我正在编写一个隧道内核模块，我想为其注册自己的特定 UDP 端口处理程序。最好的方法是什么？这个想法是注册该处理程序，以便当该端口上的流量到达时，Linux 堆栈将调用我的处理程序。
[编辑1]
通过套接字 API 的一种方法是绑定(bind)到这样的套接字
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = htonl(INADDR_ANY);
sin.sin_port = htons(my_port);
err = kernel_bind(rcv_socket, (struct sockaddr *)&sin,
sizeof(struct sockaddr_in));
udp_sk(rcv_socket->sk)->encap_rcv = my_handler;
问题在于该套接字与 INADDR_ANY 关联，该套接字对应于计算机上的任何主机 IP。我想对数据包中的任何 IP 执行此操作？如何才能实现这一目标？
我认为在这种情况下不能使用套接字，因为任何 IP 都意味着在堆栈中数据包会通过 ip_forward 路径而不是 ip_local_delivery。不会为这样的数据包创建套接字。在这种情况下如何实现？
最佳答案
反对投票者:请评论为什么您反对这个经过测试的答案？
以下示例很有帮助。您可以根据需要添加过滤器来修改示例。
对于 UDP，下面的示例中需要出现以下更改
sock_raw = 套接字(AF_INET, SOCK_RAW, IPPROTO_UDP);
http://www.binarytides.com/packet-sniffer-code-in-c-using-linux-sockets-bsd/ http://www.binarytides.com/packet-sniffer-code-in-c-using-linux-sockets-bsd-part-2/ [相关性]
我列出代码仅供引用
#include<netinet/in.h>
#include<errno.h>
#include<netdb.h>
#include<stdio.h> //For standard things
#include<stdlib.h> //malloc
#include<string.h> //strlen
#include<netinet/ip_icmp.h> //Provides declarations for icmp header
#include<netinet/udp.h> //Provides declarations for udp header
#include<netinet/tcp.h> //Provides declarations for tcp header
#include<netinet/ip.h> //Provides declarations for ip header
#include<netinet/if_ether.h> //For ETH_P_ALL
#include<net/ethernet.h> //For ether_header
#include<sys/socket.h>
#include<arpa/inet.h>
#include<sys/ioctl.h>
#include<sys/time.h>
#include<sys/types.h>
#include<unistd.h>
void ProcessPacket(unsigned char* , int);
void print_ip_header(unsigned char* , int);
void print_tcp_packet(unsigned char * , int );
void print_udp_packet(unsigned char * , int );
void print_icmp_packet(unsigned char* , int );
void PrintData (unsigned char* , int);
FILE *logfile;
struct sockaddr_in source,dest;
int tcp=0,udp=0,icmp=0,others=0,igmp=0,total=0,i,j;
int main()
{
int saddr_size , data_size;
struct sockaddr saddr;
unsigned char *buffer = (unsigned char *) malloc(65536); //Its Big!
logfile=fopen("log.txt","w");
if(logfile==NULL)
{
printf("Unable to create log.txt file.");
}
printf("Starting...\n");
int sock_raw = socket( AF_PACKET , SOCK_RAW , htons(ETH_P_ALL)) ;
//setsockopt(sock_raw , SOL_SOCKET , SO_BINDTODEVICE , "eth0" , strlen("eth0")+ 1 );
if(sock_raw < 0)
{
//Print the error with proper message
perror("Socket Error");
return 1;
}
while(1)
{
saddr_size = sizeof saddr;
//Receive a packet
data_size = recvfrom(sock_raw , buffer , 65536 , 0 , &saddr , (socklen_t*)&saddr_size);
if(data_size <0 )
{
printf("Recvfrom error , failed to get packets\n");
return 1;
}
//Now process the packet
ProcessPacket(buffer , data_size);
}
close(sock_raw);
printf("Finished");
return 0;
}
void ProcessPacket(unsigned char* buffer, int size)
{
//Get the IP Header part of this packet , excluding the ethernet header
struct iphdr *iph = (struct iphdr*)(buffer + sizeof(struct ethhdr));
++total;
switch (iph->protocol) //Check the Protocol and do accordingly...
{
case 1: //ICMP Protocol
++icmp;
print_icmp_packet( buffer , size);
break;
case 2: //IGMP Protocol
++igmp;
break;
case 6: //TCP Protocol
++tcp;
print_tcp_packet(buffer , size);
break;
case 17: //UDP Protocol
++udp;
print_udp_packet(buffer , size);
break;
default: //Some Other Protocol like ARP etc.
