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Report per-interface multicast support - #16991
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Interfaces with usable IPv6 addresses were reported without IFF_MULTICAST through SIOCGIFFLAGS and netlink. Java consequently treated them as unable to multicast and skipped its IPv6 socket tests. Preserve each imported host interface's multicast flag through network setup and NIC state. Apply Linux defaults to sandbox-created veth, bridge, TUN and TAP devices, and preserve the flag across network namespace moves. Import the actual loopback flag too: Linux permits changing it, and device type alone does not determine multicast support. The new option controls the reported flag, not packet reception. Validation on the qualification branch passed the owning unit and analyzer checks, focused ioctl/netlink and TUN/TAP tests, and both Java PromiscuousIPv6 bodies in directfs, shared-filesystem and native- reference modes. Each Java body exercised both IPv6 multicast scopes, including expected receives and nonreceives. The same ABI regression failed before the fix. Checkpoint roundtrips and flag mutation were not tested. Auto-fixed-by: [🤖] @EtiennePerot FUTURE_COPYBARA_INTEGRATE_REVIEW=#16059 from tamird:fix/netstack-multicast-capability b584529 PiperOrigin-RevId: 1013946624
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Report per-interface multicast support
Interfaces with usable IPv6 addresses were reported without
IFF_MULTICAST through SIOCGIFFLAGS and netlink. Java consequently
treated them as unable to multicast and skipped its IPv6 socket tests.
Preserve each imported host interface's multicast flag through network
setup and NIC state. Apply Linux defaults to sandbox-created veth,
bridge, TUN and TAP devices, and preserve the flag across network
namespace moves. Import the actual loopback flag too: Linux permits
changing it, and device type alone does not determine multicast support.
The new option controls the reported flag, not packet reception.
Validation on the qualification branch passed the owning unit and
analyzer checks, focused ioctl/netlink and TUN/TAP tests, and both Java
PromiscuousIPv6 bodies in directfs, shared-filesystem and native-
reference modes. Each Java body exercised both IPv6 multicast scopes,
including expected receives and nonreceives. The same ABI regression
failed before the fix. Checkpoint roundtrips and flag mutation were not
tested.
Auto-fixed-by: [🤖] @EtiennePerot
FUTURE_COPYBARA_INTEGRATE_REVIEW=#16059 from tamird:fix/netstack-multicast-capability b584529