7568f4cbbe
Add C based test for a few bpf_sysctl_* helpers and bpf_strtoul. Make sure that sysctl can be identified by name and that multiple integers can be parsed from sysctl value with bpf_strtoul. net/ipv4/tcp_mem is chosen as a testing sysctl, it contains 3 unsigned longs, they all are parsed and compared (val[0] < val[1] < val[2]). Example of output: # ./test_sysctl ... Test case: C prog: deny all writes .. [PASS] Test case: C prog: deny access by name .. [PASS] Test case: C prog: read tcp_mem .. [PASS] Summary: 39 PASSED, 0 FAILED Signed-off-by: Andrey Ignatov <rdna@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
71 lines
1.5 KiB
C
71 lines
1.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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// Copyright (c) 2019 Facebook
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#include <stdint.h>
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#include <string.h>
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#include <linux/stddef.h>
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#include <linux/bpf.h>
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#include "bpf_helpers.h"
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#include "bpf_util.h"
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/* Max supported length of a string with unsigned long in base 10 (pow2 - 1). */
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#define MAX_ULONG_STR_LEN 0xF
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/* Max supported length of sysctl value string (pow2). */
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#define MAX_VALUE_STR_LEN 0x40
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static __always_inline int is_tcp_mem(struct bpf_sysctl *ctx)
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{
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char tcp_mem_name[] = "net/ipv4/tcp_mem";
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unsigned char i;
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char name[64];
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int ret;
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memset(name, 0, sizeof(name));
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ret = bpf_sysctl_get_name(ctx, name, sizeof(name), 0);
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if (ret < 0 || ret != sizeof(tcp_mem_name) - 1)
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return 0;
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#pragma clang loop unroll(full)
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for (i = 0; i < sizeof(tcp_mem_name); ++i)
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if (name[i] != tcp_mem_name[i])
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return 0;
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return 1;
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}
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SEC("cgroup/sysctl")
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int sysctl_tcp_mem(struct bpf_sysctl *ctx)
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{
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unsigned long tcp_mem[3] = {0, 0, 0};
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char value[MAX_VALUE_STR_LEN];
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unsigned char i, off = 0;
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int ret;
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if (ctx->write)
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return 0;
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if (!is_tcp_mem(ctx))
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return 0;
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ret = bpf_sysctl_get_current_value(ctx, value, MAX_VALUE_STR_LEN);
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if (ret < 0 || ret >= MAX_VALUE_STR_LEN)
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return 0;
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#pragma clang loop unroll(full)
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for (i = 0; i < ARRAY_SIZE(tcp_mem); ++i) {
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ret = bpf_strtoul(value + off, MAX_ULONG_STR_LEN, 0,
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tcp_mem + i);
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if (ret <= 0 || ret > MAX_ULONG_STR_LEN)
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return 0;
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off += ret & MAX_ULONG_STR_LEN;
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}
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return tcp_mem[0] < tcp_mem[1] && tcp_mem[1] < tcp_mem[2];
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}
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char _license[] SEC("license") = "GPL";
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