Network Programming: Returning your ip (Linux)

[kardon33]

Hello Bytes,

To start I am running Debian Linux on x86.

I am doing some network programing, Ive managed to create my UDP server that listens on a port for incoming packets.

However my problem is that I catch my own broadcast packets which I do not want. I would like a way to check if the incoming packet is from my IP if so ignore it.

So how do you return your ip in c/c++.

Ill post how I create the socket:

    int sockfd;
    struct addrinfo hints, *servinfo, *p;
    int rv;
    

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC; // set to AF_INET to force IPv4
    hints.ai_socktype = SOCK_DGRAM;
    hints.ai_flags = AI_PASSIVE; // use my IP

    if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        return 1;
    }

    // loop through all the results and bind to the first we can
    for (p = servinfo; p != NULL; p = p->ai_next) {
        if ((sockfd = socket(p->ai_family, p->ai_socktype,
                p->ai_protocol)) == -1) {
            perror("udpServer: socket");
            continue;
        }
        

        if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
            close(sockfd);
            perror("udpServer: bind");
            continue;
        }

        break;
    }


    if (p == NULL) {
        fprintf(stderr, "udpServer: failed to bind socket\n");
        return 2;
    }



    struct timeval tv;
    tv.tv_sec = 2; /* 30 Secs Timeout */
    setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, (struct timeval *) & tv, sizeof (struct timeval));
    
    freeaddrinfo(servinfo);

Thanks in advance.

[kardon33]

I managed to figure it out, here is my solution.

 #include <ifaddrs.h>


    struct ifaddrs * ifAddrStruct = NULL;
    void * tmpAddrPtr = NULL;
    char s[INET6_ADDRSTRLEN];

    getifaddrs(&ifAddrStruct);
    localAddress.clear();

    while (ifAddrStruct != NULL) {
        if (ifAddrStruct->ifa_addr->sa_family == AF_INET && strcmp(ifAddrStruct->ifa_name, "lo0") != 0) { // check it is IP4 and not lo0
            // is a valid IP4 Address
            tmpAddrPtr = &((struct sockaddr_in *) ifAddrStruct->ifa_addr)->sin_addr;

            inet_ntop(AF_INET, tmpAddrPtr, s, sizeof (s));
          
         
            printf("Address: %s \n",s);
           
        }
        ifAddrStruct = ifAddrStruct->ifa_next;
    }