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 #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 7 18 #define MAX_VALUE_STR_LEN (TCP_MEM_LOOPS * MAX_ULONG_STR_LEN) 19 20 const char tcp_mem_name[] = "net/ipv4/tcp_mem/very_very_very_very_long_pointless_string"; 21 static __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_unroll 33 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 40 SEC("cgroup/sysctl") 41 int 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 generating 47 * 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_unroll 62 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 73 char _license[] SEC("license") = "GPL"; 74