| // SPDX-License-Identifier: GPL-2.0 |
| // Copyright (c) 2019 Facebook |
| |
| #include <stdint.h> |
| #include <string.h> |
| |
| #include <linux/stddef.h> |
| #include <linux/bpf.h> |
| |
| #include "bpf_helpers.h" |
| |
| /* Max supported length of a string with unsigned long in base 10 (pow2 - 1). */ |
| #define MAX_ULONG_STR_LEN 0xF |
| |
| /* Max supported length of sysctl value string (pow2). */ |
| #define MAX_VALUE_STR_LEN 0x40 |
| |
| #ifndef ARRAY_SIZE |
| #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) |
| #endif |
| |
| static __always_inline int is_tcp_mem(struct bpf_sysctl *ctx) |
| { |
| char tcp_mem_name[] = "net/ipv4/tcp_mem"; |
| unsigned char i; |
| char name[64]; |
| int ret; |
| |
| memset(name, 0, sizeof(name)); |
| ret = bpf_sysctl_get_name(ctx, name, sizeof(name), 0); |
| if (ret < 0 || ret != sizeof(tcp_mem_name) - 1) |
| return 0; |
| |
| #pragma clang loop unroll(full) |
| for (i = 0; i < sizeof(tcp_mem_name); ++i) |
| if (name[i] != tcp_mem_name[i]) |
| return 0; |
| |
| return 1; |
| } |
| |
| SEC("cgroup/sysctl") |
| int sysctl_tcp_mem(struct bpf_sysctl *ctx) |
| { |
| unsigned long tcp_mem[3] = {0, 0, 0}; |
| char value[MAX_VALUE_STR_LEN]; |
| unsigned char i, off = 0; |
| int ret; |
| |
| if (ctx->write) |
| return 0; |
| |
| if (!is_tcp_mem(ctx)) |
| return 0; |
| |
| ret = bpf_sysctl_get_current_value(ctx, value, MAX_VALUE_STR_LEN); |
| if (ret < 0 || ret >= MAX_VALUE_STR_LEN) |
| return 0; |
| |
| #pragma clang loop unroll(full) |
| for (i = 0; i < ARRAY_SIZE(tcp_mem); ++i) { |
| ret = bpf_strtoul(value + off, MAX_ULONG_STR_LEN, 0, |
| tcp_mem + i); |
| if (ret <= 0 || ret > MAX_ULONG_STR_LEN) |
| return 0; |
| off += ret & MAX_ULONG_STR_LEN; |
| } |
| |
| |
| return tcp_mem[0] < tcp_mem[1] && tcp_mem[1] < tcp_mem[2]; |
| } |
| |
| char _license[] SEC("license") = "GPL"; |