Implement splice and tee syscalls for zero-copy I/O #618
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Add support for the Linux splice(2) and tee(2) syscalls, enabling zero-copy data transfer between file descriptors using pipes as intermediary buffers. New syscalls implemented: - splice: Move data between a pipe and a file descriptor (or two pipes) - tee: Duplicate pipe content without consuming it Implementation details: - SpliceFlags bitflags type for SPLICE_F_MOVE, SPLICE_F_NONBLOCK, etc. - Validates that at least one fd is a pipe for splice - Validates that both fds are pipes for tee - Rejects offset pointers for pipe fds (returns ESPIPE) - Uses temporary buffer (max 64KB) for efficient data transfer - Respects SPLICE_F_NONBLOCK for non-blocking operation Files modified: - litebox_common_linux/src/lib.rs: SpliceFlags type, syscall variants - litebox_shim_linux/src/lib.rs: Syscall dispatch - litebox_shim_linux/src/syscalls/file.rs: sys_splice, sys_tee - litebox_shim_linux/src/syscalls/tests.rs: 8 unit tests Co-Authored-By: Claude <[email protected]>
Address code review feedback: Security fixes: - TOCTOU vulnerability: Read offset only once, store in local variable - Integer overflow: Use checked_add() with EOVERFLOW error - Same-pipe check: Add fd_in != fd_out validation for splice - Negative offset validation: Explicit check before conversion Correctness fixes: - tee partial write: Only write back bytes_written to input pipe to avoid data inconsistency on partial writes Documentation: - Add Implementation Notes section to sys_tee explaining limitations - Update clippy expect reasons to be more accurate (bytes_written ≤ 65536) Co-Authored-By: Claude <[email protected]>
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🤖 SemverChecks 🤖 No breaking API changes detected Note: this does not mean API is unchanged, or even that there are no breaking changes; simply, none of the detections triggered. |
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Summary
Add support for the Linux
splice(2)andtee(2)syscalls, enabling zero-copy data transfer between file descriptors using pipes as intermediary buffers.New Syscalls
Implementation Details
SpliceFlags
SPLICE_F_MOVE(0x01): Hint to move pages instead of copying (advisory)SPLICE_F_NONBLOCK(0x02): Don't block on pipe I/OSPLICE_F_MORE(0x04): More data will be coming (hint for sockets)SPLICE_F_GIFT(0x08): Pages are a gift (vmsplice only)splice Behavior
ESPIPE)SPLICE_F_NONBLOCKfor non-blocking operationtee Behavior
EINVAL)Files Modified
litebox_common_linux/src/lib.rs:SpliceFlagstype,Splice/Teesyscall variants, parsinglitebox_shim_linux/src/lib.rs: Syscall dispatchlitebox_shim_linux/src/syscalls/file.rs:sys_splice,sys_teeimplementationslitebox_shim_linux/src/syscalls/tests.rs: 8 unit testsTesting
References
man 2 splice,man 2 tee/fs/splice.c