74 lines · c
1// SPDX-License-Identifier: GPL-2.02// Copyright (c) 2019 Facebook3 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#include "bpf_misc.h"14 15/* tcp_mem sysctl has only 3 ints, but this test is doing TCP_MEM_LOOPS */16#define TCP_MEM_LOOPS 28 /* because 30 doesn't fit into 512 bytes of stack */17#define MAX_ULONG_STR_LEN 718#define MAX_VALUE_STR_LEN (TCP_MEM_LOOPS * MAX_ULONG_STR_LEN)19 20const char tcp_mem_name[] = "net/ipv4/tcp_mem/very_very_very_very_long_pointless_string";21static __always_inline int is_tcp_mem(struct bpf_sysctl *ctx)22{23 unsigned char i;24 char name[sizeof(tcp_mem_name)];25 int ret;26 27 memset(name, 0, sizeof(name));28 ret = bpf_sysctl_get_name(ctx, name, sizeof(name), 0);29 if (ret < 0 || ret != sizeof(tcp_mem_name) - 1)30 return 0;31 32 __pragma_loop_no_unroll33 for (i = 0; i < sizeof(tcp_mem_name); ++i)34 if (name[i] != tcp_mem_name[i])35 return 0;36 37 return 1;38}39 40SEC("cgroup/sysctl")41int sysctl_tcp_mem(struct bpf_sysctl *ctx)42{43 unsigned long tcp_mem[TCP_MEM_LOOPS] = {};44 char value[MAX_VALUE_STR_LEN];45 unsigned char i, off = 0;46 /* a workaround to prevent compiler from generating47 * codes verifier cannot handle yet.48 */49 volatile int ret;50 51 if (ctx->write)52 return 0;53 54 if (!is_tcp_mem(ctx))55 return 0;56 57 ret = bpf_sysctl_get_current_value(ctx, value, MAX_VALUE_STR_LEN);58 if (ret < 0 || ret >= MAX_VALUE_STR_LEN)59 return 0;60 61 __pragma_loop_no_unroll62 for (i = 0; i < ARRAY_SIZE(tcp_mem); ++i) {63 ret = bpf_strtoul(value + off, MAX_ULONG_STR_LEN, 0,64 tcp_mem + i);65 if (ret <= 0 || ret > MAX_ULONG_STR_LEN)66 return 0;67 off += ret & MAX_ULONG_STR_LEN;68 }69 70 return tcp_mem[0] < tcp_mem[1] && tcp_mem[1] < tcp_mem[2];71}72 73char _license[] SEC("license") = "GPL";74