83 lines
2.1 KiB
C
83 lines
2.1 KiB
C
#include "state.h"
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#include <netinet/ether.h>
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#include <netinet/ip.h>
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#include <netinet/tcp.h>
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#include <netinet/ip_icmp.h>
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#include <netinet/udp.h>
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#ifndef HEADER_ZMAP_PACKET_H
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#define HEADER_ZMAP_PACKET_H
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#define MAX_PACKET_SIZE 4096
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typedef unsigned short __attribute__((__may_alias__)) alias_unsigned_short;
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void make_eth_header(struct ethhdr *ethh, macaddr_t *src, macaddr_t *dst);
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void make_ip_header(struct iphdr *iph, uint8_t, uint16_t);
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void make_tcp_header(struct tcphdr*, port_h_t);
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void make_icmp_header(struct icmp *);
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void make_udp_header(struct udphdr *udp_header, port_h_t dest_port,
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uint16_t len);
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static inline unsigned short in_checksum(unsigned short *ip_pkt, int len)
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{
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unsigned long sum = 0;
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for (int nwords = len/2; nwords > 0; nwords--) {
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sum += *ip_pkt++;
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}
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sum = (sum >> 16) + (sum & 0xffff);
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sum += (sum >> 16);
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return (unsigned short) (~sum);
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}
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__attribute__((unused)) static inline unsigned short ip_checksum(
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unsigned short *buf)
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{
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return in_checksum(buf, (int) sizeof(struct iphdr));
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}
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__attribute__((unused)) static inline unsigned short icmp_checksum(
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unsigned short *buf)
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{
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return in_checksum(buf, (int) sizeof(struct icmp));
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}
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static __attribute__((unused)) uint16_t tcp_checksum(unsigned short len_tcp,
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uint32_t saddr, uint32_t daddr, struct tcphdr *tcp_pkt)
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{
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alias_unsigned_short *src_addr = (alias_unsigned_short *) &saddr;
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alias_unsigned_short *dest_addr = (alias_unsigned_short *) &daddr;
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unsigned char prot_tcp = 6;
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unsigned long sum = 0;
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int nleft = len_tcp;
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unsigned short *w;
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w = (unsigned short *) tcp_pkt;
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// calculate the checksum for the tcp header and tcp data
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while(nleft > 1) {
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sum += *w++;
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nleft -= 2;
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}
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// if nleft is 1 there ist still on byte left.
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// We add a padding byte (0xFF) to build a 16bit word
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if (nleft > 0) {
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sum += *w & ntohs(0xFF00);
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}
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// add the pseudo header
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sum += src_addr[0];
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sum += src_addr[1];
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sum += dest_addr[0];
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sum += dest_addr[1];
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sum += htons(len_tcp);
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sum += htons(prot_tcp);
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sum = (sum >> 16) + (sum & 0xFFFF);
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sum += (sum >> 16);
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// Take the one's complement of sum
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return (unsigned short) (~sum);
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}
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#endif
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