我正在尝试使用Raw Socket自己实现ICMP回显ping数据包。在Linux机器上使用tcpdump时，我发现Echo ping请求已成功发送，但是当我使用Wireshark观察Windows机器中的传入数据包时，未观察到传入的ICMP请求。
我编写了以下代码来实现ICMP回显请求和答复。
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <netinet/ip_icmp.h>
#include <time.h>
#include <fcntl.h>
#include <signal.h>
#include <time.h>
#include <string.h>
#include <netinet/if_ether.h>
#include <netpacket/packet.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <sys/ioctl.h>
#define PING_PKT_S 64
#define PORT_NO 0
#define PING_SLEEP_RATE 1000000
#define RECV_TIMEOUT 1
int pingloop=1;
struct ping_pkt
{
struct ethhdr eth;
struct ip ip;
struct icmphdr hdr;
char msg[PING_PKT_S-sizeof(struct icmphdr)];
}g_pckt;
typedef struct ping_ctx{
int tos;
int ttl;
char srcIP[200];
char dstIP[200];
int r_sock;
}ping_ctx;
unsigned short checksum(void *b, int len)
{
unsigned short *buf = b;
unsigned int sum=0;
unsigned short result;
for ( sum = 0; len > 1; len -= 2 )
sum += *buf++;
if ( len == 1 )
sum += *(unsigned char*)buf;
sum = (sum >> 16) + (sum & 0xFFFF);
sum += (sum >> 16);
result = ~sum;
return result;
}
void intHandler(int dummy)
{
pingloop=0;
}
void fill_ip_h(struct ip *ip, ping_ctx* ctx)
{
ip->ip_src.s_addr = inet_addr(ctx->srcIP);
ip->ip_dst.s_addr = inet_addr(ctx->dstIP);
ip->ip_v = 4;
ip->ip_hl = sizeof*ip >> 2;
ip->ip_tos = (unsigned char)(ctx->tos);
ip->ip_len = htons(sizeof(g_pckt)-sizeof(struct ethhdr));
ip->ip_id = htons(4321);
ip->ip_off = htons(0);
ip->ip_ttl = (unsigned char)(ctx->ttl);
ip->ip_p = 1;
ip->ip_sum = 0; /* Let kernel fills in */
}
void fill_icmp_h(struct icmphdr* hdr,int *msg_count)
{
hdr->type = ICMP_ECHO;
hdr->un.echo.id = 1;
hdr->un.echo.sequence = (*msg_count)++;
}
void fill_data(unsigned char * data)
{
memset(data, 'J', PING_PKT_S-sizeof(struct icmphdr));
}
void fill_eth(struct ethhdr* eth){
eth->h_source[0] = 0x78;
eth->h_source[1] = 0xe7;
eth->h_source[2] = 0xd1;
eth->h_source[3] = 0xe2;
eth->h_source[4] = 0xc3;
eth->h_source[5] = 0x48;
eth->h_dest[0] = 0xc0;
eth->h_dest[1] = 0x42;
eth->h_dest[2] = 0xd0;
eth->h_dest[3] = 0x6e;
eth->h_dest[4] = 0xe1;
eth->h_dest[5] = 0xd9;
eth->h_proto = htons(ETH_P_IP);
}
int recv_ping(int ping_sockfd)
{
int addr_len,msg_received_count=0,on =1;
struct sockaddr_ll r_addr;
/*struct timespec time_start, time_end, tfs, tfe;
long double rtt_msec=0, total_msec=0;
struct timeval tv_out;*/
char* buffer = (char*) malloc (65536);
/*Timer Settings*/
//tv_out.tv_sec = RECV_TIMEOUT;
//tv_out.tv_usec = 0;
//clock_gettime(CLOCK_MONOTONIC, &tfs);
addr_len=sizeof(r_addr);
memset(buffer,0,65536);
if ( recvfrom(ping_sockfd, buffer, 65536, 0,
(struct sockaddr*)&r_addr, &addr_len) <= 0 ) {
printf("\nPacket receive failed!\n");
}
else{
/*clock_gettime(CLOCK_MONOTONIC, &time_end);
double timeElapsed = ((double)(time_end.tv_nsec -
