Add trait to reduce duplicated code between socket address types, implement netlink addresses #1004

kevinmehall · 2024-01-29T06:50:16Z

This adds a trait SockAddr, and implements it for SocketAddrV4, SocketAddrV6, SocketAddrUnix, SocketAddrXdp, SocketAddr, SocketAddrAny, and the newly-added SocketAddrNetlink. The syscalls that take a sockaddr are reimplemented in terms of this trait, removing hundreds of lines of duplicated code. It also simplifies the public interface, allowing rustix::net::{bind, connect, sendto, sendmsg_addr} to take an (addr: &impl SockAddr), rather than needing separate functions bind_v4, bind_v6, bind_unix, bind_xdp, bind_any etc.

The SocketAddrAny enum is replaced by a struct wrapping SocketAddrStorage. This allows SocketAddrAny be fully generic and allows syscalls returning addresses to be used with any address type not known to rustix. Address types use .into() / .try_into() to convert to / from SocketAddrAny.

sunfishcode · 2024-02-06T01:13:14Z

As a quick update here, I am looking forward to reviewing this; I've just been busy.

niklaswimmer

I like this approach, it allows me to very easily define a socket address not yet present in this crate, like so

#[derive(Debug, Clone, Copy)]
#[allow(dead_code)] // fields are never read directly because they get memcp'd into another struct
#[repr(C)]
struct SocketAddressHci {
    hci_family: rustix::net::AddressFamily,
    hci_dev: u16,
    hci_channel: u16,
}

unsafe impl SocketAddress for SocketAddressHci {
    /// SAFETY: `SocketAddressHci` has the same layout as the type in the kernel and can therefore safely be passed in a syscall
    type CSockAddr = Self;

    fn encode(&self) -> Self::CSockAddr {
        self.clone()
    }
}

I left some comment about the code structure, most of it more nit than anything else. I am interested to here your opinion on using something like a Bow for the return value of encode tho. It would allow impl's to avoid the clone without having to reimplement write_sockaddr and with_sockaddr again :)

src/backend/linux_raw/net/mod.rs

src/backend/linux_raw/net/addr.rs

src/backend/libc/net/msghdr.rs

src/net/socket_address.rs

kevinmehall · 2024-06-01T23:33:30Z

Given that sockaddr was included on the list of libc types to remove in #1063, I slimmed down the SockAddr trait further to only with_sockaddr and made the raw pointer type an opaque struct to avoid all libc types in the API.

I also rebased to clean up the messy history for easier review. Full history archived here.

al8n · 2025-01-13T16:03:15Z

Hi, any updates on this PR? Looking forward rustix supporting netlink.

raftario · 2025-01-23T16:36:51Z

This would be very nice to have in 1.0
#753

sunfishcode · 2025-01-23T17:15:34Z

Thanks for the pings here, and your patience! I'll make an effort to review this before 1.0.

sunfishcode

This looks really nice!

I was initially worried about the safety of the f called by the with_sockaddr function, however I now see that the safety requirements are covered by the pub unsafe trait, so it looks good.

And I was initially worried about generic functions in src/backend, to keep code duplication down, however they're in fact replacing manually duplicated code, so that doesn't seem to be a problem.

I agree that it'd be good to continue to evolve this as you discussed. #1171 adds a RawSocketAddr type which is very close to what you describe for return values, and sounds like a good general direction.

I have have a few relatively minor comments, plus this needs a rebase. If you'd like help with the rebase please let me know.

sunfishcode · 2025-01-31T01:04:47Z

src/net/socket_address.rs

+
+/// A trait abstracting over the types that can be passed as a `sockaddr`.
+///
+/// Safety: implementers of this trait must ensure that `with_sockaddr` calls


As a minor style nit, this should be a # Safety section header.

sunfishcode · 2025-01-31T01:25:09Z

src/net/socket_address.rs

+#[repr(C)]
+pub struct SockAddrRaw {
+    _data: [u8; 0],
+}


What would you think of renaming SockAddrRaw to SocketAddrOpaque?

There are two changes there:

Sock -> Socket, because if we have some things prefixed Socket and some prefixed Sock I expect I'll frequently forget which things use which prefixes.

Raw -> Opaque`, which I think better captures that this struct type doesn't describe the data layout.

sunfishcode · 2025-01-31T01:38:49Z

src/net/mod.rs

 mod send_recv;
 mod socket;
 mod socket_addr_any;
+mod socket_address;


Could we make this a pub mod, and perhaps name it addr, to keep SockAddr and SockAddrRaw from cluttering the rest of the net API? It seems like most users won't ever need to use those directly.

Is it confusing that rustix::net::addr then only contains those two, and not any of the other address types (SocketAddrUnix, SocketAddrV4, SocketAddrV6, SocketAddr, SocketAddrAny, SocketAddrStorage) that are one level up? Seems like at least SocketAddrStorage and SocketAddrOpaque should be next to each other since they represent similar C types.

