// SPDX-License-Identifier: GPL-2.0
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// Copyright (c) 2020 Facebook
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#include <linux/bpf.h>
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#include <bpf/bpf_endian.h>
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#include <bpf/bpf_helpers.h>
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#include <linux/if_ether.h>
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#include <linux/in.h>
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#include <linux/in6.h>
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#include <linux/ipv6.h>
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#include <linux/tcp.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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int _version SEC("version") = 1;
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char _license[] SEC("license") = "GPL";
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__u16 g_serv_port = 0;
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static inline void set_ip(__u32 *dst, const struct in6_addr *src)
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{
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dst[0] = src->in6_u.u6_addr32[0];
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dst[1] = src->in6_u.u6_addr32[1];
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dst[2] = src->in6_u.u6_addr32[2];
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dst[3] = src->in6_u.u6_addr32[3];
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}
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static inline void set_tuple(struct bpf_sock_tuple *tuple,
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const struct ipv6hdr *ip6h,
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const struct tcphdr *tcph)
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{
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set_ip(tuple->ipv6.saddr, &ip6h->daddr);
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set_ip(tuple->ipv6.daddr, &ip6h->saddr);
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tuple->ipv6.sport = tcph->dest;
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tuple->ipv6.dport = tcph->source;
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}
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static inline int is_allowed_peer_cg(struct __sk_buff *skb,
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const struct ipv6hdr *ip6h,
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const struct tcphdr *tcph)
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{
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__u64 cgid, acgid, peer_cgid, peer_acgid;
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struct bpf_sock_tuple tuple;
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size_t tuple_len = sizeof(tuple.ipv6);
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struct bpf_sock *peer_sk;
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set_tuple(&tuple, ip6h, tcph);
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peer_sk = bpf_sk_lookup_tcp(skb, &tuple, tuple_len,
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BPF_F_CURRENT_NETNS, 0);
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if (!peer_sk)
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return 0;
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cgid = bpf_skb_cgroup_id(skb);
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peer_cgid = bpf_sk_cgroup_id(peer_sk);
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acgid = bpf_skb_ancestor_cgroup_id(skb, 2);
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peer_acgid = bpf_sk_ancestor_cgroup_id(peer_sk, 2);
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bpf_sk_release(peer_sk);
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return cgid && cgid == peer_cgid && acgid && acgid == peer_acgid;
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}
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SEC("cgroup_skb/ingress")
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int ingress_lookup(struct __sk_buff *skb)
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{
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__u32 serv_port_key = 0;
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struct ipv6hdr ip6h;
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struct tcphdr tcph;
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if (skb->protocol != bpf_htons(ETH_P_IPV6))
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return 1;
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/* For SYN packets coming to listening socket skb->remote_port will be
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* zero, so IPv6/TCP headers are loaded to identify remote peer
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* instead.
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*/
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if (bpf_skb_load_bytes(skb, 0, &ip6h, sizeof(ip6h)))
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return 1;
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if (ip6h.nexthdr != IPPROTO_TCP)
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return 1;
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if (bpf_skb_load_bytes(skb, sizeof(ip6h), &tcph, sizeof(tcph)))
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return 1;
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if (!g_serv_port)
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return 0;
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if (tcph.dest != g_serv_port)
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return 1;
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return is_allowed_peer_cg(skb, &ip6h, &tcph);
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}
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