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handle gracefully add/delete of vethwedu dummy interface #3459

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handle gracefully add/delete of vethwedu dummy interface #3459

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4b903b3
handle gracefully add/delete of vethwedu dummy interface
murali-reddy Nov 23, 2018
cd788fc
addressing review comment. use defer right after link creation.
murali-reddy Jan 4, 2019
c814651
rename the dummy interface name
murali-reddy Jan 10, 2019
db47f17
reuse dummy variable
murali-reddy Jan 22, 2019
7f85a01
reuse dummy netlink object to delete the interface
murali-reddy Feb 12, 2019
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19 changes: 11 additions & 8 deletions net/bridge.go
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,7 @@ datapath of old kernel versions (https://github.com/weaveworks/weave/issues/1577

const (
WeaveBridgeName = "weave"
WeaveDummyIfName = "vethwedu"
DatapathName = "datapath"
DatapathIfName = "vethwe-datapath"
BridgeIfName = "vethwe-bridge"
Expand Down Expand Up @@ -327,22 +328,24 @@ func (b bridgeImpl) initPrep(config *BridgeConfig) error {
// fails. Bridges take the lowest MTU of their interfaces. So
// instead we create a temporary interface with the desired MTU,
// attach that to the bridge, and then remove it again.
dummy := &netlink.Dummy{LinkAttrs: netlink.NewLinkAttrs()}
dummy.LinkAttrs.Name = "vethwedu"
if err = netlink.LinkAdd(dummy); err != nil {
var dummy netlink.Link
dummy = &netlink.Dummy{LinkAttrs: netlink.NewLinkAttrs()}
dummy.Attrs().Name = WeaveDummyIfName
if err = LinkAddIfNotExist(dummy); err != nil {
return errors.Wrap(err, "creating dummy interface")
}
defer func() {
if err = netlink.LinkDel(dummy); err != nil {
err = errors.Wrap(err, "deleting dummy interface")
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I think assigning to the local variable err at this point has no effect.
If err is made a named return value from initPrep it would work, but suppose both LinkSetMTU and LinkDel fail, we'd only see one error.
Maybe use a different err to record the LinkDel() result and use Wrap() to add the previous error (if any).

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Hmm, Wrap() can only wrap one error. Maybe just add the text of this one to the previous one, if it exists.

}
}()
if err := netlink.LinkSetMTU(dummy, config.MTU); err != nil {
return errors.Wrapf(err, "setting dummy interface mtu to %d", config.MTU)
}
if err := netlink.LinkSetMasterByIndex(dummy, b.bridge.Attrs().Index); err != nil {
return errors.Wrap(err, "setting dummy interface master")
}
if err := netlink.LinkDel(dummy); err != nil {
return errors.Wrap(err, "deleting dummy interface")
}

return nil
return err
}

func (b bridgeImpl) init(config *BridgeConfig) error {
Expand Down