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// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2018 Facebook
#include <string.h>
#include <linux/stddef.h>
#include <linux/bpf.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <sys/socket.h>
#include "bpf_helpers.h"
#include "bpf_endian.h"
#define SRC_REWRITE_IP4 0x7f000004U
#define DST_REWRITE_IP4 0x7f000001U
#define DST_REWRITE_PORT4 4444
int _version SEC("version") = 1;
SEC("cgroup/connect4")
int connect_v4_prog(struct bpf_sock_addr *ctx)
{
struct bpf_sock_tuple tuple = {};
struct sockaddr_in sa;
struct bpf_sock *sk;
/* Verify that new destination is available. */
memset(&tuple.ipv4.saddr, 0, sizeof(tuple.ipv4.saddr));
memset(&tuple.ipv4.sport, 0, sizeof(tuple.ipv4.sport));
tuple.ipv4.daddr = bpf_htonl(DST_REWRITE_IP4);
tuple.ipv4.dport = bpf_htons(DST_REWRITE_PORT4);
if (ctx->type != SOCK_STREAM && ctx->type != SOCK_DGRAM)
return 0;
else if (ctx->type == SOCK_STREAM)
sk = bpf_sk_lookup_tcp(ctx, &tuple, sizeof(tuple.ipv4),
BPF_F_CURRENT_NETNS, 0);
else
sk = bpf_sk_lookup_udp(ctx, &tuple, sizeof(tuple.ipv4),
BPF_F_CURRENT_NETNS, 0);
if (!sk)
return 0;
if (sk->src_ip4 != tuple.ipv4.daddr ||
sk->src_port != DST_REWRITE_PORT4) {
bpf_sk_release(sk);
return 0;
}
bpf_sk_release(sk);
/* Rewrite destination. */
ctx->user_ip4 = bpf_htonl(DST_REWRITE_IP4);
ctx->user_port = bpf_htons(DST_REWRITE_PORT4);
/* Rewrite source. */
memset(&sa, 0, sizeof(sa));
sa.sin_family = AF_INET;
sa.sin_port = bpf_htons(0);
sa.sin_addr.s_addr = bpf_htonl(SRC_REWRITE_IP4);
if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0)
return 0;
return 1;
}
char _license[] SEC("license") = "GPL";
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