++others;
break;
}
printf("TCP : %d UDP : %d ICMP : %d IGMP : %d Others : %d Total : %d\r", tcp , udp , icmp , igmp , others , total);
}
void print_ethernet_header(unsigned char* Buffer, int Size)
{
struct ethhdr *eth = (struct ethhdr *)Buffer;
fprintf(logfile , "\n");
fprintf(logfile , "Ethernet Header\n");
fprintf(logfile , " |-Destination Address : %.2X-%.2X-%.2X-%.2X-%.2X-%.2X \n", eth->h_dest[0] , eth->h_dest[1] , eth->h_dest[2] , eth->h_dest[3] , eth->h_dest[4] , eth->h_dest[5] );
fprintf(logfile , " |-Source Address : %.2X-%.2X-%.2X-%.2X-%.2X-%.2X \n", eth->h_source[0] , eth->h_source[1] , eth->h_source[2] , eth->h_source[3] , eth->h_source[4] , eth->h_source[5] );
fprintf(logfile , " |-Protocol : %u \n",(unsigned short)eth->h_proto);
}
void print_ip_header(unsigned char* Buffer, int Size)
{
print_ethernet_header(Buffer , Size);
unsigned short iphdrlen;
struct iphdr *iph = (struct iphdr *)(Buffer + sizeof(struct ethhdr) );
iphdrlen =iph->ihl*4;
memset(&source, 0, sizeof(source));
source.sin_addr.s_addr = iph->saddr;
memset(&dest, 0, sizeof(dest));
dest.sin_addr.s_addr = iph->daddr;
fprintf(logfile , "\n");
fprintf(logfile , "IP Header\n");
fprintf(logfile , " |-IP Version : %d\n",(unsigned int)iph->version);
fprintf(logfile , " |-IP Header Length : %d DWORDS or %d Bytes\n",(unsigned int)iph->ihl,((unsigned int)(iph->ihl))*4);
fprintf(logfile , " |-Type Of Service : %d\n",(unsigned int)iph->tos);
fprintf(logfile , " |-IP Total Length : %d Bytes(Size of Packet)\n",ntohs(iph->tot_len));
fprintf(logfile , " |-Identification : %d\n",ntohs(iph->id));
//fprintf(logfile , " |-Reserved ZERO Field : %d\n",(unsigned int)iphdr->ip_reserved_zero);
//fprintf(logfile , " |-Dont Fragment Field : %d\n",(unsigned int)iphdr->ip_dont_fragment);
//fprintf(logfile , " |-More Fragment Field : %d\n",(unsigned int)iphdr->ip_more_fragment);
fprintf(logfile , " |-TTL : %d\n",(unsigned int)iph->ttl);
fprintf(logfile , " |-Protocol : %d\n",(unsigned int)iph->protocol);
fprintf(logfile , " |-Checksum : %d\n",ntohs(iph->check));
fprintf(logfile , " |-Source IP : %s\n",inet_ntoa(source.sin_addr));
fprintf(logfile , " |-Destination IP : %s\n",inet_ntoa(dest.sin_addr));
}
void print_tcp_packet(unsigned char* Buffer, int Size)
{
unsigned short iphdrlen;
struct iphdr *iph = (struct iphdr *)( Buffer + sizeof(struct ethhdr) );
iphdrlen = iph->ihl*4;
struct tcphdr *tcph=(struct tcphdr*)(Buffer + iphdrlen + sizeof(struct ethhdr));
int header_size = sizeof(struct ethhdr) + iphdrlen + tcph->doff*4;
fprintf(logfile , "\n\n***********************TCP Packet*************************\n");
print_ip_header(Buffer,Size);
fprintf(logfile , "\n");
fprintf(logfile , "TCP Header\n");
fprintf(logfile , " |-Source Port : %u\n",ntohs(tcph->source));
fprintf(logfile , " |-Destination Port : %u\n",ntohs(tcph->dest));
fprintf(logfile , " |-Sequence Number : %u\n",ntohl(tcph->seq));
fprintf(logfile , " |-Acknowledge Number : %u\n",ntohl(tcph->ack_seq));
fprintf(logfile , " |-Header Length : %d DWORDS or %d BYTES\n" ,(unsigned int)tcph->doff,(unsigned int)tcph->doff*4);
//fprintf(logfile , " |-CWR Flag : %d\n",(unsigned int)tcph->cwr);
//fprintf(logfile , " |-ECN Flag : %d\n",(unsigned int)tcph->ece);
fprintf(logfile , " |-Urgent Flag : %d\n",(unsigned int)tcph->urg);
fprintf(logfile , " |-Acknowledgement Flag : %d\n",(unsigned int)tcph->ack);
fprintf(logfile , " |-Push Flag : %d\n",(unsigned int)tcph->psh);
fprintf(logfile , " |-Reset Flag : %d\n",(unsigned int)tcph->rst);
fprintf(logfile , " |-Synchronise Flag : %d\n",(unsigned int)tcph->syn);
fprintf(logfile , " |-Finish Flag : %d\n",(unsigned int)tcph->fin);
fprintf(logfile , " |-Window : %d\n",ntohs(tcph->window));
fprintf(logfile , " |-Checksum : %d\n",ntohs(tcph->check));
fprintf(logfile , " |-Urgent Pointer : %d\n",tcph->urg_ptr);
fprintf(logfile , "\n");
fprintf(logfile , " DATA Dump ");
