[strongSwan] Progress on packet flow issue with StrongSwan and IPv6

[Jason White]

I've posted here before regarding a lack of packet flow after setting up IPSec
connections with StrongSwan on my system. To summarize: there's an ADSL card
that provides external connectivity; pppd sets up a ppp0 interface. DHCPv6
prefix delegation then supplies a block of addresses and the eth0 interface is
configured with a /64 prefix.

After an IPv6 tunnel is established, pinging the remote side fails. IPv4
tunnels are fine. Packet monitoring shows that the IPv6 packets are not sent
out.

Having returned to the issue recently, I've discovered that if I shut down the
ppp0 interface, stop StrongSwan, restart StrongSwan, bring up ppp0, then
establish a tunnel, all works as it should. I've looked at the logs of the
boot process, and everything seems to be started in proper sequence there.

Does anything in the above suggest what the problem might be?