UDP multicast receiving duplicate packets - c++

Question

Am trying to develop a reader for multicast UDP broadcast.
Written a sample code to test on server.
In server I can see 2 NIC interfaces.
While executing the code, I can see the same packet being received twice.
What other changes do I need to do to eliminate duplicate packets?
Server is CentOS 7.9
gcc version 9.1.0
I hope this shouldn't matter
sample code
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <time.h>
#include <string.h>
#include <stdio.h>
#include <iostream>
#include <string>
using namespace std;
#define HELLO_PORT 12345
#define HELLO_GROUP "227.0.0.376"
#define INTRF "10.0.21.1"
#define MSGBUFSIZE 256
int main(int argc, char *argv[])
{
string source_iface(INTRF);
string group(HELLO_GROUP);
int port(HELLO_PORT);
int fd;
if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
{
perror("socket");
exit(1);
}
u_int yes = 1;
if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes)) < 0)
{
perror("Reusing ADDR failed");
exit(1);
}
struct sockaddr_in addr;
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(port);
addr.sin_addr.s_addr = inet_addr(group.c_str());
if (bind(fd,(struct sockaddr *)&addr, sizeof(addr)) < 0)
{
perror("bind");
exit(1);
}
struct ip_mreq mreq;
mreq.imr_multiaddr.s_addr = inet_addr(group.c_str());
mreq.imr_interface.s_addr = inet_addr(source_iface.c_str());
if (setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
{
perror("setsockopt");
exit(1);
}
socklen_t addrlen;
int nbytes;
char msgbuf[MSGBUFSIZE];
while (1)
{
memset(&msgbuf, 0, MSGBUFSIZE);
addrlen = sizeof(addr);
if ((nbytes = recvfrom(fd, msgbuf, MSGBUFSIZE, 0, (struct sockaddr *)&addr, &addrlen)) < 0)
{
perror("recvfrom");
exit(1);
}
//msgbuf will be a structure, inside that there is a unique ID
}
return 0;
}