fprintf(logfile , "\n");
fprintf(logfile , "IP Header\n");
PrintData(Buffer,iphdrlen);
fprintf(logfile , "TCP Header\n");
PrintData(Buffer+iphdrlen,tcph->doff*4);
fprintf(logfile , "Data Payload\n");
PrintData(Buffer + header_size , Size - header_size );
fprintf(logfile , "\n###########################################################");
}
void print_udp_packet(unsigned char *Buffer , int Size)
{
unsigned short iphdrlen;
struct iphdr *iph = (struct iphdr *)(Buffer + sizeof(struct ethhdr));
iphdrlen = iph->ihl*4;
struct udphdr *udph = (struct udphdr*)(Buffer + iphdrlen + sizeof(struct ethhdr));
int header_size = sizeof(struct ethhdr) + iphdrlen + sizeof udph;
fprintf(logfile , "\n\n***********************UDP Packet*************************\n");
print_ip_header(Buffer,Size);
fprintf(logfile , "\nUDP Header\n");
fprintf(logfile , " |-Source Port : %d\n" , ntohs(udph->source));
fprintf(logfile , " |-Destination Port : %d\n" , ntohs(udph->dest));
fprintf(logfile , " |-UDP Length : %d\n" , ntohs(udph->len));
fprintf(logfile , " |-UDP Checksum : %d\n" , ntohs(udph->check));
fprintf(logfile , "\n");
fprintf(logfile , "IP Header\n");
PrintData(Buffer , iphdrlen);
fprintf(logfile , "UDP Header\n");
PrintData(Buffer+iphdrlen , sizeof udph);
fprintf(logfile , "Data Payload\n");
//Move the pointer ahead and reduce the size of string
PrintData(Buffer + header_size , Size - header_size);
fprintf(logfile , "\n###########################################################");
}
void print_icmp_packet(unsigned char* Buffer , int Size)
{
unsigned short iphdrlen;
struct iphdr *iph = (struct iphdr *)(Buffer + sizeof(struct ethhdr));
iphdrlen = iph->ihl * 4;
struct icmphdr *icmph = (struct icmphdr *)(Buffer + iphdrlen + sizeof(struct ethhdr));
int header_size = sizeof(struct ethhdr) + iphdrlen + sizeof icmph;
fprintf(logfile , "\n\n***********************ICMP Packet*************************\n");
print_ip_header(Buffer , Size);
fprintf(logfile , "\n");
fprintf(logfile , "ICMP Header\n");
fprintf(logfile , " |-Type : %d",(unsigned int)(icmph->type));
if((unsigned int)(icmph->type) == 11)
{
fprintf(logfile , " (TTL Expired)\n");
}
else if((unsigned int)(icmph->type) == ICMP_ECHOREPLY)
{
fprintf(logfile , " (ICMP Echo Reply)\n");
}
fprintf(logfile , " |-Code : %d\n",(unsigned int)(icmph->code));
fprintf(logfile , " |-Checksum : %d\n",ntohs(icmph->checksum));
//fprintf(logfile , " |-ID : %d\n",ntohs(icmph->id));
//fprintf(logfile , " |-Sequence : %d\n",ntohs(icmph->sequence));
fprintf(logfile , "\n");
fprintf(logfile , "IP Header\n");
PrintData(Buffer,iphdrlen);
fprintf(logfile , "UDP Header\n");
PrintData(Buffer + iphdrlen , sizeof icmph);
fprintf(logfile , "Data Payload\n");
//Move the pointer ahead and reduce the size of string
PrintData(Buffer + header_size , (Size - header_size) );
fprintf(logfile , "\n###########################################################");
}
void PrintData (unsigned char* data , int Size)
{
int i , j;
for(i=0 ; i < Size ; i++)
{
if( i!=0 && i%16==0) //if one line of hex printing is complete...
{
fprintf(logfile , " ");
for(j=i-16 ; j<i ; j++)
{
if(data[j]>=32 && data[j]<=128)
fprintf(logfile , "%c",(unsigned char)data[j]); //if its a number or alphabet
else fprintf(logfile , "."); //otherwise print a dot
}
fprintf(logfile , "\n");
}
if(i%16==0) fprintf(logfile , " ");
fprintf(logfile , " %02X",(unsigned int)data[i]);
if( i==Size-1) //print the last spaces
{
for(j=0;j<15-i%16;j++)
{
fprintf(logfile , " "); //extra spaces
}
fprintf(logfile , " ");
for(j=i-i%16 ; j<=i ; j++)
{
if(data[j]>=32 && data[j]<=128)
{
fprintf(logfile , "%c",(unsigned char)data[j]);
}
else
{
fprintf(logfile , ".");
}
}
fprintf(logfile , "\n" );
}
}
}
在 Linux 上运行带有前缀“sudo”的代码。 :)
关于Linux内核:Register a handler for a specific UDP port traffic?，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/14242338/