Limit TCP MSS

• impose a maximum TCP MSS of 1460 to avoid sending over-large datagrams on 1500 MTU links
  (#309, by @hannesm)

Parsing fixes, lwt 2.7.0+ compat

• fix parsing 20-byte cstructs as ipv4 packets (#307, by @yomimono)
• udp: payload length parse fix (#307, by @yomimono)
• support lwt >= 2.7.0 (#308, by @djs55)

MTU + bugfixes

• implement MTU setting and querying in the Ethernet module (compatibility with mirage-protocols version 1.1.0), and use this value to inform TCP's MSS. (#288, by @djs55)
• rename the ~payload argument of TCP/UDP marshallers to ~payload_len, in an attempt to clarify that the payload will not be copied to the Cstruct.t returned by these functions (#301, by @talex5)
• functorize ipv6 over a random implementation (#298, by @olleolleolle and @hannesm)
• add tests for sending and receiving UDP packets over IPv6 (#300, by @mattgray)
• avoid float in TCP RTO calculations. (#295, by @olleolleolle and @mattgray)
• numerous bugfixes in header marshallers and unmarshallers (#301, by @talex5 and @yomimono)
• replace polymorphic equality in _packet.equals functions (#302, by @yomimono)

MirageOS 3 + many improvements

• adapt to MirageOS 3 API changes (many PRs, from @hannesm, @samoht, and @yomimono):
  • replace error polyvars in many functions with result types
  • define and use error types
  • connect in various modules now returns the device directly or raises an exception
  • refer to mirage-protocols and mirage-stacks, rather than mirage-types
• remove DHCP module. Users may be interested in the replacement charrua-core (#260, by @yomimono)
• the Ethernet layer now uses source and destination, the IP layer uses src and dst, and the TCP and UDP layers use src_port and dst_port consistently. TCP.get_dest, for getting an IP and port from a given flow, has been replaced by TCP.dst. (#214 by @yomimono)
• if no UDP source port is given to UDP.write, choose a random one (#272, by @hannesm)
• remove exceptions Ipv4.Routing.No_route_to_destination_address exception and Tcp.Refused
• Ipv6.connect takes a list of IPs (#268, by @yomimono)
• move Ipv4 to Static_ipv4, which can be used by other IPv4 modules with their own configuration logic (#260, by @yomimono)
• remove mode from STACKV4 record and configuration; Ipv4.connect now requires address parameters and the module exposes no methods for modifying them. (#260, by @yomimono)
• remove unused id types no longer required by mirage-types (#255, by @yomimono)
• overhaul how random is used and handled (#254 and others, by @hannesm)
• fix redundant memset that zeroed out options in Tcp_packet.Marshal.into_cstruct (#250, by @balrajsingh)
• add vnetif backend for triggering fast retransmit in iperf tests (#248, by @MagnusS)
• fixes for incorrect timer values (#247, by @balrajsingh)
• add vnetif backend that drops packets with no payload (#246, by @MagnusS)
• fix a race when closing test pcap files (#246, by @MagnusS)

Better TCP fast-retransmission

• Set the TCP congestion window correctly when going into fast-recovery mode. (#244, by @balrajsingh)
• When TCP packet loss is discovered by timeout, allow transition into fast-recovery mode. (#244, by @balrajsingh)

Independent ICMP

• Provide an implementation for the ICMPV4 module type defined in mirage-types 2.8.0. Remove default ICMP handling from the IPv4 module, but preserve it in tcpip-stack-direct. (#195 by @yomimono)
• Explicitly require the use of an OCaml compiler >= 4.02.3 . (#195 by @yomimono)
• Explicitly depend on result. (#195 by @yomimono)

Lots of fixes, better tests, no more camlp4 dependency

• Raise Invalid_argument if given an invalid port number in listen_{tcp,udp}v4
  (#173 by @matildah and #175 by @hannesm)
• Improve TCP options marshalling/unmarshalling (#174 by @yomimono)
• Add state tests and fixes for closure conditions (#177 #176 by @yomimono)
• Remove bogus warning (#178 by @talex5)
• Clean up IPv6 stack (#179 by @nojb)
• RST checking from RFC5961 (#182 by @ppolv)
• Transform EPIPE exceptions into `Eof (#183 by @djs55)
• Improve error strings in IPv4 (#184 by @yomimono)
• Replace use of cstruct.syntax with cstruct.ppx (#188 by @djs55)
• Make the Unix subpackages optional, so the core builds on Win32
  (#191 by @djs55)

Expose IPv4 exception and add optional arguments to the connect functions

• Add optional arguments for settings in ip v6 and v4 connects (#170, by @Drup)
• Expose Ipv4.Routing.No_route_to_destination_address (#166, by @yomimono)

Better ARP

• ARP now handles ARP frames, not Ethernet frames with ARP payload
  (#164, by @hannesm)
• Check length of received ethernet frame to avoid cstruct exceptions
  (#117, by @hannesm)
• Pull arpv4 module out of ipv4. Also add unit-tests for the newly created
  ARP library (#155, by @yomimono)

Fix regression which causes slow-downs on packet loss, close connection cleanly and extract the channels out

• Fix regression introduced in 2.5.0 where packet loss could lead to the
  connection to become very slow (#157, MagnusS, @talex5, @yomimono and
  @balrajsingh)
• Improve the tests: more logging, more tracing and compile to native code when
  available, etc (@MagnusS and @talex5)
• Do not raise Invalid_argument("Lwt.wakeup_result") everytime a connection
  is closed. Also now pass the raised exceptions to Lwt.async_exception_hook
  instead of ignoring them transparently, so the user can decide to shutdown
  its application if something wrong happens (#153, #156, @yomomino and @talex5)
• The channel library now lives in a separate repository and is released
  separately (#159, @samoht)