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 char _license[] SEC("license") = "GPL"; 40 41 /* Fill 'tuple' with L3 info, and attempt to find L4. On fail, return NULL. */ 42 static inline struct bpf_sock_tuple * 43 get_tuple(struct __sk_buff *skb, bool *ipv4, bool *tcp) 44 { 45 void *data_end = (void *)(long)skb->data_end; 46 void *data = (void *)(long)skb->data; 47 struct bpf_sock_tuple *result; 48 struct ethhdr *eth; 49 __u64 tuple_len; 50 __u8 proto = 0; 51 __u64 ihl_len; 52 53 eth = (struct ethhdr *)(data); 54 if (eth + 1 > data_end) 55 return NULL; 56 57 if (eth->h_proto == bpf_htons(ETH_P_IP)) { 58 struct iphdr *iph = (struct iphdr *)(data + sizeof(*eth)); 59 60 if (iph + 1 > data_end) 61 return NULL; 62 if (iph->ihl != 5) 63 /* Options are not supported */ 64 return NULL; 65 ihl_len = iph->ihl * 4; 66 proto = iph->protocol; 67 *ipv4 = true; 68 result = (struct bpf_sock_tuple *)&iph->saddr; 69 } else if (eth->h_proto == bpf_htons(ETH_P_IPV6)) { 70 struct ipv6hdr *ip6h = (struct ipv6hdr *)(data + sizeof(*eth)); 71 72 if (ip6h + 1 > data_end) 73 return NULL; 74 ihl_len = sizeof(*ip6h); 75 proto = ip6h->nexthdr; 76 *ipv4 = false; 77 result = (struct bpf_sock_tuple *)&ip6h->saddr; 78 } else { 79 return (struct bpf_sock_tuple *)data; 80 } 81 82 if (proto != IPPROTO_TCP && proto != IPPROTO_UDP) 83 return NULL; 84 85 *tcp = (proto == IPPROTO_TCP); 86 return result; 87 } 88 89 static inline int 90 handle_udp(struct __sk_buff *skb, struct bpf_sock_tuple *tuple, bool ipv4) 91 { 92 struct bpf_sock_tuple ln = {0}; 93 struct bpf_sock *sk; 94 const int zero = 0; 95 size_t tuple_len; 96 __be16 dport; 97 int ret; 98 99 tuple_len = ipv4 ? sizeof(tuple->ipv4) : sizeof(tuple->ipv6); 100 if ((void *)tuple + tuple_len > (void *)(long)skb->data_end) 101 return TC_ACT_SHOT; 102 103 sk = bpf_sk_lookup_udp(skb, tuple, tuple_len, BPF_F_CURRENT_NETNS, 0); 104 if (sk) 105 goto assign; 106 107 dport = ipv4 ? tuple->ipv4.dport : tuple->ipv6.dport; 108 if (dport != bpf_htons(4321)) 109 return TC_ACT_OK; 110 111 sk = bpf_map_lookup_elem(&server_map, &zero); 112 if (!sk) 113 return TC_ACT_SHOT; 114 115 assign: 116 ret = bpf_sk_assign(skb, sk, 0); 117 bpf_sk_release(sk); 118 return ret; 119 } 120 121 static inline int 122 handle_tcp(struct __sk_buff *skb, struct bpf_sock_tuple *tuple, bool ipv4) 123 { 124 struct bpf_sock_tuple ln = {0}; 125 struct bpf_sock *sk; 126 const int zero = 0; 127 size_t tuple_len; 128 __be16 dport; 129 int ret; 130 131 tuple_len = ipv4 ? sizeof(tuple->ipv4) : sizeof(tuple->ipv6); 132 if ((void *)tuple + tuple_len > (void *)(long)skb->data_end) 133 return TC_ACT_SHOT; 134 135 sk = bpf_skc_lookup_tcp(skb, tuple, tuple_len, BPF_F_CURRENT_NETNS, 0); 136 if (sk) { 137 if (sk->state != BPF_TCP_LISTEN) 138 goto assign; 139 bpf_sk_release(sk); 140 } 141 142 dport = ipv4 ? tuple->ipv4.dport : tuple->ipv6.dport; 143 if (dport != bpf_htons(4321)) 144 return TC_ACT_OK; 145 146 sk = bpf_map_lookup_elem(&server_map, &zero); 147 if (!sk) 148 return TC_ACT_SHOT; 149 150 if (sk->state != BPF_TCP_LISTEN) { 151 bpf_sk_release(sk); 152 return TC_ACT_SHOT; 153 } 154 155 assign: 156 ret = bpf_sk_assign(skb, sk, 0); 157 bpf_sk_release(sk); 158 return ret; 159 } 160 161 SEC("tc") 162 int bpf_sk_assign_test(struct __sk_buff *skb) 163 { 164 struct bpf_sock_tuple *tuple, ln = {0}; 165 bool ipv4 = false; 166 bool tcp = false; 167 int tuple_len; 168 int ret = 0; 169 170 tuple = get_tuple(skb, &ipv4, &tcp); 171 if (!tuple) 172 return TC_ACT_SHOT; 173 174 /* Note that the verifier socket return type for bpf_skc_lookup_tcp() 175 * differs from bpf_sk_lookup_udp(), so even though the C-level type is 176 * the same here, if we try to share the implementations they will 177 * fail to verify because we're crossing pointer types. 178 */ 179 if (tcp) 180 ret = handle_tcp(skb, tuple, ipv4); 181 else 182 ret = handle_udp(skb, tuple, ipv4); 183 184 return ret == 0 ? TC_ACT_OK : TC_ACT_SHOT; 185 } 186