55 lines
1.2 KiB
C
55 lines
1.2 KiB
C
|
// SPDX-License-Identifier: GPL-2.0
|
||
|
|
// Copyright (c) 2018 Facebook
|
||
|
|
|
||
|
|
#include <linux/stddef.h>
|
||
|
|
#include <linux/bpf.h>
|
||
|
|
#include <sys/socket.h>
|
||
|
|
|
||
|
|
#include <bpf/bpf_helpers.h>
|
||
|
|
#include <bpf/bpf_endian.h>
|
||
|
|
|
||
|
|
#include <bpf_sockopt_helpers.h>
|
||
|
|
|
||
|
|
#define SRC1_IP4 0xAC100001U /* 172.16.0.1 */
|
||
|
|
#define SRC2_IP4 0x00000000U
|
||
|
|
#define SRC_REWRITE_IP4 0x7f000004U
|
||
|
|
#define DST_IP4 0xC0A801FEU /* 192.168.1.254 */
|
||
|
|
#define DST_REWRITE_IP4 0x7f000001U
|
||
|
|
#define DST_PORT 4040
|
||
|
|
#define DST_REWRITE_PORT4 4444
|
||
|
|
|
||
|
|
SEC("cgroup/sendmsg4")
|
||
|
|
int sendmsg_v4_prog(struct bpf_sock_addr *ctx)
|
||
|
|
{
|
||
|
|
int prio;
|
||
|
|
|
||
|
|
if (ctx->type != SOCK_DGRAM)
|
||
|
|
return 0;
|
||
|
|
|
||
|
|
if (!get_set_sk_priority(ctx))
|
||
|
|
return 0;
|
||
|
|
|
||
|
|
/* Rewrite source. */
|
||
|
|
if (ctx->msg_src_ip4 == bpf_htonl(SRC1_IP4) ||
|
||
|
|
ctx->msg_src_ip4 == bpf_htonl(SRC2_IP4)) {
|
||
|
|
ctx->msg_src_ip4 = bpf_htonl(SRC_REWRITE_IP4);
|
||
|
|
} else {
|
||
|
|
/* Unexpected source. Reject sendmsg. */
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Rewrite destination. */
|
||
|
|
if ((ctx->user_ip4 >> 24) == (bpf_htonl(DST_IP4) >> 24) &&
|
||
|
|
ctx->user_port == bpf_htons(DST_PORT)) {
|
||
|
|
ctx->user_ip4 = bpf_htonl(DST_REWRITE_IP4);
|
||
|
|
ctx->user_port = bpf_htons(DST_REWRITE_PORT4);
|
||
|
|
} else {
|
||
|
|
/* Unexpected source. Reject sendmsg. */
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
return 1;
|
||
|
|
}
|
||
|
|
|
||
|
|
char _license[] SEC("license") = "GPL";
|