Maybe move them all into rustix::net::addr?

Good idea to keep SocketAddrStorage next to SocketAddrOpaque.

It seems nice to keep SocketAddrV4, SocketAddrV6, SocketAddrUnix, in rustix::net where all the rest of the API that uses them are though, because that's the "regular" API.

What if we put SocketAddrOpaque, SocketAddrArg, and SocketAddrStorage into a pub mod named rustix::net::abstract?

Sounds good. abstract might be confused with the abstract namespace for unix sockets, but I don't have a better name to propose.

Also, abstract is a Rust reserved keyword.

sunfishcode · 2025-01-31T01:40:22Z

src/net/socket_address.rs

+/// `f` with a pointer that is readable for the passed length, and points
+/// to data that is a valid socket address for the system calls that accept
+/// `sockaddr` as a const pointer.
+pub unsafe trait SockAddr {


And, what would you think of renaming this to SocketAddrArg? Sock -> Socket for the same reason as above, and Arg since it is for describing arguments; return values will need to use some other mechanism as you noted in the top comment.

kevinmehall · 2025-01-31T07:02:17Z

Rebased and made the requested changes. I named the new module rustix::net::addr since abstract is a reserved keyword, and I moved SocketAddrStorage into it. It could use a better name if we can come up with one.

I'll take a look at updating SocketAddrAny with #1171 RawSocketAddr.

Since it looks like you're merging breaking changes to main for 1.0, should I go ahead and remove the address type specific functions?

bind_any, bind_unix, bind_v4, bind_v6, bind_xdp in favor of bind,
connect_any, connect_unix, connect_v4, connect_v6 in favor of connect (leaving address-less connect_unspec)
sendmsg_v4, sendmsg_v6, sendmsg_unix, sendmsg_xdp, sendmsg_any in favor of sendmsg_addr (leaving address-less sendmsg)
sendto_any, sendto_v4, sendto_v6, sendto_unix, sendto_xdp in favor of sendto

sunfishcode · 2025-01-31T17:14:41Z

Rebased and made the requested changes. I named the new module rustix::net::addr since abstract is a reserved keyword, and I moved SocketAddrStorage into it. It could use a better name if we can come up with one.

I haven't thought of a better name yet, but I'll keep thinking 😄 .

I'll take a look at updating SocketAddrAny with #1171 RawSocketAddr.

👍

Since it looks like you're merging breaking changes to main for 1.0, should I go ahead and remove the address type specific functions?

* `bind_any`, `bind_unix`, `bind_v4`, `bind_v6`, `bind_xdp` in favor of `bind`,

* `connect_any`, `connect_unix`, `connect_v4`, `connect_v6` in favor of `connect` (leaving address-less `connect_unspec`)

* `sendmsg_v4`, `sendmsg_v6`, `sendmsg_unix`, `sendmsg_xdp`, `sendmsg_any` in favor of `sendmsg_addr` (leaving address-less `sendmsg`)

* `sendto_any`, `sendto_v4`, `sendto_v6`, `sendto_unix`, `sendto_xdp` in favor of `sendto`

Yes, that'd be great!

kevinmehall · 2025-02-02T01:59:08Z

Removed the address-type-specific variants of bind, connect, sendmsg, and sendto, and changed SocketAddrAny from an enum to a struct wrapping SocketAddrStorage.

sunfishcode

Cool, overall this looks great!

sunfishcode · 2025-02-02T17:41:21Z

src/net/socket_addr_any.rs

+    ///
+    /// `storage` must point to valid memory for decoding a socket
+    /// address. `len` bytes must be initialized.
+    pub unsafe fn read(src: *const SocketAddrOpaque, len: usize) -> Self {


This is pre-existing, but: it appears every user of this has a socklen_t rather than a usize, what would you think about making this argument take a socklen_t, to save all users from having to .try_into().unwrap()?

Changed the internal callers to construct it through a new SocketAddrBuf that handles this. Not sure if the new public constructor pub unsafe fn new(storage: MaybeUninit<SocketAddrStorage>, len: usize) -> Self should take usize or socklen_t -- I lean towards usize as the convention in Rust, and to avoid needing to re-export socklen_t (SocketAddrLen?)

The thing that has me leaning toward socklen_t is seeing places like this that silently cast the usize back to socklen_t. Perhaps we could make those .try_into().unwrap() to eliminate the (admittedly remote, but perhaps not impossible) chance of silently truncating an address, but it seems cleaner to keep socket lengths in the type that the OS them to us in.

And yeah, I think it would be SocketAddrLen. If you like, I can make that change.

Sounds good. The same rationale might apply to the usize closure argument in SocketAddrArg::with_sockaddr.

If you like, I can make that change.

