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4c79579b44
For ACLs implemented using either FIB rules or FIB entries, the BPF program needs the FIB lookup status to be able to drop the packet. Since the bpf_fib_lookup API has not reached a released kernel yet, change the return code to contain an encoding of the FIB lookup result and return the nexthop device index in the params struct. In addition, inform the BPF program of any post FIB lookup reason as to why the packet needs to go up the stack. The fib result for unicast routes must have an egress device, so remove the check that it is non-NULL. Signed-off-by: David Ahern <dsahern@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
138 lines
3.6 KiB
C
138 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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u16 h_proto;
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u64 nh_off;
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int rc;
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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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rc = 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 (rc == 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, fib_params.ifindex, 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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