maps: MapFd and SockMapFd are owned
#770
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Hey @alessandrod, this pull request changes the Aya Public API and requires your review. |
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cc @nrxus |
aya/src/bpf.rs
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| @@ -510,7 +510,7 @@ impl<'a> BpfLoader<'a> { | |||
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| obj.relocate_maps( | |||
| maps.iter() | |||
| .map(|(s, data)| (s.as_str(), data.fd, &data.obj)), | |||
| .map(|(s, data)| (s.as_str(), data.fd().as_fd().as_raw_fd(), &data.obj)), | |||
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why not pass a BorrowedFd<'_> here instead? The less references we have to RawFds the easier it'll be gauge that our file descriptors are all valid.
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IIRC the function we're calling here is available in no_std, so BorrowedFd can't appear in its signature.
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Made that function available only in std. Unclear to me how anyone would use such a thing without access to real file descriptors.
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I think we should undo the aya-obj bit. Relocation puts file descriptors in the instruction stream where they must be cast as integers anyway, so lifetime tracking doesn't buy us much and it makes aya-obj essentially useless on no_std.
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I can do that. But can you help me understand how someone would use this in no_std given you can't get your hands on an FD? Or is the idea that the user has an FD through some other means?
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Yes, it's unfortunate that *Fd are defined in std::os, in an ideal world some of the os definitions should be moved to core like it happened for net. But in a no_std program it's easy to imagine that one could still create fds using lower level linux APIs, and it seems silly that we would preclude them from using aya-obj just for a type alias.
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I don't think this is equivalent to the core::net types since those are just scalars like IP addresses. Anyway, done -- I just defined a local alias for RawFd in this crate in no_std.
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| impl Clone for MapData { |
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should we implement a try_clone() for MapData so maps can still be cloned?
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We can. In light of #703 I'm not sure how much it matters.
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aya-obj/src/relocation.rs
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| @@ -105,7 +110,11 @@ pub(crate) struct Symbol { | |||
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| impl Object { | |||
| /// Relocates the map references | |||
| pub fn relocate_maps<'a, I: Iterator<Item = (&'a str, i32, &'a Map)>>( | |||
| #[cfg(feature = "std")] | |||
| pub fn relocate_maps< | |||
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This makes aya-obj a lot less useful without std. Do you think it would be too
painful to make this work with both RawFd and BorrowedFd? (Doesn't seem like but
I haven't tried)
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The previous discussion on this topic is here. How do you get your hands on an FD in no_std?
`MapData::fd` is now a `MapFd`. This means that `MapData` now closes the file descriptor on drop. In the future we might consider making `MapFd` hold a `BorrowedFd` but this requires API design work due to overlapping borrows. Since `SockMapFd` is no longer `Copy`, attach methods to take it by reference to allow callers to use it multiple times as they are accustomed to doing. `SockMapFd` implements `try_clone`. `MapFd` and `SockMapFd` are now returned by reference to allow callers to avoid file descriptor cloning when desired. This is an API breaking change. Updates #612.
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MapData::fdis now aMapFd. This means thatMapDatanow closes thefile descriptor on drop. In the future we might consider making
MapFdhold a
BorrowedFdbut this requires API design work due to overlappingborrows.
Since
SockMapFdis no longerCopy, attach methods to take it byreference to allow callers to use it multiple times as they are
accustomed to doing.
SockMapFdimplementstry_clone.MapFdandSockMapFdare nowreturned by reference to allow callers to avoid file descriptor cloning
when desired.
This is an API breaking change.
Updates #612.