svn commit: r334875 - head/sys/net

[Rodney W. Grimes]

> Author: ae
> Date: Sat Jun  9 09:57:14 2018
> New Revision: 334875
> URL: https://svnweb.freebsd.org/changeset/base/334875
> 
> Log:
>   Explicitly change the link state when we assingn an address.
>   
>   Since we are setting IFF_UP flag on SIOCSIFADDR, it is possible, that
>   after this link state information still not initialized properly.
>   This leads to problems with routing, since now interface has
>   IFCAP_LINKSTATE capability and a route is considered as working only
>   when interface's link state is in LINK_STATE_UP (see RT_LINK_IS_UP()
>   macro).

I was going to say something when the ability to up and down
the loopback interfaces was added as it perturbed me but I
could not put my finger on places it may cause problems so
remained silent on the matter.

Now that I see this issue, having lo0 go DOWN can kill a network
that is using exported from lo0 into a routing protocol routes that 
are used for management purposes.

How does Cisco, Juniper, etc at handle this?
Do any of them or all of them allow you to "down" loopback?

>   
>   Reported by:	Marek Zarychta
>   MFC after:	3 days
> 
> Modified:
>   head/sys/net/if_loop.c
> 
> Modified: head/sys/net/if_loop.c
> ==============================================================================
> --- head/sys/net/if_loop.c	Sat Jun  9 04:54:36 2018	(r334874)
> +++ head/sys/net/if_loop.c	Sat Jun  9 09:57:14 2018	(r334875)
> @@ -380,6 +380,7 @@ loioctl(struct ifnet *ifp, u_long cmd, caddr_t data)
>  	case SIOCSIFADDR:
>  		ifp->if_flags |= IFF_UP;
>  		ifp->if_drv_flags |= IFF_DRV_RUNNING;
> +		if_link_state_change(ifp, LINK_STATE_UP);
>  		/*
>  		 * Everything else is done at a higher level.
>  		 */
> 
> 

-- 
Rod Grimes                                                 rgrimes at freebsd.org