1 // SPDX-License-Identifier: GPL-2.0 2 #include <string.h> 3 #include <stdbool.h> 4 5 #include <linux/bpf.h> 6 #include <linux/in.h> 7 #include <linux/in6.h> 8 #include <sys/socket.h> 9 10 #include <bpf/bpf_helpers.h> 11 #include <bpf/bpf_endian.h> 12 13 #include <bpf_sockopt_helpers.h> 14 15 char _license[] SEC("license") = "GPL"; 16 int _version SEC("version") = 1; 17 18 struct svc_addr { 19 __be32 addr; 20 __be16 port; 21 }; 22 23 struct { 24 __uint(type, BPF_MAP_TYPE_SK_STORAGE); 25 __uint(map_flags, BPF_F_NO_PREALLOC); 26 __type(key, int); 27 __type(value, struct svc_addr); 28 } service_mapping SEC(".maps"); 29 30 SEC("cgroup/connect4") 31 int connect4(struct bpf_sock_addr *ctx) 32 { 33 struct sockaddr_in sa = {}; 34 struct svc_addr *orig; 35 36 /* Force local address to 127.0.0.1:22222. */ 37 sa.sin_family = AF_INET; 38 sa.sin_port = bpf_htons(22222); 39 sa.sin_addr.s_addr = bpf_htonl(0x7f000001); 40 41 if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0) 42 return 0; 43 44 /* Rewire service 1.2.3.4:60000 to backend 127.0.0.1:60123. */ 45 if (ctx->user_port == bpf_htons(60000)) { 46 orig = bpf_sk_storage_get(&service_mapping, ctx->sk, 0, 47 BPF_SK_STORAGE_GET_F_CREATE); 48 if (!orig) 49 return 0; 50 51 orig->addr = ctx->user_ip4; 52 orig->port = ctx->user_port; 53 54 ctx->user_ip4 = bpf_htonl(0x7f000001); 55 ctx->user_port = bpf_htons(60123); 56 } 57 return 1; 58 } 59 60 SEC("cgroup/getsockname4") 61 int getsockname4(struct bpf_sock_addr *ctx) 62 { 63 if (!get_set_sk_priority(ctx)) 64 return 1; 65 66 /* Expose local server as 1.2.3.4:60000 to client. */ 67 if (ctx->user_port == bpf_htons(60123)) { 68 ctx->user_ip4 = bpf_htonl(0x01020304); 69 ctx->user_port = bpf_htons(60000); 70 } 71 return 1; 72 } 73 74 SEC("cgroup/getpeername4") 75 int getpeername4(struct bpf_sock_addr *ctx) 76 { 77 struct svc_addr *orig; 78 79 if (!get_set_sk_priority(ctx)) 80 return 1; 81 82 /* Expose service 1.2.3.4:60000 as peer instead of backend. */ 83 if (ctx->user_port == bpf_htons(60123)) { 84 orig = bpf_sk_storage_get(&service_mapping, ctx->sk, 0, 0); 85 if (orig) { 86 ctx->user_ip4 = orig->addr; 87 ctx->user_port = orig->port; 88 } 89 } 90 return 1; 91 } 92