| 1 | // SPDX-License-Identifier: GPL-2.0 |
|---|---|
| 2 | #include <netinet/in.h> |
| 3 | #include <linux/bpf.h> |
| 4 | #include <bpf/bpf_helpers.h> |
| 5 | |
| 6 | char _license[] SEC("license") = "GPL"; |
| 7 | |
| 8 | __s32 page_size = 0; |
| 9 | |
| 10 | SEC("cgroup/getsockopt") |
| 11 | int _getsockopt_child(struct bpf_sockopt *ctx) |
| 12 | { |
| 13 | __u8 *optval_end = ctx->optval_end; |
| 14 | __u8 *optval = ctx->optval; |
| 15 | |
| 16 | if (ctx->level != SOL_IP || ctx->optname != IP_TOS) |
| 17 | goto out; |
| 18 | |
| 19 | if (optval + 1 > optval_end) |
| 20 | return 0; /* EPERM, bounds check */ |
| 21 | |
| 22 | if (optval[0] != 0x80) |
| 23 | return 0; /* EPERM, unexpected optval from the kernel */ |
| 24 | |
| 25 | ctx->retval = 0; /* Reset system call return value to zero */ |
| 26 | |
| 27 | optval[0] = 0x90; |
| 28 | ctx->optlen = 1; |
| 29 | |
| 30 | return 1; |
| 31 | |
| 32 | out: |
| 33 | /* optval larger than PAGE_SIZE use kernel's buffer. */ |
| 34 | if (ctx->optlen > page_size) |
| 35 | ctx->optlen = 0; |
| 36 | return 1; |
| 37 | } |
| 38 | |
| 39 | SEC("cgroup/getsockopt") |
| 40 | int _getsockopt_parent(struct bpf_sockopt *ctx) |
| 41 | { |
| 42 | __u8 *optval_end = ctx->optval_end; |
| 43 | __u8 *optval = ctx->optval; |
| 44 | |
| 45 | if (ctx->level != SOL_IP || ctx->optname != IP_TOS) |
| 46 | goto out; |
| 47 | |
| 48 | if (optval + 1 > optval_end) |
| 49 | return 0; /* EPERM, bounds check */ |
| 50 | |
| 51 | if (optval[0] != 0x90) |
| 52 | return 0; /* EPERM, unexpected optval from the kernel */ |
| 53 | |
| 54 | ctx->retval = 0; /* Reset system call return value to zero */ |
| 55 | |
| 56 | optval[0] = 0xA0; |
| 57 | ctx->optlen = 1; |
| 58 | |
| 59 | return 1; |
| 60 | |
| 61 | out: |
| 62 | /* optval larger than PAGE_SIZE use kernel's buffer. */ |
| 63 | if (ctx->optlen > page_size) |
| 64 | ctx->optlen = 0; |
| 65 | return 1; |
| 66 | } |
| 67 | |
| 68 | SEC("cgroup/setsockopt") |
| 69 | int _setsockopt(struct bpf_sockopt *ctx) |
| 70 | { |
| 71 | __u8 *optval_end = ctx->optval_end; |
| 72 | __u8 *optval = ctx->optval; |
| 73 | |
| 74 | if (ctx->level != SOL_IP || ctx->optname != IP_TOS) |
| 75 | goto out; |
| 76 | |
| 77 | if (optval + 1 > optval_end) |
| 78 | return 0; /* EPERM, bounds check */ |
| 79 | |
| 80 | optval[0] += 0x10; |
| 81 | ctx->optlen = 1; |
| 82 | |
| 83 | return 1; |
| 84 | |
| 85 | out: |
| 86 | /* optval larger than PAGE_SIZE use kernel's buffer. */ |
| 87 | if (ctx->optlen > page_size) |
| 88 | ctx->optlen = 0; |
| 89 | return 1; |
| 90 | } |
| 91 |