1 | // SPDX-License-Identifier: GPL-2.0 |
2 | // Copyright (c) 2019 Facebook |
3 | |
4 | #include <stdint.h> |
5 | #include <string.h> |
6 | |
7 | #include <linux/stddef.h> |
8 | #include <linux/bpf.h> |
9 | |
10 | #include <bpf/bpf_helpers.h> |
11 | |
12 | #include "bpf_compiler.h" |
13 | |
14 | /* Max supported length of a string with unsigned long in base 10 (pow2 - 1). */ |
15 | #define MAX_ULONG_STR_LEN 0xF |
16 | |
17 | /* Max supported length of sysctl value string (pow2). */ |
18 | #define MAX_VALUE_STR_LEN 0x40 |
19 | |
20 | #ifndef ARRAY_SIZE |
21 | #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) |
22 | #endif |
23 | |
24 | const char tcp_mem_name[] = "net/ipv4/tcp_mem" ; |
25 | static __always_inline int is_tcp_mem(struct bpf_sysctl *ctx) |
26 | { |
27 | unsigned char i; |
28 | char name[sizeof(tcp_mem_name)]; |
29 | int ret; |
30 | |
31 | memset(name, 0, sizeof(name)); |
32 | ret = bpf_sysctl_get_name(ctx, name, sizeof(name), 0); |
33 | if (ret < 0 || ret != sizeof(tcp_mem_name) - 1) |
34 | return 0; |
35 | |
36 | __pragma_loop_unroll_full |
37 | for (i = 0; i < sizeof(tcp_mem_name); ++i) |
38 | if (name[i] != tcp_mem_name[i]) |
39 | return 0; |
40 | |
41 | return 1; |
42 | } |
43 | |
44 | SEC("cgroup/sysctl" ) |
45 | int sysctl_tcp_mem(struct bpf_sysctl *ctx) |
46 | { |
47 | unsigned long tcp_mem[3] = {0, 0, 0}; |
48 | char value[MAX_VALUE_STR_LEN]; |
49 | unsigned char i, off = 0; |
50 | volatile int ret; |
51 | |
52 | if (ctx->write) |
53 | return 0; |
54 | |
55 | if (!is_tcp_mem(ctx)) |
56 | return 0; |
57 | |
58 | ret = bpf_sysctl_get_current_value(ctx, value, MAX_VALUE_STR_LEN); |
59 | if (ret < 0 || ret >= MAX_VALUE_STR_LEN) |
60 | return 0; |
61 | |
62 | __pragma_loop_unroll_full |
63 | for (i = 0; i < ARRAY_SIZE(tcp_mem); ++i) { |
64 | ret = bpf_strtoul(value + off, MAX_ULONG_STR_LEN, 0, |
65 | tcp_mem + i); |
66 | if (ret <= 0 || ret > MAX_ULONG_STR_LEN) |
67 | return 0; |
68 | off += ret & MAX_ULONG_STR_LEN; |
69 | } |
70 | |
71 | |
72 | return tcp_mem[0] < tcp_mem[1] && tcp_mem[1] < tcp_mem[2]; |
73 | } |
74 | |
75 | char _license[] SEC("license" ) = "GPL" ; |
76 | |