| 1 | //! Raw Linux Bluetooth sockets through libc. This is the only module in budctl allowed to use |
| 2 | //! `unsafe`; everything above it gets safe functions that return `io::Result`. |
| 3 | //! Constants and struct layouts: docs/protocol/transport.md#sockets. |
| 4 | #![allow(unsafe_code)] |
| 5 | |
| 6 | use std::io; |
| 7 | use std::mem::size_of; |
| 8 | use std::os::fd::{AsRawFd, FromRawFd, OwnedFd}; |
| 9 | use std::time::{Duration, Instant}; |
| 10 | |
| 11 | use crate::bt::BdAddr; |
| 12 | |
| 13 | /// Spec: transport.md#sockets |
| 14 | const BTPROTO_L2CAP: libc::c_int = 0; |
| 15 | /// Spec: transport.md#sockets |
| 16 | const BTPROTO_RFCOMM: libc::c_int = 3; |
| 17 | |
| 18 | /// `struct sockaddr_rc`. Spec: transport.md#sockets |
| 19 | #[repr(C)] |
| 20 | struct SockaddrRc { |
| 21 | family: libc::sa_family_t, |
| 22 | bdaddr: [u8; 6], |
| 23 | channel: u8, |
| 24 | } |
| 25 | |
| 26 | /// `struct sockaddr_l2`. Spec: transport.md#sockets |
| 27 | #[repr(C)] |
| 28 | struct SockaddrL2 { |
| 29 | family: libc::sa_family_t, |
| 30 | psm: u16, |
| 31 | bdaddr: [u8; 6], |
| 32 | cid: u16, |
| 33 | bdaddr_type: u8, |
| 34 | } |
| 35 | |
| 36 | pub(crate) enum Target { |
| 37 | /// A stream socket to an RFCOMM channel. |
| 38 | Rfcomm { channel: u8 }, |
| 39 | /// A packet socket to an L2CAP PSM (SDP is PSM 1). |
| 40 | L2cap { psm: u16 }, |
| 41 | } |
| 42 | |
| 43 | /// Open a Bluetooth socket and connect it. `timeout` bounds the connect and every later send. |
| 44 | pub(crate) fn connect(address: BdAddr, target: Target, timeout: Duration) -> io::Result<OwnedFd> { |
| 45 | let (kind, protocol) = match target { |
| 46 | Target::Rfcomm { .. } => (libc::SOCK_STREAM, BTPROTO_RFCOMM), |
| 47 | Target::L2cap { .. } => (libc::SOCK_SEQPACKET, BTPROTO_L2CAP), |
| 48 | }; |
| 49 | // SAFETY: a plain syscall with constant arguments; the result is checked below. |
| 50 | let raw = unsafe { libc::socket(libc::AF_BLUETOOTH, kind | libc::SOCK_CLOEXEC, protocol) }; |
| 51 | if raw < 0 { |
| 52 | return Err(io::Error::last_os_error()); |
| 53 | } |
| 54 | // SAFETY: `raw` is a fresh, valid descriptor that nothing else owns. |
| 55 | let fd = unsafe { OwnedFd::from_raw_fd(raw) }; |
| 56 | |
| 57 | // A blocking connect waits at most SO_SNDTIMEO, then fails with EINPROGRESS. |
| 58 | // Spec: transport.md#connect-timeout |
| 59 | set_timeout(&fd, libc::SO_SNDTIMEO, timeout)?; |
| 60 | |
| 61 | let family = libc::sa_family_t::try_from(libc::AF_BLUETOOTH).map_err(io::Error::other)?; |
| 62 | let bdaddr = address.kernel_order(); |
| 63 | match target { |
| 64 | Target::Rfcomm { channel } => connect_to( |
| 65 | &fd, |
| 66 | &SockaddrRc { |
| 67 | family, |
| 68 | bdaddr, |
| 69 | channel, |
| 70 | }, |
| 71 | )?, |
| 72 | Target::L2cap { psm } => connect_to( |
| 73 | &fd, |
| 74 | &SockaddrL2 { |
| 75 | family, |
| 76 | psm: psm.to_le(), |
| 77 | bdaddr, |
| 78 | cid: 0, |
| 79 | bdaddr_type: 0, |
| 80 | }, |
| 81 | )?, |
| 82 | } |
| 83 | Ok(fd) |
| 84 | } |
| 85 | |
| 86 | fn connect_to<T>(fd: &OwnedFd, address: &T) -> io::Result<()> { |
| 87 | let len = libc::socklen_t::try_from(size_of::<T>()).map_err(io::Error::other)?; |
| 88 | // SAFETY: `address` points to a live, initialised #[repr(C)] sockaddr of exactly `len` bytes. |
| 89 | let rc = unsafe { |
| 90 | libc::connect( |
| 91 | fd.as_raw_fd(), |
| 92 | std::ptr::from_ref(address).cast::<libc::sockaddr>(), |
| 93 | len, |
| 94 | ) |
| 95 | }; |
| 96 | if rc < 0 { |
| 97 | Err(io::Error::last_os_error()) |
| 98 | } else { |
| 99 | Ok(()) |
| 100 | } |
| 101 | } |
| 102 | |
| 103 | fn set_timeout(fd: &OwnedFd, option: libc::c_int, timeout: Duration) -> io::Result<()> { |
