Match localnetwork is not supported on Windows (no getifaddrs in win32compat)

[steffen-heil-secforge]

Summary

On Windows, the ssh_config Match localnetwork criterion never matches and logs:

match localnetwork: not supported on this platform

Cause

check_match_ifaddrs() in readconf.c is gated on HAVE_IFADDRS_H. The Windows build (contrib/win32/openssh/config.h.vs) does not define it, and contrib/win32/win32compat/ provides no getifaddrs() implementation, so the #else branch (which prints "not supported on this platform") is what gets compiled. The same gate also disables the getifaddrs() path used by BindInterface in sshconnect.c.

Repro

ssh_config:

Match localnetwork 127.0.0.0/8
    Compression yes

ssh -G -F <cfg> somehost -> compression stays no; with -v you get match localnetwork: not supported on this platform. (OpenSSH_for_Windows_10.0p2)

Proposed fix

Add a getifaddrs()/freeifaddrs() shim in win32compat, implemented over the Win32 GetAdaptersAddresses() API; define HAVE_IFADDRS_H; register the new sources in the build. This enables Match localnetwork (client-side in 10.0) and the BindInterface interface enumeration. Disabled/disconnected adapters are returned without IFF_UP, so the existing consumers skip them (matches POSIX getifaddrs(3) semantics).

I have an implementation with a unit test, built and verified on Windows x64 — PR to follow.

[steffen-heil-secforge]

Issues are tracked in PowerShell/Win32-OpenSSH, not here. Refiled as PowerShell/Win32-OpenSSH#2440. Fix: #859. Closing this misplaced one.