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https://github.com/h3xduck/TripleCross.git
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67 lines
1.6 KiB
C
67 lines
1.6 KiB
C
#ifndef __IP_HELPER_H__
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#define __IP_HELPER_H__
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#include <linux/ip.h>
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#include <linux/types.h>
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#include <linux/bpf.h>
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#include <bpf/bpf_endian.h>
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#include <bpf/bpf_helpers.h>
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/**
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* IP checksum calculation.
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* Following RFC 1071.
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* In essence 1's complement of 16-bit groups.
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* Taken from my own library https://github.com/h3xduck/RawTCP_Lib/blob/master/src/packet.c
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*/
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static __always_inline unsigned short checksum(unsigned short *addr, int nbytes){
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long sum = 0;
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unsigned short checksum;
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while(nbytes>1){
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sum += (unsigned short) *addr++;
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nbytes -= 2;
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}
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if(nbytes>0){
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sum +=htons((unsigned char)*addr);
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}
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while (sum>>16){
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sum = (sum & 0xffff) + (sum >> 16);
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}
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checksum = ~sum;
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return checksum;
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}
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static __always_inline __u16 csum_fold_helper(__u32 csum)
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{
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//return ~((csum & 0xffff) + (csum >> 16));
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//The following solves some errors where the last summatory overflows
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#pragma unroll
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for (int i = 0; i < 4; i ++) {
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if (csum >> 16){
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csum = (csum & 0xffff) + (csum >> 16);
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}
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}
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return ~csum;
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}
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/**
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* IP checksum calculation.
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* Following RFC 1071, using BPFs.*
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*/
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static __always_inline void ipv4_csum(void *data_start, int data_size, __u32 *csum)
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{
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//WITH EBPF HELPERS
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bpf_printk("csum: %u for data_start %u, data_size %i\n", *csum, data_start, data_size);
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unsigned char* p = (unsigned char*) data_start;
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for(int ii = 0; ii<20; ii++){
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bpf_printk("B%i: %x\n", ii, p[ii]);
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}
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*csum = bpf_csum_diff(0, 0, data_start, data_size, *csum);
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*csum = csum_fold_helper(*csum);
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}
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#endif |