Cygwin's ioctl(SIOCGIFFLAGS) always sets the IFF_UP flag

[Jonathan Lennox]

I've discovered that Cygwin's ioctl(SIOCGIFFLAGS) call always sets the
IFF_UP flag, even if the interface being queried is disabled or
unconfigured.

Compare the output of the program local-if.c (attached below) to the output
of ipconfig.exe, when I have one interface disabled:

$ ./local-if
eth0: AF=2 (INET): flags=0x63 (up broadcast notrailers running) addr=0.0.0.0
lo: AF=2 (INET): flags=0x69 (up loopback notrailers running) addr=127.0.0.1
eth1: AF=2 (INET): flags=0x63 (up broadcast notrailers running) addr=192.168.1.104
eth2: AF=2 (INET): flags=0x63 (up broadcast notrailers running) addr=192.168.1.173

$ ipconfig     

Windows IP Configuration

Ethernet adapter Wireless Network Connection:

        IP Address. . . . . . . . . . . . : 192.168.1.104
        Subnet Mask . . . . . . . . . . . : 255.255.255.0
        Default Gateway . . . . . . . . . : 192.168.1.1

Ethernet adapter Local Area Connection 3:

        IP Address. . . . . . . . . . . . : 192.168.1.173
        Subnet Mask . . . . . . . . . . . : 255.255.255.0
        Default Gateway . . . . . . . . . : 

Ethernet adapter Local Area Connection 4:

        Media State . . . . . . . . . . . : Media disconnected



Some experimentation shows that following get_2k_ifconf's call to
GetIfEntry, Windows does indeed set MIB_IFROW.dwOperStatus to
MIB_IF_OPER_STATUS_NON_OPERATIONAL, but the cygwin library
ignores this field.

A non-configured interface should be easily reproducable; any DHCP interface
should enter this state following "ipconfig /release".

This is on Windows XP SP2; the actual unconfigured interface I'm using is an
OpenVPN tunnel.

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-- 
Jonathan Lennox
lennox@cs.columbia.edu

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