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

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