Yes, please do.

src/net/socket_addr_any.rs

src/backend/libc/net/sockopt.rs

src/net/socket_addr_any.rs

src/net/addr.rs

src/backend/libc/net/read_sockaddr.rs

src/net/socket_addr_any.rs

src/backend/linux_raw/net/syscalls.rs

sunfishcode · 2025-02-08T20:34:17Z

Thanks! The socklen_t question is my only outstanding question now.

colinmarc · 2025-02-10T14:27:52Z

Should I rebase #1171 onto this?

Specifically, I would use &'a mut SockAddrAny instead of my RawSocketAddr, since they fulfill the same function after these changes.

sunfishcode · 2025-02-11T02:30:23Z

@colinmarc Yes, please do rebase it on top of this.

I've now added the SocketAddrLen patch, so this should be ready to land soon.

To support extensibility over address types, use sockaddr_storage and Into / TryInto conversions.

Removes: * `bind_any`, `bind_unix`, `bind_v4`, `bind_v6`, `bind_xdp` in favor of `bind`, * `connect_any`, `connect_unix`, `connect_v4`, `connect_v6` in favor of `connect` (leaving address-less `connect_unspec`) * `sendmsg_v4`, `sendmsg_v6`, `sendmsg_unix`, `sendmsg_xdp`, `sendmsg_any` in favor of `sendmsg_addr` (leaving address-less `sendmsg`) * `sendto_any`, `sendto_v4`, `sendto_v6`, `sendto_unix`, `sendto_xdp` in favor of `sendto`

…zes.

sunfishcode · 2025-02-11T03:02:33Z

Interesting. It appears this PR breaks code like bind(s, &"[::1]:0".parse().unwrap()), which no longer compiles, because Rust can't infer the type of the .parse() due to the impl SocketAddrArg. And by quite a coincidence, #132 just landed today adding tests which do just that.

I've now changed the tests to avoid doing this. It's a little unfortunate that this common idiom doesn't work, but my guess is it's ok.

sunfishcode · 2025-02-11T05:34:48Z

Thanks!

kevinmehall force-pushed the socket-addr-trait branch 4 times, most recently from f694272 to 4c1c746 Compare January 29, 2024 16:50

kevinmehall mentioned this pull request Feb 2, 2024

Hotplug events on device connect and disconnect kevinmehall/nusb#5

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niklaswimmer reviewed Apr 1, 2024

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kevinmehall force-pushed the socket-addr-trait branch from 4c1c746 to 013792a Compare April 28, 2024 18:47

kevinmehall mentioned this pull request May 24, 2024

Hotplug events kevinmehall/nusb#20

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kevinmehall marked this pull request as ready for review June 1, 2024 23:34

kevinmehall mentioned this pull request Jun 6, 2024

Add support for sockaddr_vm #1070

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ids1024 mentioned this pull request Jun 20, 2024

Add support for Netlink sockets #1079

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kevinmehall mentioned this pull request Jan 12, 2025

Question: How to bind to netlink on Linux? #1260

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sunfishcode reviewed Jan 31, 2025

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kevinmehall force-pushed the socket-addr-trait branch 3 times, most recently from f5ecd5e to 7214eea Compare January 31, 2025 06:48

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src/backend/linux_raw/net/syscalls.rs Show resolved Hide resolved

sunfishcode mentioned this pull request Feb 8, 2025

Panic on Unix-domain sockets with length 108 #1316

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colinmarc mentioned this pull request Feb 10, 2025

Add support for sendmmsg(2) on linux #1171

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kevinmehall and others added 7 commits February 10, 2025 18:40

Add SocketAddrArg trait to reduce code duplicated across address types

2554ff1

Move SocketAddrStorage to crate::net::addr

549baee

Replace SocketAddrAny enum with a safe wrapper for SocketAddrStorage

021d2d3

To support extensibility over address types, use sockaddr_storage and Into / TryInto conversions.

Add support for Netlink socket addresses

7eebda1

Introduce a SocketAddrLen type and use it for SocketAddrOpaque si…

8554139

…zes.

Fix bind(&s, &"127.0.0.1:0".parse().unwrap()) in tests.

f8a00a6

sunfishcode force-pushed the socket-addr-trait branch from 49e8170 to f8a00a6 Compare February 11, 2025 02:52

Fix compilation on Android.

cccf01d

sunfishcode added 2 commits February 10, 2025 19:05

Fix compilation on Windows.

a492260

Fix test compilation on Windows.

9a349f0

sunfishcode merged commit 5654c11 into bytecodealliance:main Feb 11, 2025
45 checks passed

niklaswimmer mentioned this pull request May 5, 2025

Support abritrary socket adresses #918

Closed

Add trait to reduce duplicated code between socket address types, implement netlink addresses #1004

Add trait to reduce duplicated code between socket address types, implement netlink addresses #1004

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