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