Arch Linux

Description:
I try to connect over a GRE-tunnel in a 5 to 6 machine setup.

On my 5 machines each of the other 6 machines are configured via netctl for a gre-tunnel.

With nmap I confirmed that the connections are possible (I've masked the IPv6-Numbers):

-----------------------------

# nmap -6 -p179 2a03:1234:2345:3456::1

Starting Nmap 7.12 ( https://nmap.org ) at 2016-07-13 14:53 CEST
Nmap scan report for 2a03:1234:2345:3456::1
Host is up (0.011s latency).
PORT STATE SERVICE
179/tcp open bgp

Nmap done: 1 IP address (1 host up) scanned in 6.79 seconds

-----------------------------

Additional info:
* package version(s)
1.6.0-1
* log shows to all peers something like this:
bb_b_ix_dus_abc: Connecting to 2a03:1234:2345:3456::1 from local address 2a03:1234:2345:3456::2


I've tcpdumped it locally, the SYN from bird6 never get responded, so I think there is an issue that this package never get it thru the GRE tunnel.

The exact same looking SYN from Telnet or Nmap got responded very well.