| // 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"; |