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package system
import (
"bytes"
"context"
"errors"
"fmt"
"log"
"reflect"
"strings"
"sync"
"syscall"
"hakurei.app/container"
"hakurei.app/hst"
"hakurei.app/internal/dbus"
)
// ErrDBusConfig is returned when a required [hst.BusConfig] argument is nil.
var ErrDBusConfig = errors.New("dbus config not supplied")
// MustProxyDBus calls ProxyDBus and panics if an error is returned.
func (sys *I) MustProxyDBus(
session, system *hst.BusConfig,
sessionBus, systemBus dbus.ProxyPair,
) *I {
if err := sys.ProxyDBus(session, system, sessionBus, systemBus); err != nil {
panic(err.Error())
} else {
return sys
}
}
// ProxyDBus finalises configuration ahead of time and starts xdg-dbus-proxy via
// [dbus] and terminates it on revert.
//
// This [Op] is always [Process] scoped.
func (sys *I) ProxyDBus(
session, system *hst.BusConfig,
sessionBus, systemBus dbus.ProxyPair,
) error {
d := new(dbusProxyOp)
// session bus is required as otherwise this is effectively a very expensive noop
if session == nil {
return newOpErrorMessage("dbus", ErrDBusConfig,
"attempted to create message bus proxy args without session bus config", false)
}
// system bus is optional
d.system = system != nil
d.out = &linePrefixWriter{println: log.Println, prefix: "(dbus) ", buf: new(strings.Builder)}
if final, err := sys.dbusFinalise(sessionBus, systemBus, session, system); err != nil {
if errors.Is(err, syscall.EINVAL) {
return newOpErrorMessage("dbus", err,
"message bus proxy configuration contains NUL byte", false)
}
return newOpErrorMessage("dbus", err,
fmt.Sprintf("cannot finalise message bus proxy: %v", err), false)
} else {
if sys.msg.IsVerbose() {
sys.msg.Verbose("session bus proxy:", dbus.Args(session, sessionBus))
if system != nil {
sys.msg.Verbose("system bus proxy:", dbus.Args(system, systemBus))
}
// this calls the argsWt String method
sys.msg.Verbose("message bus proxy final args:", final.WriterTo)
}
d.final = final
}
sys.ops = append(sys.ops, d)
return nil
}
// dbusProxyOp implements [I.ProxyDBus].
type dbusProxyOp struct {
proxy *dbus.Proxy // populated during apply
final *dbus.Final
out *linePrefixWriter
// whether system bus proxy is enabled
system bool
}
func (d *dbusProxyOp) Type() hst.Enablements { return Process }
func (d *dbusProxyOp) apply(sys *I) error {
sys.msg.Verbosef("session bus proxy on %q for upstream %q", d.final.Session[1], d.final.Session[0])
if d.system {
sys.msg.Verbosef("system bus proxy on %q for upstream %q", d.final.System[1], d.final.System[0])
}
d.proxy = dbus.New(sys.ctx, sys.msg, d.final, d.out)
if err := sys.dbusProxyStart(d.proxy); err != nil {
d.out.Dump()
return newOpErrorMessage("dbus", err,
fmt.Sprintf("cannot start message bus proxy: %v", err), false)
}
sys.msg.Verbose("starting message bus proxy", d.proxy)
return nil
}
func (d *dbusProxyOp) revert(sys *I, _ *Criteria) error {
// criteria ignored here since dbus is always process-scoped
sys.msg.Verbose("terminating message bus proxy")
sys.dbusProxyClose(d.proxy)
exitMessage := "message bus proxy exit"
defer func() { sys.msg.Verbose(exitMessage) }()
if d.out != nil {
d.out.Dump()
}
err := sys.dbusProxyWait(d.proxy)
if errors.Is(err, context.Canceled) {
exitMessage = "message bus proxy canceled upstream"
err = nil
}
return newOpErrorMessage("dbus", err,
fmt.Sprintf("message bus proxy error: %v", err), true)
}
func (d *dbusProxyOp) Is(o Op) bool {
target, ok := o.(*dbusProxyOp)
return ok && d != nil && target != nil &&
d.system == target.system &&
d.final != nil && target.final != nil &&
d.final.Session == target.final.Session &&
d.final.System == target.final.System &&
dbus.EqualAddrEntries(d.final.SessionUpstream, target.final.SessionUpstream) &&
dbus.EqualAddrEntries(d.final.SystemUpstream, target.final.SystemUpstream) &&
reflect.DeepEqual(d.final.WriterTo, target.final.WriterTo)
}
func (d *dbusProxyOp) Path() string { return container.Nonexistent }
func (d *dbusProxyOp) String() string { return d.proxy.String() }
const (
// lpwSizeThreshold is the threshold of bytes written to linePrefixWriter which,
// if reached or exceeded, causes linePrefixWriter to drop all future writes.
lpwSizeThreshold = 1 << 24
)
// linePrefixWriter calls println with a prefix for every line written.
type linePrefixWriter struct {
prefix string
println func(v ...any)
n int
msg []string
buf *strings.Builder
mu sync.RWMutex
}
func (s *linePrefixWriter) Write(p []byte) (n int, err error) {
s.mu.Lock()
defer s.mu.Unlock()
return s.write(p, 0)
}
func (s *linePrefixWriter) write(p []byte, a int) (int, error) {
if s.n >= lpwSizeThreshold {
if len(p) == 0 {
return a, nil
}
return a, syscall.ENOMEM
}
if i := bytes.IndexByte(p, '\n'); i == -1 {
n, _ := s.buf.Write(p)
s.n += n
return a + n, nil
} else {
n, _ := s.buf.Write(p[:i])
s.n += n + 1
v := s.buf.String()
if strings.HasPrefix(v, "init: ") {
s.n -= len(v) + 1
// pass through container init messages
s.println(s.prefix + v)
} else {
s.msg = append(s.msg, v)
}
s.buf.Reset()
return s.write(p[i+1:], a+n+1)
}
}
func (s *linePrefixWriter) Dump() {
s.mu.RLock()
for _, m := range s.msg {
s.println(s.prefix + m)
}
if s.buf != nil && s.buf.Len() != 0 {
s.println("*" + s.prefix + s.buf.String())
}
if s.n >= lpwSizeThreshold {
s.println("+" + s.prefix + "write threshold reached, output may be incomplete")
}
s.mu.RUnlock()
}
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