time_start.tv_nsec))/1000000.0;
rtt_msec = (time_end.tv_sec - time_start.tv_sec) * 1000.0 + timeElapsed;
msg_received_count++;*/
struct ethhdr *eth = (struct ethhdr*) (buffer);
unsigned short iphdrlen;
struct iphdr *ip = (struct iphdr*)(buffer + sizeof(struct ethhdr));
if((unsigned int)ip->protocol==1){
printf("\n Ethernet Header \n");
printf("\t|Source Address : %.2X - %.2X - %.2X - %.2X - %.2X - %.2X",eth->h_source[0],eth->h_source[1],eth->h_source[2],eth->h_source[3],eth->h_source[4],eth->h_source[5]);
printf("\t|Destination Address : %.2X - %.2X - %.2X - %.2X - %.2X - %.2X",eth->h_dest[0],eth->h_dest[1],eth->h_dest[2],eth->h_dest[3],eth->h_dest[4],eth->h_dest[5]);
printf("\n Internet header \n");
printf("\t|-Version : %d\n",(unsigned int)ip->version);
printf("\t|-Internet Header Length : %d DWORDS or %d Bytes\n",(unsigned int)ip->ihl,((unsigned int)(ip->ihl))*4);
printf("\t|-Type Of Service : %d\n",(unsigned int)ip->tos);
printf("\t|-Total Length : %d Bytes\n",ntohs(ip->tot_len));
printf("\t|-Identification : %d\n",ntohs(ip->id));
printf("\t|-Time To Live : %d\n",(unsigned int)ip->ttl);
printf("\t|-Protocol : %d\n",(unsigned int)ip->protocol);
printf("\t|-Header Checksum : %d\n",ntohs(ip->check));
printf("\t|-Source IP : %d\n", ip->saddr);
printf("\t|-Destination IP : %d\n",ip->daddr);
return 1;
}
else{
return 0;
}
}
}
void send_ping(ping_ctx* ctx,int r_sock)
{
int msg_count=0, i, addr_len, pkt_sent=1,
msg_received_count=0,on =1;
struct sockaddr_ll remote_addr;
struct ip *ip = NULL;
struct icmphdr* icmph = NULL;
unsigned char* data = NULL;
struct ethhdr* eth = NULL;
struct sockaddr_ll r_addr;
struct timespec time_start, time_end, tfs, tfe;
long double rtt_msec=0, total_msec=0;
struct timeval tv_out;
/*Set params*/
char *to = ctx->dstIP;
char *from = ctx->srcIP;
int ping_sockfd = ctx->r_sock;
int ttl = ctx->ttl;
int tos =ctx->tos;
/*Timer Settings*/
tv_out.tv_sec = RECV_TIMEOUT;
tv_out.tv_usec = 0;
//clock_gettime(CLOCK_MONOTONIC, &tfs);
//GET INTERFACE INDEX FOR INTERFACE enp0s3
/*struct ifreq ifr;
size_t if_name_len = strlen(if_name);
if(if_name_len<sizeof(ifr.ifr_name)){
memcpy(ifr.ifr_name,if_name,if_name_len);
ifr.ifr_name[if_name_len]=0;
}
else{
die("Interface name is too long");
}
memset(&ifr,0,sizeof(ifr));
strncpy(ifr.ifr_name,enp0s3,IFNAMSIZ-1);
int fd = socket(AF_UNIX,SOCK_DGRAM,0);
if(fd==-1)
printf("Error opening socket");
if(ioctl(fd,SIOCGIFINDEX,&ifr)==-1){
printf("Error getting index name");
}*/
//int ifindex = ifr.ifr_ifindex;
int ifindex = if_nametoindex("enp2s0f0");
printf("The interface number is : %d \n",ifindex);
remote_addr.sll_ifindex = ifindex;
remote_addr.sll_halen = ETH_ALEN;
remote_addr.sll_addr[0] = 0xc0;
remote_addr.sll_addr[1] = 0x42;
remote_addr.sll_addr[2] = 0xd0;
remote_addr.sll_addr[3] = 0x6e;
