1 // SPDX-License-Identifier: GPL-2.0 2 // Copyright (c) 2019 Cloudflare Ltd. 3 // Copyright (c) 2020 Isovalent, Inc. 4 5 #include <stddef.h> 6 #include <stdbool.h> 7 #include <string.h> 8 #include <linux/bpf.h> 9 #include <linux/if_ether.h> 10 #include <linux/in.h> 11 #include <linux/ip.h> 12 #include <linux/ipv6.h> 13 #include <linux/pkt_cls.h> 14 #include <linux/tcp.h> 15 #include <sys/socket.h> 16 #include <bpf/bpf_helpers.h> 17 #include <bpf/bpf_endian.h> 18 19 /* Pin map under /sys/fs/bpf/tc/globals/<map name> */ 20 #define PIN_GLOBAL_NS 2 21 22 /* Must match struct bpf_elf_map layout from iproute2 */ 23 struct { 24 __u32 type; 25 __u32 size_key; 26 __u32 size_value; 27 __u32 max_elem; 28 __u32 flags; 29 __u32 id; 30 __u32 pinning; 31 } server_map SEC("maps") = { 32 .type = BPF_MAP_TYPE_SOCKMAP, 33 .size_key = sizeof(int), 34 .size_value = sizeof(__u64), 35 .max_elem = 1, 36 .pinning = PIN_GLOBAL_NS, 37 }; 38 39 int _version SEC("version") = 1; 40 char _license[] SEC("license") = "GPL"; 41 42 /* Fill 'tuple' with L3 info, and attempt to find L4. On fail, return NULL. */ 43 static inline struct bpf_sock_tuple * 44 get_tuple(struct __sk_buff *skb, bool *ipv4, bool *tcp) 45 { 46 void *data_end = (void *)(long)skb->data_end; 47 void *data = (void *)(long)skb->data; 48 struct bpf_sock_tuple *result; 49 struct ethhdr *eth; 50 __u64 tuple_len; 51 __u8 proto = 0; 52 __u64 ihl_len; 53 54 eth = (struct ethhdr *)(data); 55 if (eth + 1 > data_end) 56 return NULL; 57 58 if (eth->h_proto == bpf_htons(ETH_P_IP)) { 59 struct iphdr *iph = (struct iphdr *)(data + sizeof(*eth)); 60 61 if (iph + 1 > data_end) 62 return NULL; 63 if (iph->ihl != 5) 64 /* Options are not supported */ 65 return NULL; 66 ihl_len = iph->ihl * 4; 67 proto = iph->protocol; 68 *ipv4 = true; 69 result = (struct bpf_sock_tuple *)&iph->saddr; 70 } else if (eth->h_proto == bpf_htons(ETH_P_IPV6)) { 71 struct ipv6hdr *ip6h = (struct ipv6hdr *)(data + sizeof(*eth)); 72 73 if (ip6h + 1 > data_end) 74 return NULL; 75 ihl_len = sizeof(*ip6h); 76 proto = ip6h->nexthdr; 77 *ipv4 = false; 78 result = (struct bpf_sock_tuple *)&ip6h->saddr; 79 } else { 80 return (struct bpf_sock_tuple *)data; 81 } 82 83 if (proto != IPPROTO_TCP && proto != IPPROTO_UDP) 84 return NULL; 85 86 *tcp = (proto == IPPROTO_TCP); 87 return result; 88 } 89 90 static inline int 91 handle_udp(struct __sk_buff *skb, struct bpf_sock_tuple *tuple, bool ipv4) 92 { 93 struct bpf_sock_tuple ln = {0}; 94 struct bpf_sock *sk; 95 const int zero = 0; 96 size_t tuple_len; 97 __be16 dport; 98 int ret; 99 100 tuple_len = ipv4 ? sizeof(tuple->ipv4) : sizeof(tuple->ipv6); 101 if ((void *)tuple + tuple_len > (void *)(long)skb->data_end) 102 return TC_ACT_SHOT; 103 104 sk = bpf_sk_lookup_udp(skb, tuple, tuple_len, BPF_F_CURRENT_NETNS, 0); 105 if (sk) 106 goto assign; 107 108 dport = ipv4 ? tuple->ipv4.dport : tuple->ipv6.dport; 109 if (dport != bpf_htons(4321)) 110 return TC_ACT_OK; 111 112 sk = bpf_map_lookup_elem(&server_map, &zero); 113 if (!sk) 114 return TC_ACT_SHOT; 115 116 assign: 117 ret = bpf_sk_assign(skb, sk, 0); 118 bpf_sk_release(sk); 119 return ret; 120 } 121 122 static inline int 123 handle_tcp(struct __sk_buff *skb, struct bpf_sock_tuple *tuple, bool ipv4) 124 { 125 struct bpf_sock_tuple ln = {0}; 126 struct bpf_sock *sk; 127 const int zero = 0; 128 size_t tuple_len; 129 __be16 dport; 130 int ret; 131 132 tuple_len = ipv4 ? sizeof(tuple->ipv4) : sizeof(tuple->ipv6); 133 if ((void *)tuple + tuple_len > (void *)(long)skb->data_end) 134 return TC_ACT_SHOT; 135 136 sk = bpf_skc_lookup_tcp(skb, tuple, tuple_len, BPF_F_CURRENT_NETNS, 0); 137 if (sk) { 138 if (sk->state != BPF_TCP_LISTEN) 139 goto assign; 140 bpf_sk_release(sk); 141 } 142 143 dport = ipv4 ? tuple->ipv4.dport : tuple->ipv6.dport; 144 if (dport != bpf_htons(4321)) 145 return TC_ACT_OK; 146 147 sk = bpf_map_lookup_elem(&server_map, &zero); 148 if (!sk) 149 return TC_ACT_SHOT; 150 151 if (sk->state != BPF_TCP_LISTEN) { 152 bpf_sk_release(sk); 153 return TC_ACT_SHOT; 154 } 155 156 assign: 157 ret = bpf_sk_assign(skb, sk, 0); 158 bpf_sk_release(sk); 159 return ret; 160 } 161 162 SEC("classifier/sk_assign_test") 163 int bpf_sk_assign_test(struct __sk_buff *skb) 164 { 165 struct bpf_sock_tuple *tuple, ln = {0}; 166 bool ipv4 = false; 167 bool tcp = false; 168 int tuple_len; 169 int ret = 0; 170 171 tuple = get_tuple(skb, &ipv4, &tcp); 172 if (!tuple) 173 return TC_ACT_SHOT; 174 175 /* Note that the verifier socket return type for bpf_skc_lookup_tcp() 176 * differs from bpf_sk_lookup_udp(), so even though the C-level type is 177 * the same here, if we try to share the implementations they will 178 * fail to verify because we're crossing pointer types. 179 */ 180 if (tcp) 181 ret = handle_tcp(skb, tuple, ipv4); 182 else 183 ret = handle_udp(skb, tuple, ipv4); 184 185 return ret == 0 ? TC_ACT_OK : TC_ACT_SHOT; 186 } 187