[FS#1452] [netifd] gretap instantiation fails on and after commit 1cd76e2 on "master"

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Jeff Kletsky (jeffsf) 

Attached to Project - OpenWrt/LEDE Project
Summary - [netifd] gretap instantiation fails on and after commit 1cd76e2 on "master"
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Low
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - ====Summary====

Prior to the indicated commit, gretap interfaces could be initialized through ''/etc/config/network''

After the indicated commit, gretap interfaces fail to be configured.

gretap interfaces can be initialized "by hand" using ''ip'' from ''ip-full'' in both cases

====Impact====

Unable to utilize gretap interfaces with UCI-based configuration


====To Replicate====

  * Build an Archer C7 image and "clean flash" onto an Archer C7
  * Add the following stanza to ''/etc/network/config'' (also occurs without ''force_link'')

config interface 'gt'
	option proto 'gretap'
	option ipaddr '192.168.1.1'
	option peeraddr '192.168.1.2'
	option force_link '1'

  * reboot
  * note that ''iw link'' does not show the link as even present
  * note that the logs indicate that the ''gt'' interface comes up and is immediately brought down


root at OpenWrt:~# logread | fgrep gt
Tue Mar 13 12:35:25 2018 daemon.notice netifd: Interface 'gt' is setting up now
Tue Mar 13 12:35:26 2018 daemon.notice netifd: Interface 'gt' is now down


====Expected Behavior====

  * ''iw link'' would show the link present and up, as in the proceeding commit on ''master'', 9004fc3c76324f669df3ff402faf78dc847af58a

13: gre4t-gt99 at NONE:  mtu 1280 qdisc fq_codel state UNKNOWN qlen 1000
    link/ether ba:e1:b8:b7:fa:f5 brd ff:ff:ff:ff:ff:ff

  * the link would be usable and connect to its peer (if available)
  * ''logread'' would show the interface coming up

root at OpenWrt:~# logread | fgrep gt
Tue Mar 13 12:17:18 2018 daemon.notice netifd: Interface 'gt' is setting up now
Tue Mar 13 12:17:19 2018 daemon.notice netifd: Interface 'gt' is now up
Tue Mar 13 12:17:19 2018 daemon.notice netifd: tunnel 'gre4t-gt' link is up
Tue Mar 13 12:17:20 2018 user.notice firewall: Reloading firewall due to ifup of gt (gre4t-gt)
   
====Potential Cause====

commit 1cd76e2d85d86356868db731a5cacfb84150b2a1
Author: Felix Fietkau 
Date:   Tue Mar 13 13:33:04 2018 +0100

    netifd: update to the latest version (fixes FS#1358)
    
    1f5a29c ip: do not add local routes for host dependencies
    c06f842 device: add support for setting the isolate options for bridge ports
    69aeaab interface-ip: fix route selection for host dependencies
    
    Signed-off-by: Felix Fietkau 

More information can be found at the following URL:
https://bugs.openwrt.org/index.php?do=details&task_id=1452