ggsn: encaps_tun: Avoid forwarding packet if EUA is unassigned, fix crash

Check (before forwarding received GTP packets into the tun) if the pdp ctx
associated with the packet requested was assigned an EUA of the given IP version.
This way we avoid for instance forwarding an IPv6 packet (or sending
back a response to a Router Solicitation packet) in case the APN was
configured without IPv6 support or if the MS/SGSN didn't ask for an IPv6
while requesting an EUA.

As a side effect, this commit fixes an OSMO_ASSERT hit introduced in handle_router_mcast
in 2d6a69e69a4b4cb2b8cc63c4810dae44e5a4d8f6 due to a deffective MS
sending an icmpv6 Router Solicitation over IPv6 after having been
requesting and assigned an IPv4 EUA (so no IPv6 packets expected).
Before that commit, there was no crash but the message was being wrongly
answered and used an uninitialized .v6 addr field from the peer struct.

Fixes: OS#2843

Change-Id: Ib6d18a64c2b71f3bcf6cb7e3a978d2d3f9c7a79b

0 files changed, 0 insertions, 0 deletions