1 // SPDX-License-Identifier: GPL-2.0 2 // Copyright (c) 2018 Facebook 3 4 #include <string.h> 5 6 #include <linux/stddef.h> 7 #include <linux/bpf.h> 8 #include <linux/in.h> 9 #include <linux/in6.h> 10 #include <sys/socket.h> 11 12 #include "bpf_helpers.h" 13 #include "bpf_endian.h" 14 15 #define SRC_REWRITE_IP4 0x7f000004U 16 #define DST_REWRITE_IP4 0x7f000001U 17 #define DST_REWRITE_PORT4 4444 18 19 int _version SEC("version") = 1; 20 21 SEC("cgroup/connect4") 22 int connect_v4_prog(struct bpf_sock_addr *ctx) 23 { 24 struct bpf_sock_tuple tuple = {}; 25 struct sockaddr_in sa; 26 struct bpf_sock *sk; 27 28 /* Verify that new destination is available. */ 29 memset(&tuple.ipv4.saddr, 0, sizeof(tuple.ipv4.saddr)); 30 memset(&tuple.ipv4.sport, 0, sizeof(tuple.ipv4.sport)); 31 32 tuple.ipv4.daddr = bpf_htonl(DST_REWRITE_IP4); 33 tuple.ipv4.dport = bpf_htons(DST_REWRITE_PORT4); 34 35 if (ctx->type != SOCK_STREAM && ctx->type != SOCK_DGRAM) 36 return 0; 37 else if (ctx->type == SOCK_STREAM) 38 sk = bpf_sk_lookup_tcp(ctx, &tuple, sizeof(tuple.ipv4), 39 BPF_F_CURRENT_NETNS, 0); 40 else 41 sk = bpf_sk_lookup_udp(ctx, &tuple, sizeof(tuple.ipv4), 42 BPF_F_CURRENT_NETNS, 0); 43 44 if (!sk) 45 return 0; 46 47 if (sk->src_ip4 != tuple.ipv4.daddr || 48 sk->src_port != DST_REWRITE_PORT4) { 49 bpf_sk_release(sk); 50 return 0; 51 } 52 53 bpf_sk_release(sk); 54 55 /* Rewrite destination. */ 56 ctx->user_ip4 = bpf_htonl(DST_REWRITE_IP4); 57 ctx->user_port = bpf_htons(DST_REWRITE_PORT4); 58 59 /* Rewrite source. */ 60 memset(&sa, 0, sizeof(sa)); 61 62 sa.sin_family = AF_INET; 63 sa.sin_port = bpf_htons(0); 64 sa.sin_addr.s_addr = bpf_htonl(SRC_REWRITE_IP4); 65 66 if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0) 67 return 0; 68 69 return 1; 70 } 71 72 char _license[] SEC("license") = "GPL"; 73