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// SPDX-License-Identifier: GPL-2.0
#include <string.h>
#include <linux/bpf.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <sys/socket.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
char _license[] SEC("license") = "GPL";
int _version SEC("version") = 1;
struct svc_addr {
__be32 addr[4];
__be16 port;
};
struct {
__uint(type, BPF_MAP_TYPE_SK_STORAGE);
__uint(map_flags, BPF_F_NO_PREALLOC);
__type(key, int);
__type(value, struct svc_addr);
} service_mapping SEC(".maps");
SEC("cgroup/connect6")
int connect6(struct bpf_sock_addr *ctx)
{
struct sockaddr_in6 sa = {};
struct svc_addr *orig;
/* Force local address to [::1]:22223. */
sa.sin6_family = AF_INET6;
sa.sin6_port = bpf_htons(22223);
sa.sin6_addr.s6_addr32[3] = bpf_htonl(1);
if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0)
return 0;
/* Rewire service [fc00::1]:60000 to backend [::1]:60124. */
if (ctx->user_port == bpf_htons(60000)) {
orig = bpf_sk_storage_get(&service_mapping, ctx->sk, 0,
BPF_SK_STORAGE_GET_F_CREATE);
if (!orig)
return 0;
orig->addr[0] = ctx->user_ip6[0];
orig->addr[1] = ctx->user_ip6[1];
orig->addr[2] = ctx->user_ip6[2];
orig->addr[3] = ctx->user_ip6[3];
orig->port = ctx->user_port;
ctx->user_ip6[0] = 0;
ctx->user_ip6[1] = 0;
ctx->user_ip6[2] = 0;
ctx->user_ip6[3] = bpf_htonl(1);
ctx->user_port = bpf_htons(60124);
}
return 1;
}
SEC("cgroup/getsockname6")
int getsockname6(struct bpf_sock_addr *ctx)
{
/* Expose local server as [fc00::1]:60000 to client. */
if (ctx->user_port == bpf_htons(60124)) {
ctx->user_ip6[0] = bpf_htonl(0xfc000000);
ctx->user_ip6[1] = 0;
ctx->user_ip6[2] = 0;
ctx->user_ip6[3] = bpf_htonl(1);
ctx->user_port = bpf_htons(60000);
}
return 1;
}
SEC("cgroup/getpeername6")
int getpeername6(struct bpf_sock_addr *ctx)
{
struct svc_addr *orig;
/* Expose service [fc00::1]:60000 as peer instead of backend. */
if (ctx->user_port == bpf_htons(60124)) {
orig = bpf_sk_storage_get(&service_mapping, ctx->sk, 0, 0);
if (orig) {
ctx->user_ip6[0] = orig->addr[0];
ctx->user_ip6[1] = orig->addr[1];
ctx->user_ip6[2] = orig->addr[2];
ctx->user_ip6[3] = orig->addr[3];
ctx->user_port = orig->port;
}
}
return 1;
}
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