| 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 | 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 | if (!get_set_sk_priority(ctx)) |
| 32 | return 0; |
| 33 | |
| 34 | /* Rewrite source. */ |
| 35 | if (ctx->msg_src_ip6[3] == bpf_htonl(1) || |
| 36 | ctx->msg_src_ip6[3] == bpf_htonl(0)) { |
| 37 | ctx->msg_src_ip6[0] = bpf_htonl(SRC_REWRITE_IP6_0); |
| 38 | ctx->msg_src_ip6[1] = bpf_htonl(SRC_REWRITE_IP6_1); |
| 39 | ctx->msg_src_ip6[2] = bpf_htonl(SRC_REWRITE_IP6_2); |
| 40 | ctx->msg_src_ip6[3] = bpf_htonl(SRC_REWRITE_IP6_3); |
| 41 | } else { |
| 42 | /* Unexpected source. Reject sendmsg. */ |
| 43 | return 0; |
| 44 | } |
| 45 | |
| 46 | /* Rewrite destination. */ |
| 47 | if (ctx->user_ip6[0] == bpf_htonl(0xFACEB00C)) { |
| 48 | ctx->user_ip6[0] = bpf_htonl(DST_REWRITE_IP6_0); |
| 49 | ctx->user_ip6[1] = bpf_htonl(DST_REWRITE_IP6_1); |
| 50 | ctx->user_ip6[2] = bpf_htonl(DST_REWRITE_IP6_2); |
| 51 | ctx->user_ip6[3] = bpf_htonl(DST_REWRITE_IP6_3); |
| 52 | |
| 53 | ctx->user_port = bpf_htons(DST_REWRITE_PORT6); |
| 54 | } else { |
| 55 | /* Unexpected destination. Reject sendmsg. */ |
| 56 | return 0; |
| 57 | } |
| 58 | |
| 59 | return 1; |
| 60 | } |
| 61 | |
| 62 | char _license[] SEC("license") = "GPL"; |
| 63 |