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const std = @import("std");
const ControlMessage = extern struct {
const Level = enum(u32) {
socket = std.posix.SOL.SOCKET,
};
// WARNING: this kind enum might be wrong for non-linux posix systems.
const Kind = enum(u32) {
rights = 1,
credentials = 2,
};
const Header = extern struct {
length: usize,
level: Level,
kind: Kind,
};
header: Header,
payload: extern union {
fd: [255]std.posix.fd_t,
},
pub fn alignment(length: usize) usize {
return (length + @sizeOf(usize) - 1) & ~(@as(usize, @sizeOf(usize) - 1));
}
pub fn space(length: usize) usize {
return alignment(length) + alignment(@sizeOf(Header));
}
pub fn from_fds(fds: []std.posix.fd_t) @This() {
var self: @This() = undefined;
self.header.level = .socket;
self.header.kind = .rights;
self.header.length = alignment(@sizeOf(Header)) + (fds.len * @sizeOf(std.posix.fd_t));
@memcpy(self.payload.fd[0..fds.len], fds);
return self;
}
};
pub fn send_fds(socket: std.posix.socket_t, fds: []std.posix.fd_t, data: []const u8) !void {
var cmsg: ControlMessage = .from_fds(fds);
const io = std.posix.iovec {
.base = @constCast(@ptrCast(data)),
.len = data.len,
};
const msghdr = std.posix.msghdr_const {
.name = null,
.namelen = 0,
.iov = @ptrCast(&io),
.iovlen = 1,
.control = &cmsg,
.controllen = @intCast(ControlMessage.space(fds.len)),
.flags = 0,
};
_ = try std.posix.sendmsg(socket, &msghdr, 0);
}
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