1// SPDX-License-Identifier: GPL-2.0
  2#include <string.h>
  3
  4#include <linux/bpf.h>
  5#include <linux/in.h>
  6#include <linux/in6.h>
  7#include <sys/socket.h>
  8
  9#include <bpf/bpf_helpers.h>
 10#include <bpf/bpf_endian.h>
 11
 12#include <bpf_sockopt_helpers.h>
 13
 14char _license[] SEC("license") = "GPL";
 15
 16struct svc_addr {
 17	__be32 addr[4];
 18	__be16 port;
 19};
 20
 21struct {
 22	__uint(type, BPF_MAP_TYPE_SK_STORAGE);
 23	__uint(map_flags, BPF_F_NO_PREALLOC);
 24	__type(key, int);
 25	__type(value, struct svc_addr);
 26} service_mapping SEC(".maps");
 27
 28SEC("cgroup/connect6")
 29int connect6(struct bpf_sock_addr *ctx)
 30{
 31	struct sockaddr_in6 sa = {};
 32	struct svc_addr *orig;
 33
 34	/* Force local address to [::1]:22223. */
 35	sa.sin6_family = AF_INET6;
 36	sa.sin6_port = bpf_htons(22223);
 37	sa.sin6_addr.s6_addr32[3] = bpf_htonl(1);
 38
 39	if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0)
 40		return 0;
 41
 42	/* Rewire service [fc00::1]:60000 to backend [::1]:60124. */
 43	if (ctx->user_port == bpf_htons(60000)) {
 44		orig = bpf_sk_storage_get(&service_mapping, ctx->sk, 0,
 45					  BPF_SK_STORAGE_GET_F_CREATE);
 46		if (!orig)
 47			return 0;
 48
 49		orig->addr[0] = ctx->user_ip6[0];
 50		orig->addr[1] = ctx->user_ip6[1];
 51		orig->addr[2] = ctx->user_ip6[2];
 52		orig->addr[3] = ctx->user_ip6[3];
 53		orig->port = ctx->user_port;
 54
 55		ctx->user_ip6[0] = 0;
 56		ctx->user_ip6[1] = 0;
 57		ctx->user_ip6[2] = 0;
 58		ctx->user_ip6[3] = bpf_htonl(1);
 59		ctx->user_port = bpf_htons(60124);
 60	}
 61	return 1;
 62}
 63
 64SEC("cgroup/getsockname6")
 65int getsockname6(struct bpf_sock_addr *ctx)
 66{
 67	if (!get_set_sk_priority(ctx))
 68		return 1;
 69
 70	/* Expose local server as [fc00::1]:60000 to client. */
 71	if (ctx->user_port == bpf_htons(60124)) {
 72		ctx->user_ip6[0] = bpf_htonl(0xfc000000);
 73		ctx->user_ip6[1] = 0;
 74		ctx->user_ip6[2] = 0;
 75		ctx->user_ip6[3] = bpf_htonl(1);
 76		ctx->user_port = bpf_htons(60000);
 77	}
 78	return 1;
 79}
 80
 81SEC("cgroup/getpeername6")
 82int getpeername6(struct bpf_sock_addr *ctx)
 83{
 84	struct svc_addr *orig;
 85
 86	if (!get_set_sk_priority(ctx))
 87		return 1;
 88
 89	/* Expose service [fc00::1]:60000 as peer instead of backend. */
 90	if (ctx->user_port == bpf_htons(60124)) {
 91		orig = bpf_sk_storage_get(&service_mapping, ctx->sk, 0, 0);
 92		if (orig) {
 93			ctx->user_ip6[0] = orig->addr[0];
 94			ctx->user_ip6[1] = orig->addr[1];
 95			ctx->user_ip6[2] = orig->addr[2];
 96			ctx->user_ip6[3] = orig->addr[3];
 97			ctx->user_port = orig->port;
 98		}
 99	}
100	return 1;
101}