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 #include <bpf_sockopt_helpers.h> 12 13 #define SRC_REWRITE_IP6_0 0 14 #define SRC_REWRITE_IP6_1 0 15 #define SRC_REWRITE_IP6_2 0 16 #define SRC_REWRITE_IP6_3 6 17 18 #define DST_REWRITE_IP6_0 0 19 #define DST_REWRITE_IP6_1 0 20 #define DST_REWRITE_IP6_2 0 21 #define DST_REWRITE_IP6_3 1 22 23 #define DST_REWRITE_PORT6 6666 24 25 int _version SEC("version") = 1; 26 27 SEC("cgroup/sendmsg6") 28 int sendmsg_v6_prog(struct bpf_sock_addr *ctx) 29 { 30 if (ctx->type != SOCK_DGRAM) 31 return 0; 32 33 if (!get_set_sk_priority(ctx)) 34 return 0; 35 36 /* Rewrite source. */ 37 if (ctx->msg_src_ip6[3] == bpf_htonl(1) || 38 ctx->msg_src_ip6[3] == bpf_htonl(0)) { 39 ctx->msg_src_ip6[0] = bpf_htonl(SRC_REWRITE_IP6_0); 40 ctx->msg_src_ip6[1] = bpf_htonl(SRC_REWRITE_IP6_1); 41 ctx->msg_src_ip6[2] = bpf_htonl(SRC_REWRITE_IP6_2); 42 ctx->msg_src_ip6[3] = bpf_htonl(SRC_REWRITE_IP6_3); 43 } else { 44 /* Unexpected source. Reject sendmsg. */ 45 return 0; 46 } 47 48 /* Rewrite destination. */ 49 if (ctx->user_ip6[0] == bpf_htonl(0xFACEB00C)) { 50 ctx->user_ip6[0] = bpf_htonl(DST_REWRITE_IP6_0); 51 ctx->user_ip6[1] = bpf_htonl(DST_REWRITE_IP6_1); 52 ctx->user_ip6[2] = bpf_htonl(DST_REWRITE_IP6_2); 53 ctx->user_ip6[3] = bpf_htonl(DST_REWRITE_IP6_3); 54 55 ctx->user_port = bpf_htons(DST_REWRITE_PORT6); 56 } else { 57 /* Unexpected destination. Reject sendmsg. */ 58 return 0; 59 } 60 61 return 1; 62 } 63 64 char _license[] SEC("license") = "GPL"; 65