Enum nix::sys::socket::ControlMessageOwned

#[non_exhaustive]
pub enum ControlMessageOwned {
    ScmRights(Vec<RawFd>),
    ScmCredentials(UnixCredentials),
    ScmTimestamp(TimeVal),
    ScmTimestampns(TimeSpec),
    Ipv4PacketInfo(in_pktinfo),
    Ipv6PacketInfo(in6_pktinfo),
    UdpGroSegments(u16),
    RxqOvfl(u32),
    Ipv4RecvErr(sock_extended_err, Option<sockaddr_in>),
    Ipv6RecvErr(sock_extended_err, Option<sockaddr_in6>),
    // some variants omitted
}

A type-safe wrapper around a single control message, as used with recvmsg.

Further reading

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

ScmRights(Vec<RawFd>)

Tuple Fields

0: Vec<RawFd>

Received version of ControlMessage::ScmRights

ScmCredentials(UnixCredentials)

Tuple Fields

0: UnixCredentials

Received version of ControlMessage::ScmCredentials

ScmTimestamp(TimeVal)

Tuple Fields

0: TimeVal

A message of type SCM_TIMESTAMP, containing the time the packet was received by the kernel.

See the kernel’s explanation in “SO_TIMESTAMP” of networking/timestamping.

Examples

// Set up
let message = "Ohayō!".as_bytes();
let in_socket = socket(
    AddressFamily::Inet,
    SockType::Datagram,
    SockFlag::empty(),
    None).unwrap();
setsockopt(in_socket, sockopt::ReceiveTimestamp, &true).unwrap();
let localhost = InetAddr::new(IpAddr::new_v4(127, 0, 0, 1), 0);
bind(in_socket, &SockAddr::new_inet(localhost)).unwrap();
let address = getsockname(in_socket).unwrap();
// Get initial time
let time0 = SystemTime::now();
// Send the message
let iov = [IoVec::from_slice(message)];
let flags = MsgFlags::empty();
let l = sendmsg(in_socket, &iov, &[], flags, Some(&address)).unwrap();
assert_eq!(message.len(), l);
// Receive the message
let mut buffer = vec![0u8; message.len()];
let mut cmsgspace = cmsg_space!(TimeVal);
let iov = [IoVec::from_mut_slice(&mut buffer)];
let r = recvmsg(in_socket, &iov, Some(&mut cmsgspace), flags).unwrap();
let rtime = match r.cmsgs().next() {
    Some(ControlMessageOwned::ScmTimestamp(rtime)) => rtime,
    Some(_) => panic!("Unexpected control message"),
    None => panic!("No control message")
};
// Check the final time
let time1 = SystemTime::now();
// the packet's received timestamp should lie in-between the two system
// times, unless the system clock was adjusted in the meantime.
let rduration = Duration::new(rtime.tv_sec() as u64,
                              rtime.tv_usec() as u32 * 1000);
assert!(time0.duration_since(UNIX_EPOCH).unwrap() <= rduration);
assert!(rduration <= time1.duration_since(UNIX_EPOCH).unwrap());
// Close socket
nix::unistd::close(in_socket).unwrap();

ScmTimestampns(TimeSpec)

Tuple Fields

0: TimeSpec

Nanoseconds resolution timestamp

Further reading

Ipv4PacketInfo(in_pktinfo)

Tuple Fields

0: in_pktinfo

Ipv6PacketInfo(in6_pktinfo)

Tuple Fields

0: in6_pktinfo

UdpGroSegments(u16)

Tuple Fields

0: u16

UDP Generic Receive Offload (GRO) allows receiving multiple UDP packets from a single sender. Fixed-size payloads are following one by one in a receive buffer. This Control Message indicates the size of all smaller packets, except, maybe, the last one.

UdpGroSegment socket option should be enabled on a socket to allow receiving GRO packets.

RxqOvfl(u32)

Tuple Fields

0: u32

SO_RXQ_OVFL indicates that an unsigned 32 bit value ancilliary msg (cmsg) should be attached to recieved skbs indicating the number of packets dropped by the socket between the last recieved packet and this received packet.

RxqOvfl socket option should be enabled on a socket to allow receiving the drop counter.

Ipv4RecvErr(sock_extended_err, Option<sockaddr_in>)

Tuple Fields

0: sock_extended_err

1: Option<sockaddr_in>

Socket error queue control messages read with the MSG_ERRQUEUE flag.

Ipv6RecvErr(sock_extended_err, Option<sockaddr_in6>)

Tuple Fields

0: sock_extended_err

1: Option<sockaddr_in6>

Socket error queue control messages read with the MSG_ERRQUEUE flag.

Trait Implementations

impl Clone for ControlMessageOwned

fn clone(&self) -> ControlMessageOwned

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ControlMessageOwned

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq<ControlMessageOwned> for ControlMessageOwned

fn eq(&self, other: &ControlMessageOwned) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &ControlMessageOwned) -> bool

This method tests for !=.

impl Eq for ControlMessageOwned

impl StructuralEq for ControlMessageOwned

impl StructuralPartialEq for ControlMessageOwned