programs: ProgramFd is owned

`ProgramData::fd` is now owned. This means that `ProgramData` now closes
the file descriptor on drop. In the future we might consider making
`ProgramFd` hold a `BorrowedFd` but this requires API design work due to
overlapping borrows.

Updates #612.

aya/src/maps/array/program_array.rs

@@ -2,7 +2,7 @@
 
 use std::{
     borrow::{Borrow, BorrowMut},
-    os::fd::{AsRawFd, RawFd},
+    os::fd::{AsFd as _, AsRawFd as _, RawFd},
 };
 
 use crate::{
@@ -77,7 +77,8 @@ impl<T: BorrowMut<MapData>> ProgramArray<T> {
         let data = self.inner.borrow_mut();
         check_bounds(data, index)?;
         let fd = data.fd_or_err()?;
-        let prog_fd = program.as_raw_fd();
+        let prog_fd = program.as_fd();
+        let prog_fd = prog_fd.as_raw_fd();
 
         bpf_map_update_elem(fd, Some(&index), &prog_fd, flags).map_err(|(_, io_error)| {
             SyscallError {

aya/src/maps/perf/async_perf_event_array.rs

@@ -1,7 +1,7 @@
 use bytes::BytesMut;
 use std::{
     borrow::{Borrow, BorrowMut},
-    os::fd::{AsRawFd, RawFd},
+    os::fd::{AsRawFd as _, RawFd},
 };
 
 // See https://doc.rust-lang.org/cargo/reference/features.html#mutually-exclusive-features.

aya/src/programs/cgroup_device.rs

@@ -62,6 +62,7 @@ impl CgroupDevice {
     /// The returned value can be used to detach, see [CgroupDevice::detach]
     pub fn attach<T: AsRawFd>(&mut self, cgroup: T) -> Result<CgroupDeviceLinkId, ProgramError> {
         let prog_fd = self.data.fd_or_err()?;
+        let prog_fd = prog_fd.as_raw_fd();
         let cgroup_fd = cgroup.as_raw_fd();
 
         if KernelVersion::current().unwrap() >= KernelVersion::new(5, 7, 0) {

aya/src/programs/cgroup_skb.rs

@@ -89,6 +89,7 @@ impl CgroupSkb {
         attach_type: CgroupSkbAttachType,
     ) -> Result<CgroupSkbLinkId, ProgramError> {
         let prog_fd = self.data.fd_or_err()?;
+        let prog_fd = prog_fd.as_raw_fd();
         let cgroup_fd = cgroup.as_raw_fd();
 
         let attach_type = match attach_type {

aya/src/programs/cgroup_sock.rs

@@ -68,6 +68,7 @@ impl CgroupSock {
     /// The returned value can be used to detach, see [CgroupSock::detach].
     pub fn attach<T: AsRawFd>(&mut self, cgroup: T) -> Result<CgroupSockLinkId, ProgramError> {
         let prog_fd = self.data.fd_or_err()?;
+        let prog_fd = prog_fd.as_raw_fd();
         let cgroup_fd = cgroup.as_raw_fd();
         let attach_type = self.data.expected_attach_type.unwrap();
         if KernelVersion::current().unwrap() >= KernelVersion::new(5, 7, 0) {

aya/src/programs/cgroup_sock_addr.rs

@@ -69,6 +69,7 @@ impl CgroupSockAddr {
     /// The returned value can be used to detach, see [CgroupSockAddr::detach].
     pub fn attach<T: AsRawFd>(&mut self, cgroup: T) -> Result<CgroupSockAddrLinkId, ProgramError> {
         let prog_fd = self.data.fd_or_err()?;
+        let prog_fd = prog_fd.as_raw_fd();
         let cgroup_fd = cgroup.as_raw_fd();
         let attach_type = self.data.expected_attach_type.unwrap();
         if KernelVersion::current().unwrap() >= KernelVersion::new(5, 7, 0) {

