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") sendmsg_v6_prog(struct bpf_sock_addr * ctx)26int 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