139 lines
3.6 KiB
C
139 lines
3.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2017-18 David Ahern <dsahern@gmail.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#define KBUILD_MODNAME "foo"
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#include <uapi/linux/bpf.h>
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#include <linux/in.h>
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#include <linux/if_ether.h>
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#include <linux/if_packet.h>
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#include <linux/if_vlan.h>
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#include <linux/ip.h>
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#include <linux/ipv6.h>
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#include "bpf_helpers.h"
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#define IPV6_FLOWINFO_MASK cpu_to_be32(0x0FFFFFFF)
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struct bpf_map_def SEC("maps") tx_port = {
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.type = BPF_MAP_TYPE_DEVMAP,
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.key_size = sizeof(int),
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.value_size = sizeof(int),
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.max_entries = 64,
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};
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/* from include/net/ip.h */
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static __always_inline int ip_decrease_ttl(struct iphdr *iph)
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{
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u32 check = (__force u32)iph->check;
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check += (__force u32)htons(0x0100);
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iph->check = (__force __sum16)(check + (check >= 0xFFFF));
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return --iph->ttl;
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}
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static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags)
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{
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void *data_end = (void *)(long)ctx->data_end;
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void *data = (void *)(long)ctx->data;
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struct bpf_fib_lookup fib_params;
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struct ethhdr *eth = data;
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struct ipv6hdr *ip6h;
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struct iphdr *iph;
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int out_index;
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u16 h_proto;
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u64 nh_off;
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nh_off = sizeof(*eth);
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if (data + nh_off > data_end)
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return XDP_DROP;
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__builtin_memset(&fib_params, 0, sizeof(fib_params));
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h_proto = eth->h_proto;
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if (h_proto == htons(ETH_P_IP)) {
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iph = data + nh_off;
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if (iph + 1 > data_end)
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return XDP_DROP;
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if (iph->ttl <= 1)
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return XDP_PASS;
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fib_params.family = AF_INET;
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fib_params.tos = iph->tos;
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fib_params.l4_protocol = iph->protocol;
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fib_params.sport = 0;
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fib_params.dport = 0;
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fib_params.tot_len = ntohs(iph->tot_len);
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fib_params.ipv4_src = iph->saddr;
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fib_params.ipv4_dst = iph->daddr;
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} else if (h_proto == htons(ETH_P_IPV6)) {
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struct in6_addr *src = (struct in6_addr *) fib_params.ipv6_src;
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struct in6_addr *dst = (struct in6_addr *) fib_params.ipv6_dst;
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ip6h = data + nh_off;
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if (ip6h + 1 > data_end)
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return XDP_DROP;
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if (ip6h->hop_limit <= 1)
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return XDP_PASS;
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fib_params.family = AF_INET6;
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fib_params.flowinfo = *(__be32 *)ip6h & IPV6_FLOWINFO_MASK;
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fib_params.l4_protocol = ip6h->nexthdr;
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fib_params.sport = 0;
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fib_params.dport = 0;
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fib_params.tot_len = ntohs(ip6h->payload_len);
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*src = ip6h->saddr;
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*dst = ip6h->daddr;
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} else {
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return XDP_PASS;
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}
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fib_params.ifindex = ctx->ingress_ifindex;
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out_index = bpf_fib_lookup(ctx, &fib_params, sizeof(fib_params), flags);
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/* verify egress index has xdp support
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* TO-DO bpf_map_lookup_elem(&tx_port, &key) fails with
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* cannot pass map_type 14 into func bpf_map_lookup_elem#1:
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* NOTE: without verification that egress index supports XDP
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* forwarding packets are dropped.
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*/
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if (out_index > 0) {
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if (h_proto == htons(ETH_P_IP))
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ip_decrease_ttl(iph);
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else if (h_proto == htons(ETH_P_IPV6))
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ip6h->hop_limit--;
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memcpy(eth->h_dest, fib_params.dmac, ETH_ALEN);
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memcpy(eth->h_source, fib_params.smac, ETH_ALEN);
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return bpf_redirect_map(&tx_port, out_index, 0);
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}
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return XDP_PASS;
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}
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SEC("xdp_fwd")
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int xdp_fwd_prog(struct xdp_md *ctx)
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{
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return xdp_fwd_flags(ctx, 0);
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}
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SEC("xdp_fwd_direct")
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int xdp_fwd_direct_prog(struct xdp_md *ctx)
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{
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return xdp_fwd_flags(ctx, BPF_FIB_LOOKUP_DIRECT);
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}
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char _license[] SEC("license") = "GPL";
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