aya/src/programs/cgroup_sockopt.rs

@@ -66,6 +66,7 @@ impl CgroupSockopt {
     /// The returned value can be used to detach, see [CgroupSockopt::detach].
     pub fn attach<T: AsRawFd>(&mut self, cgroup: T) -> Result<CgroupSockoptLinkId, ProgramError> {
         let prog_fd = self.data.fd_or_err()?;
+        let prog_fd = prog_fd.as_raw_fd();
         let cgroup_fd = cgroup.as_raw_fd();
         let attach_type = self.data.expected_attach_type.unwrap();
         if KernelVersion::current().unwrap() >= KernelVersion::new(5, 7, 0) {

aya/src/programs/cgroup_sysctl.rs

@@ -61,6 +61,7 @@ impl CgroupSysctl {
     /// The returned value can be used to detach, see [CgroupSysctl::detach].
     pub fn attach<T: AsRawFd>(&mut self, cgroup: T) -> Result<CgroupSysctlLinkId, ProgramError> {
         let prog_fd = self.data.fd_or_err()?;
+        let prog_fd = prog_fd.as_raw_fd();
         let cgroup_fd = cgroup.as_raw_fd();
 
         if KernelVersion::current().unwrap() >= KernelVersion::new(5, 7, 0) {

aya/src/programs/extension.rs

@@ -1,5 +1,5 @@
 //! Extension programs.
-use std::os::fd::{AsFd as _, AsRawFd as _, OwnedFd};
+use std::os::fd::{AsFd as _, AsRawFd as _, BorrowedFd, OwnedFd};
 use thiserror::Error;
 
 use object::Endianness;
@@ -69,11 +69,11 @@ impl Extension {
     /// There are no restrictions on what functions may be replaced, so you could replace
     /// the main entry point of your program with an extension.
     pub fn load(&mut self, program: ProgramFd, func_name: &str) -> Result<(), ProgramError> {
-        let target_prog_fd = program.as_raw_fd();
+        let target_prog_fd = program.as_fd();
         let (btf_fd, btf_id) = get_btf_info(target_prog_fd, func_name)?;
 
         self.data.attach_btf_obj_fd = Some(btf_fd);
-        self.data.attach_prog_fd = Some(target_prog_fd);
+        self.data.attach_prog_fd = Some(target_prog_fd.as_raw_fd());
         self.data.attach_btf_id = Some(btf_id);
         load_program(BPF_PROG_TYPE_EXT, &mut self.data)
     }
@@ -87,6 +87,7 @@ impl Extension {
     /// original function, see [Extension::detach].
     pub fn attach(&mut self) -> Result<ExtensionLinkId, ProgramError> {
         let prog_fd = self.data.fd_or_err()?;
+        let prog_fd = prog_fd.as_raw_fd();
         let target_fd = self.data.attach_prog_fd.ok_or(ProgramError::NotLoaded)?;
         let btf_id = self.data.attach_btf_id.ok_or(ProgramError::NotLoaded)?;
         // the attach type must be set as 0, which is bpf_attach_type::BPF_CGROUP_INET_INGRESS
@@ -116,15 +117,22 @@ impl Extension {
         program: ProgramFd,
         func_name: &str,
     ) -> Result<ExtensionLinkId, ProgramError> {
-        let target_fd = program.as_raw_fd();
+        let target_fd = program.as_fd();
         let (_, btf_id) = get_btf_info(target_fd, func_name)?;
         let prog_fd = self.data.fd_or_err()?;
+        let prog_fd = prog_fd.as_raw_fd();
         // the attach type must be set as 0, which is bpf_attach_type::BPF_CGROUP_INET_INGRESS
-        let link_fd = bpf_link_create(prog_fd, target_fd, BPF_CGROUP_INET_INGRESS, Some(btf_id), 0)
-            .map_err(|(_, io_error)| SyscallError {
-                call: "bpf_link_create",
-                io_error,
-            })?;
+        let link_fd = bpf_link_create(
+            prog_fd,
+            target_fd.as_raw_fd(),
+            BPF_CGROUP_INET_INGRESS,
+            Some(btf_id),
+            0,
+        )
+        .map_err(|(_, io_error)| SyscallError {
+            call: "bpf_link_create",
+            io_error,
+        })?;
         self.data
             .links
             .insert(ExtensionLink::new(FdLink::new(link_fd)))
@@ -149,7 +157,7 @@ impl Extension {
 
