1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (c) 2020 Facebook
3
4 #include <linux/bpf.h>
5 #include <bpf/bpf_endian.h>
6 #include <bpf/bpf_helpers.h>
7
8 #include <linux/if_ether.h>
9 #include <linux/in.h>
10 #include <linux/in6.h>
11 #include <linux/ipv6.h>
12 #include <linux/tcp.h>
13
14 #include <sys/types.h>
15 #include <sys/socket.h>
16
17 char _license[] SEC("license") = "GPL";
18
19 __u16 g_serv_port = 0;
20
set_ip(__u32 * dst,const struct in6_addr * src)21 static inline void set_ip(__u32 *dst, const struct in6_addr *src)
22 {
23 dst[0] = src->in6_u.u6_addr32[0];
24 dst[1] = src->in6_u.u6_addr32[1];
25 dst[2] = src->in6_u.u6_addr32[2];
26 dst[3] = src->in6_u.u6_addr32[3];
27 }
28
set_tuple(struct bpf_sock_tuple * tuple,const struct ipv6hdr * ip6h,const struct tcphdr * tcph)29 static inline void set_tuple(struct bpf_sock_tuple *tuple,
30 const struct ipv6hdr *ip6h,
31 const struct tcphdr *tcph)
32 {
33 set_ip(tuple->ipv6.saddr, &ip6h->daddr);
34 set_ip(tuple->ipv6.daddr, &ip6h->saddr);
35 tuple->ipv6.sport = tcph->dest;
36 tuple->ipv6.dport = tcph->source;
37 }
38
is_allowed_peer_cg(struct __sk_buff * skb,const struct ipv6hdr * ip6h,const struct tcphdr * tcph)39 static inline int is_allowed_peer_cg(struct __sk_buff *skb,
40 const struct ipv6hdr *ip6h,
41 const struct tcphdr *tcph)
42 {
43 __u64 cgid, acgid, peer_cgid, peer_acgid;
44 struct bpf_sock_tuple tuple;
45 size_t tuple_len = sizeof(tuple.ipv6);
46 struct bpf_sock *peer_sk;
47
48 set_tuple(&tuple, ip6h, tcph);
49
50 peer_sk = bpf_sk_lookup_tcp(skb, &tuple, tuple_len,
51 BPF_F_CURRENT_NETNS, 0);
52 if (!peer_sk)
53 return 0;
54
55 cgid = bpf_skb_cgroup_id(skb);
56 peer_cgid = bpf_sk_cgroup_id(peer_sk);
57
58 acgid = bpf_skb_ancestor_cgroup_id(skb, 2);
59 peer_acgid = bpf_sk_ancestor_cgroup_id(peer_sk, 2);
60
61 bpf_sk_release(peer_sk);
62
63 return cgid && cgid == peer_cgid && acgid && acgid == peer_acgid;
64 }
65
66 SEC("cgroup_skb/ingress")
ingress_lookup(struct __sk_buff * skb)67 int ingress_lookup(struct __sk_buff *skb)
68 {
69 struct ipv6hdr ip6h;
70 struct tcphdr tcph;
71
72 if (skb->protocol != bpf_htons(ETH_P_IPV6))
73 return 1;
74
75 /* For SYN packets coming to listening socket skb->remote_port will be
76 * zero, so IPv6/TCP headers are loaded to identify remote peer
77 * instead.
78 */
79 if (bpf_skb_load_bytes(skb, 0, &ip6h, sizeof(ip6h)))
80 return 1;
81
82 if (ip6h.nexthdr != IPPROTO_TCP)
83 return 1;
84
85 if (bpf_skb_load_bytes(skb, sizeof(ip6h), &tcph, sizeof(tcph)))
86 return 1;
87
88 if (!g_serv_port)
89 return 0;
90
91 if (tcph.dest != g_serv_port)
92 return 1;
93
94 return is_allowed_peer_cg(skb, &ip6h, &tcph);
95 }
96