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libnetwork: Controller.NewNetwork: use named error-return

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It's used in various defers, but was using `err` as name, which can be
confusing, and increases the risk of accidentally shadowing the error.

This patch:

- introduces a `retErr` output variable, to be used in defer statements.
- explicitly changes some `err` uses to locally-scoped variables.
- moves some variable definitions closer to where they're used (where possible).

While working on this change, there was one point in the code where
error handling was ambiguous. I added a note for that, in case this
was not a bug:

> This code was previously assigning the error to the global "err"
> variable (before it was renamed to "retErr"), but in case of a
> "MaskableError" did not *return* the error:
> b325dcbff6/libnetwork/controller.go (L566-L573)
>
> Depending on code paths further down, that meant that this error
> was either overwritten by other errors (and thus not handled in
> defer statements) or handled (if no other code was overwriting it.
>
> I suspect this was a bug (but possible without effect), but it could
> have been intentional. This logic is confusing at least, and even
> more so combined with the handling in defer statements that check for
> both the "err" return AND "skipCfgEpCount":
> b325dcbff6/libnetwork/controller.go (L586-L602)
>
> To save future visitors some time to dig up history:
>
> - config-only networks were added in 25082206df
> - the special error-handling and "skipCfgEpcoung" was added in ddd22a8198
> - and updated in 87b082f365 to don't use string-matching

