我的服务器将在工作日的某个时期接收UDP多播数据包。我写了一个C插座应用程序来接收这些UDP多播数据包。由于我的服务器只能在某个时期内接收数据包，因此我用TCPDUMP捕获了数据包。
tcpdump -i enp0s25 -s 1600 -w /home/user/log/capture.pcap
然后，我用tcpreplay重播捕获的数据包。
tcpreplay -i p1p2 --pktlen /home/user/log/capture.pcap
这是" ifconfig"输出。
enp0s25: flags=4163<UP,BROADCAST,RUNNING,MULTICAST mtu 1500
inet 192.168.3.6 netmask 255.255.255.0 broadcast 192.168.3.255
inet6 2400:2410:2a41:2e00:1d6f:2fde:2436:608f prefixlen 64 scopeid 0x0<global
inet6 fe80::555d:f7f2:a114:51df prefixlen 64 scopeid 0x20<link
ether 98:90:96:a7:6f:f3 txqueuelen 1000 (Ethernet)
RX packets 45031 bytes 50053845 (47.7 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 14129 bytes 1784865 (1.7 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 20 memory 0xf9100000-f9120000
lo: flags=73<UP,LOOPBACK,RUNNING mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host
loop txqueuelen 1 (Local Loopback)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
p1p1: flags=4099<UP,BROADCAST,MULTICAST mtu 1500
ether 00:02:c9:5a:77:62 txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 218 dropped 207 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
p1p2: flags=4163<UP,BROADCAST,RUNNING,MULTICAST mtu 1500
inet6 fe80::2acf:23a9:3c1a:89a0 prefixlen 64 scopeid 0x20<link
ether 00:02:c9:5a:77:63 txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 329583 bytes 50655424 (48.3 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
p4p1: flags=4099<UP,BROADCAST,MULTICAST mtu 1500
ether 00:0f:53:29:e9:30 txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 26
p4p2: flags=4163<UP,BROADCAST,RUNNING,MULTICAST mtu 1500
ether 00:0f:53:29:e9:31 txqueuelen 1000 (Ethernet)
RX packets 329583 bytes 51973756 (49.5 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 35
在我的服务器中安装了三个NIC。其中两个是纤维通道NIC。他们每个人都有两个端口。P1P1和P1P2是相同的物理NIC，P4P1和P4P2是相同的物理NIC。 i将光纤电缆从P1P2连接到P4P2 ，因此TCPReplay应将数据包从P1P2发送到P4P2。
然后，我检查了是否有数据包进入P4P2。
tcpdump -i p4p2 -nnn
输出的一部分：
18:05:21.062023 IP 10.10.31.31.3131 > 239.239.31.31.3131: UDP, length 97
18:05:21.062035 IP 10.10.31.31.3131 > 239.239.31.31.3131: UDP, length 97
看来TCPReplay确实将捕获的数据包重新发送到P4P2。但是问题是我的袜子应用程序无法接收这些数据包。以下是我的C插槽应用程序的一部分。
#pragma pack(1)
#include <stdio.h>
#include <string.h>
#include <float.h>
#include <stdlib.h>
#include <ctype.h>
#include <signal.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/types.h>
#include <sys/socket.h>
#define MAXBUFSIZE 65536 // Max UDP Packet size is 64 Kbyte
int main() {
int sock, status, socklen;
uint8_t buffer[MAXBUFSIZE];
struct sockaddr_in saddr;
struct ip_mreq imreq;
memset(&saddr, 0x00, sizeof(saddr));
memset(&imreq, 0x00, sizeof(imreq));
memset(buffer, 0x00, MAXBUFSIZE);
// open a UDP socket
sock = socket(PF_INET, SOCK_DGRAM, 0);
if ( sock < 0 ) {
perror("Error creating socket");
return(0);
}
imreq.imr_multiaddr.s_addr = inet_addr("239.239.31.31");
imreq.imr_interface.s_addr = htonl(INADDR_ANY); // use DEFAULT interface
// JOIN multicast group on default interface
setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, (const void *)&imreq, sizeof(struct ip_mreq));
saddr.sin_family = AF_INET;
saddr.sin_port = htons(3131);
saddr.sin_addr.s_addr = htonl(INADDR_ANY);
status = bind(sock, (struct sockaddr *)&saddr, sizeof(struct sockaddr_in));
if ( status < 0 ) {
perror("Error binding socket to interface");
return(0);
}
socklen = sizeof(struct sockaddr_in);
// receive 500 packets from socket
int m = 0;
for (; m < 500; m++) {
status = recvfrom(sock, buffer, MAXBUFSIZE, 0, (struct sockaddr *)&saddr, &socklen);
if(status < 0) {
perror("receive error!n");
} else if (status > 0) {
// DO sth usefully here.
}
}
// shutdown socket
shutdown(sock, 2);
// close socket
close(sock);
return 0;
}
当我运行上面的应用程序时，它将停止在RECVFROM函数上。谁能告诉我为什么我的应用程序无法接收这些数据包？
根据TCPREPLAY文档，无法在同一计算机上发送数据包：TCP/IP堆栈和网络卡的设备驱动程序之间注入数据包，因此TCP/IP运行TCPREPLAR的堆栈永远不会看到数据包。尝试在同一台计算机上的虚拟化环境中运行TCPREPLAY，主机OS应该查看数据包。
参考：http：//tcpreplay.synfin.net/wiki/faq