1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (c) 2019 Facebook
7 #include <linux/stddef.h>
10 #include <bpf/bpf_helpers.h>
13 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
16 /* tcp_mem sysctl has only 3 ints, but this test is doing TCP_MEM_LOOPS */
17 #define TCP_MEM_LOOPS 28 /* because 30 doesn't fit into 512 bytes of stack */
18 #define MAX_ULONG_STR_LEN 7
19 #define MAX_VALUE_STR_LEN (TCP_MEM_LOOPS * MAX_ULONG_STR_LEN)
21 const char tcp_mem_name[] = "net/ipv4/tcp_mem/very_very_very_very_long_pointless_string";
22 static __always_inline int is_tcp_mem(struct bpf_sysctl *ctx)
25 char name[sizeof(tcp_mem_name)];
28 memset(name, 0, sizeof(name));
29 ret = bpf_sysctl_get_name(ctx, name, sizeof(name), 0);
30 if (ret < 0 || ret != sizeof(tcp_mem_name) - 1)
33 #pragma clang loop unroll(disable)
34 for (i = 0; i < sizeof(tcp_mem_name); ++i)
35 if (name[i] != tcp_mem_name[i])
42 int sysctl_tcp_mem(struct bpf_sysctl *ctx)
44 unsigned long tcp_mem[TCP_MEM_LOOPS] = {};
45 char value[MAX_VALUE_STR_LEN];
46 unsigned char i, off = 0;
47 /* a workaround to prevent compiler from generating
48 * codes verifier cannot handle yet.
58 ret = bpf_sysctl_get_current_value(ctx, value, MAX_VALUE_STR_LEN);
59 if (ret < 0 || ret >= MAX_VALUE_STR_LEN)
62 #pragma clang loop unroll(disable)
63 for (i = 0; i < ARRAY_SIZE(tcp_mem); ++i) {
64 ret = bpf_strtoul(value + off, MAX_ULONG_STR_LEN, 0,
66 if (ret <= 0 || ret > MAX_ULONG_STR_LEN)
68 off += ret & MAX_ULONG_STR_LEN;
71 return tcp_mem[0] < tcp_mem[1] && tcp_mem[1] < tcp_mem[2];
74 char _license[] SEC("license") = "GPL";