1 // SPDX-License-Identifier: GPL-2.0 2 // Copyright (c) 2018 Facebook 3 4 #include <linux/stddef.h> 5 #include <linux/bpf.h> 6 #include <sys/socket.h> 7 8 #include <bpf/bpf_helpers.h> 9 #include <bpf/bpf_endian.h> 10 11 #define SRC_REWRITE_IP6_0 0 12 #define SRC_REWRITE_IP6_1 0 13 #define SRC_REWRITE_IP6_2 0 14 #define SRC_REWRITE_IP6_3 6 15 16 #define DST_REWRITE_IP6_0 0 17 #define DST_REWRITE_IP6_1 0 18 #define DST_REWRITE_IP6_2 0 19 #define DST_REWRITE_IP6_3 1 20 21 #define DST_REWRITE_PORT6 6666 22 23 int _version SEC("version") = 1; 24 25 SEC("cgroup/sendmsg6") 26 int sendmsg_v6_prog(struct bpf_sock_addr *ctx) 27 { 28 if (ctx->type != SOCK_DGRAM) 29 return 0; 30 31 /* Rewrite source. */ 32 if (ctx->msg_src_ip6[3] == bpf_htonl(1) || 33 ctx->msg_src_ip6[3] == bpf_htonl(0)) { 34 ctx->msg_src_ip6[0] = bpf_htonl(SRC_REWRITE_IP6_0); 35 ctx->msg_src_ip6[1] = bpf_htonl(SRC_REWRITE_IP6_1); 36 ctx->msg_src_ip6[2] = bpf_htonl(SRC_REWRITE_IP6_2); 37 ctx->msg_src_ip6[3] = bpf_htonl(SRC_REWRITE_IP6_3); 38 } else { 39 /* Unexpected source. Reject sendmsg. */ 40 return 0; 41 } 42 43 /* Rewrite destination. */ 44 if (ctx->user_ip6[0] == bpf_htonl(0xFACEB00C)) { 45 ctx->user_ip6[0] = bpf_htonl(DST_REWRITE_IP6_0); 46 ctx->user_ip6[1] = bpf_htonl(DST_REWRITE_IP6_1); 47 ctx->user_ip6[2] = bpf_htonl(DST_REWRITE_IP6_2); 48 ctx->user_ip6[3] = bpf_htonl(DST_REWRITE_IP6_3); 49 50 ctx->user_port = bpf_htons(DST_REWRITE_PORT6); 51 } else { 52 /* Unexpected destination. Reject sendmsg. */ 53 return 0; 54 } 55 56 return 1; 57 } 58 59 char _license[] SEC("license") = "GPL"; 60