 /// Retrieves the FD of the BTF object for the provided `prog_fd` and the BTF ID of the function
 /// with the name `func_name` within that BTF object.
-fn get_btf_info(prog_fd: i32, func_name: &str) -> Result<(OwnedFd, u32), ProgramError> {
+fn get_btf_info(prog_fd: BorrowedFd<'_>, func_name: &str) -> Result<(OwnedFd, u32), ProgramError> {
     // retrieve program information
     let info = sys::bpf_prog_get_info_by_fd(prog_fd, &mut [])?;
 

aya/src/programs/lirc_mode2.rs

@@ -1,5 +1,5 @@
 //! Lirc programs.
-use std::os::fd::{AsRawFd, IntoRawFd as _, RawFd};
+use std::os::fd::{AsRawFd, BorrowedFd, IntoRawFd as _, RawFd};
 
 use crate::{
     generated::{bpf_attach_type::BPF_LIRC_MODE2, bpf_prog_type::BPF_PROG_TYPE_LIRC_MODE2},
@@ -65,6 +65,7 @@ impl LircMode2 {
     /// The returned value can be used to detach, see [LircMode2::detach].
     pub fn attach<T: AsRawFd>(&mut self, lircdev: T) -> Result<LircLinkId, ProgramError> {
         let prog_fd = self.data.fd_or_err()?;
+        let prog_fd = prog_fd.as_raw_fd();
         let lircdev_fd = lircdev.as_raw_fd();
 
         bpf_prog_attach(prog_fd, lircdev_fd, BPF_LIRC_MODE2).map_err(|(_, io_error)| {
@@ -131,7 +132,9 @@ impl LircLink {
 
     /// Get ProgramInfo from this link
     pub fn info(&self) -> Result<ProgramInfo, ProgramError> {
-        bpf_prog_get_info_by_fd(self.prog_fd, &mut [])
+        // SAFETY: TODO(https://github.com/aya-rs/aya/issues/612): make this safe by not holding `RawFd`s.
+        let prog_fd = unsafe { BorrowedFd::borrow_raw(self.prog_fd) };
+        bpf_prog_get_info_by_fd(prog_fd, &mut [])
             .map(ProgramInfo)
             .map_err(Into::into)
     }

aya/src/programs/mod.rs

@@ -68,7 +68,7 @@ use libc::ENOSPC;
 use std::{
     ffi::CString,
     io,
-    os::fd::{AsFd, AsRawFd, IntoRawFd as _, OwnedFd, RawFd},
+    os::fd::{AsFd, AsRawFd, BorrowedFd, IntoRawFd as _, OwnedFd, RawFd},
     path::{Path, PathBuf},
     sync::Arc,
 };
@@ -211,12 +211,12 @@ pub enum ProgramError {
 }
 
 /// A [`Program`] file descriptor.
-#[derive(Copy, Clone)]
-pub struct ProgramFd(RawFd);
+pub struct ProgramFd(OwnedFd);
 
-impl AsRawFd for ProgramFd {
-    fn as_raw_fd(&self) -> RawFd {
-        self.0
+impl AsFd for ProgramFd {
+    fn as_fd(&self) -> BorrowedFd<'_> {
+        let Self(fd) = self;
+        fd.as_fd()
     }
 }
 
@@ -369,7 +369,7 @@ impl Program {
     ///
     /// Can be used to add a program to a [`crate::maps::ProgramArray`] or attach an [`Extension`] program.
     /// Can be converted to [`RawFd`] using [`AsRawFd`].
-    pub fn fd(&self) -> Option<ProgramFd> {
+    pub fn fd(&self) -> Result<ProgramFd, ProgramError> {
         match self {
             Program::KProbe(p) => p.fd(),
             Program::UProbe(p) => p.fd(),
@@ -403,7 +403,7 @@ impl Program {
 pub(crate) struct ProgramData<T: Link> {
     pub(crate) name: Option<String>,
     pub(crate) obj: Option<(obj::Program, obj::Function)>,
-    pub(crate) fd: Option<RawFd>,
+    pub(crate) fd: Option<OwnedFd>,
     pub(crate) links: LinkMap<T>,
     pub(crate) expected_attach_type: Option<bpf_attach_type>,
     pub(crate) attach_btf_obj_fd: Option<OwnedFd>,
@@ -457,7 +457,7 @@ impl<T: Link> ProgramData<T> {
         Ok(ProgramData {
             name,
             obj: None,
-            fd: Some(fd.into_raw_fd()),
+            fd: Some(fd),
             links: LinkMap::new(),
             expected_attach_type: None,
             attach_btf_obj_fd,
@@ -481,15 +481,18 @@ impl<T: Link> ProgramData<T> {
             io_error,
         })?;
 