| 104 | let tv = libc::timeval { |
| 105 | tv_sec: libc::time_t::try_from(timeout.as_secs()).map_err(io::Error::other)?, |
| 106 | tv_usec: libc::suseconds_t::from(timeout.subsec_micros()), |
| 107 | }; |
| 108 | let len = libc::socklen_t::try_from(size_of::<libc::timeval>()).map_err(io::Error::other)?; |
| 109 | // SAFETY: `tv` lives for the duration of the call and `len` is its size. |
| 110 | let rc = unsafe { |
| 111 | libc::setsockopt( |
| 112 | fd.as_raw_fd(), |
| 113 | libc::SOL_SOCKET, |
| 114 | option, |
| 115 | std::ptr::from_ref(&tv).cast::<libc::c_void>(), |
| 116 | len, |
| 117 | ) |
| 118 | }; |
| 119 | if rc < 0 { |
| 120 | Err(io::Error::last_os_error()) |
| 121 | } else { |
| 122 | Ok(()) |
| 123 | } |
| 124 | } |
| 125 | |
| 126 | /// Wait until the socket has something to read (data, end of stream or an error). |
| 127 | /// `Ok(false)` means `deadline` passed first. |
| 128 | pub(crate) fn wait_readable(fd: &OwnedFd, deadline: Instant) -> io::Result<bool> { |
| 129 | loop { |
| 130 | let left = deadline.saturating_duration_since(Instant::now()); |
| 131 | let ms = libc::c_int::try_from(left.as_millis()).unwrap_or(libc::c_int::MAX); |
| 132 | let mut poll = libc::pollfd { |
| 133 | fd: fd.as_raw_fd(), |
| 134 | events: libc::POLLIN, |
| 135 | revents: 0, |
| 136 | }; |
| 137 | // SAFETY: `poll` is one valid pollfd that lives for the duration of the call. |
| 138 | let rc = unsafe { libc::poll(&mut poll, 1, ms) }; |
| 139 | if rc >= 0 { |
| 140 | return Ok(rc > 0); |
| 141 | } |
| 142 | let error = io::Error::last_os_error(); |
| 143 | if error.kind() != io::ErrorKind::Interrupted { |
| 144 | return Err(error); |
| 145 | } |
| 146 | } |
| 147 | } |
| 148 | |
| 149 | /// One `recv()`. Returns 0 when the other side closed the connection. |
| 150 | pub(crate) fn read(fd: &OwnedFd, buffer: &mut [u8]) -> io::Result<usize> { |
| 151 | loop { |
| 152 | // SAFETY: `buffer` is valid for writes of `buffer.len()` bytes. |
| 153 | let n = unsafe { libc::recv(fd.as_raw_fd(), buffer.as_mut_ptr().cast(), buffer.len(), 0) }; |
| 154 | if let Ok(n) = usize::try_from(n) { |
| 155 | return Ok(n); |
| 156 | } |
| 157 | let error = io::Error::last_os_error(); |
| 158 | if error.kind() != io::ErrorKind::Interrupted { |
| 159 | return Err(error); |
| 160 | } |
| 161 | } |
| 162 | } |
| 163 | |
| 164 | /// Send every byte. `MSG_NOSIGNAL` turns a dead link into `EPIPE` instead of `SIGPIPE`. |
| 165 | pub(crate) fn write_all(fd: &OwnedFd, bytes: &[u8]) -> io::Result<()> { |
| 166 | let mut rest = bytes; |
| 167 | while !rest.is_empty() { |
| 168 | // SAFETY: `rest` is valid for reads of `rest.len()` bytes. |
| 169 | let n = unsafe { libc::send(fd.as_raw_fd(), rest.as_ptr().cast(), rest.len(), libc::MSG_NOSIGNAL) }; |
| 170 | match usize::try_from(n) { |
| 171 | Ok(0) => return Err(io::ErrorKind::WriteZero.into()), |
| 172 | Ok(sent) => rest = rest.get(sent..).unwrap_or_default(), |
| 173 | Err(_) => { |
| 174 | let error = io::Error::last_os_error(); |
| 175 | if error.kind() != io::ErrorKind::Interrupted { |
| 176 | return Err(error); |
| 177 | } |
| 178 | } |
| 179 | } |
| 180 | } |
| 181 | Ok(()) |
| 182 | } |
| 183 | |
| 184 | #[cfg(test)] |
| 185 | mod tests { |
| 186 | use super::*; |
| 187 | |
| 188 | #[test] |
| 189 | fn sockaddr_layouts_match_the_kernel() { |
| 190 | // Spec: transport.md#sockets |
| 191 | assert_eq!(size_of::<SockaddrRc>(), 10); |
| 192 | assert_eq!(size_of::<SockaddrL2>(), 14); |
| 193 | assert_eq!(std::mem::offset_of!(SockaddrRc, channel), 8); |
| 194 | assert_eq!(std::mem::offset_of!(SockaddrL2, cid), 10); |
| 195 | assert_eq!(std::mem::offset_of!(SockaddrL2, bdaddr_type), 12); |
| 196 | } |
| 197 | } |