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| 2 | |
| 3 |
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| 4 | #include <stdint.h>
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| 5 | #include <string.h>
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| 6 |
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| 7 | #include <linux/stddef.h>
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| 8 | #include <linux/bpf.h>
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| 9 |
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| 10 | #include <bpf/bpf_helpers.h>
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| 11 |
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| 12 | #include "bpf_compiler.h"
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| 13 | #include "bpf_misc.h"
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| 14 |
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| 15 |
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| 16 | #define TCP_MEM_LOOPS 20
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| 17 | #define MAX_ULONG_STR_LEN 7
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| 18 | #define MAX_VALUE_STR_LEN (TCP_MEM_LOOPS * MAX_ULONG_STR_LEN)
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| 19 |
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| 20 | const char tcp_mem_name[] = "net/ipv4/tcp_mem/very_very_very_very_long_pointless_string_to_stress_byte_loop";
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| 21 | static __attribute__((noinline)) int is_tcp_mem(struct bpf_sysctl *ctx)
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| 22 | {
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| 23 | unsigned char i;
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| 24 | char name[sizeof(tcp_mem_name)];
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| 25 | int ret;
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| 26 |
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| 27 | memset(name, 0, sizeof(name));
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| 28 | ret = bpf_sysctl_get_name(ctx, name, sizeof(name), 0);
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| 29 | if (ret < 0 || ret != sizeof(tcp_mem_name) - 1)
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| 30 | return 0;
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| 31 |
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| 32 | __pragma_loop_no_unroll
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| 33 | for (i = 0; i < sizeof(tcp_mem_name); ++i)
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| 34 | if (name[i] != tcp_mem_name[i])
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| 35 | return 0;
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| 36 |
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| 37 | return 1;
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| 38 | }
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| 39 |
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| 40 |
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| 41 | SEC("cgroup/sysctl")
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| 42 | int sysctl_tcp_mem(struct bpf_sysctl *ctx)
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| 43 | {
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| 44 | unsigned long tcp_mem[TCP_MEM_LOOPS] = {};
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| 45 | char value[MAX_VALUE_STR_LEN];
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| 46 | unsigned char i, off = 0;
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| 47 | int ret;
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| 48 |
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| 49 | if (ctx->write)
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| 50 | return 0;
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| 51 |
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| 52 | if (!is_tcp_mem(ctx))
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| 53 | return 0;
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| 54 |
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| 55 | ret = bpf_sysctl_get_current_value(ctx, value, MAX_VALUE_STR_LEN);
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| 56 | if (ret < 0 || ret >= MAX_VALUE_STR_LEN)
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| 57 | return 0;
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| 58 |
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| 59 | __pragma_loop_no_unroll
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| 60 | for (i = 0; i < ARRAY_SIZE(tcp_mem); ++i) {
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| 61 | ret = bpf_strtoul(value + off, MAX_ULONG_STR_LEN, 0,
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| 62 | tcp_mem + i);
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| 63 | if (ret <= 0 || ret > MAX_ULONG_STR_LEN)
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| 64 | return 0;
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| 65 | off += ret & MAX_ULONG_STR_LEN;
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| 66 | }
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| 67 |
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| 68 | return tcp_mem[0] < tcp_mem[1] && tcp_mem[1] < tcp_mem[2];
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| 69 | }
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| 70 |
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| 71 | char _license[] SEC("license") = "GPL";
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