fix(macos): skip SO_BINDTODEVICE and use IP_BOUND_IF paths#20
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On macOS, SO_BINDTODEVICE is not a supported way to bind datagram sockets to an interface. The existing Linux-only branch also uses struct ifreq.ifr_ifrn, which does not exist on Darwin (ifr_name is used instead), so the project fails to compile with AppleClang. Guard the SO_BINDTODEVICE blocks with !defined(__APPLE__) so macOS builds use the existing IP_BOUND_IF / IPV6_BOUND_IF branches in new_recv_socket(). Tested on macOS 15 (Apple Silicon): cmake build succeeds; reflector starts with -fn4 between en0 and an OrbStack bridge interface.
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Summary
macOS cannot use Linux
SO_BINDTODEVICEfor interface-scoped mDNS sockets. The current#if defined(SO_BINDTODEVICE)blocks also referencestruct ifreq.ifr_ifrn, which is a Linux/glibc field name — Darwin usesifr_name, so the project does not compile with AppleClang today.This change guards those blocks with
!defined(__APPLE__), allowing the existingIP_BOUND_IF/IPV6_BOUND_IFbranches innew_recv_socket()to be used on macOS (same pattern as mDNSResponder and other portable networking code).Test plan
cmake -S . -B build && cmake --build buildon macOS 15 (Apple Silicon)./build/src/mdns-reflector -fn4 en0 <bridge>starts and reflects between LAN and a VM bridge (OrbStack)Notes
No new socket options — only enables the
#elif defined(IP_BOUND_IF)/IPV6_BOUND_IFpaths that are already present for Apple platforms.