1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2020 Facebook */
3
4 #include <string.h>
5 #include <errno.h>
6 #include <netinet/in.h>
7 #include <linux/stddef.h>
8 #include <linux/bpf.h>
9 #include <linux/ipv6.h>
10 #include <linux/tcp.h>
11 #include <linux/if_ether.h>
12 #include <linux/pkt_cls.h>
13
14 #include <bpf/bpf_helpers.h>
15 #include <bpf/bpf_endian.h>
16 #include "bpf_tcp_helpers.h"
17
18 struct sockaddr_in6 srv_sa6 = {};
19 __u16 listen_tp_sport = 0;
20 __u16 req_sk_sport = 0;
21 __u32 recv_cookie = 0;
22 __u32 gen_cookie = 0;
23 __u32 linum = 0;
24
25 #define LOG() ({ if (!linum) linum = __LINE__; })
26
test_syncookie_helper(struct ipv6hdr * ip6h,struct tcphdr * th,struct tcp_sock * tp,struct __sk_buff * skb)27 static void test_syncookie_helper(struct ipv6hdr *ip6h, struct tcphdr *th,
28 struct tcp_sock *tp,
29 struct __sk_buff *skb)
30 {
31 if (th->syn) {
32 __s64 mss_cookie;
33 void *data_end;
34
35 data_end = (void *)(long)(skb->data_end);
36
37 if (th->doff * 4 != 40) {
38 LOG();
39 return;
40 }
41
42 if ((void *)th + 40 > data_end) {
43 LOG();
44 return;
45 }
46
47 mss_cookie = bpf_tcp_gen_syncookie(tp, ip6h, sizeof(*ip6h),
48 th, 40);
49 if (mss_cookie < 0) {
50 if (mss_cookie != -ENOENT)
51 LOG();
52 } else {
53 gen_cookie = (__u32)mss_cookie;
54 }
55 } else if (gen_cookie) {
56 /* It was in cookie mode */
57 int ret = bpf_tcp_check_syncookie(tp, ip6h, sizeof(*ip6h),
58 th, sizeof(*th));
59
60 if (ret < 0) {
61 if (ret != -ENOENT)
62 LOG();
63 } else {
64 recv_cookie = bpf_ntohl(th->ack_seq) - 1;
65 }
66 }
67 }
68
handle_ip6_tcp(struct ipv6hdr * ip6h,struct __sk_buff * skb)69 static int handle_ip6_tcp(struct ipv6hdr *ip6h, struct __sk_buff *skb)
70 {
71 struct bpf_sock_tuple *tuple;
72 struct bpf_sock *bpf_skc;
73 unsigned int tuple_len;
74 struct tcphdr *th;
75 void *data_end;
76
77 data_end = (void *)(long)(skb->data_end);
78
79 th = (struct tcphdr *)(ip6h + 1);
80 if (th + 1 > data_end)
81 return TC_ACT_OK;
82
83 /* Is it the testing traffic? */
84 if (th->dest != srv_sa6.sin6_port)
85 return TC_ACT_OK;
86
87 tuple_len = sizeof(tuple->ipv6);
88 tuple = (struct bpf_sock_tuple *)&ip6h->saddr;
89 if ((void *)tuple + tuple_len > data_end) {
90 LOG();
91 return TC_ACT_OK;
92 }
93
94 bpf_skc = bpf_skc_lookup_tcp(skb, tuple, tuple_len,
95 BPF_F_CURRENT_NETNS, 0);
96 if (!bpf_skc) {
97 LOG();
98 return TC_ACT_OK;
99 }
100
101 if (bpf_skc->state == BPF_TCP_NEW_SYN_RECV) {
102 struct request_sock *req_sk;
103
104 req_sk = (struct request_sock *)bpf_skc_to_tcp_request_sock(bpf_skc);
105 if (!req_sk) {
106 LOG();
107 goto release;
108 }
109
110 if (bpf_sk_assign(skb, req_sk, 0)) {
111 LOG();
112 goto release;
113 }
114
115 req_sk_sport = req_sk->__req_common.skc_num;
116
117 bpf_sk_release(req_sk);
118 return TC_ACT_OK;
119 } else if (bpf_skc->state == BPF_TCP_LISTEN) {
120 struct tcp_sock *tp;
121
122 tp = bpf_skc_to_tcp_sock(bpf_skc);
123 if (!tp) {
124 LOG();
125 goto release;
126 }
127
128 if (bpf_sk_assign(skb, tp, 0)) {
129 LOG();
130 goto release;
131 }
132
133 listen_tp_sport = tp->inet_conn.icsk_inet.sk.__sk_common.skc_num;
134
135 test_syncookie_helper(ip6h, th, tp, skb);
136 bpf_sk_release(tp);
137 return TC_ACT_OK;
138 }
139
140 if (bpf_sk_assign(skb, bpf_skc, 0))
141 LOG();
142
143 release:
144 bpf_sk_release(bpf_skc);
145 return TC_ACT_OK;
146 }
147
148 SEC("classifier/ingress")
cls_ingress(struct __sk_buff * skb)149 int cls_ingress(struct __sk_buff *skb)
150 {
151 struct ipv6hdr *ip6h;
152 struct ethhdr *eth;
153 void *data_end;
154
155 data_end = (void *)(long)(skb->data_end);
156
157 eth = (struct ethhdr *)(long)(skb->data);
158 if (eth + 1 > data_end)
159 return TC_ACT_OK;
160
161 if (eth->h_proto != bpf_htons(ETH_P_IPV6))
162 return TC_ACT_OK;
163
164 ip6h = (struct ipv6hdr *)(eth + 1);
165 if (ip6h + 1 > data_end)
166 return TC_ACT_OK;
167
168 if (ip6h->nexthdr == IPPROTO_TCP)
169 return handle_ip6_tcp(ip6h, skb);
170
171 return TC_ACT_OK;
172 }
173
174 char _license[] SEC("license") = "GPL";
175