Enum ControlMessageOwned

#[non_exhaustive]
pub enum ControlMessageOwned {
    ScmRights(Vec<RawFd>),
    ScmCredentials(UnixCredentials),
    ScmTimestamp(TimeVal),
    ScmTimestampsns(Timestamps),
    ScmTimestampns(TimeSpec),
    Ipv4PacketInfo(in_pktinfo),
    Ipv6PacketInfo(in6_pktinfo),
    Ipv4OrigDstAddr(sockaddr_in),
    Ipv6OrigDstAddr(sockaddr_in6),
    UdpGroSegments(u16),
    RxqOvfl(u32),
    Ipv4RecvErr(sock_extended_err, Option<sockaddr_in>),
    Ipv6RecvErr(sock_extended_err, Option<sockaddr_in6>),
}

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>)

Received version of ControlMessage::ScmRights

ScmCredentials(UnixCredentials)

Received version of ControlMessage::ScmCredentials

ScmTimestamp(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 = SockaddrIn::from_str("127.0.0.1:0").unwrap();
bind(in_socket, &localhost).unwrap();
let address: SockaddrIn = getsockname(in_socket).unwrap();
// Get initial time
let time0 = SystemTime::now();
// Send the message
let iov = [IoSlice::new(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 mut iov = [IoSliceMut::new(&mut buffer)];
let r = recvmsg::<SockaddrIn>(in_socket, &mut 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();

ScmTimestampsns(Timestamps)

A set of nanosecond resolution timestamps

Further reading

ScmTimestampns(TimeSpec)

Nanoseconds resolution timestamp

Further reading

Ipv4PacketInfo(in_pktinfo)

Ipv6PacketInfo(in6_pktinfo)

Ipv4OrigDstAddr(sockaddr_in)

Ipv6OrigDstAddr(sockaddr_in6)

UdpGroSegments(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)

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>)

Socket error queue control messages read with the MSG_ERRQUEUE flag.

Ipv6RecvErr(sock_extended_err, 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 for ControlMessageOwned

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for ControlMessageOwned

impl StructuralPartialEq for ControlMessageOwned