tree 0851e43c00d3faef3411ee83220437a1a021ceec
parent d6ede37b7e62ca7e3544b7319b9234c564365dca
author Pau Espin Pedrol <pespin@sysmocom.de> 1507897929 +0200
committer Pau Espin Pedrol <pespin@sysmocom.de> 1507900204 +0200

ippool: Implement and use blacklist instead of blindly using IPPOOL_NOGATEWAY

Commit dda21ed7d4a897c9284c69175d0da598598eae40 modified previous calls
to ippool_new() removing the pass of flags to avoid allocating certain
problematic IPs from the pool to MS, such as the network, gateway and
broadcast IPs.

Today I did some unsucessful tests with osmo-ggsn with a pool "ip prefix
dynamic 176.16.222.0/24", and thus IP 176.16.222.0 was being assigned to
the MS. De-capsulated DNS packets were received in the tun interface,
but the Linux system in there was unable to correctly forward the
packets to the gateway interface connected to the Internet. However,
adding a second MS which got 176.16.222.1 had its packets forwarded
correctly.

However, previous implementation relies on flag IPPOOL_NOGATEWAY flag to
blindly blacklist first IP after the network ip (ie, .0 and .1 are
removed), which limits the IP reserved for the tun device to be .1. If a
different IP in the range is assigned, it may cause issues. As a result,
a blacklist is introduced in this commit to dynamically fetch the tun IP
address and exlucde it from the pool of available IPs.

Change-Id: I8e91f7280d60490c858a769dd578c1c8e54e9243