// 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";