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This commit is contained in:
Sebastiaan van Stijn 2023-08-16 13:17:01 +02:00
parent b325dcbff6
commit cbe692ffd1
No known key found for this signature in database
GPG key ID: 76698F39D527CE8C
1 changed files with 59 additions and 36 deletions
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95
libnetwork/controller.go
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@ -465,19 +465,12 @@ const overlayDSROptionString = "dsr"
// NewNetwork creates a new network of the specified network type. The options
// are network specific and modeled in a generic way.
func (c *Controller) NewNetwork(networkType, name string, id string, options ...NetworkOption) (*Network, error) {
var (
caps driverapi.Capability
err error
t *Network
skipCfgEpCount bool
)
func (c *Controller) NewNetwork(networkType, name string, id string, options ...NetworkOption) (_ *Network, retErr error) {
if id != "" {
c.networkLocker.Lock(id)
defer c.networkLocker.Unlock(id) //nolint:errcheck
if _, err = c.NetworkByID(id); err == nil {
if _, err := c.NetworkByID(id); err == nil {
return nil, NetworkNameError(id)
}
}
@ -506,10 +499,19 @@ func (c *Controller) NewNetwork(networkType, name string, id string, options ...
}
nw.processOptions(options...)
if err = nw.validateConfiguration(); err != nil {
if err := nw.validateConfiguration(); err != nil {
return nil, err
}
// These variables must be defined here, as declaration would otherwise
// be skipped by the "goto addToStore"
var (
caps driverapi.Capability
err error
skipCfgEpCount bool
)
// Reset network types, force local scope and skip allocation and
// plumbing for configuration networks. Reset of the config-only
// network drivers is needed so that this special network is not
@ -555,36 +557,57 @@ func (c *Controller) NewNetwork(networkType, name string, id string, options ...
// From this point on, we need the network specific configuration,
// which may come from a configuration-only network
if nw.configFrom != "" {
t, err = c.getConfigNetwork(nw.configFrom)
configNetwork, err := c.getConfigNetwork(nw.configFrom)
if err != nil {
return nil, types.NotFoundErrorf("configuration network %q does not exist", nw.configFrom)
}
if err = t.applyConfigurationTo(nw); err != nil {
if err := configNetwork.applyConfigurationTo(nw); err != nil {
return nil, types.InternalErrorf("Failed to apply configuration: %v", err)
}
nw.generic[netlabel.Internal] = nw.internal
defer func() {
if err == nil && !skipCfgEpCount {
if err := t.getEpCnt().IncEndpointCnt(); err != nil {
log.G(context.TODO()).Warnf("Failed to update reference count for configuration network %q on creation of network %q: %v",
t.Name(), nw.Name(), err)
if retErr == nil && !skipCfgEpCount {
if err := configNetwork.getEpCnt().IncEndpointCnt(); err != nil {
log.G(context.TODO()).Warnf("Failed to update reference count for configuration network %q on creation of network %q: %v", configNetwork.Name(), nw.name, err)
}
}
}()
}
err = nw.ipamAllocate()
if err != nil {
if err := nw.ipamAllocate(); err != nil {
return nil, err
}
defer func() {
if err != nil {
if retErr != nil {
nw.ipamRelease()
}
}()
err = c.addNetwork(nw)
if err != nil {
// Note from thaJeztah to future code visitors, or "future self".
//
// This code was previously assigning the error to the global "err"
// variable (before it was renamed to "retErr"), but in case of a
// "MaskableError" did not *return* the error:
// https://github.com/moby/moby/blob/b325dcbff60a04cedbe40eb627465fc7379d05bf/libnetwork/controller.go#L566-L573
//
// Depending on code paths further down, that meant that this error
// was either overwritten by other errors (and thus not handled in
// defer statements) or handled (if no other code was overwriting it.
//
// I suspect this was a bug (but possible without effect), but it could
// have been intentional. This logic is confusing at least, and even
// more so combined with the handling in defer statements that check for
// both the "err" return AND "skipCfgEpCount":
// https://github.com/moby/moby/blob/b325dcbff60a04cedbe40eb627465fc7379d05bf/libnetwork/controller.go#L586-L602
//
// To save future visitors some time to dig up history:
//
// - config-only networks were added in 25082206df465d1c11dd1276a65b4a1dc701bd43
// - the special error-handling and "skipCfgEpcoung" was added in ddd22a819867faa0cd7d12b0c3fad1099ac3eb26
// - and updated in 87b082f3659f9ec245ab15d781e6bfffced0af83 to don't use string-matching
//
// To cut a long story short: if this broke anything, you know who to blame :)
if err := c.addNetwork(nw); err != nil {
if _, ok := err.(types.MaskableError); ok { //nolint:gosimple
// This error can be ignored and set this boolean
// value to skip a refcount increment for configOnly networks
@ -594,9 +617,9 @@ func (c *Controller) NewNetwork(networkType, name string, id string, options ...
}
}
defer func() {
if err != nil {
if e := nw.deleteNetwork(); e != nil {
log.G(context.TODO()).Warnf("couldn't roll back driver network on network %s creation failure: %v", nw.name, err)
if retErr != nil {
if err := nw.deleteNetwork(); err != nil {
log.G(context.TODO()).Warnf("couldn't roll back driver network on network %s creation failure: %v", nw.name, retErr)
}
}
}()
@ -621,25 +644,25 @@ addToStore:
// end up with a datastore containing a network and not an epCnt,
// in case of an ungraceful shutdown during this function call.
epCnt := &endpointCnt{n: nw}
if err = c.updateToStore(epCnt); err != nil {
if err := c.updateToStore(epCnt); err != nil {
return nil, err
}
defer func() {
if err != nil {
if e := c.deleteFromStore(epCnt); e != nil {
log.G(context.TODO()).Warnf("could not rollback from store, epCnt %v on failure (%v): %v", epCnt, err, e)
if retErr != nil {
if err := c.deleteFromStore(epCnt); err != nil {
log.G(context.TODO()).Warnf("could not rollback from store, epCnt %v on failure (%v): %v", epCnt, retErr, err)
}
}
}()
nw.epCnt = epCnt
if err = c.updateToStore(nw); err != nil {
if err := c.updateToStore(nw); err != nil {
return nil, err
}
defer func() {
if err != nil {
if e := c.deleteFromStore(nw); e != nil {
log.G(context.TODO()).Warnf("could not rollback from store, network %v on failure (%v): %v", nw, err, e)
if retErr != nil {
if err := c.deleteFromStore(nw); err != nil {
log.G(context.TODO()).Warnf("could not rollback from store, network %v on failure (%v): %v", nw, retErr, err)
}
}
}()
@ -650,16 +673,16 @@ addToStore:
joinCluster(nw)
defer func() {
if err != nil {
if retErr != nil {
nw.cancelDriverWatches()
if e := nw.leaveCluster(); e != nil {
log.G(context.TODO()).Warnf("Failed to leave agent cluster on network %s on failure (%v): %v", nw.name, err, e)
if err := nw.leaveCluster(); err != nil {
log.G(context.TODO()).Warnf("Failed to leave agent cluster on network %s on failure (%v): %v", nw.name, retErr, err)
}
}
}()
if nw.hasLoadBalancerEndpoint() {
if err = nw.createLoadBalancerSandbox(); err != nil {
if err := nw.createLoadBalancerSandbox(); err != nil {
return nil, err
}
}