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 #ifndef ARRAY_SIZE 13 #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) 14 #endif 15 16 /* tcp_mem sysctl has only 3 ints, but this test is doing TCP_MEM_LOOPS */ 17 #define TCP_MEM_LOOPS 20 /* 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) 20 21 static __attribute__((noinline)) int is_tcp_mem(struct bpf_sysctl *ctx) 22 { 23 volatile char tcp_mem_name[] = "net/ipv4/tcp_mem/very_very_very_very_long_pointless_string_to_stress_byte_loop"; 24 unsigned char i; 25 char name[64]; 26 int ret; 27 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) 31 return 0; 32 33 #pragma clang loop unroll(disable) 34 for (i = 0; i < sizeof(tcp_mem_name); ++i) 35 if (name[i] != tcp_mem_name[i]) 36 return 0; 37 38 return 1; 39 } 40 41 42 SEC("cgroup/sysctl") 43 int sysctl_tcp_mem(struct bpf_sysctl *ctx) 44 { 45 unsigned long tcp_mem[TCP_MEM_LOOPS] = {}; 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(disable) 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 return tcp_mem[0] < tcp_mem[1] && tcp_mem[1] < tcp_mem[2]; 70 } 71 72 char _license[] SEC("license") = "GPL"; 73