Fix UInt32 underflow when sizing the address allocator for small subnets#1864
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radheradhe01 wants to merge 1 commit into
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Fix UInt32 underflow when sizing the address allocator for small subnets#1864radheradhe01 wants to merge 1 commit into
radheradhe01 wants to merge 1 commit into
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### Problem `DefaultNetworkService.init` computes the allocatable address count as: ```swift let size = Int(subnet.upper.value - subnet.lower.value - 3) ``` `upper.value` and `lower.value` are `UInt32`, so the subtraction happens in `UInt32` **before** the widening to `Int`. For a subnet where `upper - lower < 3` (e.g. a `/31`), this underflows and traps at runtime instead of producing a negative/zero count. ### Fix Widen to `Int` before subtracting, and guard that the resulting size is positive — throwing `invalidState` for a subnet too small to allocate from, rather than trapping. ### Notes No change for normally-sized subnets; this only affects degenerate small subnets that previously crashed.
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Problem
DefaultNetworkService.initcomputes the allocatable address count as:upper.valueandlower.valueareUInt32, so the subtraction happens inUInt32before the widening toInt. For a subnet whereupper - lower < 3(e.g. a/31), this underflows and traps at runtime instead of producing a negative/zero count.Fix
Widen to
Intbefore subtracting, and guard that the resulting size is positive — throwinginvalidStatefor a subnet too small to allocate from, rather than trapping.Notes
No change for normally-sized subnets; this only affects degenerate small subnets that previously crashed.