getifaddrs - Memory leak

[kardon33]

Hello Bytes,

I am using getifaddrs from ifadddrs.h on Debian Linux (Lenny).

Im using valgrind to check for memory leaks in my program. It seems that I have a memory leak in the code below but I cant figure out how to fix it. I thought i was freeing the address structure right but no luck.

If I do not run the loop and call "ifAddrStru ct = ifAddrStruct->ifa_next;" I don't get a memory leak but it also destroys the functionality of my method.

Any thoughts?

#include <ifaddrs.h> // Used for getting local address

    struct ifaddrs * ifAddrStruct = NULL;
    getifaddrs(&ifAddrStruct);

    while (ifAddrStruct != NULL) {

        if (ifAddrStruct->ifa_addr->sa_family == AF_INET && strcmp(ifAddrStruct->ifa_name, "lo0") != 0) { // check it is IP4 and not lo0

        }
        ifAddrStruct = ifAddrStruct->ifa_next;
    }

    freeifaddrs(ifAddrStruct);
    ifAddrStruct = NULL;

[kardon33]

Well i figured it out.

I had to create a second address structure like:

struct ifaddrs * ipa = NULL;

Then set ipa equal to ifAddrStruct before using ipa in the while loop.

This allows the code to keep a copy of linked list head ifAddrStruct for freeing.

Final Code looks like:

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

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

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

            inet_ntop(AF_INET, tmpAddrPtr, s, sizeof (s));


        }

         ipa = ipa->ifa_next;
    }

    freeifaddrs(ifAddrStruct);