-        let info = bpf_prog_get_info_by_fd(fd.as_raw_fd(), &mut [])?;
+        let info = bpf_prog_get_info_by_fd(fd.as_fd(), &mut [])?;
         let name = ProgramInfo(info).name_as_str().map(|s| s.to_string());
         ProgramData::from_bpf_prog_info(name, fd, path.as_ref(), info, verifier_log_level)
     }
 }
 
 impl<T: Link> ProgramData<T> {
-    fn fd_or_err(&self) -> Result<RawFd, ProgramError> {
-        self.fd.ok_or(ProgramError::NotLoaded)
+    fn fd_or_err(&self) -> Result<BorrowedFd<'_>, ProgramError> {
+        self.fd
+            .as_ref()
+            .map(AsFd::as_fd)
+            .ok_or(ProgramError::NotLoaded)
     }
 
     pub(crate) fn take_link(&mut self, link_id: T::Id) -> Result<T, ProgramError> {
@@ -499,15 +502,14 @@ impl<T: Link> ProgramData<T> {
 
 fn unload_program<T: Link>(data: &mut ProgramData<T>) -> Result<(), ProgramError> {
     data.links.remove_all()?;
-    let fd = data.fd.take().ok_or(ProgramError::NotLoaded)?;
-    unsafe {
-        libc::close(fd);
-    }
-    Ok(())
+    data.fd
+        .take()
+        .ok_or(ProgramError::NotLoaded)
+        .map(|_: OwnedFd| ())
 }
 
 fn pin_program<T: Link, P: AsRef<Path>>(data: &ProgramData<T>, path: P) -> Result<(), PinError> {
-    let fd = data.fd.ok_or(PinError::NoFd {
+    let fd = data.fd.as_ref().ok_or(PinError::NoFd {
         name: data
             .name
             .as_deref()
@@ -519,7 +521,7 @@ fn pin_program<T: Link, P: AsRef<Path>>(data: &ProgramData<T>, path: P) -> Resul
             error: e.to_string(),
         }
     })?;
-    bpf_pin_object(fd, &path_string).map_err(|(_, io_error)| SyscallError {
+    bpf_pin_object(fd.as_raw_fd(), &path_string).map_err(|(_, io_error)| SyscallError {
         call: "BPF_OBJ_PIN",
         io_error,
     })?;
@@ -613,7 +615,7 @@ fn load_program<T: Link>(
 
     match ret {
         Ok(prog_fd) => {
-            *fd = Some(prog_fd as RawFd);
+            *fd = Some(prog_fd);
             Ok(())
         }
         Err((_, io_error)) => Err(ProgramError::LoadError {
@@ -718,8 +720,12 @@ macro_rules! impl_fd {
         $(
             impl $struct_name {
                 /// Returns the file descriptor of this Program.
-                pub fn fd(&self) -> Option<ProgramFd> {
-                    self.data.fd.map(|fd| ProgramFd(fd))
+                pub fn fd(&self) -> Result<ProgramFd, ProgramError> {
+                    self.data.fd
+                        .as_ref()
+                        .ok_or(ProgramError::NotLoaded)
+                        .and_then(|fd| fd.try_clone().map_err(Into::into))
+                        .map(ProgramFd)
                 }
             }
         )+
@@ -948,7 +954,7 @@ impl ProgramInfo {
             io_error,
         })?;
 
-        let info = bpf_prog_get_info_by_fd(fd.as_raw_fd(), &mut [])?;
+        let info = bpf_prog_get_info_by_fd(fd.as_fd(), &mut [])?;
         Ok(ProgramInfo(info))
     }
 }
@@ -984,7 +990,7 @@ pub fn loaded_programs() -> impl Iterator<Item = Result<ProgramInfo, ProgramErro
         })
         .map(|fd| {
             let fd = fd?;
-            bpf_prog_get_info_by_fd(fd.as_raw_fd(), &mut [])
+            bpf_prog_get_info_by_fd(fd.as_fd(), &mut [])
         })
         .map(|result| result.map(ProgramInfo).map_err(Into::into))
 }

aya/src/programs/perf_event.rs

@@ -1,6 +1,6 @@
 //! Perf event programs.
 
