1 // SPDX-License-Identifier: GPL-2.0 2 3 #include <string.h> 4 5 #include <linux/stddef.h> 6 #include <linux/bpf.h> 7 #include <linux/in.h> 8 #include <linux/in6.h> 9 #include <sys/socket.h> 10 #include <netinet/tcp.h> 11 #include <linux/if.h> 12 #include <errno.h> 13 14 #include <bpf/bpf_helpers.h> 15 #include <bpf/bpf_endian.h> 16 17 #define SERV4_IP 0xc0a801feU /* 192.168.1.254 */ 18 #define SERV4_PORT 4040 19 #define SERV4_REWRITE_IP 0x7f000001U /* 127.0.0.1 */ 20 #define SERV4_REWRITE_PORT 4444 21 22 #ifndef IFNAMSIZ 23 #define IFNAMSIZ 16 24 #endif 25 26 static __inline int bind_to_device(struct bpf_sock_addr *ctx) 27 { 28 char veth1[IFNAMSIZ] = "test_sock_addr1"; 29 char veth2[IFNAMSIZ] = "test_sock_addr2"; 30 char missing[IFNAMSIZ] = "nonexistent_dev"; 31 char del_bind[IFNAMSIZ] = ""; 32 33 if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE, 34 &veth1, sizeof(veth1))) 35 return 1; 36 if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE, 37 &veth2, sizeof(veth2))) 38 return 1; 39 if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE, 40 &missing, sizeof(missing)) != -ENODEV) 41 return 1; 42 if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE, 43 &del_bind, sizeof(del_bind))) 44 return 1; 45 46 return 0; 47 } 48 49 SEC("cgroup/bind4") 50 int bind_v4_prog(struct bpf_sock_addr *ctx) 51 { 52 struct bpf_sock *sk; 53 __u32 user_ip4; 54 __u16 user_port; 55 56 sk = ctx->sk; 57 if (!sk) 58 return 0; 59 60 if (sk->family != AF_INET) 61 return 0; 62 63 if (ctx->type != SOCK_STREAM && ctx->type != SOCK_DGRAM) 64 return 0; 65 66 if (ctx->user_ip4 != bpf_htonl(SERV4_IP) || 67 ctx->user_port != bpf_htons(SERV4_PORT)) 68 return 0; 69 70 // u8 narrow loads: 71 user_ip4 = 0; 72 user_ip4 |= ((volatile __u8 *)&ctx->user_ip4)[0] << 0; 73 user_ip4 |= ((volatile __u8 *)&ctx->user_ip4)[1] << 8; 74 user_ip4 |= ((volatile __u8 *)&ctx->user_ip4)[2] << 16; 75 user_ip4 |= ((volatile __u8 *)&ctx->user_ip4)[3] << 24; 76 if (ctx->user_ip4 != user_ip4) 77 return 0; 78 79 user_port = 0; 80 user_port |= ((volatile __u8 *)&ctx->user_port)[0] << 0; 81 user_port |= ((volatile __u8 *)&ctx->user_port)[1] << 8; 82 if (ctx->user_port != user_port) 83 return 0; 84 85 // u16 narrow loads: 86 user_ip4 = 0; 87 user_ip4 |= ((volatile __u16 *)&ctx->user_ip4)[0] << 0; 88 user_ip4 |= ((volatile __u16 *)&ctx->user_ip4)[1] << 16; 89 if (ctx->user_ip4 != user_ip4) 90 return 0; 91 92 /* Bind to device and unbind it. */ 93 if (bind_to_device(ctx)) 94 return 0; 95 96 ctx->user_ip4 = bpf_htonl(SERV4_REWRITE_IP); 97 ctx->user_port = bpf_htons(SERV4_REWRITE_PORT); 98 99 return 1; 100 } 101 102 char _license[] SEC("license") = "GPL"; 103