dope-uring 0.37.0

Owned io_uring backend for dope
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133

use std::{mem, net, ptr, slice};

use dope_sys::io::socket::msg::source;

use crate::{Uring, sockets::controls};

// SAFETY: CMSG_SPACE only aligns these fixed native packet-info payload sizes.
const V4: usize = unsafe { libc::CMSG_SPACE(mem::size_of::<libc::in_pktinfo>() as u32) as usize };
const V6: usize = unsafe { libc::CMSG_SPACE(mem::size_of::<libc::in6_pktinfo>() as u32) as usize };

/// Precomputed source selection retained through each datagram submission.
#[derive(Clone, Copy, Debug)]
#[repr(C, align(8))]
pub struct Control {
    bytes: [u8; V6],
}

/// One source with its optional retained segmentation capability.
#[repr(transparent)]
pub struct Combined(Kind);

enum Kind {
    Source(Control),
    Segmented(Segmented),
}

/// One contiguous native GSO message followed by its selected source message.
#[repr(C)]
struct Segmented {
    gso: controls::Control,
    source: Control,
}

impl source::Source for Uring {
    type Control = Control;
    type Combined = Combined;

    fn control(source: source::Address) -> Self::Control {
        let address = source.get();
        let mut control = Control { bytes: [0; V6] };
        let header = control.bytes.as_mut_ptr().cast::<libc::cmsghdr>();
        // SAFETY: Control owns aligned, zero-initialized storage for either
        // complete native message. Both packet-info layouts have no padding.
        unsafe {
            let payload = libc::CMSG_DATA(header);
            let length = match address {
                net::SocketAddr::V4(address) => {
                    (*header).cmsg_level = libc::IPPROTO_IP;
                    (*header).cmsg_type = libc::IP_PKTINFO;
                    payload.cast::<libc::in_pktinfo>().write(libc::in_pktinfo {
                        ipi_ifindex: 0,
                        ipi_spec_dst: libc::in_addr {
                            s_addr: u32::from_ne_bytes(address.ip().octets()),
                        },
                        ipi_addr: libc::in_addr { s_addr: 0 },
                    });
                    mem::size_of::<libc::in_pktinfo>()
                }
                net::SocketAddr::V6(address) => {
                    (*header).cmsg_level = libc::IPPROTO_IPV6;
                    (*header).cmsg_type = libc::IPV6_PKTINFO;
                    payload
                        .cast::<libc::in6_pktinfo>()
                        .write(libc::in6_pktinfo {
                            ipi6_addr: libc::in6_addr {
                                s6_addr: address.ip().octets(),
                            },
                            ipi6_ifindex: address.scope_id(),
                        });
                    mem::size_of::<libc::in6_pktinfo>()
                }
            };
            (*header).cmsg_len = libc::CMSG_LEN(length as u32) as _;
        }
        control
    }

    fn compose(source: Control, gso: Option<controls::Control>) -> Combined {
        Combined(match gso {
            Some(gso) => Kind::Segmented(Segmented { gso, source }),
            None => Kind::Source(source),
        })
    }

    fn release(control: Combined) -> (Control, Option<controls::Control>) {
        match control.0 {
            Kind::Source(source) => (source, None),
            Kind::Segmented(control) => (control.source, Some(control.gso)),
        }
    }

    fn bytes(control: &mut Combined) -> &[u8] {
        match &control.0 {
            Kind::Source(source) => source.as_ref(),
            Kind::Segmented(control) => {
                let length = mem::size_of::<controls::Control>() + control.source.as_ref().len();
                // SAFETY: this repr(C) payload, excluding the enclosing enum, keeps
                // the initialized GSO message and padding immediately before the
                // source message. Its final CMSG_LEN bounds this exact owner.
                unsafe { slice::from_raw_parts(ptr::from_ref(control).cast(), length) }
            }
        }
    }
}

impl AsRef<[u8]> for Control {
    fn as_ref(&self) -> &[u8] {
        // SAFETY: the private constructor writes this aligned header's length
        // once, bounded by the initialized native message storage. A final
        // control message does not need trailing CMSG_SPACE padding.
        unsafe {
            let length = (*self.bytes.as_ptr().cast::<libc::cmsghdr>()).cmsg_len;
            slice::from_raw_parts(self.bytes.as_ptr(), length)
        }
    }
}

const _: () = {
    assert!(V4 <= V6);
    assert!(mem::size_of::<libc::in_pktinfo>() == 12);
    assert!(mem::size_of::<libc::in6_pktinfo>() == 20);
    assert!(mem::align_of::<Control>() >= mem::align_of::<libc::cmsghdr>());
    assert!(mem::align_of::<Control>() >= mem::align_of::<libc::in_pktinfo>());
    assert!(mem::align_of::<Control>() >= mem::align_of::<libc::in6_pktinfo>());
    assert!(mem::size_of::<Control>() == 40);
    assert!(mem::offset_of!(Segmented, gso) == 0);
    assert!(mem::offset_of!(Segmented, source) == mem::size_of::<controls::Control>());
    assert!(
        mem::size_of::<Segmented>()
            == mem::size_of::<controls::Control>() + mem::size_of::<Control>()
    );
    assert!(mem::align_of::<Segmented>() == mem::align_of::<Control>());
};