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dbus: make SetSubStateSubscriber safer #249

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Merged
lucab merged 1 commit into from
Feb 2, 2018
Merged

dbus: make SetSubStateSubscriber safer #249

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58 changes: 49 additions & 9 deletions dbus/subscription.go
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ package dbus

import (
"errors"
"log"
"time"

"github.com/godbus/dbus"
Expand Down Expand Up @@ -176,6 +177,16 @@ type SubStateUpdate struct {
// is full, it attempts to write an error to errCh; if errCh is full, the error
// passes silently.
func (c *Conn) SetSubStateSubscriber(updateCh chan<- *SubStateUpdate, errCh chan<- error) {
if c == nil {
msg := "nil receiver"
select {
case errCh <- errors.New(msg):
default:
log.Printf("full error channel while reporting: %s\n", msg)
}
return
}

c.subStateSubscriber.Lock()
defer c.subStateSubscriber.Unlock()
c.subStateSubscriber.updateCh = updateCh
Expand All @@ -190,7 +201,9 @@ func (c *Conn) sendSubStateUpdate(unitPath dbus.ObjectPath) {
return
}

if c.shouldIgnore(unitPath) {
isIgnored := c.shouldIgnore(unitPath)
defer c.cleanIgnore()
if isIgnored {
return
}

Expand All @@ -199,23 +212,45 @@ func (c *Conn) sendSubStateUpdate(unitPath dbus.ObjectPath) {
select {
case c.subStateSubscriber.errCh <- err:
default:
log.Printf("full error channel while reporting: %s\n", err)
}
return
}
defer c.updateIgnore(unitPath, info)

name := info["Id"].(string)
substate := info["SubState"].(string)
name, ok := info["Id"].(string)
if !ok {
msg := "failed to cast info.Id"
select {
case c.subStateSubscriber.errCh <- errors.New(msg):
default:
log.Printf("full error channel while reporting: %s\n", err)
}
return
}
substate, ok := info["SubState"].(string)
if !ok {
msg := "failed to cast info.SubState"
select {
case c.subStateSubscriber.errCh <- errors.New(msg):
default:
log.Printf("full error channel while reporting: %s\n", msg)
}
return
}

update := &SubStateUpdate{name, substate}
select {
case c.subStateSubscriber.updateCh <- update:
default:
msg := "update channel is full"
select {
case c.subStateSubscriber.errCh <- errors.New("update channel full!"):
case c.subStateSubscriber.errCh <- errors.New(msg):
default:
log.Printf("full error channel while reporting: %s\n", msg)
}
return
}

c.updateIgnore(unitPath, info)
}

// The ignore functions work around a wart in the systemd dbus interface.
Expand All @@ -238,10 +273,13 @@ func (c *Conn) shouldIgnore(path dbus.ObjectPath) bool {
}

func (c *Conn) updateIgnore(path dbus.ObjectPath, info map[string]interface{}) {
c.cleanIgnore()
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@dtnaylor dtnaylor Jan 31, 2018

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Why move this out of here?

(seems fine to me either way, but if anyone other than sendSubStateUpdate starts using the ignore functions, then they'll have to remember to call cleanIgnore themselves)

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@lucab lucab Jan 31, 2018 •
edited
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Because updateIgnore is only called after we get a proper and non-ignored info, while cleanIgnore is generic bookkeeping that doesn't need any of it. I was just reading the code, and I felt it was out of place, so I turned it into a non-conditional defer.

You are right about the multiple callers. This code may need some more intrusive re-architecting once we get there, the whole ignore thing is quite hackish.

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@dtnaylor dtnaylor Feb 1, 2018

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Makes sense—sounds good.

loadState, ok := info["LoadState"].(string)
if !ok {
return
}

// unit is unloaded - it will trigger bad systemd dbus behavior
if info["LoadState"].(string) == "not-found" {
if loadState == "not-found" {
c.subStateSubscriber.ignore[path] = time.Now().UnixNano() + ignoreInterval
}
}
Expand Down Expand Up @@ -294,9 +332,11 @@ func (c *Conn) sendPropertiesUpdate(unitPath dbus.ObjectPath, changedProps map[s
select {
case c.propertiesSubscriber.updateCh <- update:
default:
msg := "update channel is full"
select {
case c.propertiesSubscriber.errCh <- errors.New("update channel is full"):
case c.propertiesSubscriber.errCh <- errors.New(msg):
default:
log.Printf("full error channel while reporting: %s\n", msg)
}
return
}
Expand Down