Fix pipe ref counts and UDP socket unbind during dup/clone #59
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Two bugs fixed:
1. Pipe reference counts not updated during dup/clone operations:
- dup(), dup2(), and FdTable::clone() were cloning the Arc<Mutex<PipeBuffer>>
but not incrementing the readers/writers counts inside PipeBuffer
- This caused premature EOF (writers=0) or broken pipe (readers=0) errors
when a duplicated fd was closed
- Added add_reader() and add_writer() methods to PipeBuffer
- Updated dup(), dup2(), and clone() to properly maintain ref counts
2. UDP socket unbinds prematurely when fd is closed:
- sys_close explicitly called unbind_udp() when closing a socket fd
- With Arc<Mutex<UdpSocket>> design, multiple fds can share a socket
- Closing one fd would unbind the socket while other fds still referenced it
- Removed explicit unbind since UdpSocket::Drop already handles it
when the last Arc reference is released
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Bug: Race condition in dup2 when duplicating to same fd
When old_fd == new_fd, dup2 calls close_read()/close_write() and then add_reader()/add_writer() in separate lock operations. Between these calls, the pipe's reader/writer count can temporarily be zero. A concurrent write during this window will see readers == 0 and return EPIPE, even though the pipe isn't actually closed. Per POSIX, dup2(fd, fd) should return fd immediately without modifying anything. Adding an early return when old_fd == new_fd would prevent this race.
Summary
dup(),dup2(), andFdTable::clone()operationsadd_reader()andadd_writer()methods toPipeBufferfor proper ref count managementTest plan
🤖 Generated with Claude Code
Note
Fixes pipe reader/writer reference handling in dup/dup2/FdTable::clone and prevents premature UDP unbind by deferring to Drop when the last reference closes.
FdTable::clone(): increment pipe reader/writer counts for clonedPipeRead/PipeWritefds.FdTable::dup2(): close existing target fd with proper pipe ref decrement; increment counts for duplicated fd.FdTable::dup(): increment counts for duplicated fd; rollback increments if no slot available (EMFILE).PipeBuffer::add_reader()andadd_writer()for ref management.sys_close: stop unbindingUdpSocketon close; rely onUdpSocket::Dropwhen lastArcis released; adjust logging.Written by Cursor Bugbot for commit 60d9c1f. This will update automatically on new commits. Configure here.