To support proxy LCP negotiation.
Note: we *have* to take the auth id from the proxy answer, otherwise we would
replay previous ids, for which the client might cache the answer and thus
ignore our new challenge and just repeat their outdated answer.
With IP_MULTICAST_LOOP they can see each other. We "just" have to make sure
they use different IP addresses and route metrics to distinguish from each
other.
The default 4 is really small, and imposes very sequential processing of
reconnections in case we lose all sessions. Nowadays we easily have
memory for a lot more.
controlc doesn't mean we will send more messages, but only that some of them
are pending ack. If we have already sent them and the peer has just not
acked them yet, controlnull() would not send a ZLB, and once the peer
has acked our control messages, we wouldn't send a ZLB with an updated Nr.
Previously, when we got a call to be forwarded to another LNS and we didn't
have a tunnel to it yet, we would wait for a PAP/CHAP re-send to trigger the
creation of a session in the fresh tunnel. We do not have to wait, we can
trigger that on SCCCN ack.
Retransmissions are done very slowly, so we'd really better store the
Out-of-Order messages so that we can catch up quickly once we get the
missing piece.
Creating/destroying interfaces etc. does take some time. When e.g. receiving
a lot of sessions as new slave, we don't want to stay stuck creating
hundreds of interfaces while we are already receiving control messages
that we have to forward to master not too late. Switching kernel
acceleration can wait a bit most of the time.
fmtaddr formats the string to a static buffer that must be selected
manually, but this log message was re-using the same buffer.
Use another index for 2nd IP so we get to know which is what.
Fixes: 2429969bd04d ("Add L2TP offloading support")
Otherwise with kernel acceleration we would only have the same /64 route
on all ppp devices. We need separate /96 routes on each ppp device for
packets of the /96 subprefix to be routed to the correct session.
