sgsnemu: Fix assumption ipv6 Interface-Identifier of public addr == announced Prefix

Until now, sgsnemu was able to identify pdp contexts of incoming packets
in the tun based on the assumption that the Interface-Identifier part of
public IPv6 addresses in incoming packets was equal to the announced
prefix path during Create Pdp Context Response (see changes in cb_tun_ind()).
This assumption works fine with osmo-ggsn due to implementation details but
breaks on other spec-conformant GGSNs.

In order to fix it, a new placeholder struct pdp_peer_sgsnemu_ctx is
introduced which will be assigned to each pdp_t "peer[0]" user-defined
pointer. This way, each pdp_t ctx upgrades from having only 1 iphash_t
item to 3 (hence being able to match against 3 different ip addresses).
This way, in IPv6 we can match against 2 different IP addresses set on
the tun iface:
* link-local: "fe80::IfId", where IfId is the Interface-Identifier
  received during Pdp Context Resp and which can be used to communicate
  with the nearest router (the GGSN).
* global: The global IPv6 addr set after SLAAC procedure, containing a
  the prefix announced by CreatePdpContextResp/RouterAdvertisement and
  an Interface-Identifier chosen by sgsnemu itself (currently ::ff).

This change is also a step forward towards supporting IPv4v6 APNs in sgsnemu.

Related: OS#4434
Change-Id: I0d36145250185e4cce699fdaedfe96bd969f5fa1

0 files changed, 0 insertions, 0 deletions