Summary: dhcp/dhcp6: Ensure that DHCP/DHCPv6 DNS server
updates don't overlap
Project: lwIP - A Lightweight TCP/IP stack
Submitted by: davefiddes
Submitted on: Thu 03 Oct 2019 12:05:06 PM UTC
Priority: 5 - Normal
Assigned to: None
Discussion Lock: Any
Planned Release: None
This change changes the DHCP and DHCPv6 DNS server option update
processing so that both IPv4 and IPv6 servers can be held in the
list of active DNS servers. Previously when a DHCP offer is processed
the list of active DNS servers is replaced. This can lead to failed
DNS resolution when there is a connectivity over one IP protocol
but not over the other. This change improves the possibility of
DNS resolution falling back to a working DNS server.
- On LWIP configured to use 2 DNS server entries. Configure DHCP and
DHCPv6 to have 0,1 or 2 DNS servers on each protcol. Ensure that
the list of active DNS servers reflects the network configuration.
In the case of overflow ensure that one protocol wins based on the
first processed DHCP response.
- On a network with intermittent IPv6 connectivity ensure that DNS
resolution continues to function as DHCP and DHCPv6 updates are