Support F_GETFL and F_SETFL for fcntl #4212
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tiif
commented
Feb 26, 2025
| let [flag] = check_min_vararg_count(cmd_name, varargs)?; | ||
| let flag = this.read_scalar(flag)?.to_i32()?; | ||
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| // FIXME: File access mode and file creation flags should be ignored. |
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From the man page:
F_SETFL (int)
Set the file status flags to the value specified by arg.
File access mode (O_RDONLY, O_WRONLY, O_RDWR) and file
creation flags (i.e., O_CREAT, O_EXCL, O_NOCTTY, O_TRUNC)
in arg are ignored.
There are quite a few file access mode and file creation flags, would prefer to open an issue for this and do it later.
RalfJung
reviewed
Apr 9, 2025
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| // We only support F_GETFL for socketpair and pipe. | ||
| let anonsocket_fd = fd.downcast::<AnonSocket>().ok_or_else(|| { | ||
| err_unsup_format!("fcntl: only socketpair / pipe are supported for F_SETFL") |
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Suggested change
| err_unsup_format!("fcntl: only socketpair / pipe are supported for F_SETFL") | |
| err_unsup_format!("fcntl: only socketpair / pipe are supported for F_GETFL") |
| })?; | ||
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| if anonsocket_fd.is_nonblock() { | ||
| // socketpair's SOCK_NONBLOCK and pipe's O_NONBLOCK have the same value. |
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The fcntl docs seem to anyway indicate that we always return the O_* flags here. So this fact should not matter.
If it actually did matter, we should have an assert_eq! here.
| err_unsup_format!("fcntl: only socketpair / pipe are supported for F_GETFL") | ||
| })?; | ||
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| let cmd_name = "fcntl(fd, F_SETFL, ...)"; |
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| if flag == this.eval_libc_i32("O_NONBLOCK") { | ||
| anonsocket_fd.set_nonblock(); | ||
| } else { | ||
| throw_unsup_format!("fcntl: only O_NONBLOCK are supported for F_GETFL") | ||
| } |
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This should also support un-setting the O_NONBLOCK flag, right? I assume that's what happens on flag == 0.
| @@ -40,7 +40,7 @@ struct AnonSocket { | |||
| /// A list of thread ids blocked because the buffer was full. | |||
| /// Once another thread reads some bytes, these threads will be unblocked. | |||
| blocked_write_tid: RefCell<Vec<ThreadId>>, | |||
| is_nonblock: bool, | |||
| is_nonblock: Cell<bool>, | |||
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Suggested change
| is_nonblock: Cell<bool>, | |
| /// Whether this is a non-blocking socket or not. | |
| is_nonblock: Cell<bool>, |
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| // 2. Thread 1 set O_NONBLOCK flag on fds[0], then check the value of F_GETFL. | ||
| // 3. Thread 2 writes to fds[1] to unblock the `read` in main thread. |
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Why is this done by 2 different threads?
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Reminder, once the PR becomes ready for a review, use |
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This PR supports
F_SETFLandF_GETFLflags forfcntl. In this implementation,F_SETFLcan only setO_NONBLOCKflag.The interaction between these
fcntloperations and blocking fd is summarised here.Fixes #4119