remote_addr.sll_addr[4] = 0xe1;
remote_addr.sll_addr[5] = 0xd9;
while(pingloop)
{
pkt_sent=1;
memset(&g_pckt, 0, sizeof(g_pckt));
/*ETHERNET Header*/
eth = (struct ethhdr *)&g_pckt;
fill_eth(eth);
/*IP Header*/
ip = (struct ip *)(eth + 1);
fill_ip_h(ip, ctx);
/*ICMP Header*/
icmph = (struct icmphdr*)(ip + 1);
fill_icmp_h(icmph, &msg_count);
/*Data*/
data = (unsigned char *)(icmph + 1);
fill_data(data);
/*ICMP Checksum*/
icmph->checksum = checksum(icmph, PING_PKT_S);
usleep(PING_SLEEP_RATE);
/*TX*/
clock_gettime(CLOCK_MONOTONIC, &time_start);
if ( sendto(ping_sockfd, &g_pckt, sizeof(g_pckt), 0,
(struct sockaddr*) &remote_addr,
sizeof(remote_addr)) <= 0)
{
printf("\nPacket Sending Failed!\n");
pkt_sent=0;
}
/*RX*/
/*addr_len=sizeof(r_addr);
if ( recvfrom(ping_sockfd, icmph, PING_PKT_S, 0,
(struct sockaddr*)&r_addr, &addr_len) <= 0
&& msg_count>1)
{
printf("\nPacket receive failed!\n");
} */
else
{
/*clock_gettime(CLOCK_MONOTONIC, &time_end);
double timeElapsed = ((double)(time_end.tv_nsec -
time_start.tv_nsec))/1000000.0;
rtt_msec = (time_end.tv_sec-
time_start.tv_sec) * 1000.0
+ timeElapsed;*/
// if packet was not sent, don't receive
if(pkt_sent)
{
msg_count++;
if(recv_ping(r_sock)){
msg_received_count++;
}
//printf("Total Messages received : %d\n", msg_received_count );
/*if(!(g_pckt.hdr.type ==69 && g_pckt.hdr.code==0))
{
printf("Error..Packet received with ICMP"
"type %d code %d\n",
g_pckt.hdr.type, g_pckt.hdr.code);
}
else
{
printf("%d bytes Received reply from %s: icmp_seq=:%d ttl=%d time=%Lf ms\n",PING_PKT_S, ctx->dstIP, msg_count, ctx->ttl, rtt_msec);
msg_received_count++;
} */
}
}
}
/*clock_gettime(CLOCK_MONOTONIC, &tfe);
double timeElapsed = ((double)(tfe.tv_nsec -
tfs.tv_nsec))/1000000.0;
total_msec = (tfe.tv_sec-tfs.tv_sec)*1000.0+
timeElapsed ;*/
printf("\n%d packets sent, %d packets received\n\n",
msg_count, msg_received_count);
}
int main(int argc, char *argv[])
{
ping_ctx ctx = {0};
if(argc!=3)
{
printf("sudo ./myping 10.117.157.6 10.39.51.117\n");
return 0;
}
signal(SIGINT, intHandler);
ctx.r_sock = socket(AF_PACKET, SOCK_RAW, IPPROTO_RAW);
int r_sock = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_IP));
if(r_sock <0)
{
printf("\nSocket file descriptor not received\n");
return 0;
}
if(ctx.r_sock <0)
{
printf("%d",ctx.r_sock);
printf("\nSocket file descriptor not received\n");
return 0;
}
ctx.tos = 0;
ctx.ttl = 64;
strncpy(ctx.dstIP, argv[1],strlen(argv[1]));
strncpy(ctx.srcIP, argv[2],strlen(argv[2]));
send_ping(&ctx,r_sock);
return 0;
}
同样，被调用的sendto api返回值0，表示仅发送了0个字节，这不理想，因为应该返回已发送的字节数，该字节数应等于数据包大小。
我知道发布的代码很长，但是我不确定是哪个部分导致了错误。所以我要发布整个代码。任何快速帮助将不胜感激。
Linux发送方的tcpdump捕获如下所示
答案 0 :(得分：0)
好的，所以我知道了。显然，AF_PACKET始终假定该数据包将被完全填充。完全由我表示完全。而且我正尝试省略IPv4校验和以填充内核，尽管对于AF_INET成功，但对于AF_PACKET并非如此。因此，必须强制AF_PACKET填充校验和，这样一切都很好。
