// 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" #include "bpf_util.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 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";