我正在尝试编写一个示例原始套接字程序,以清除对原始套接字的理解。我创建了一个原始的UDP套接字,然后调用sendto。我的sendto成功了,但是我从来没有看到另一方接收到数据包。我没有任何接收端运行,所以我依赖于在发送方和接收方上运行Wireshark。
我把代码片段粘贴在这里。请指出任何错误。
#include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<netinet/in.h>
#include<string.h>
#include "protHeaders.x"
#include "gen.h"
U16 csum(U16* buf, S32 nwords)
{
U32 sum;
for (sum = 0; nwords > 0; nwords--)
sum += *buf++;
sum = (sum >> 16) + (sum & 0xffff);
sum += (sum >> 16);
return ~sum;
}/*csum*/
int main(int argc,char** argv)
{
U8 datagram[MAX_IPPACKET];
U8 udpPayLoad[MAX_UDPPAYLOAD];
CustIpHeader* ipH;
CustUdpHeader* udpH;
struct sockaddr_in sin;
S32 sockFd;
S32 one = 1;
const S32* val = &one;
ipH = (CustIpHeader *)datagram;
udpH = (CustUdpHeader *)(datagram + sizeof(CustIpHeader));
memset(datagram,0,sizeof(datagram));
memset(udpPayLoad,0,sizeof(udpPayLoad));
memset(&sin,0,sizeof(struct sockaddr_in));
strcpy(udpPayLoad,"<<<<Aditya>>>>");
sin.sin_family = AF_INET;
sin.sin_port = htons(atoi(argv[4]));
/* fill the Ip header */
ipH->ip_hl = 5;
ipH->ip_v = 4;
ipH->ip_tos = 0;
ipH->ip_len = sizeof(CustIpHeader) + sizeof(CustUdpHeader) + strlen(udpPayLoad);
ipH->ip_id = htonl(54321);
ipH->ip_off = 0;
ipH->ip_p = 17;
ipH->ip_ttl = 65;
ipH->ip_sum = 0;
ipH->ip_src.s_addr = inet_addr(argv[1]);
ipH->ip_dst.s_addr = inet_addr(argv[3]);
/* fill the Udp header */
udpH->uh_sport = htons(atoi(argv[2]));
udpH->uh_dport = htons(atoi(argv[4]));
udpH->uh_len = sizeof(CustUdpHeader) + strlen(udpPayLoad);
udpH->uh_check = 0;
printf("Checksum = %u\n",udpH->uh_check);
/* copy udpPayLoad */
strcpy(datagram+sizeof(CustIpHeader)+sizeof(CustUdpHeader),udpPayLoad);
#if 1
printf("Datagram %p,UdpPayload %p\n",(void *)datagram,(void *)datagram+sizeof(CustIpHeader)+sizeof(CustUdpHeader));
printf("IpHeader %p, UdpHeader %p\n",(void *)ipH,udpH);
#endif
/* fill in the checksum */
ipH->ip_sum = csum((U16 *)datagram,ipH->ip_len >> 1);
printf("Checksum = %u\n",ipH->ip_sum);
if ((sockFd = socket(PF_INET,SOCK_RAW,IPPROTO_UDP)) < 0)
{
perror("socket:create");
RETURN(RFAILED);
}
/* doing the IP_HDRINCL call */
if (setsockopt(sockFd,IPPROTO_IP,IP_HDRINCL,val,sizeof(one)) < 0)
{
perror("Client:setsockopt");
}
while(1)
{
if ( sendto(sockFd,
datagram,
ipH->ip_len,
0,
(struct sockaddr *)&sin,
sizeof (sin)) < 0)
{ perror("Client:sendto"); }
else
printf(".");
}
RETURN(ROK);
}
IP和UDP头是:
typedef struct _ipheader
{
U8 ip_hl:4,ip_v:4; /* ip_hl: the ip header length in 32bit octets.
* ip_v : ip version (always 4 for our case).
*/
U8 ip_tos; /* reliability of the service. 0x00 is Normal */
U16 ip_len; /* totoal length including ip header,icmp/tcp/udp header
* and payload size in bytes
*/
U16 ip_id; /* sequence no. used for reassembly of fragmented IP packets */
U16 ip_off; /* the fragment offset used for reassembly of fragmented packets */
U16 ip_p; /* the transport layer protocol. can be tcp (6), udp(17) */
U8 ip_ttl; /* time to live */
U16 ip_sum; /* the datagram checksum for the whole IP packet */
struct in_addr ip_src; /* the source IP address, converted to a long format */
struct in_addr ip_dst; /* the desitnation IP address, converted to a long format */
}CustIpHeader; /* total ip header length: 20 bytes */
typedef struct _udpheader
{
U16 uh_sport; /* The source port that a client bind()s to */
U16 uh_dport; /* The desination port that a server bind()s to*/
U16 uh_len; /* The length of udp header and payload data in bytes */
U16 uh_check; /* The checksum of header and data */
}CustUdpHeader; /* total udp header length: 8 bytes (=64 bits) */
我以根用户身份运行,因此特权不是问题。
语言:C
操作系统:Linux
