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// SPDX-License-Identifier: GPL-2.0
#include <string.h>
#include <linux/stddef.h>
#include <linux/bpf.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <sys/socket.h>
#include <netinet/tcp.h>
#include <linux/if.h>
#include <errno.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
#define SERV4_IP 0xc0a801feU /* 192.168.1.254 */
#define SERV4_PORT 4040
#define SERV4_REWRITE_IP 0x7f000001U /* 127.0.0.1 */
#define SERV4_REWRITE_PORT 4444
#ifndef IFNAMSIZ
#define IFNAMSIZ 16
#endif
static __inline int bind_to_device(struct bpf_sock_addr *ctx)
{
char veth1[IFNAMSIZ] = "test_sock_addr1";
char veth2[IFNAMSIZ] = "test_sock_addr2";
char missing[IFNAMSIZ] = "nonexistent_dev";
char del_bind[IFNAMSIZ] = "";
if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
&veth1, sizeof(veth1)))
return 1;
if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
&veth2, sizeof(veth2)))
return 1;
if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
&missing, sizeof(missing)) != -ENODEV)
return 1;
if (bpf_setsockopt(ctx, SOL_SOCKET, SO_BINDTODEVICE,
&del_bind, sizeof(del_bind)))
return 1;
return 0;
}
SEC("cgroup/bind4")
int bind_v4_prog(struct bpf_sock_addr *ctx)
{
struct bpf_sock *sk;
__u32 user_ip4;
__u16 user_port;
sk = ctx->sk;
if (!sk)
return 0;
if (sk->family != AF_INET)
return 0;
if (ctx->type != SOCK_STREAM && ctx->type != SOCK_DGRAM)
return 0;
if (ctx->user_ip4 != bpf_htonl(SERV4_IP) ||
ctx->user_port != bpf_htons(SERV4_PORT))
return 0;
// u8 narrow loads:
user_ip4 = 0;
user_ip4 |= ((volatile __u8 *)&ctx->user_ip4)[0] << 0;
user_ip4 |= ((volatile __u8 *)&ctx->user_ip4)[1] << 8;
user_ip4 |= ((volatile __u8 *)&ctx->user_ip4)[2] << 16;
user_ip4 |= ((volatile __u8 *)&ctx->user_ip4)[3] << 24;
if (ctx->user_ip4 != user_ip4)
return 0;
user_port = 0;
user_port |= ((volatile __u8 *)&ctx->user_port)[0] << 0;
user_port |= ((volatile __u8 *)&ctx->user_port)[1] << 8;
if (ctx->user_port != user_port)
return 0;
// u16 narrow loads:
user_ip4 = 0;
user_ip4 |= ((volatile __u16 *)&ctx->user_ip4)[0] << 0;
user_ip4 |= ((volatile __u16 *)&ctx->user_ip4)[1] << 16;
if (ctx->user_ip4 != user_ip4)
return 0;
/* Bind to device and unbind it. */
if (bind_to_device(ctx))
return 0;
ctx->user_ip4 = bpf_htonl(SERV4_REWRITE_IP);
ctx->user_port = bpf_htons(SERV4_REWRITE_PORT);
return 1;
}
char _license[] SEC("license") = "GPL";
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