// 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/bpf_helpers.h> #ifndef ARRAY_SIZE #define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) #endif /* tcp_mem sysctl has only 3 ints, but this test is doing TCP_MEM_LOOPS */ #define TCP_MEM_LOOPS 28 /* because 30 doesn't fit into 512 bytes of stack */ #define MAX_ULONG_STR_LEN 7 #define MAX_VALUE_STR_LEN (TCP_MEM_LOOPS * MAX_ULONG_STR_LEN) const char tcp_mem_name[] = "net/ipv4/tcp_mem/very_very_very_very_long_pointless_string"; static __always_inline int is_tcp_mem(struct bpf_sysctl *ctx) { unsigned char i; char name[sizeof(tcp_mem_name)]; 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(disable) 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[TCP_MEM_LOOPS] = {}; char value[MAX_VALUE_STR_LEN]; unsigned char i, off = 0; /* a workaround to prevent compiler from generating * codes verifier cannot handle yet. */ volatile 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(disable) 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";