a999696c54
I'm planning to extend it in the next patches. It's much easier to work with C than BPF assembly. Signed-off-by: Stanislav Fomichev <sdf@google.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20201202172516.3483656-2-sdf@google.com
72 lines
1.6 KiB
C
72 lines
1.6 KiB
C
// 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
|
|
|
|
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;
|
|
|
|
ctx->user_ip4 = bpf_htonl(SERV4_REWRITE_IP);
|
|
ctx->user_port = bpf_htons(SERV4_REWRITE_PORT);
|
|
|
|
return 1;
|
|
}
|
|
|
|
char _license[] SEC("license") = "GPL";
|