# include & lt; Stdio. H> 

# include & lt; Stdlib. H> 

# include & lt; String. H> 

# include & lt; Unistd. H> 

# include & lt; Errno. H> 

# include & lt; Sys/socket. H> 

# include & lt; Sys/ioctl. H> 

# include & lt; Sys/types. H> 

# include & lt; Netinet/in. H> 

# include & lt; Netinet/IP. H> 

# include & lt; Netinet/if_ether. H> 

# include & lt; Net/if_arp. H> 

# include & lt; Netpacket/packet. H> 

# include & lt; Net/if. H> 

# include & lt; Net/Ethernet. H> 

# include & lt; Linux/TCP. H> 

# define BUFLEN 54 

//CRC checksum calculation 

Unsigned short check_sum (unsigned short * addr, int len) {

The register int nleft=len; 

The register int sum=0; 

The register short * w=addr. 

Short answer=0; 



While (nleft> 1) 

{

The sum +=* w++; 

Nleft -=2; 

} 

If (nleft==1) 

{

* (unsigned char *) (& amp; Answer)=* (unsigned char *) w; 

The sum +=answer; 

} 



Sum=(sum> 16) + (sum& 0 XFFFF); 

The sum +=(sum> 16); 

Answer=~ sum; 

Return (answer); 

} 

Int main (int arg c, char * * argv) 
{

Int SKFD, n; 

Char buf [BUFLEN]={0}; 

Struct ether_header * eth; 

Struct sockaddr_ll toaddr; 

Struct in_addr targetIP srcIP; 

Struct IP * IP; 

Struct TCPHDR * TCP; 

Struct ifreq ifr. 



Unsigned char src_mac [ETH_ALEN]={0}; 

Unsigned char dst_mac [ETH_ALEN]={0}; 

Unsigned char src_ip [15]={0}; 

Unsigned char dst_ip [15]={0}; 

Unsigned srcport dstport; 

MAC: printf (" source "); 
The scanf (" % % % % x: x: x: x: x: % % x ", 
& Src_mac [0], & amp; Src_mac [1], & amp; Src_mac [2], 
& Src_mac [3], & amp; Src_mac [4], & amp; Src_mac [5]); 

MAC: printf (" target "); 
The scanf (" % % % % x: x: x: x: x: % % x ", 
& Dst_mac [0], & amp; Dst_mac [1], & amp; Dst_mac [2], 
& Dst_mac [3], & amp; Dst_mac [4], & amp; Dst_mac [5]); 

Printf (" source IP: "); 
The scanf (" % s ", & amp; Src_ip); 

Printf (" target IP: "); 
The scanf (" % s ", & amp; Dst_ip); 

Printf (" target port: "); 
The scanf (" % d ", & amp; Dstport); 

Printf (" source port: "); 
The scanf (" % d ", & amp; Srcport); 


If ((SKFD=socket (PF_PACKET SOCK_RAW, htons (ETH_P_ALL))) & lt; 0) 
{

Perror (" Create Error "); 

exit(1); 

} 



Bzero (& amp; Toaddr, sizeof (toaddr)); 

Bzero (& amp; Ifr, sizeof (ifr)); 

Strcpy (ifr) ifr_name, argv [1]). 




//access interface index 

If (1==ioctl (SKFD SIOCGIFINDEX, & amp; Ifr)) {

Perror (" get dev index error: "); 

exit(1); 

} 

Toaddr. Sll_ifindex=ifr. Ifr_ifindex; 

Printf (" interface Index: % d \ n ", ifr, ifr_ifindex); 



//fill, construct the etheric head 

Buf eth=(struct ether_header *); 

Memcpy (eth - & gt; Ether_dhost dst_mac, ETH_ALEN); 

Memcpy (eth - & gt; Ether_shost src_mac, ETH_ALEN); 

The eth - & gt; Ether_type=htons (ETHERTYPE_IP); 


//fill the IP header 

IP=(struct IP *) (buf + sizeof (struct ether_header)); 



IP - & gt; Ip_v=IPVERSION; 

IP - & gt; Ip_hl=sizeof (struct IP) & gt;> 2; 

IP - & gt; Ip_tos=0; 

IP - & gt; Ip_len=htons (sizeof (struct IP) + sizeof (struct TCPHDR)); 

IP - & gt; Ip_id=0; 

IP - & gt; Ip_off=0; 

IP - & gt; Ip_ttl=MAXTTL; 

IP - & gt; Ip_p=IPPROTO_TCP; 

//IP - & gt; Ip_sum=check_sum ((unsigned short *) IP, sizeof (struct IP)); 

IP - & gt; Ip_sum=0; 

Inet_pton (AF_INET, dst_ip, & amp; TargetIP); 

IP - & gt; Ip_dst=targetIP; 

Inet_pton (AF_INET, src_ip, & amp; SrcIP); 

IP - & gt; Ip_src=https://bbs.csdn.net/topics/srcIP; 

//start filling the TCP header 

TCP=(struct TCPHDR *) (buf + sizeof (struct IP) + sizeof (struct ether_header)); 

TCP - & gt; Source=htons (srcport); 

TCP - & gt; Dest=htons (dstport); 

TCP - & gt; Seq=0; 

TCP - & gt; Ack=0; 

TCP - & gt; The window=htons (8192); 

TCP - & gt; Doff=5; 

TCP - & gt; The syn=1; 

TCP - & gt; Check=0; 

Toaddr. Sll_family=PF_PACKET; 

TCP - & gt; Check=check_sum ((unsigned short *) TCP, sizeof (struct TCPHDR)); 
IP - & gt; Ip_sum=check_sum ((unsigned short *) IP, sizeof (struct IP)); 



N=sendto (SKFD, buf BUFLEN, 0, (struct sockaddr *) & amp; Toaddr, sizeof (toaddr)); 


Close (SKFD); 

return 0; 

} 

Above for the C program source code



Above is two Windows machine under.net application connects caught the results



Above is under Linux in C programs to the Windows of the SYN packet result (.net applications to monitor), don't get reply

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