[FS#785] dnsmasq: /tmp/resolv.conf not set to localhost when noresolv=1 and resolvfile is unset

[LEDE Bugs]

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

User who did this - Paul Oranje (por) 

Attached to Project - LEDE Project
Summary - dnsmasq: /tmp/resolv.conf not set to localhost when noresolv=1 and resolvfile is unset
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Laag
Priority - Normaal
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - For up-stream name resolution dnsmasq normally uses the name servers in the resolvfile, unless noresolv is true (and then a up-stream DNS server should explicitly have been configured).

The file /etc/resolv.conf defines the name servers to be used by processes that run on the router. This file is a soft link to /tmp/resolv.conf.

The dnsmasq init script dnsmasq_start() routine normally writes the file /tmp/resolv.conf and sets the name server to 127.0.0.1; the dnsmasq_stop() routine restores /tmp/resolv.conf to its previous state (being a soft link to /tmp/resolv.conf.auto)

These init script routines execute these steps only when UCI dhcp.dnsmasq.resolvfile equals '/tmp/resolv.conf.auto', but resolvfile only defaults to that value when UCI dhcp.dnsmasq.noresolv is not set to '1'.

Not using the local running DNS service when noresolv is true does not make sence; the semantics of that config value do not imply this.

The latter may typically occur when using unbound as DNS service with dnsmasq as dpcp-link (see unbound documentation).


work-around: explicitly set UCI dhcp.dnsmasq.resolvfile to '/tmp/resolv.conf.auto'.


possible fixes:

Write (and restore) /tmp/resolv.conf also when noresolv is true, e.g. guard it with:

  [ "$noreolv" -eq '1' -o "$resolvfile" = "/tmp/resolv.conf.auto" ]

or, probably a better fix, just test if a service runs on 127.0.0.1:53; advise on how to accomplish that are welcome.


More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=785