Tinc uses Kruskal's algorithm to calculate a MST. However, this was broken in
commit 6e80da3370. Revert back to the working
algorithm from tinc 1.0.
Thanks to Cheng LI for spotting the problem.
There are several reasons for this:
- MacOS/X doesn't support polling the tap device using kqueue, requiring a
workaround to fall back to select().
- On Windows only sockets are properly handled, therefore tinc uses a second
thread that does a blocking ReadFile() on the TAP-Win32/64 device. However,
this does not mix well with libevent.
- Libevent, event just the core, is quite large, and although it is easy to get
and install on many platforms, it can be a burden.
- Libev is more lightweight and seems technically superior, but it doesn't
abstract away all the platform differences (for example, async events are not
supported on Windows).
The tree functions were never used on the connection_tree, a list is more appropriate.
Also be more paranoid about connections disappearing while traversing the list.
Similar to old style key exchange requests, keep track of whether a key
exchange is already in progress and how long it took. If no key is known yet
or if key exchange takes too long, (re)start a new key exchange.
When two nodes which support SPTPS want to send packets to each other, they now
always use SPTPS. The node initiating the SPTPS session send the first SPTPS
packet via an extended REQ_KEY messages. All other handshake messages are sent
using ANS_KEY messages. This ensures that intermediate nodes using an older
version of tinc can still help with NAT traversal. After the authentication
phase is over, SPTPS packets are sent via UDP, or are encapsulated in extended
REQ_KEY messages instead of PACKET messages.
This allows tincctl to receive log messages from a running tincd,
independent of what is logged to syslog or to file. Tincctl can receive
debug messages with an arbitrary level.
Since tinc now handles UDP packets with a different source address and port
than used for TCP connections, the heuristic to treat edges as indirect when
tinc could detect that multiple addresses were used does not make sense
anymore, and can actually reduce performance.
When we got a key request for or from a node we don't know, we disconnected the
node that forwarded us that request. However, especially in TunnelServer mode,
disconnecting does not help. We now ignore such requests, but since there is no
way of telling the original sender that the request was dropped, we now retry
sending REQ_KEY requests when we don't get an ANS_KEY back.
We clear the cached address used for UDP connections when a node becomes
unreachable. This also prevents host-up scripts from passing the old, cached
address from when the host becomes reachable again from a different address.
The control socket code was completely different from how meta connections are
handled, resulting in lots of extra code to handle requests. Also, not every
operating system has UNIX sockets, so we have to resort to another type of
sockets or pipes for those anyway. To reduce code duplication and make control
sockets work the same on all platforms, we now just connect to the TCP port
where tincd is already listening on.
To authenticate, the program that wants to control a running tinc daemon must
send the contents of a cookie file. The cookie is a random 256 bits number that
is regenerated every time tincd starts. The cookie file should only be readable
by the same user that can start a tincd.
Instead of the binary-ish protocol previously used, we now use an ASCII
protocol similar to that of the meta connections, but this can still change.
This feature is not necessary anymore since we have tools like valgrind today
that can catch stack overflow errors before they make a backtrace in gdb
impossible.
Previously, tinc used a fixed address and port for each node for UDP packet
exchange. The port was the one advertised by that node as its listening port.
However, due to NAT the port might be different. Now, tinc sends a different
session key to each node. This way, the sending node can be determined from
incoming packets by checking the MAC against all session keys. If a match is
found, the address and port for that node are updated.