-use std::os::fd::AsFd as _;
+use std::os::fd::{AsFd as _, AsRawFd as _};
 
 pub use crate::generated::{
     perf_hw_cache_id, perf_hw_cache_op_id, perf_hw_cache_op_result_id, perf_hw_id, perf_sw_ids,
@@ -146,6 +146,8 @@ impl PerfEvent {
         scope: PerfEventScope,
         sample_policy: SamplePolicy,
     ) -> Result<PerfEventLinkId, ProgramError> {
+        let prog_fd = self.data.fd_or_err()?;
+        let prog_fd = prog_fd.as_raw_fd();
         let (sample_period, sample_frequency) = match sample_policy {
             SamplePolicy::Period(period) => (period, None),
             SamplePolicy::Frequency(frequency) => (0, Some(frequency)),
@@ -172,7 +174,7 @@ impl PerfEvent {
             io_error,
         })?;
 
-        let link = perf_attach(self.data.fd_or_err()?, fd)?;
+        let link = perf_attach(prog_fd, fd)?;
         self.data.links.insert(PerfEventLink::new(link))
     }
 

aya/src/programs/probe.rs

@@ -3,7 +3,7 @@ use libc::pid_t;
 use std::{
     fs::{self, OpenOptions},
     io::{self, Write},
-    os::fd::OwnedFd,
+    os::fd::{AsRawFd as _, OwnedFd},
     path::Path,
     process,
     sync::atomic::{AtomicUsize, Ordering},
@@ -57,19 +57,16 @@ pub(crate) fn attach<T: Link + From<PerfLinkInner>>(
 ) -> Result<T::Id, ProgramError> {
     // https://github.com/torvalds/linux/commit/e12f03d7031a977356e3d7b75a68c2185ff8d155
     // Use debugfs to create probe
-    if KernelVersion::current().unwrap() < KernelVersion::new(4, 17, 0) {
+    let prog_fd = program_data.fd_or_err()?;
+    let prog_fd = prog_fd.as_raw_fd();
+    let link = if KernelVersion::current().unwrap() < KernelVersion::new(4, 17, 0) {
         let (fd, event_alias) = create_as_trace_point(kind, fn_name, offset, pid)?;
-        let link = T::from(perf_attach_debugfs(
-            program_data.fd_or_err()?,
-            fd,
-            ProbeEvent { kind, event_alias },
-        )?);
-        return program_data.links.insert(link);
-    };
-
-    let fd = create_as_probe(kind, fn_name, offset, pid)?;
-    let link = T::from(perf_attach(program_data.fd_or_err()?, fd)?);
-    program_data.links.insert(link)
+        perf_attach_debugfs(prog_fd, fd, ProbeEvent { kind, event_alias })
+    } else {
+        let fd = create_as_probe(kind, fn_name, offset, pid)?;
+        perf_attach(prog_fd, fd)
+    }?;
+    program_data.links.insert(T::from(link))
 }
 
 pub(crate) fn detach_debug_fs(event: ProbeEvent) -> Result<(), ProgramError> {

aya/src/programs/sk_lookup.rs

@@ -62,6 +62,7 @@ impl SkLookup {
     /// The returned value can be used to detach, see [SkLookup::detach].
     pub fn attach<T: AsRawFd>(&mut self, netns: T) -> Result<SkLookupLinkId, ProgramError> {
         let prog_fd = self.data.fd_or_err()?;
+        let prog_fd = prog_fd.as_raw_fd();
         let netns_fd = netns.as_raw_fd();
 
         let link_fd = bpf_link_create(prog_fd, netns_fd, BPF_SK_LOOKUP, None, 0).map_err(