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macoskernelnetwork-interfaceifconfig

Why are ifconfig's FLAGS values different from each interface's ifa_flags value and how can I get ifconfigs values?

running the following code prints out the ifa_flags value for each interface. Running ifconfig immediately after will show different FLAGS values for each interface. Why is this? How can I get ifconfig's FLAGS value without parsing a shell command's output?

void printFlags(){
 struct ifaddrs *addrs, *nextAddr;
 getifaddrs(&addrs);
 nextAddr = addrs;
 while(nextAddr){
   fprintf(stdout, "%s\' FLAGS: %u\n", nextAddr->ifa_name, nextAddr->ifa_flags);
   nextAddr = nextAddr->ifa_next;
 }
}
Solution

  • The reason they are different is because ifconfig decides to print the flags in hex format. Despite the Kernel passing this value around as an int or a short etc... Whatever... Simple way to see it: fprint("Flags: %x", flags);