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pythonlinuxnetworkingipv4procfs

Get local network interface addresses using only proc?

How can I obtain the (IPv4) addresses for all network interfaces using only proc? After some extensive investigation I've discovered the following:

  1. ifconfig makes use of SIOCGIFADDR, which requires open sockets and advance knowledge of all the interface names. It also isn't documented in any manual pages on Linux.
  2. proc contains /proc/net/dev, but this is a list of interface statistics.
  3. proc contains /proc/net/if_inet6, which is exactly what I need but for IPv6.
  4. Generally interfaces are easy to find in proc, but actual addresses are very rarely used except where explicitly part of some connection.
  5. There's a system call called getifaddrs, which is very much a "magical" function you'd expect to see in Windows. It's also implemented on BSD. However it's not very text-oriented, which makes it difficult to use from non-C languages.
Solution

  • There is no IPv4 analog of /proc/net/if_inet6

    ifconfig does:

    fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP)
ioctl(fd, SIOCGIFCONF, ...)

    You'll get something like this:

    ioctl(4, SIOCGIFCONF, {120, {{"lo", {AF_INET, inet_addr("127.0.0.1")}}, {"eth0", {AF_INET, inet_addr("10.6.23.69")}}, {"tun0", {AF_INET, inet_addr("10.253.10.151")}}}})