195 lines · c
1// SPDX-License-Identifier: GPL-2.02// 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#include "bpf_misc.h"19 20#if defined(IPROUTE2_HAVE_LIBBPF)21/* Use a new-style map definition. */22struct {23 __uint(type, BPF_MAP_TYPE_SOCKMAP);24 __type(key, int);25 __type(value, __u64);26 __uint(pinning, LIBBPF_PIN_BY_NAME);27 __uint(max_entries, 1);28} server_map SEC(".maps");29#else30/* Pin map under /sys/fs/bpf/tc/globals/<map name> */31#define PIN_GLOBAL_NS 232 33/* Must match struct bpf_elf_map layout from iproute2 */34struct {35 __u32 type;36 __u32 size_key;37 __u32 size_value;38 __u32 max_elem;39 __u32 flags;40 __u32 id;41 __u32 pinning;42} server_map SEC("maps") = {43 .type = BPF_MAP_TYPE_SOCKMAP,44 .size_key = sizeof(int),45 .size_value = sizeof(__u64),46 .max_elem = 1,47 .pinning = PIN_GLOBAL_NS,48};49#endif50 51char _license[] SEC("license") = "GPL";52 53/* Fill 'tuple' with L3 info, and attempt to find L4. On fail, return NULL. */54static inline struct bpf_sock_tuple *55get_tuple(struct __sk_buff *skb, bool *ipv4, bool *tcp)56{57 void *data_end = (void *)(long)skb->data_end;58 void *data = (void *)(long)skb->data;59 struct bpf_sock_tuple *result;60 struct ethhdr *eth;61 __u8 proto = 0;62 __u64 ihl_len;63 64 eth = (struct ethhdr *)(data);65 if (eth + 1 > data_end)66 return NULL;67 68 if (eth->h_proto == bpf_htons(ETH_P_IP)) {69 struct iphdr *iph = (struct iphdr *)(data + sizeof(*eth));70 71 if (iph + 1 > data_end)72 return NULL;73 if (iph->ihl != 5)74 /* Options are not supported */75 return NULL;76 ihl_len = iph->ihl * 4;77 proto = iph->protocol;78 *ipv4 = true;79 result = (struct bpf_sock_tuple *)&iph->saddr;80 } else if (eth->h_proto == bpf_htons(ETH_P_IPV6)) {81 struct ipv6hdr *ip6h = (struct ipv6hdr *)(data + sizeof(*eth));82 83 if (ip6h + 1 > data_end)84 return NULL;85 ihl_len = sizeof(*ip6h);86 proto = ip6h->nexthdr;87 *ipv4 = false;88 result = (struct bpf_sock_tuple *)&ip6h->saddr;89 } else {90 return (struct bpf_sock_tuple *)data;91 }92 93 if (proto != IPPROTO_TCP && proto != IPPROTO_UDP)94 return NULL;95 96 *tcp = (proto == IPPROTO_TCP);97 __sink(ihl_len);98 return result;99}100 101static inline int102handle_udp(struct __sk_buff *skb, struct bpf_sock_tuple *tuple, bool ipv4)103{104 struct bpf_sock *sk;105 const int zero = 0;106 size_t tuple_len;107 __be16 dport;108 int ret;109 110 tuple_len = ipv4 ? sizeof(tuple->ipv4) : sizeof(tuple->ipv6);111 if ((void *)tuple + tuple_len > (void *)(long)skb->data_end)112 return TC_ACT_SHOT;113 114 sk = bpf_sk_lookup_udp(skb, tuple, tuple_len, BPF_F_CURRENT_NETNS, 0);115 if (sk)116 goto assign;117 118 dport = ipv4 ? tuple->ipv4.dport : tuple->ipv6.dport;119 if (dport != bpf_htons(4321))120 return TC_ACT_OK;121 122 sk = bpf_map_lookup_elem(&server_map, &zero);123 if (!sk)124 return TC_ACT_SHOT;125 126assign:127 ret = bpf_sk_assign(skb, sk, 0);128 bpf_sk_release(sk);129 return ret;130}131 132static inline int133handle_tcp(struct __sk_buff *skb, struct bpf_sock_tuple *tuple, bool ipv4)134{135 struct bpf_sock *sk;136 const int zero = 0;137 size_t tuple_len;138 __be16 dport;139 int ret;140 141 tuple_len = ipv4 ? sizeof(tuple->ipv4) : sizeof(tuple->ipv6);142 if ((void *)tuple + tuple_len > (void *)(long)skb->data_end)143 return TC_ACT_SHOT;144 145 sk = bpf_skc_lookup_tcp(skb, tuple, tuple_len, BPF_F_CURRENT_NETNS, 0);146 if (sk) {147 if (sk->state != BPF_TCP_LISTEN)148 goto assign;149 bpf_sk_release(sk);150 }151 152 dport = ipv4 ? tuple->ipv4.dport : tuple->ipv6.dport;153 if (dport != bpf_htons(4321))154 return TC_ACT_OK;155 156 sk = bpf_map_lookup_elem(&server_map, &zero);157 if (!sk)158 return TC_ACT_SHOT;159 160 if (sk->state != BPF_TCP_LISTEN) {161 bpf_sk_release(sk);162 return TC_ACT_SHOT;163 }164 165assign:166 ret = bpf_sk_assign(skb, sk, 0);167 bpf_sk_release(sk);168 return ret;169}170 171SEC("tc")172int bpf_sk_assign_test(struct __sk_buff *skb)173{174 struct bpf_sock_tuple *tuple;175 bool ipv4 = false;176 bool tcp = false;177 int ret = 0;178 179 tuple = get_tuple(skb, &ipv4, &tcp);180 if (!tuple)181 return TC_ACT_SHOT;182 183 /* Note that the verifier socket return type for bpf_skc_lookup_tcp()184 * differs from bpf_sk_lookup_udp(), so even though the C-level type is185 * the same here, if we try to share the implementations they will186 * fail to verify because we're crossing pointer types.187 */188 if (tcp)189 ret = handle_tcp(skb, tuple, ipv4);190 else191 ret = handle_udp(skb, tuple, ipv4);192 193 return ret == 0 ? TC_ACT_OK : TC_ACT_SHOT;194}195