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