c - ifreq's ifr_names are incorrect? -

the following function determines if given string valid network device name.

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int isvalidndevice(char *name) {      char data[4096];     struct ifconf ifc;     struct ifreq *ifr;     int sk;     int nintfcs;      sk = socket(af_inet, sock_dgram, 0);     if(sk < 0)     {         perror("socket");         return 0;     }      ifc.ifc_len = sizeof(data);     ifc.ifc_buf = (caddr_t)data;     if(ioctl(sk, siocgifconf, &ifc) < 0)     {         perror("ioctl(siocgifconf)");         return 0;     }      ifr = (struct ifreq*)data;     nintfcs = ifc.ifc_len / sizeof(struct ifreq);     for(int i=0; < nintfcs; i++)     {         safe_printf("%s\n", (&ifr[i])->ifr_name);         if (!strcmp((&ifr[i])->ifr_name, name)) {             return 1;         }     }      return 0; } 

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when run function, receive following output.

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lo0

stf0

�2�>s

en1j

0

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this code worked fine few months ago. has changed? doing incorrectly?

os: osx el capitan

the array of structures returned siocgifconf ioctl not of same size in osx. have field ifr->ifr_addr.sa_lenwhich different each structure

modified function take care of this. hope helps:

int isvalidndevice(char *name) {      char data[4096];     struct ifconf ifc;     struct ifreq *ifr;     int sk,length;      sk = socket(af_inet, sock_dgram, 0);     if(sk < 0)     {         perror("socket");         return 0;     }      ifc.ifc_len = sizeof(data);     ifc.ifc_buf = (caddr_t)data;     if(ioctl(sk, siocgifconf, &ifc) < 0)     {         perror("ioctl(siocgifconf)");         return 0;     }      ifr = (struct ifreq*)data;     for(int i=0;i<ifc.ifc_len;)     {         length=ifnamsiz + ifr->ifr_addr.sa_len;         printf("%s\n", ifr->ifr_name);         if (!strcmp(ifr->ifr_name,name)) {             printf("interface found!\n");             return 1;         }         ifr=(struct ifr*)((char*)ifr+length);         i+=length;     }      return 0; }