ippool: Implement and use blacklist instead of blindly using IPPOOL_NOGATEWAYpespin/ippool

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

1 files changed, 259 insertions, 5 deletions

diff --git a/tests/lib/ippool_test.ok b/tests/lib/ippool_test.ok
index a0eeb4b..263494e 100644
--- a/tests/lib/ippool_test.ok
+++ b/tests/lib/ippool_test.ok
@@ -1,4 +1,4 @@
-testing pool for prefix 192.168.23.0/24, flags=0x0, expected_size=256
+testing pool for prefix 192.168.23.0/24, flags=0x0, blacklist_size=0, expected_size=256
 allocated address 192.168.23.0
 allocated address 192.168.23.1
 allocated address 192.168.23.2
@@ -255,7 +255,7 @@ allocated address 192.168.23.252
 allocated address 192.168.23.253
 allocated address 192.168.23.254
 allocated address 192.168.23.255
-testing pool for prefix 192.168.23.0/24, flags=0x1, expected_size=255
+testing pool for prefix 192.168.23.0/24, flags=0x1, blacklist_size=0, expected_size=255
 allocated address 192.168.23.1
 allocated address 192.168.23.2
 allocated address 192.168.23.3
@@ -511,7 +511,7 @@ allocated address 192.168.23.252
 allocated address 192.168.23.253
 allocated address 192.168.23.254
 allocated address 192.168.23.255
-testing pool for prefix 192.168.23.0/24, flags=0x3, expected_size=254
+testing pool for prefix 192.168.23.0/24, flags=0x3, blacklist_size=0, expected_size=254
 allocated address 192.168.23.1
 allocated address 192.168.23.2
 allocated address 192.168.23.3
@@ -766,7 +766,7 @@ allocated address 192.168.23.251
 allocated address 192.168.23.252
 allocated address 192.168.23.253
 allocated address 192.168.23.254
-testing pool for prefix 192.168.0.0/16, flags=0x3, expected_size=65534
+testing pool for prefix 192.168.0.0/16, flags=0x3, blacklist_size=0, expected_size=65534
 allocated address 192.168.0.1
 allocated address 192.168.0.2
 allocated address 192.168.0.3
@@ -66301,7 +66301,7 @@ allocated address 192.168.255.251
 allocated address 192.168.255.252
 allocated address 192.168.255.253
 allocated address 192.168.255.254
-testing pool for prefix 2001:DB8::/56, flags=0x0, expected_size=256
+testing pool for prefix 2001:DB8::/56, flags=0x0, blacklist_size=0, expected_size=256
 allocated address 2001:db8::
 allocated address 2001:db8:0:1::
 allocated address 2001:db8:0:2::
@@ -66558,3 +66558,257 @@ allocated address 2001:db8:0:fc::
 allocated address 2001:db8:0:fd::
 allocated address 2001:db8:0:fe::
 allocated address 2001:db8:0:ff::
+testing pool for prefix 192.168.23.0/24, flags=0x3, blacklist_size=3, expected_size=253
+allocated address 192.168.23.2
+allocated address 192.168.23.3
+allocated address 192.168.23.4
+allocated address 192.168.23.5
+allocated address 192.168.23.6
+allocated address 192.168.23.7
+allocated address 192.168.23.8
+allocated address 192.168.23.9
+allocated address 192.168.23.10
+allocated address 192.168.23.11
+allocated address 192.168.23.12
+allocated address 192.168.23.13
+allocated address 192.168.23.14
+allocated address 192.168.23.15
+allocated address 192.168.23.16
+allocated address 192.168.23.17
+allocated address 192.168.23.18
+allocated address 192.168.23.19
+allocated address 192.168.23.20
+allocated address 192.168.23.21
+allocated address 192.168.23.22
+allocated address 192.168.23.23
+allocated address 192.168.23.24
+allocated address 192.168.23.25
+allocated address 192.168.23.26
+allocated address 192.168.23.27
+allocated address 192.168.23.28
+allocated address 192.168.23.29
+allocated address 192.168.23.30
+allocated address 192.168.23.31
+allocated address 192.168.23.32
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+allocated address 192.168.23.34
+allocated address 192.168.23.35
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+allocated address 192.168.23.37
+allocated address 192.168.23.38
+allocated address 192.168.23.39
+allocated address 192.168.23.40
+allocated address 192.168.23.41
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+allocated address 192.168.23.47
+allocated address 192.168.23.48
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+allocated address 192.168.23.50
+allocated address 192.168.23.51
+allocated address 192.168.23.52
+allocated address 192.168.23.53
+allocated address 192.168.23.54
+allocated address 192.168.23.55
+allocated address 192.168.23.56
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+allocated address 192.168.23.58
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+allocated address 192.168.23.65
+allocated address 192.168.23.66
+allocated address 192.168.23.67
+allocated address 192.168.23.68
+allocated address 192.168.23.69
+allocated address 192.168.23.70
+allocated address 192.168.23.71
+allocated address 192.168.23.72
+allocated address 192.168.23.73
+allocated address 192.168.23.74
+allocated address 192.168.23.75
+allocated address 192.168.23.76
+allocated address 192.168.23.77
+allocated address 192.168.23.78
+allocated address 192.168.23.79
+allocated address 192.168.23.80
+allocated address 192.168.23.81
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+allocated address 192.168.23.84
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+allocated address 192.168.23.86
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+allocated address 192.168.23.89
+allocated address 192.168.23.90
+allocated address 192.168.23.91
+allocated address 192.168.23.92
+allocated address 192.168.23.93
+allocated address 192.168.23.94
+allocated address 192.168.23.95
+allocated address 192.168.23.96
+allocated address 192.168.23.97
+allocated address 192.168.23.98
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