Please update to 3.0

This is a backwards incompatible release, but better security by default (keys are 3072 bit and configurable now.)

Upstream changelog:

3.0 Thu Nov 10 15:39:58 CET 2016
        - INCOMPATIBLE CHANGE: core protocol version 1.0.
        - INCOMPATIBLE CHANGE: node sections are now introduced
          with "node nodename", not "node = nodename".
        - INCOMPATIBLE CHANGE: gvpectrl -g will now generate a single
          keypair, while -G will try to generate all keypairs as before.
        - openssl 1.0.2 is the latest supported openssl release,
          openssl 1.1.0 is not supported at the moment as the work to
          make it compatible to both versions is just too much. a switch
          to openssl 1.1 or another library will be done in a future release.
        - update examples to not generate keys centrally, but locally on each
          node.
        - add workaround for temporary/rare ENOBUFS condition.
        - while individual packets couldn't be replayed, a whole session
          could be replayed - this has been fixed by an extra key exchange.
        - fix a delete vs. delete [] mismatch in the central logging function.
        - in addition to rsa key exchange and authentication, the handshake now
          adds a diffie-hellman key exchange (using curve25119) for perfect
          forward secrecy. mac and cipher keys are derived using HKDF.
        - rsa key sizes are now configurable and larger (default is 3072).
          correspondingly, the minimum mtu is no longer 296 but 576.
        - fixed a potential (unverified) buffer overrun on rsa decryption.
        - new per-node low-power setting that tries to reduce cpu/network usage.
        - router reconnects could cause excessive rekeying on other connections.
        - gvpectrl no longer generates all missing public keys, but
          only missing private keys. private keys are also put
          into the configured location.
        - the pid-file now accepts %s as nodename as elsewhere.
        - switch to counter mode (only aes supported at the moment in
          openssl). this gets rid of the need to generate a random iv,
          is likely more secure (and, as a side effect, gets rid of
          slow randomness generation. counter mode is often faster
          then cbc mode as well, and packets are smaller).
        - no longer use RAND_bytes to generate session keys - you NEED
          a real source of entropy now (e.g. egd or /dev/random - see the
          openssl documentation).
        - multiple node statements for the same node are now supported
          and will be merged.
        - a new directive "global" switches back to the global section
          of the config file.
        - if-up scripts can now be specified with absolute paths.
        - new global option: serial, to detect configuration mismatches.
        - use HKDF as authentication proof, not HMAC or a plain hash
          (hint by Ilmari Karonen).
        - during rekeying or connection establishments, hmac authentication
          errors could occur and reset the connection. Transient hmac
          authentication errors are now being ignored for 3 seconds.
        - log the reason for a conneciton loss.
        - use a (hopefully) constant time memcmp to compare internal secrets.
        - fix a (harmless) errornous out of bounds stack read that would trigger
          gcc's -fsanitize=address.
        - bump old packet window size from 512 to 65536.
        - update for big changes in openssl 1.1 API, wrap primitives
          to make further changes easier.
        - correctly check return values for openssl 1.0.0 and later.
        - check for both public and private key file when deciding whether
          to skip generating a key to avoid accidental overwrites.