern@gmail.com> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of version 2 of the GNU General Public + * License as published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + */ +#define KBUILD_MODNAME "foo" +#include <uapi/linux/bpf.h> +#include <linux/in.h> +#include <linux/if_ether.h> +#include <linux/if_packet.h> +#include <linux/if_vlan.h> +#include <linux/ip.h> +#include <linux/ipv6.h> + +#include "bpf_helpers.h" + +#define IPV6_FLOWINFO_MASK cpu_to_be32(0x0FFFFFFF) + +struct bpf_map_def SEC("maps") tx_port = { + .type = BPF_MAP_TYPE_DEVMAP, + .key_size = sizeof(int), + .value_size = sizeof(int), + .max_entries = 64, +}; + +/* from include/net/ip.h */ +static __always_inline int ip_decrease_ttl(struct iphdr *iph) +{ + u32 check = (__force u32)iph->check; + + check += (__force u32)htons(0x0100); + iph->check = (__force __sum16)(check + (check >= 0xFFFF)); + return --iph->ttl; +} + +static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags) +{ + void *data_end = (void *)(long)ctx->data_end; + void *data = (void *)(long)ctx->data; + struct bpf_fib_lookup fib_params; + struct ethhdr *eth = data; + struct ipv6hdr *ip6h; + struct iphdr *iph; + u16 h_proto; + u64 nh_off; + int rc; + + nh_off = sizeof(*eth); + if (data + nh_off > data_end) + return XDP_DROP; + + __builtin_memset(&fib_params, 0, sizeof(fib_params)); + + h_proto = eth->h_proto; + if (h_proto == htons(ETH_P_IP)) { + iph = data + nh_off; + + if (iph + 1 > data_end) + return XDP_DROP; + + if (iph->ttl <= 1) + return XDP_PASS; + + fib_params.family = AF_INET; + fib_params.tos = iph->tos; + fib_params.l4_protocol = iph->protocol; + fib_params.sport = 0; + fib_params.dport = 0; + fib_params.tot_len = ntohs(iph->tot_len); + fib_params.ipv4_src = iph->saddr; + fib_params.ipv4_dst = iph->daddr; + } else if (h_proto == htons(ETH_P_IPV6)) { + struct in6_addr *src = (struct in6_addr *) fib_params.ipv6_src; + struct in6_addr *dst = (struct in6_addr *) fib_params.ipv6_dst; + + ip6h = data + nh_off; + if (ip6h + 1 > data_end) + return XDP_DROP; + + if (ip6h->hop_limit <= 1) + return XDP_PASS; + + fib_params.family = AF_INET6; + fib_params.flowinfo = *(__be32 *)ip6h & IPV6_FLOWINFO_MASK; + fib_params.l4_protocol = ip6h->nexthdr; + fib_params.sport = 0; + fib_params.dport = 0; + fib_params.tot_len = ntohs(ip6h->payload_len); + *src = ip6h->saddr; + *dst = ip6h->daddr; + } else { + return XDP_PASS; + } + + 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. + */ + if (rc == 0) { + if (h_proto == htons(ETH_P_IP)) + ip_decrease_ttl(iph); + else if (h_proto == htons(ETH_P_IPV6)) + ip6h->hop_limit--; + + 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 XDP_PASS; +} + +SEC("xdp_fwd") +int xdp_fwd_prog(struct xdp_md *ctx) +{ + return xdp_fwd_flags(ctx, 0); +} + +SEC("xdp_fwd_direct") +int xdp_fwd_direct_prog(struct xdp_md *ctx) +{ + return xdp_fwd_flags(ctx, BPF_FIB_LOOKUP_DIRECT); +} + +char _license[] SEC("license") = "GPL"; |