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56 lines
1.8 KiB
56 lines
1.8 KiB
/* Copyright (c) 2016 Sargun Dhillon <[email protected]> |
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* |
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* This program is free software; you can redistribute it and/or |
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* modify it under the terms of version 2 of the GNU General Public |
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* License as published by the Free Software Foundation. |
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*/ |
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#include <linux/skbuff.h> |
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#include <linux/netdevice.h> |
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#include <uapi/linux/bpf.h> |
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#include <linux/version.h> |
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#include <bpf/bpf_helpers.h> |
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#include <bpf/bpf_tracing.h> |
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#include <bpf/bpf_core_read.h> |
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#include "trace_common.h" |
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struct { |
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__uint(type, BPF_MAP_TYPE_HASH); |
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__type(key, struct sockaddr_in); |
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__type(value, struct sockaddr_in); |
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__uint(max_entries, 256); |
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} dnat_map SEC(".maps"); |
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/* kprobe is NOT a stable ABI |
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* kernel functions can be removed, renamed or completely change semantics. |
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* Number of arguments and their positions can change, etc. |
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* In such case this bpf+kprobe example will no longer be meaningful |
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* |
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* This example sits on a syscall, and the syscall ABI is relatively stable |
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* of course, across platforms, and over time, the ABI may change. |
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*/ |
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SEC("kprobe/" SYSCALL(sys_connect)) |
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int bpf_prog1(struct pt_regs *ctx) |
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{ |
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struct pt_regs *real_regs = (struct pt_regs *)PT_REGS_PARM1_CORE(ctx); |
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void *sockaddr_arg = (void *)PT_REGS_PARM2_CORE(real_regs); |
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int sockaddr_len = (int)PT_REGS_PARM3_CORE(real_regs); |
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struct sockaddr_in new_addr, orig_addr = {}; |
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struct sockaddr_in *mapped_addr; |
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if (sockaddr_len > sizeof(orig_addr)) |
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return 0; |
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if (bpf_probe_read_user(&orig_addr, sizeof(orig_addr), sockaddr_arg) != 0) |
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return 0; |
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mapped_addr = bpf_map_lookup_elem(&dnat_map, &orig_addr); |
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if (mapped_addr != NULL) { |
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memcpy(&new_addr, mapped_addr, sizeof(new_addr)); |
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bpf_probe_write_user(sockaddr_arg, &new_addr, |
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sizeof(new_addr)); |
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} |
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return 0; |
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} |
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char _license[] SEC("license") = "GPL"; |
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u32 _version SEC("version") = LINUX_VERSION_CODE;
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